fix(adminui): the cluster-node editor was dead — 500 on load, silent no-op on save

Both defects are PRE-EXISTING (present on master, unrelated to #499) and were found
live-verifying the #499 guard, which lives on this page and was unreachable without
them fixed.

1. **HTTP 500 on load.** `FormModel.ServiceLevelBase` was `byte` to match the
   entity, and `InputNumber<T>`'s static constructor throws outright for
   `System.Byte` — "The type 'System.Byte' is not a supported numeric type". That
   escapes `BuildRenderTree` unhandled, which in Blazor takes the WHOLE page down,
   not one field. `/clusters/{id}/nodes/{nodeId}` and `.../nodes/new` have never
   rendered. Now `int` with the same `[Range(0, 255)]` and a cast on the way to the
   entity, so the stored type is unchanged. (Same failure mode as #504: an
   unhandled throw inside the render tree is a page-kill.)

2. **Save did nothing, silently.** `NodeId` was validated against
   `^[A-Za-z0-9_-]+$`, which forbids the colon — but every NodeId in this system is
   `host:port` (`ClusterRoleInfo` and `ConfigPublishCoordinator` derive it as
   `member.Address.Host:Port`, the seed writes `central-1:4053`, and
   `NodeDeploymentState.NodeId` is FK-bound to it). So every existing node failed
   validation, `OnValidSubmit` never ran, and the button was inert. Pattern now
   allows `:` and `.` (hostnames may be dotted).

3. **Added the missing `<ValidationSummary/>`.** The form had a
   `DataAnnotationsValidator` but nothing rendering its output, so a validation
   failure produced no feedback at all — which is precisely how (2) stayed
   invisible. This is the change that stops the next such defect being silent.

Live-verified on docker-dev (both central nodes rebuilt, since :9200 round-robins
the pair): page 500 → 200 on both routes, and a real edit now persists.

Directory.Packages.props

@@ -77,6 +77,10 @@
     <PackageVersion Include="Moq" Version="4.20.72" />
     <PackageVersion Include="Novell.Directory.Ldap.NETStandard" Version="3.6.0" />
     <PackageVersion Include="OPCFoundation.NetStandard.Opc.Ua.Client" Version="1.5.378.106" />
+    <!-- Core carries Opc.Ua.StatusCodes, the oracle StatusCodeParityTests checks the drivers'
+         hard-coded uint constants against. Referenced by that TEST project only — the drivers
+         themselves stay SDK-free by design and keep spelling status codes as bare uints. -->
+    <PackageVersion Include="OPCFoundation.NetStandard.Opc.Ua.Core" Version="1.5.378.106" />
     <PackageVersion Include="OPCFoundation.NetStandard.Opc.Ua.Configuration" Version="1.5.378.106" />
     <PackageVersion Include="OPCFoundation.NetStandard.Opc.Ua.Server" Version="1.5.378.106" />
     <!-- OpenTelemetry.Api < 1.15.3 has GHSA-g94r-2vxg-569j (header-parsing memory DoS). The trio

ZB.MOM.WW.OtOpcUa.slnx

@@ -29,6 +29,9 @@
     <Project Path="src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus/ZB.MOM.WW.OtOpcUa.Driver.Modbus.csproj" />
     <Project Path="src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Addressing/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Addressing.csproj" />
     <Project Path="src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Contracts/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Contracts.csproj" />
+    <Project Path="src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql/ZB.MOM.WW.OtOpcUa.Driver.Sql.csproj" />
+    <Project Path="src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser/ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser.csproj" />
+    <Project Path="src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts/ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts.csproj" />
     <Project Path="src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7/ZB.MOM.WW.OtOpcUa.Driver.S7.csproj" />
     <Project Path="src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7.Contracts/ZB.MOM.WW.OtOpcUa.Driver.S7.Contracts.csproj" />
     <Project Path="src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbCip/ZB.MOM.WW.OtOpcUa.Driver.AbCip.csproj" />
@@ -90,6 +93,9 @@
     <Project Path="tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Tests.csproj" />
     <Project Path="tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Addressing.Tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Addressing.Tests.csproj" />
     <Project Path="tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests.csproj" />
+    <Project Path="tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql.Tests/ZB.MOM.WW.OtOpcUa.Driver.Sql.Tests.csproj" />
+    <Project Path="tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser.Tests/ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser.Tests.csproj" />
+    <Project Path="tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql.IntegrationTests/ZB.MOM.WW.OtOpcUa.Driver.Sql.IntegrationTests.csproj" />
     <Project Path="tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7.Tests/ZB.MOM.WW.OtOpcUa.Driver.S7.Tests.csproj" />
     <Project Path="tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7.IntegrationTests/ZB.MOM.WW.OtOpcUa.Driver.S7.IntegrationTests.csproj" />
     <Project Path="tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbCip.Tests/ZB.MOM.WW.OtOpcUa.Driver.AbCip.Tests.csproj" />

docker-dev/docker-compose.yml

@@ -272,6 +272,12 @@ services:
       OTOPCUA_ROLES: "admin,driver,cluster-MAIN"
       ASPNETCORE_URLS: "http://+:9000"
       ConnectionStrings__ConfigDb: "Server=sql,1433;Database=OtOpcUa;User Id=sa;Password=OtOpcUa!Dev123;TrustServerCertificate=True;"
+      # Sql poll driver — the named connection string a Sql driver instance references by
+      # `connectionStringRef: "DevSql"`. Resolved in-process by SqlConnectionStringResolver (driver
+      # node) and SqlDriverBrowser (AdminUI browse), env-only, never persisted to ConfigDb. Points at
+      # the rig's own `sql` container, a SEPARATE `DevSql` database seeded with dbo.TagValues (KeyValue)
+      # + dbo.LatestStatus (WideRow). Committed-dev-secret exception, same as ConfigDb above.
+      Sql__ConnectionStrings__DevSql: "Server=sql,1433;Database=DevSql;User Id=sa;Password=OtOpcUa!Dev123;TrustServerCertificate=True;"
       Cluster__Hostname: "0.0.0.0"
       Cluster__Port: "4053"
       Cluster__PublicHostname: "central-1"
@@ -391,6 +397,12 @@ services:
       OTOPCUA_ROLES: "admin,driver,cluster-MAIN"
       ASPNETCORE_URLS: "http://+:9000"
       ConnectionStrings__ConfigDb: "Server=sql,1433;Database=OtOpcUa;User Id=sa;Password=OtOpcUa!Dev123;TrustServerCertificate=True;"
+      # Sql poll driver — the named connection string a Sql driver instance references by
+      # `connectionStringRef: "DevSql"`. Resolved in-process by SqlConnectionStringResolver (driver
+      # node) and SqlDriverBrowser (AdminUI browse), env-only, never persisted to ConfigDb. Points at
+      # the rig's own `sql` container, a SEPARATE `DevSql` database seeded with dbo.TagValues (KeyValue)
+      # + dbo.LatestStatus (WideRow). Committed-dev-secret exception, same as ConfigDb above.
+      Sql__ConnectionStrings__DevSql: "Server=sql,1433;Database=DevSql;User Id=sa;Password=OtOpcUa!Dev123;TrustServerCertificate=True;"
       Cluster__Hostname: "0.0.0.0"
       Cluster__Port: "4053"
       Cluster__PublicHostname: "central-2"

docker-dev/seed/seed-clusters.sql

@@ -106,6 +106,28 @@ IF NOT EXISTS (SELECT 1 FROM dbo.ClusterNode WHERE NodeId = 'site-b-2:4053')
         (NodeId, ClusterId, Host, OpcUaPort, DashboardPort, AkkaPort, GrpcPort, ApplicationUri, ServiceLevelBase, Enabled, CreatedBy)
     VALUES ('site-b-2:4053', 'SITE-B', 'site-b-2', 4840, 8081, 4053, 4056, 'urn:OtOpcUa:site-b-2', 150, 1, 'docker-dev-seed');
 
+------------------------------------------------------------------------------
+-- Backfill: GrpcPort on rows that predate the column (#493)
+--
+-- Every insert above is INSERT-if-not-exists, which is the right shape for a re-runnable seed
+-- but means a *new nullable* column never reaches rows created by an earlier version of this
+-- file. On a persisted volume that is exactly what happened when Phase 5 added GrpcPort: the
+-- six ClusterNode rows already existed, so they kept NULL, TelemetryNodeSource found no dial
+-- targets, and TelemetryDial:Mode=Grpc silently connected to nothing (throttled Warning per
+-- node — the code degrades gracefully, so nothing failed loudly).
+--
+-- Backfills NULL only. It must not overwrite a port an operator set deliberately on a
+-- long-lived dev volume; a NULL is the unambiguous "this row predates the column" marker.
+--
+-- AkkaPort deliberately has no equivalent here: it is NOT NULL with a default of 4053, so
+-- pre-existing rows already carry a usable value and there is nothing to backfill.
+------------------------------------------------------------------------------
+
+UPDATE dbo.ClusterNode
+   SET GrpcPort = 4056          -- matches Telemetry__GrpcListenPort on all six nodes in docker-compose.yml
+ WHERE GrpcPort IS NULL
+   AND CreatedBy = 'docker-dev-seed';
+
 ------------------------------------------------------------------------------
 -- Galaxy MxAccess gateway — INTENTIONALLY NOT SEEDED (retired 2026-06-15)
 --

docs/ScriptedAlarms.md

@@ -102,6 +102,45 @@ Persisted scope per plan decision #14: `Enabled`, `Acked`, `Confirmed`, `Shelvin
 
 Every mutation the state machine produces is immediately persisted inside the engine's `_evalGate` semaphore, so the store's view is always consistent with the in-memory state.
 
+### Post-(re)load condition-node re-assert (#487)
+
+A deploy that triggers a **full address-space rebuild** clears `_alarmConditions` and re-materialises every
+condition node fresh — inactive, acked, confirmed, unshelved. The engine, reloading in parallel, restores each
+alarm's persisted state and re-derives `Active` from the predicate, so it ends up *correct*; but a still-active
+alarm has **no transition to report**, so `LoadAsync` yields `EmissionKind.None` and `OnEngineEmission` drops it.
+Nothing then writes the node. Before this fix, an active alarm with static dependencies read **normal** to every
+OPC UA client after such a deploy, until its next real transition — which for a static-dependency alarm may
+never come.
+
+`ScriptedAlarmHostActor.ReassertConditionNodes` closes it. After each load completes it reads
+`ScriptedAlarmEngine.GetProjections()` — a plain read returning `ScriptedAlarmProjection` (condition state +
+the definition's severity + the resolved message template + last-observed worst-input quality) — and sends one
+`OpcUaPublishActor.AlarmStateUpdate` per alarm that is **not** in the Part 9 no-event position.
+
+Four properties are load-bearing:
+
+- **Node-only.** It sends `AlarmStateUpdate` and nothing else — never the `alerts` topic, never the telemetry
+  hub. `alerts` is the historization path, so an alerts row per alarm per deploy would append a duplicate
+  historian / AVEVA record every time anyone deploys. This is why the re-assert reads a projection instead of
+  re-emitting: `ScriptedAlarmProjection` carries no `EmissionKind`, so there is nothing for the emission
+  machinery — or a future refactor — to mistake for a transition.
+- **Only non-normal alarms.** An alarm in the no-event position (enabled, inactive, acked, confirmed,
+  unshelved) already matches what the materialise built, so it is skipped. That keeps a never-fired alarm
+  byte-identical to a deploy without this pass — including its Message, which the materialise seeds with the
+  alarm's display name — and writes nothing at all on the common all-normal deploy.
+- **Ordering.** `DriverHostActor` tells `RebuildAddressSpace` to the publish actor *before* it tells
+  `ApplyScriptedAlarms` to the host, and the re-assert runs later still (after an awaited `LoadAsync` pipes
+  back). Both are local `Tell`s, which enqueue synchronously, so the re-materialise is already queued ahead of
+  these writes.
+- **No duplicate Part 9 events.** `WriteAlarmCondition`'s delta-gate compares the incoming snapshot against
+  the node's *current* state: a re-assert onto a freshly materialised (normal) node is a genuine delta and
+  fires exactly one condition event — correct, since the rebuild reset what clients see — while a re-assert
+  onto a surgically-preserved node that already holds the same state is suppressed. The write is ungated by
+  redundancy role, like every other node write here; the Secondary keeps its address space warm for failover.
+
+The timestamp carried is the condition's own `LastTransitionUtc`, **not** the deploy instant, so a client
+reading `Time` / `ReceiveTime` after a rebuild still sees when the alarm actually went active.
+
 ## Source integration
 
 `ScriptedAlarmSource` (`ScriptedAlarmSource.cs`) adapts the engine to the driver-agnostic `IAlarmSource` interface. The existing `AlarmSurfaceInvoker` + `GenericDriverNodeManager` fan-out consumes it the same way it consumes Galaxy / AB CIP / FOCAS sources — there is no scripted-alarm-specific code path in the server plumbing. From that point on, the flow into `AlarmConditionState` nodes, the `AlarmAck` session check, and the Historian sink is shared — see [AlarmTracking.md](AlarmTracking.md).

docs/Telemetry.md

@@ -128,6 +128,39 @@ transports. ScadaBridge itself has since closed that gap with this identical
 interceptor pattern, so Phase 5 ships authenticated from the start rather than deferring auth to a
 later hardening pass. See the design doc's superseded note for the full history.
 
+## Upgrading an existing deployment: populate `ClusterNode.GrpcPort` first (#493)
+
+`GrpcPort` is a **nullable column added by Phase 5**, and nothing backfills it onto rows that
+already existed. On an upgraded deployment every `ClusterNode` row therefore carries `NULL`,
+central finds **no dial targets**, and flipping `TelemetryDial:Mode` to `Grpc` connects to
+nothing. Fresh installs are unaffected. `AkkaPort` did not have this problem only because it is
+`NOT NULL` with a default of 4053.
+
+Nothing fails loudly, which is what makes this worth stating up front — the code degrades
+gracefully, once per node, throttled:
+
+```
+ClusterNode <id> has no GrpcPort; it exposes no telemetry stream and is skipped in this dial refresh
+(further skips of this node are silent)
+```
+
+Other symptoms: no `ESTABLISHED` sockets on the telemetry port (a `LISTEN` but nothing else in
+`docker exec <node> cat /proc/net/tcp6`), and the `/alerts` / `/script-log` pill never turning
+live in `Grpc` mode.
+
+**Before flipping any node to `Grpc`**, set each driver node's `GrpcPort` to that node's own
+`Telemetry:GrpcListenPort` — via the AdminUI node editor, or directly:
+
+```sql
+UPDATE dbo.ClusterNode SET GrpcPort = <that node's Telemetry:GrpcListenPort> WHERE NodeId = '<node>';
+```
+
+There is deliberately **no EF data migration** backfilling this. The correct value is that node's
+own listener port, which is per-deployment configuration the database cannot derive; a migration
+could only invent one, and a *wrong* dial target is worse than the `NULL` the dialer already skips
+explicitly. The docker-dev seed does backfill (`GrpcPort IS NULL AND CreatedBy = 'docker-dev-seed'`
+→ 4056) because there the port is fixed by `docker-compose.yml` and therefore actually knowable.
+
 ## Reconnect and reliability
 
 Central's `TelemetryDialSupervisor` (an admin-role actor) runs **one reconnecting dialer per

docs/plans/2026-06-26-otopcua-historian-gateway-integration.md

@@ -271,7 +271,7 @@ public sealed class GatewayQualityMapperTests
 {
     [Theory]
     [InlineData(192, 0x00000000u)] // Good
-    [InlineData(216, 0x00D80000u)] // Good_LocalOverride
+    [InlineData(216, 0x00960000u)] // Good_LocalOverride
     [InlineData(64,  0x40000000u)] // Uncertain
     [InlineData(0,   0x80000000u)] // Bad
     [InlineData(8,   0x808A0000u)] // Bad_NotConnected
@@ -307,7 +307,7 @@ public sealed class SampleMapperTests
     {
         var a = new HistorianAggregateSample { Tag = "T", /* Value unset */ EndTime = Ts(2026,1,1,0,0,0) };
         var snap = SampleMapper.ToAggregateSnapshot(a);
-        Assert.Equal(0x800E0000u, snap.StatusCode); // BadNoData
+        Assert.Equal(0x809B0000u, snap.StatusCode); // BadNoData
         Assert.Null(snap.Value);
     }
     // Ts(...) builds a Google.Protobuf.WellKnownTypes.Timestamp from UTC parts.
@@ -323,7 +323,7 @@ public sealed class SampleMapperTests
   - `StatusCode`: `GatewayQualityMapper.Map((byte)s.OpcQuality)` (prefer `opc_quality`; if zero/unset and `quality` carries the OPC-DA byte, fall back to `quality` — match whatever the gateway populates; document the choice).
   - `SourceTimestampUtc`: `s.Timestamp.ToDateTime()` (UTC kind).
   - `ServerTimestampUtc`: `DateTime.UtcNow`.
-- `SampleMapper.ToAggregateSnapshot(HistorianAggregateSample)` → null aggregate value ⇒ `StatusCode 0x800E0000` (BadNoData), non-null ⇒ Good (`0x00000000`) with the value; `SourceTimestampUtc` ← the bucket end/start timestamp (match the Wonderware `ToAggregateSnapshots` convention — it stamps the bucket timestamp). Provide `IReadOnlyList<>` batch helpers too.
+- `SampleMapper.ToAggregateSnapshot(HistorianAggregateSample)` → null aggregate value ⇒ `StatusCode 0x809B0000` (BadNoData), non-null ⇒ Good (`0x00000000`) with the value; `SourceTimestampUtc` ← the bucket end/start timestamp (match the Wonderware `ToAggregateSnapshots` convention — it stamps the bucket timestamp). Provide `IReadOnlyList<>` batch helpers too.
 
 **Step 4: run, expect PASS.**
 

docs/plans/2026-07-15-mtconnect-driver-design.md

@@ -98,7 +98,7 @@ Pure function in `.Contracts` (shared by driver, browser-commit, and the typed e
 | `EVENT` free text (`Program`, `Block`, `Message`) | `String` |
 | `CONDITION` | `String` (state word; §3.6) |
 
-**Quality mapping (`DataValueSnapshot.StatusCode`):** an observation value of `UNAVAILABLE` (MTConnect's explicit no-data sentinel) → **`BadNoCommunication` (`0x80310000u`)** with a null value, not the literal string — this is *the* UNAVAILABLE code, used everywhere in this design (read, subscribe, and the §8 fixtures). Rationale + fleet fit: semantically, `UNAVAILABLE` means the Agent is reachable but has no device-backed value (the adapter↔device link is down or the item has never reported) — exactly OPC UA's `BadNoCommunication` ("communication to the data source has failed"). The fleet grep shows no competing convention for this case: every existing driver's `BadCommunicationError` (`0x80050000u`, Modbus/FOCAS/TwinCAT/OpcUaClient/S7/AbCip/AbLegacy/Galaxy) marks the **driver's own transport failure** to its peer — a different failure (and the code this driver also uses when the *Agent* HTTP call fails, per §7) — while `BadNoData` (`0x800E0000u`) is historian-domain only (`Historian.Gateway/Mapping/SampleMapper.cs`). `BadNoCommunication` is already in the CLI's `SnapshotFormatter` name table (`src/Drivers/Cli/ZB.MOM.WW.OtOpcUa.Driver.Cli.Common/SnapshotFormatter.cs`), so it renders by name, not hex. Declare it as a `private const uint` in `MTConnectDriver` (the Modbus `StatusBadCommunicationError` pattern). Missing dataItem / empty condition → `Bad`. `observation.timestamp` → `SourceTimestamp` (not a separate node).
+**Quality mapping (`DataValueSnapshot.StatusCode`):** an observation value of `UNAVAILABLE` (MTConnect's explicit no-data sentinel) → **`BadNoCommunication` (`0x80310000u`)** with a null value, not the literal string — this is *the* UNAVAILABLE code, used everywhere in this design (read, subscribe, and the §8 fixtures). Rationale + fleet fit: semantically, `UNAVAILABLE` means the Agent is reachable but has no device-backed value (the adapter↔device link is down or the item has never reported) — exactly OPC UA's `BadNoCommunication` ("communication to the data source has failed"). The fleet grep shows no competing convention for this case: every existing driver's `BadCommunicationError` (`0x80050000u`, Modbus/FOCAS/TwinCAT/OpcUaClient/S7/AbCip/AbLegacy/Galaxy) marks the **driver's own transport failure** to its peer — a different failure (and the code this driver also uses when the *Agent* HTTP call fails, per §7) — while `BadNoData` (`0x809B0000u`) is historian-domain only (`Historian.Gateway/Mapping/SampleMapper.cs`). `BadNoCommunication` is already in the CLI's `SnapshotFormatter` name table (`src/Drivers/Cli/ZB.MOM.WW.OtOpcUa.Driver.Cli.Common/SnapshotFormatter.cs`), so it renders by name, not hex. Declare it as a `private const uint` in `MTConnectDriver` (the Modbus `StatusBadCommunicationError` pattern). Missing dataItem / empty condition → `Bad`. `observation.timestamp` → `SourceTimestamp` (not a separate node).
 
 ### 3.4 `IReadable` — `/current`
 

docs/plans/2026-07-15-sql-poll-driver-design.md

@@ -588,6 +588,40 @@ SQL Server client works cross-platform, so `Sql` runs on macOS dev too (unlike G
   `dialect.QuoteIdentifier` (which escapes/rejects embedded quote characters). A table/column string
   in a `TagConfig` is validated against the live catalog (or an allow-list) before it's ever quoted
   into text; an unknown identifier rejects the tag (→ `BadNodeIdUnknown`) rather than executing.
+
+  **Implemented (Gitea #496).** `SqlCatalogGate` + `SqlCatalogLoader`, run from
+  `SqlDriver.InitializeAsync` after the liveness check and before the driver reports Healthy. Shape,
+  and the decisions worth knowing before touching it:
+
+  - **The catalog's spelling is substituted, not merely checked.** An accepted identifier is rewritten
+    to the string the catalog returned, so the text quoted into a poll query is one this driver read
+    back out of `ListSchemas`/`ListTables`/`ListColumns` — not operator input. Matching is
+    exact-ordinal first, then a *unique* case-insensitive hit (SQL Server's default collation is CI, so
+    case variants have always worked and rejecting them would break valid configs); an ambiguous CI
+    match under a case-sensitive collation is refused rather than guessed, because picking one would
+    publish another column's data under the operator's node.
+  - **Charset check first, catalog lookup second.** Each identifier goes through `QuoteIdentifier` for
+    its rejection rules *before* being looked up, so a name carrying a control or Unicode format
+    character is rejected **without its value being echoed** into a log line (Trojan-Source). A name
+    that passes is safe to render, which is why catalog-miss messages *do* name it — an operator
+    hunting a typo has to see what they wrote.
+  - **Rejection is per-tag and keeps the node.** The rejected tag is dropped from the *polled* table
+    but stays in the *authored* table, so it still materializes as a node and reads
+    `BadNodeIdUnknown` (§8.1's specified outcome) instead of vanishing from the address space. Every
+    drop is logged at Warning with the tag, the field and the reason.
+  - **A catalog that cannot be read faults Initialize; it does not reject every tag.** An unreadable
+    catalog is the *absence* of evidence about the tags, not evidence against them — rejecting all of
+    them would serve a confidently-empty address space and send the operator hunting typos that do not
+    exist. Zero visible schemas is treated the same way, because that is what a missing GRANT looks
+    like. Faulting lands `DriverInstanceActor` in Reconnecting with its retry timer running.
+  - **Bounded load:** one schema-list query, one default-schema scalar (`ISqlDialect.DefaultSchemaSql`,
+    added for this — an unqualified `TagValues` must resolve in whatever schema the *server* says, not
+    a guessed `dbo`), then one `ListTables` per distinct authored schema and one `ListColumns` per
+    distinct authored relation. It never enumerates the whole catalog, and the load runs under the same
+    wall-clock bound as the liveness check (R2-01 / STAB-14).
+  - **Accepted v1 limitation:** a 3-part `db.schema.table` (or a linked-server name) addresses a
+    catalog this connection cannot enumerate, so it cannot be allow-listed and is rejected with a
+    message pointing at the fix — expose the data through a view in the connected database.
 - **Treat any code path that builds SQL by string-concatenating a tag field as a defect** — enforce
   with a review checklist item + a unit test that feeds a malicious `keyValue`/`table`
   (`'; DROP TABLE …`) and asserts it either binds harmlessly (value) or is rejected (identifier),
@@ -607,8 +641,15 @@ comment) and the env-overridable ConfigDb connection string:
   file. Direct env read (not `IConfiguration`) is deliberate: the factory registry materializes
   drivers via a static `(id, json)` closure (Modbus pattern) with no `IConfiguration` in reach, so
   this keeps the factory shape unchanged.
-- If an inline `connectionString` is ever permitted (dev convenience only), the AdminUI **redacts** it
-  in display/logging and flags it dev-only.
+- **An inline `connectionString` is not permitted at all** — the earlier "dev convenience, redacted in
+  the UI" carve-out is withdrawn (Gitea #498). Redaction only hides a credential that has *already been
+  written* to the config DB and replicated to every node's artifact cache. `SqlDriverConfigDto` has no
+  such property and `UnmappedMemberHandling.Skip` drops the key on read, but that protects only the read
+  path; config blobs are schemaless JSON columns, so nothing stopped the key being **written**.
+  `DraftValidator.ValidateSqlConnectionStringNotPersisted` now fails the deploy
+  (`SqlConnectionStringPersisted`) for a `connectionString` key at the top level of a Sql driver's
+  `DriverConfig` **or** of the `DeviceConfig` of any device beneath it (the two are merged before the DTO
+  sees them). The key is matched case-insensitively, and the error text never echoes the value.
 - **Never log the resolved connection string.** Log only provider + server host + database name.
 - Prefer integrated/managed auth where the estate supports it (`Integrated Security=true` / Azure AD /
   Kerberos) so no password transits config at all.

docs/plans/2026-07-16-v3-batch4-PR.md

@@ -94,7 +94,14 @@ dual-namespace + event-delivery), Runtime 377 (+ VT reassert regression), AdminU
 
 ## Documented follow-ups (non-blocking)
 
-- **Scripted-alarm redeploy recovery (CONFIRMED pre-existing bug, deferred — deserves its own careful fix). Filed as issue #487.**
+- **Scripted-alarm redeploy recovery — FIXED (issue #487), see `docs/ScriptedAlarms.md` §"Post-(re)load
+  condition-node re-assert".** Landed as the proposed shape below: `ScriptedAlarmHostActor.ReassertConditionNodes`
+  in `OnAlarmsLoaded`, node-only, never the `alerts` topic. Two deviations from the sketch, both deliberate:
+  it reads a new `ScriptedAlarmEngine.GetProjections()` rather than `GetState(alarmId)` + `LoadedAlarmIds`
+  (a projection also carries the definition's severity, the resolved message template, and the last-observed
+  worst-input quality — `GetState` alone would have clobbered severity/message on the node); and it skips
+  alarms sitting in the Part 9 no-event position, so a deploy where nothing is in alarm writes no condition
+  nodes at all. The original deferral text follows for context.
   The scripted-alarm Part 9 condition node has the same redeploy-reset race the VT `ReassertValue` fix closed:
   `RebuildAddressSpace` clears `_alarmConditions` and `MaterialiseScriptedAlarms` recreates each condition
   fresh/normal, but `ScriptedAlarmEngine.LoadAsync` reloads from the persisted state and yields

docs/plans/2026-07-24-driver-expansion-tracking.md

@@ -30,7 +30,7 @@ it reaches 📝.
 | Wave | Deliverable | Design | Impl. plan | Status | Effort | Fixture / hardware |
 |---|---|---|---|---|---|---|
 | **0** | Universal Discover-backed browser | [design](2026-07-15-universal-discovery-browser-design.md) | [plan](2026-07-15-universal-discovery-browser-implementation.md) · [tasks](2026-07-15-universal-discovery-browser-implementation.md.tasks.json) | 🟡 **Live gate open** | S–M | none (retrofits shipped drivers) |
-| **1** | Modbus RTU (extend Modbus) | [design](2026-07-15-modbus-rtu-driver-design.md) | [plan](2026-07-24-modbus-rtu-driver.md) · [tasks](2026-07-24-modbus-rtu-driver.md.tasks.json) | 🟢 **Built — live gate PASSED** (11 tasks, branch `feat/modbus-rtu-driver`, pending merge) | **S (lowest)** | `pymodbus` `rtu_over_tcp` — CI-simulatable, no new infra |
+| **1** | Modbus RTU (extend Modbus) | [design](2026-07-15-modbus-rtu-driver-design.md) | [plan](2026-07-24-modbus-rtu-driver.md) · [tasks](2026-07-24-modbus-rtu-driver.md.tasks.json) | 📝 **Plan ready** (11 tasks) | **S (lowest)** | `pymodbus` `rtu_over_tcp` — CI-simulatable, no new infra |
 | **1** | SQL poll | [design](2026-07-15-sql-poll-driver-design.md) | [plan](2026-07-24-sql-poll-driver.md) · [tasks](2026-07-24-sql-poll-driver.md.tasks.json) | 📝 **Plan ready** (22 tasks) | S–M | **existing central SQL Server** `10.100.0.35,14330` + SQLite unit |
 | **2** | MTConnect Agent | [design](2026-07-15-mtconnect-driver-design.md) | [plan](2026-07-24-mtconnect-driver.md) · [tasks](2026-07-24-mtconnect-driver.md.tasks.json) | 📝 **Plan ready** (23 tasks) | S–M | Dockerized `mtconnect/cppagent` — CI-simulatable |
 | **2** | MQTT / Sparkplug B | [design](2026-07-15-mqtt-sparkplug-driver-design.md) | [plan](2026-07-24-mqtt-sparkplug-driver.md) · [tasks](2026-07-24-mqtt-sparkplug-driver.md.tasks.json) | 📝 **Plan ready** (27 tasks, P1+P2) | M–L | Mosquitto/EMQX + C# Sparkplug sim — CI-simulatable |
@@ -92,30 +92,16 @@ marginal cost.
 Both are **fully CI-simulatable with zero new hardware**; Modbus RTU needs no new infra at all, and
 SQL poll reuses the always-on central SQL Server. This is the recommended next build.
 
-### Modbus RTU — 🟢 Built, live gate PASSED (branch `feat/modbus-rtu-driver`, pending merge)
+### Modbus RTU — 📝 Plan ready
 - **Design:** [`2026-07-15-modbus-rtu-driver-design.md`](2026-07-15-modbus-rtu-driver-design.md)
-- **Implementation plan:** [`2026-07-24-modbus-rtu-driver.md`](2026-07-24-modbus-rtu-driver.md) · [`.tasks.json`](2026-07-24-modbus-rtu-driver.md.tasks.json) — **11 tasks** (1 trivial / 5 small / 2 standard / 3 high-risk), all complete via subagent-driven-development.
+- **Implementation plan:** [`2026-07-24-modbus-rtu-driver.md`](2026-07-24-modbus-rtu-driver.md) · [`.tasks.json`](2026-07-24-modbus-rtu-driver.md.tasks.json) — **11 tasks** (1 trivial / 5 small / 2 standard / 3 high-risk).
 - **Scope:** extend the existing Modbus driver with a `Transport` selector (RTU CRC-16 + FC-aware
   length, no TxId) + a `rtu_over_tcp` `pymodbus` docker profile + the AdminUI selector.
   **Direct-serial transport is descoped** (user, 2026-07-15) — RTU-over-TCP via a serial→Ethernet
   gateway is the only shipped mode, so there is no serial hardware gate.
-- **Fixture:** added the `rtu_over_tcp` profile (`framer=rtu`, host `:5021`, co-runs with `standard`)
-  to the Modbus integration fixture. **Unknown confirmed:** pymodbus 3.13's simulator DOES honour
-  `framer=rtu` on a TCP server (wire-probed a pure RTU FC03 response, no MBAP) — so the simple profile
-  path was taken; **no stdlib fallback server was needed.**
-- **Verification (all green):** unit suite **344/344**; full solution build 0 errors; the 2 RTU
-  integration tests pass **live** against the real `framer=rtu` fixture (read HR5→5, write+readback
-  HR200←4242). Per-task review chain (spec + code reviewers) + a final whole-branch review, all
-  approved-to-merge.
-- **Live `/run` gate — PASSED (2026-07-24, docker-dev rebuilt from this branch):**
-  - AdminUI `/raw` Modbus **driver** config modal renders the new **Transport** selector (with the
-    operator hint) — set to `RtuOverTcp`, saved.
-  - **Device Test Connect → `OK · 23 MS`** — the probe built a `ModbusRtuOverTcpTransport` via the
-    factory and spoke **FC03 over real RTU framing** to `10.100.0.35:5021`.
-  - Authored raw tags HR5 (r/o) + HR200 (r/w) → **deployment `06ec1632` Sealed** (all 6 nodes acked).
-  - Client.CLI on `opc.tcp://localhost:4840` (`multi-role`/`password`): **read** `ns=2;s=rtu-gate/Device1/HR5`
-    → **5, Good**; **write** `ns=2;s=rtu-gate/Device1/HR200` = 4242 → readback **4242, Good**.
-- **Effort:** **S — the lowest on the roadmap.** Delivered first, as recommended.
+- **Fixture:** add an `rtu_over_tcp` profile to the existing Modbus integration fixture. First P1
+  step is confirming the pymodbus simulator exposes the RTU framer on a TCP server.
+- **Effort:** **S — the lowest on the roadmap.** Recommended first.
 
 ### SQL poll — 📝 Plan ready
 - **Design:** [`2026-07-15-sql-poll-driver-design.md`](2026-07-15-sql-poll-driver-design.md)

src/Core/ZB.MOM.WW.OtOpcUa.Configuration/Validation/DraftValidator.cs

@@ -41,9 +41,77 @@ public static class DraftValidator
         ValidateUnsEffectiveLeafUniqueness(draft, errors);
         ValidateEquipReferenceResolution(draft, errors);
         ValidateCalculationTags(draft, errors);
+        ValidateSqlConnectionStringNotPersisted(draft, errors);
         return errors;
     }
 
+    /// <summary>
+    ///     The <c>Sql</c> driver's "a pasted literal connection string is never persisted" guarantee, enforced
+    ///     at the deploy gate (Gitea #498).
+    /// </summary>
+    /// <remarks>
+    ///     <para>A Sql driver names its credentials indirectly — <c>connectionStringRef</c> resolves from the
+    ///     environment / secret store at Initialize — so a deployed artifact carries no database password.
+    ///     Until now that guarantee rested entirely on the <b>read</b> path: <c>SqlDriverConfigDto</c> has no
+    ///     <c>connectionString</c> property and <c>UnmappedMemberHandling.Skip</c> drops the key on
+    ///     deserialization. Nothing stopped the key being <b>written</b>. Config blobs are schemaless JSON
+    ///     columns, and the fallback authoring pattern for a driver without a typed form is a raw-JSON
+    ///     textarea, so an operator pasting <c>{"connectionString":"Server=…;Password=…"}</c> would put a live
+    ///     credential in the ConfigDb — persisted, replicated to every node's artifact cache, and readable by
+    ///     anyone with config access — while the runtime silently ignored it and the driver failed to connect.
+    ///     Discarding a secret on read is not the same as refusing to store it.</para>
+    ///     <para><b>Two of the three surfaces are checked here.</b> The third — a node's
+    ///     <see cref="ClusterNode.DriverConfigOverridesJson"/> — is not reachable from
+    ///     <see cref="DraftSnapshot"/> and is gated at its save instead (#499); see
+    ///     <see cref="SqlCredentialGuard"/> for why a deploy gate is the wrong instrument for a value that
+    ///     never enters the artifact.</para>
+    ///     <para>Checked on <b>both</b> config surfaces a Sql driver reads: the instance's
+    ///     <see cref="DriverInstance.DriverConfig"/> and the <see cref="Device.DeviceConfig"/> of every device
+    ///     beneath it, because the two are merged before the DTO sees them — a credential pasted into the
+    ///     device blob lands in exactly the same place.</para>
+    ///     <para>The key is matched <b>case-insensitively</b>: <c>System.Text.Json</c> binds
+    ///     <c>ConnectionString</c> to a <c>connectionString</c> property by default, so a case variant is the
+    ///     same key, not a different one. Only the top level is scanned — the DTO is flat, so a nested
+    ///     occurrence cannot bind and is not the credential-shaped mistake this rule exists to catch.</para>
+    ///     <para><b>The message never echoes the value.</b> Validation errors reach the AdminUI, the deploy
+    ///     log and the audit trail; repeating the offending string there would leak the very credential the
+    ///     rule is refusing to store.</para>
+    /// </remarks>
+    private static void ValidateSqlConnectionStringNotPersisted(DraftSnapshot draft, List<ValidationError> errors)
+    {
+        const string ForbiddenKey = SqlCredentialGuard.ForbiddenKey;
+
+        var sqlInstanceIds = draft.DriverInstances
+            .Where(d => string.Equals(d.DriverType, Core.Abstractions.DriverTypeNames.Sql, StringComparison.Ordinal))
+            .Select(d => d.DriverInstanceId)
+            .ToHashSet(StringComparer.Ordinal);
+        if (sqlInstanceIds.Count == 0) return;
+
+        foreach (var d in draft.DriverInstances)
+        {
+            if (!sqlInstanceIds.Contains(d.DriverInstanceId)) continue;
+            if (!SqlCredentialGuard.CarriesLiteralConnectionString(d.DriverConfig)) continue;
+            errors.Add(new("SqlConnectionStringPersisted",
+                $"Sql driver instance '{d.DriverInstanceId}' has a '{ForbiddenKey}' key in its DriverConfig. " +
+                "A Sql driver must name its credentials indirectly via 'connectionStringRef', which resolves " +
+                "from the environment / secret store at Initialize; a literal connection string here would be " +
+                "stored in the config database and replicated to every node, and the runtime ignores it anyway. " +
+                "Remove the key and set 'connectionStringRef'.",
+                d.DriverInstanceId));
+        }
+
+        foreach (var dev in draft.Devices)
+        {
+            if (!sqlInstanceIds.Contains(dev.DriverInstanceId)) continue;
+            if (!SqlCredentialGuard.CarriesLiteralConnectionString(dev.DeviceConfig)) continue;
+            errors.Add(new("SqlConnectionStringPersisted",
+                $"Device '{dev.DeviceId}' on Sql driver instance '{dev.DriverInstanceId}' has a " +
+                $"'{ForbiddenKey}' key in its DeviceConfig. DeviceConfig is merged onto DriverConfig before " +
+                "the driver reads it, so this is the same leak: use 'connectionStringRef' on the driver instead.",
+                dev.DeviceId));
+        }
+    }
+
     /// <summary>WP7 Calculation-driver deploy gates. For every tag bound to a <c>Calculation</c> driver:
     /// <list type="number">
     ///   <item><b>scriptId existence</b> — the tag's <c>TagConfig.scriptId</c> must be present and resolve to

src/Core/ZB.MOM.WW.OtOpcUa.Configuration/Validation/SqlCredentialGuard.cs

@@ -0,0 +1,139 @@
+using System.Text.Json;
+
+namespace ZB.MOM.WW.OtOpcUa.Configuration.Validation;
+
+/// <summary>
+///     The one place that decides whether a persisted config blob carries a literal Sql
+///     <c>connectionString</c> (Gitea #498 / #499).
+/// </summary>
+/// <remarks>
+///     <para>
+///         A <c>Sql</c> driver names its credentials indirectly — <c>connectionStringRef</c> resolves from
+///         the environment / secret store at Initialize — so nothing persisted should ever contain a
+///         database password. The typed <c>SqlDriverConfigDto</c> already drops a <c>connectionString</c>
+///         key on <b>read</b>, but discarding a secret on read is not the same as refusing to store it:
+///         config blobs are schemaless JSON columns authored through raw-JSON textareas, so the key can
+///         be written even though the runtime ignores it.
+///     </para>
+///     <para>
+///         There are <b>three</b> surfaces a Sql driver's config is persisted on, and they need different
+///         enforcement points:
+///         <list type="bullet">
+///             <item><c>DriverInstance.DriverConfig</c> and <c>Device.DeviceConfig</c> — both in the
+///             deployed artifact, both visible to <c>DraftSnapshot</c>, both gated by
+///             <c>DraftValidator</c>.</item>
+///             <item><c>ClusterNode.DriverConfigOverridesJson</c> — the per-node override map. It is
+///             <b>not</b> in <c>DraftSnapshot</c>, and deliberately does not go there: adding a
+///             <c>ClusterNode</c> collection would widen the snapshot (and every builder of one) for a
+///             single rule about a value that is not part of the artifact at all. More to the point, a
+///             deploy gate is the wrong instrument here — the artifact never carries node overrides, so
+///             blocking a deploy would not stop the credential being stored. It is already in the
+///             database by then. This surface is therefore gated at the <b>save</b>, which is the only
+///             point where "refuse to store it" is literally true.</item>
+///         </list>
+///     </para>
+///     <para>
+///         <b>Deliberately narrow.</b> This checks the <c>Sql</c> driver's <c>connectionString</c> key
+///         only — not a general "credential-shaped key" sweep over every driver type. A broader rule
+///         would start refusing configs that are legitimate today for drivers that never made this
+///         guarantee, turning defence-in-depth into a regression. Widen it per driver, as each driver
+///         gains an indirect-credential contract of its own.
+///     </para>
+/// </remarks>
+public static class SqlCredentialGuard
+{
+    /// <summary>The config key a Sql driver must never persist. Matched case-insensitively.</summary>
+    public const string ForbiddenKey = "connectionString";
+
+    /// <summary>
+    ///     Whether <paramref name="configJson"/> is a JSON object carrying <see cref="ForbiddenKey"/> at
+    ///     its top level.
+    /// </summary>
+    /// <remarks>
+    ///     Matched <b>case-insensitively</b>: <c>System.Text.Json</c> binds <c>ConnectionString</c> to a
+    ///     <c>connectionString</c> property by default, so a case variant is the same key, not a
+    ///     different one. Only the top level is scanned — the DTO is flat, so a nested occurrence cannot
+    ///     bind and is not the credential-shaped mistake this exists to catch.
+    /// </remarks>
+    /// <param name="configJson">The config blob to inspect.</param>
+    /// <returns><see langword="true"/> when the key is present at the top level.</returns>
+    public static bool CarriesLiteralConnectionString(string? configJson)
+    {
+        if (string.IsNullOrWhiteSpace(configJson)) return false;
+        try
+        {
+            using var doc = JsonDocument.Parse(configJson);
+            return doc.RootElement.ValueKind == JsonValueKind.Object
+                   && HasTopLevelKey(doc.RootElement, ForbiddenKey);
+        }
+        catch (JsonException)
+        {
+            // A malformed blob simply has no keys. Shaping the config JSON is another rule's job, and
+            // throwing here would turn a formatting mistake into a credential-guard failure.
+            return false;
+        }
+    }
+
+    /// <summary>
+    ///     The <c>DriverInstanceId</c>s in a <c>ClusterNode.DriverConfigOverridesJson</c> map whose
+    ///     override object carries a literal connection string, restricted to instances that are actually
+    ///     Sql drivers.
+    /// </summary>
+    /// <remarks>
+    ///     The override map is shaped <c>{ "&lt;DriverInstanceId&gt;": { …driver config keys… } }</c> and is
+    ///     merged onto the cluster-level <c>DriverConfig</c>, so a credential pasted into one lands in
+    ///     exactly the place <see cref="CarriesLiteralConnectionString"/> already refuses on the driver
+    ///     itself.
+    /// </remarks>
+    /// <param name="overridesJson">The node's override map. Null / blank / malformed yields no
+    /// violations.</param>
+    /// <param name="sqlDriverInstanceIds">The ids of driver instances whose <c>DriverType</c> is
+    /// <c>Sql</c>. Keys outside this set are ignored — a non-Sql driver never made the indirect-credential
+    /// guarantee, so flagging it would be a regression, not defence in depth.</param>
+    /// <returns>The offending driver-instance ids, in document order; empty when there are none.</returns>
+    public static IReadOnlyList<string> FindNodeOverrideViolations(
+        string? overridesJson, IReadOnlyCollection<string> sqlDriverInstanceIds)
+    {
+        if (string.IsNullOrWhiteSpace(overridesJson) || sqlDriverInstanceIds.Count == 0)
+        {
+            return [];
+        }
+
+        var sqlIds = sqlDriverInstanceIds as IReadOnlySet<string>
+                     ?? sqlDriverInstanceIds.ToHashSet(StringComparer.Ordinal);
+
+        try
+        {
+            using var doc = JsonDocument.Parse(overridesJson);
+            if (doc.RootElement.ValueKind != JsonValueKind.Object) return [];
+
+            List<string>? offenders = null;
+            foreach (var entry in doc.RootElement.EnumerateObject())
+            {
+                if (!sqlIds.Contains(entry.Name)) continue;
+                if (entry.Value.ValueKind != JsonValueKind.Object) continue;
+                if (!HasTopLevelKey(entry.Value, ForbiddenKey)) continue;
+
+                (offenders ??= []).Add(entry.Name);
+            }
+
+            return (IReadOnlyList<string>?)offenders ?? [];
+        }
+        catch (JsonException)
+        {
+            return [];
+        }
+    }
+
+    /// <summary>Whether <paramref name="obj"/> carries <paramref name="key"/> at its top level,
+    /// case-insensitively.</summary>
+    private static bool HasTopLevelKey(JsonElement obj, string key)
+    {
+        foreach (var property in obj.EnumerateObject())
+        {
+            if (string.Equals(property.Name, key, StringComparison.OrdinalIgnoreCase)) return true;
+        }
+
+        return false;
+    }
+}

src/Core/ZB.MOM.WW.OtOpcUa.Core.Abstractions/DriverTypeNames.cs

@@ -53,6 +53,9 @@ public static class DriverTypeNames
     /// <summary>Calculation pseudo-driver — tags computed by C# scripts over other tags' live values.</summary>
     public const string Calculation = "Calculation";
 
+    /// <summary>Read-only SQL Server table/view poller — publishes columns as OPC UA variables.</summary>
+    public const string Sql = "Sql";
+
     /// <summary>
     ///     Every driver-type string declared above, for callers that need to enumerate
     ///     the full set (e.g. validation of an authored <c>DriverType</c>).
@@ -68,5 +71,6 @@ public static class DriverTypeNames
         OpcUaClient,
         Galaxy,
         Calculation,
+        Sql,
     ];
 }

src/Core/ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms/ScriptedAlarmEngine.cs

@@ -334,6 +334,48 @@ public sealed class ScriptedAlarmEngine : IDisposable
     public IReadOnlyCollection<AlarmConditionState> GetAllStates()
         => _alarms.Values.Select(a => a.Condition).ToArray();
 
+    /// <summary>
+    ///     #487 — the currently-held condition of every loaded alarm, packaged with the definition's
+    ///     severity, the rendered message template and the last-observed input quality, i.e. everything
+    ///     a caller needs to <b>project</b> the alarm onto an OPC UA condition node without waiting for
+    ///     the next transition.
+    /// </summary>
+    /// <remarks>
+    ///     <para>
+    ///         <b>This is a read, not an emission.</b> It deliberately returns a distinct type rather
+    ///         than a <see cref="ScriptedAlarmEvent"/>, and it never touches <see cref="OnEvent"/>. A
+    ///         still-active alarm produces <see cref="EmissionKind.None"/> at load (there is no
+    ///         transition to report), so the transition stream cannot carry the current state — that is
+    ///         exactly why the caller needs this. Routing these through the emission path instead would
+    ///         append a duplicate historian / <c>alerts</c> row on every deploy, so the shape here is
+    ///         intentionally one the emission machinery cannot consume.
+    ///     </para>
+    ///     <para>
+    ///         <b>Synchronization.</b> Reads <c>_alarms</c> and <c>_valueCache</c> — both
+    ///         <see cref="ConcurrentDictionary{TKey, TValue}"/> — without taking <c>_evalGate</c>, the
+    ///         same posture as <see cref="GetState"/> / <see cref="GetAllStates"/>. Each projection is
+    ///         individually coherent; the set as a whole is not an atomic snapshot across a concurrent
+    ///         re-evaluation. That is sufficient for the node-projection use: an evaluation racing this
+    ///         read publishes its own transition through the normal path.
+    ///     </para>
+    /// </remarks>
+    /// <returns>One projection per loaded alarm; empty before the first <see cref="LoadAsync"/>.</returns>
+    public IReadOnlyList<ScriptedAlarmProjection> GetProjections()
+    {
+        var projections = new List<ScriptedAlarmProjection>(_alarms.Count);
+        foreach (var (alarmId, state) in _alarms)
+        {
+            projections.Add(new ScriptedAlarmProjection(
+                AlarmId: alarmId,
+                Severity: state.Definition.Severity,
+                Message: MessageTemplate.Resolve(state.Definition.MessageTemplate, TryLookup),
+                Condition: state.Condition,
+                WorstInputStatusCode: LastWorstStatus(alarmId)));
+        }
+
+        return projections;
+    }
+
     /// <summary>Acknowledges the specified alarm on behalf of the given user.</summary>
     /// <param name="alarmId">The alarm identifier.</param>
     /// <param name="user">The user performing the acknowledgment.</param>
@@ -974,6 +1016,26 @@ public sealed record ScriptedAlarmEvent(
     // the top-2 severity bits. Default 0u == Good keeps every existing constructor call unchanged.
     uint WorstInputStatusCode = 0u);
 
+/// <summary>
+///     #487 — a loaded alarm's current condition, ready to be projected onto its OPC UA node.
+///     Produced by <see cref="ScriptedAlarmEngine.GetProjections"/> on demand; it is <b>not</b> an
+///     emission and never travels the <see cref="ScriptedAlarmEngine.OnEvent"/> path, so it can never
+///     become an <c>alerts</c> row or a historian record. Deliberately a separate type from
+///     <see cref="ScriptedAlarmEvent"/> — it carries no <see cref="EmissionKind"/>, so there is nothing
+///     for a future refactor to mistake for a transition.
+/// </summary>
+/// <param name="AlarmId">The alarm identifier (also its OPC UA condition NodeId).</param>
+/// <param name="Severity">The definition's severity bucket.</param>
+/// <param name="Message">The message template resolved against the current value cache.</param>
+/// <param name="Condition">The Part 9 condition state the engine currently holds.</param>
+/// <param name="WorstInputStatusCode">The last-observed worst OPC UA StatusCode across the alarm's inputs.</param>
+public sealed record ScriptedAlarmProjection(
+    string AlarmId,
+    AlarmSeverity Severity,
+    string Message,
+    AlarmConditionState Condition,
+    uint WorstInputStatusCode);
+
 /// <summary>
 ///     Upstream source abstraction — intentionally identical shape to the virtual-tag
 ///     engine's so Stream G can compose them behind one driver bridge.

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbCip/AbCipStatusMapper.cs

@@ -35,7 +35,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.AbCip;
 public static class AbCipStatusMapper
 {
     public const uint Good = 0u;
-    public const uint GoodMoreData = 0x00A70000u;
+    public const uint GoodMoreData = 0x00A60000u;
     public const uint BadInternalError = 0x80020000u;
     public const uint BadNodeIdUnknown = 0x80340000u;
     public const uint BadNotWritable = 0x803B0000u;
@@ -44,7 +44,7 @@ public static class AbCipStatusMapper
     public const uint BadDeviceFailure = 0x808B0000u;
     public const uint BadCommunicationError = 0x80050000u;
     public const uint BadTimeout = 0x800A0000u;
-    public const uint BadTypeMismatch = 0x80730000u;
+    public const uint BadTypeMismatch = 0x80740000u;
 
     /// <summary>Map a CIP general-status byte to an OPC UA StatusCode.</summary>
     /// <param name="status">The CIP general-status byte value.</param>

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy/AbLegacyStatusMapper.cs

@@ -10,7 +10,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.AbLegacy;
 public static class AbLegacyStatusMapper
 {
     public const uint Good = 0u;
-    public const uint GoodMoreData = 0x00A70000u;
+    public const uint GoodMoreData = 0x00A60000u;
     public const uint BadInternalError = 0x80020000u;
     public const uint BadNodeIdUnknown = 0x80340000u;
     public const uint BadNotWritable = 0x803B0000u;
@@ -19,7 +19,7 @@ public static class AbLegacyStatusMapper
     public const uint BadDeviceFailure = 0x808B0000u;
     public const uint BadCommunicationError = 0x80050000u;
     public const uint BadTimeout = 0x800A0000u;
-    public const uint BadTypeMismatch = 0x80730000u;
+    public const uint BadTypeMismatch = 0x80740000u;
 
     /// <summary>
     ///     Map a libplctag return/status code to an OPC UA StatusCode. The integer passed here

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS/FocasStatusMapper.cs

@@ -17,7 +17,7 @@ public static class FocasStatusMapper
     public const uint BadDeviceFailure = 0x808B0000u;
     public const uint BadCommunicationError = 0x80050000u;
     public const uint BadTimeout = 0x800A0000u;
-    public const uint BadTypeMismatch = 0x80730000u;
+    public const uint BadTypeMismatch = 0x80740000u;
 
     /// <summary>
     ///     Map common FWLIB <c>EW_*</c> return codes. The values below match Fanuc's published

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy/GalaxyDriver.cs

@@ -856,7 +856,7 @@ public sealed class GalaxyDriver
             {
                 rejectedTcs.TrySetResult(new DataValueSnapshot(
                     Value: null,
-                    StatusCode: 0x80000000u, // Bad
+                    StatusCode: StatusCodeMap.Bad,
                     SourceTimestampUtc: null,
                     ServerTimestampUtc: DateTime.UtcNow));
             }
@@ -875,7 +875,7 @@ public sealed class GalaxyDriver
                 {
                     tcs.TrySetResult(new DataValueSnapshot(
                         Value: null,
-                        StatusCode: 0x800B0000u, // BadTimeout
+                        StatusCode: StatusCodeMap.BadTimeout,
                         SourceTimestampUtc: null,
                         ServerTimestampUtc: DateTime.UtcNow));
                 }

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy/Runtime/StatusCodeMap.cs

@@ -26,14 +26,23 @@ internal static class StatusCodeMap
 {
     // OPC UA Part 4 standard StatusCodes — top-byte categories are 0x00 (Good),
     // 0x40 (Uncertain), 0x80 (Bad). Specific codes layer onto the category byte.
+    //
+    // The substatus nibbles are NOT derivable from the OPC DA quality byte this mapper consumes —
+    // they are an unrelated OPC UA enumeration and have to be looked up. Five constants here were
+    // originally written as though the DA byte could be shifted into the substatus position, which
+    // produced values naming entirely different UA codes (Gitea #497): UncertainLastUsableValue held
+    // UncertainDataSubNormal's value, UncertainSubNormal held UncertainNoCommunicationLastUsableValue's,
+    // and GoodLocalOverride / UncertainSensorNotAccurate / UncertainEngineeringUnitsExceeded held values
+    // that are not OPC UA status codes at all. StatusCodeParityTests now checks every constant below
+    // against the pinned SDK's Opc.Ua.StatusCodes.
 
     public const uint Good                            = 0x00000000u;
-    public const uint GoodLocalOverride               = 0x00D80000u;
+    public const uint GoodLocalOverride               = 0x00960000u;
     public const uint Uncertain                       = 0x40000000u;
-    public const uint UncertainLastUsableValue        = 0x40A40000u;
-    public const uint UncertainSensorNotAccurate      = 0x408D0000u;
-    public const uint UncertainEngineeringUnitsExceeded = 0x408E0000u;
-    public const uint UncertainSubNormal              = 0x408F0000u;
+    public const uint UncertainLastUsableValue        = 0x40900000u;
+    public const uint UncertainSensorNotAccurate      = 0x40930000u;
+    public const uint UncertainEngineeringUnitsExceeded = 0x40940000u;
+    public const uint UncertainSubNormal              = 0x40950000u;
     public const uint Bad                             = 0x80000000u;
     public const uint BadConfigurationError           = 0x80890000u;
     public const uint BadNotConnected                 = 0x808A0000u;
@@ -44,6 +53,14 @@ internal static class StatusCodeMap
     public const uint BadWaitingForInitialData        = 0x80320000u;
     public const uint BadInternalError                = 0x80020000u;
 
+    /// <summary>
+    ///     Fills a still-pending read when the caller's token fires before the gateway answers. Named here
+    ///     rather than written inline at the call site so <c>StatusCodeParityTests</c> can reflect over it —
+    ///     an inline literal is invisible to that guard, which is exactly how this constant spent its life
+    ///     as <c>0x800B0000</c> (<c>BadServiceUnsupported</c>) under a <c>// BadTimeout</c> comment.
+    /// </summary>
+    public const uint BadTimeout                      = 0x800A0000u;
+
     /// <summary>
     ///     Map a raw OPC DA quality byte (the low byte of an OPC DA <c>OpcQuality</c> ushort,
     ///     which is what Wonderware Historian + MXAccess surface as <c>OPCITEMSTATE.qLong</c>'s

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/Mapping/GatewayQualityMapper.cs

@@ -18,29 +18,29 @@ internal static class GatewayQualityMapper
     public static uint Map(byte q) => q switch
     {
         // Good family (192+)
-        192 => 0x00000000u,             // Good
-        216 => 0x00D80000u,             // Good_LocalOverride
+        192 => HistorianStatusCodes.Good,
+        216 => HistorianStatusCodes.GoodLocalOverride,
 
         // Uncertain family (64-191)
-        64 => 0x40000000u,              // Uncertain
-        68 => 0x40900000u,              // Uncertain_LastUsableValue
-        80 => 0x40930000u,              // Uncertain_SensorNotAccurate
-        84 => 0x40940000u,              // Uncertain_EngineeringUnitsExceeded
-        88 => 0x40950000u,              // Uncertain_SubNormal
+        64 => HistorianStatusCodes.Uncertain,
+        68 => HistorianStatusCodes.UncertainLastUsableValue,
+        80 => HistorianStatusCodes.UncertainSensorNotAccurate,
+        84 => HistorianStatusCodes.UncertainEngineeringUnitsExceeded,
+        88 => HistorianStatusCodes.UncertainSubNormal,
 
         // Bad family (0-63)
-        0 => 0x80000000u,               // Bad
-        4 => 0x80890000u,               // Bad_ConfigurationError
-        8 => 0x808A0000u,               // Bad_NotConnected
-        12 => 0x808B0000u,              // Bad_DeviceFailure
-        16 => 0x808C0000u,              // Bad_SensorFailure
-        20 => 0x80050000u,              // Bad_CommunicationError
-        24 => 0x808D0000u,              // Bad_OutOfService
-        32 => 0x80320000u,              // Bad_WaitingForInitialData
+        0 => HistorianStatusCodes.Bad,
+        4 => HistorianStatusCodes.BadConfigurationError,
+        8 => HistorianStatusCodes.BadNotConnected,
+        12 => HistorianStatusCodes.BadDeviceFailure,
+        16 => HistorianStatusCodes.BadSensorFailure,
+        20 => HistorianStatusCodes.BadCommunicationError,
+        24 => HistorianStatusCodes.BadOutOfService,
+        32 => HistorianStatusCodes.BadWaitingForInitialData,
 
         // Unknown — fall back to category bucket so callers still get something usable.
-        _ when q >= 192 => 0x00000000u,
-        _ when q >= 64 => 0x40000000u,
-        _ => 0x80000000u,
+        _ when q >= 192 => HistorianStatusCodes.Good,
+        _ when q >= 64 => HistorianStatusCodes.Uncertain,
+        _ => HistorianStatusCodes.Bad,
     };
 }

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/Mapping/HistorianStatusCodes.cs

@@ -0,0 +1,75 @@
+namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Mapping;
+
+/// <summary>
+///     The OPC UA status codes this driver publishes, as named constants.
+/// </summary>
+/// <remarks>
+///     <para>The driver layer is deliberately free of an OPC UA SDK reference, so status codes are spelled
+///     as bare <c>uint</c>s. The cost of that is a value nobody checks against the name it is written
+///     under — the defect class Gitea #497 found in six places across four drivers, one of them the
+///     <c>BadNoData</c> in <see cref="SampleMapper"/> that was really <c>BadServerHalted</c>.</para>
+///     <para><b>Named, not inline, on purpose.</b> <c>StatusCodeParityTests</c> guards these by reflecting
+///     over <c>const uint</c> fields and comparing each against <c>Opc.Ua.StatusCodes</c> in the pinned SDK.
+///     A literal written at a call site is invisible to that guard, which is exactly how
+///     <see cref="GatewayQualityMapper"/> kept an incorrect <c>Good_LocalOverride</c> through every test it
+///     had. Add a constant here rather than a literal in a <c>switch</c> arm.</para>
+/// </remarks>
+internal static class HistorianStatusCodes
+{
+    // ---- Good family ----
+
+    /// <summary>The value is good; no qualification.</summary>
+    public const uint Good = 0x00000000u;
+
+    /// <summary>The value has been overridden locally (OPC DA quality 216).</summary>
+    public const uint GoodLocalOverride = 0x00960000u;
+
+    // ---- Uncertain family ----
+
+    /// <summary>The value is uncertain; no specific reason.</summary>
+    public const uint Uncertain = 0x40000000u;
+
+    /// <summary>Communication has failed; the last known value is returned (OPC DA quality 68).</summary>
+    public const uint UncertainLastUsableValue = 0x40900000u;
+
+    /// <summary>The sensor is known not to be accurate (OPC DA quality 80).</summary>
+    public const uint UncertainSensorNotAccurate = 0x40930000u;
+
+    /// <summary>The value is outside the engineering-unit range for the sensor (OPC DA quality 84).</summary>
+    public const uint UncertainEngineeringUnitsExceeded = 0x40940000u;
+
+    /// <summary>The value is derived from fewer sources than required (OPC DA quality 88).</summary>
+    public const uint UncertainSubNormal = 0x40950000u;
+
+    // ---- Bad family ----
+
+    /// <summary>The value is bad; no specific reason.</summary>
+    public const uint Bad = 0x80000000u;
+
+    /// <summary>A configuration problem prevents the value being produced (OPC DA quality 4).</summary>
+    public const uint BadConfigurationError = 0x80890000u;
+
+    /// <summary>The source is not connected (OPC DA quality 8).</summary>
+    public const uint BadNotConnected = 0x808A0000u;
+
+    /// <summary>The device reported a failure (OPC DA quality 12).</summary>
+    public const uint BadDeviceFailure = 0x808B0000u;
+
+    /// <summary>The sensor reported a failure (OPC DA quality 16).</summary>
+    public const uint BadSensorFailure = 0x808C0000u;
+
+    /// <summary>Communication with the source failed (OPC DA quality 20).</summary>
+    public const uint BadCommunicationError = 0x80050000u;
+
+    /// <summary>The source is out of service (OPC DA quality 24).</summary>
+    public const uint BadOutOfService = 0x808D0000u;
+
+    /// <summary>No initial value has arrived from the source yet (OPC DA quality 32).</summary>
+    public const uint BadWaitingForInitialData = 0x80320000u;
+
+    /// <summary>
+    ///     The historian returned no data for the requested tag/interval. Distinct from a transport
+    ///     failure: the query succeeded and the answer was empty.
+    /// </summary>
+    public const uint BadNoData = 0x809B0000u;
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/Mapping/SampleMapper.cs

@@ -10,8 +10,8 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Mapping;
 /// </summary>
 internal static class SampleMapper
 {
-    private const uint StatusGood = 0x00000000u;
-    private const uint StatusBadNoData = 0x800E0000u;
+    private const uint StatusGood = HistorianStatusCodes.Good;
+    private const uint StatusBadNoData = HistorianStatusCodes.BadNoData;
 
     /// <summary>OPC DA "Good" family floor — a quality byte at/above this carries usable data.</summary>
     private const byte GoodQualityFloor = 192;

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Contracts/ModbusDriverOptions.cs

@@ -130,14 +130,6 @@ public sealed class ModbusDriverOptions
     /// </summary>
     public MelsecFamily MelsecSubFamily { get; init; } = MelsecFamily.Q_L_iQR;
 
-    /// <summary>
-    ///     Wire transport selector. <see cref="ModbusTransportMode.Tcp"/> (default) is the
-    ///     historical Modbus TCP/MBAP framing. <see cref="ModbusTransportMode.RtuOverTcp"/>
-    ///     frames Modbus RTU PDUs (CRC16, no MBAP header) over the same TCP socket — for
-    ///     serial-to-Ethernet gateways that bridge RS-485 without re-encapsulating to MBAP.
-    /// </summary>
-    public ModbusTransportMode Transport { get; init; } = ModbusTransportMode.Tcp;
-
     /// <summary>
     ///     When <c>true</c>, the driver suppresses redundant writes: if the most recent
     ///     successful write to a tag carried value V and a new write of V arrives, the second

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Contracts/ModbusTransportMode.cs

@@ -1,17 +0,0 @@
-namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus;
-
-/// <summary>
-///     Wire transport for a Modbus driver instance. <see cref="Tcp"/> = Modbus/TCP (MBAP + TxId);
-///     <see cref="RtuOverTcp"/> = RTU framing (address + CRC-16, no MBAP) tunnelled over a socket to
-///     a serial→Ethernet gateway. Default <see cref="Tcp"/> — existing configs omit the field.
-///     A direct-serial <c>Rtu</c> member is intentionally NOT reserved here (descoped 2026-07-15);
-///     do not number-squat it.
-/// </summary>
-public enum ModbusTransportMode
-{
-    /// <summary>Modbus/TCP — 7-byte MBAP header + transaction id (the historical default).</summary>
-    Tcp,
-
-    /// <summary>RTU framing (<c>[addr][PDU][CRC-16]</c>) tunnelled over a socket to a serial→Ethernet gateway.</summary>
-    RtuOverTcp,
-}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus/ModbusCrc.cs

@@ -1,48 +0,0 @@
-namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus;
-
-/// <summary>
-///     CRC-16/MODBUS helper: reflected polynomial <c>0xA001</c>, initial value <c>0xFFFF</c>.
-///     On the wire the CRC is appended low byte first, high byte second — <see cref="Append"/>
-///     does that; <see cref="Compute"/> just returns the 16-bit value. Byte-stream-agnostic:
-///     no socket or framing knowledge lives here.
-/// </summary>
-public static class ModbusCrc
-{
-    /// <summary>Computes the CRC-16/MODBUS checksum over <paramref name="data"/>.</summary>
-    /// <param name="data">The bytes to checksum (e.g. the RTU frame minus the trailing CRC).</param>
-    /// <returns>The 16-bit CRC value.</returns>
-    public static ushort Compute(ReadOnlySpan<byte> data)
-    {
-        ushort crc = 0xFFFF;
-        foreach (var b in data)
-        {
-            crc ^= b;
-            for (var i = 0; i < 8; i++)
-            {
-                var carry = (crc & 0x0001) != 0;
-                crc >>= 1;
-                if (carry)
-                {
-                    crc ^= 0xA001;
-                }
-            }
-        }
-
-        return crc;
-    }
-
-    /// <summary>
-    ///     Returns <paramref name="body"/> with its CRC-16/MODBUS appended, low byte first.
-    /// </summary>
-    /// <param name="body">The frame body to checksum.</param>
-    /// <returns>A new array: <paramref name="body"/> followed by <c>[crc &amp; 0xFF, crc &gt;&gt; 8]</c>.</returns>
-    public static byte[] Append(ReadOnlySpan<byte> body)
-    {
-        var crc = Compute(body);
-        var result = new byte[body.Length + 2];
-        body.CopyTo(result);
-        result[^2] = (byte)(crc & 0xFF);
-        result[^1] = (byte)(crc >> 8);
-        return result;
-    }
-}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus/ModbusDriver.cs

@@ -94,8 +94,7 @@ public sealed class ModbusDriver
     /// <summary>Initializes a new Modbus TCP driver with the specified options and transport factory.</summary>
     /// <param name="options">Driver configuration options.</param>
     /// <param name="driverInstanceId">Unique identifier for this driver instance.</param>
-    /// <param name="transportFactory">Factory to create the Modbus transport; defaults to
-    /// <see cref="ModbusTransportFactory.Create"/>, which honours <see cref="ModbusDriverOptions.Transport"/>.</param>
+    /// <param name="transportFactory">Factory to create the Modbus transport; defaults to ModbusTcpTransport.</param>
     /// <param name="logger">Logger instance; defaults to null logger if not provided.</param>
     public ModbusDriver(ModbusDriverOptions options, string driverInstanceId,
         Func<ModbusDriverOptions, IModbusTransport>? transportFactory = null,
@@ -108,7 +107,11 @@ public sealed class ModbusDriver
         _resolver = new EquipmentTagRefResolver<ModbusTagDefinition>(
             r => _tagsByRawPath.TryGetValue(r, out var t) ? t : null);
         _transportFactory = transportFactory
-            ?? (o => ModbusTransportFactory.Create(o));
+            ?? (o => new ModbusTcpTransport(
+                o.Host, o.Port, o.Timeout, o.AutoReconnect,
+                keepAlive: o.KeepAlive,
+                idleDisconnect: o.IdleDisconnectTimeout,
+                reconnect: o.Reconnect));
         _poll = new PollGroupEngine(
             reader: ReadAsync,
             onChange: (handle, tagRef, snapshot) =>

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus/ModbusDriverFactoryExtensions.cs

@@ -74,8 +74,6 @@ public static class ModbusDriverFactoryExtensions
                 : ParseEnum<ModbusFamily>(dto.Family, "<driver-level>", driverInstanceId, "Family"),
             MelsecSubFamily = dto.MelsecSubFamily is null ? MelsecFamily.Q_L_iQR
                 : ParseEnum<MelsecFamily>(dto.MelsecSubFamily, "<driver-level>", driverInstanceId, "MelsecSubFamily"),
-            Transport = dto.Transport is null ? ModbusTransportMode.Tcp
-                : ParseEnum<ModbusTransportMode>(dto.Transport, "<driver-level>", driverInstanceId, "Transport"),
             AutoProhibitReprobeInterval = dto.AutoProhibitReprobeMs is { } reprobeMs ? TimeSpan.FromMilliseconds(reprobeMs) : null,
             AutoReconnect = dto.AutoReconnect ?? true,
             // v3: the deploy artifact (Wave C) populates rawTags with the cluster's authored raw Modbus
@@ -161,8 +159,6 @@ public static class ModbusDriverFactoryExtensions
         public string? Family { get; init; }
         /// <summary>Gets or sets the Melsec subfamily.</summary>
         public string? MelsecSubFamily { get; init; }
-        /// <summary>Gets or sets the wire transport mode (Tcp / RtuOverTcp). Null defaults to Tcp.</summary>
-        public string? Transport { get; init; }
         /// <summary>Gets or sets the automatic prohibition reprobei interval in milliseconds.</summary>
         public int? AutoProhibitReprobeMs { get; init; }
         /// <summary>Gets or sets a value indicating whether automatic reconnection is enabled.</summary>

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus/ModbusDriverProbe.cs

@@ -29,19 +29,15 @@ public sealed class ModbusDriverProbe : IDriverProbe
     /// <inheritdoc />
     public string DriverType => "Modbus";
 
-    /// <summary>The parsed probe target — host/port/unitId + the effective connection timeout + the wire
-    /// transport mode, all read from the SAME factory DTO shape (<c>ModbusDriverConfigDto</c>) the driver
-    /// factory parses, so <c>timeoutMs</c> binds identically to the factory (R2-11, 05/CONV-2; the
-    /// OpcUaClient parity rule) and an <c>RtuOverTcp</c>-authored config probes over RTU framing —
-    /// matching how the driver will actually run.</summary>
-    internal readonly record struct ProbeTarget(string Host, int Port, byte UnitId, TimeSpan Timeout, ModbusTransportMode Transport);
+    /// <summary>The parsed probe target — host/port/unitId + the effective connection timeout, all read
+    /// from the SAME factory DTO shape (<c>ModbusDriverConfigDto</c>) the driver factory parses, so
+    /// <c>timeoutMs</c> binds identically to the factory (R2-11, 05/CONV-2; the OpcUaClient parity rule).</summary>
+    internal readonly record struct ProbeTarget(string Host, int Port, byte UnitId, TimeSpan Timeout);
 
     /// <summary>Parse the driver config JSON into a <see cref="ProbeTarget"/> using the factory DTO shape.
     /// Returns a null target + an error message when the JSON is invalid or has no host/port. The effective
     /// timeout mirrors the factory (<c>TimeSpan.FromMilliseconds(dto.TimeoutMs ?? …)</c>); when the config
-    /// omits <c>timeoutMs</c> the caller's <paramref name="fallbackTimeout"/> is used. <c>Transport</c>
-    /// mirrors the factory's null-defaults-to-Tcp convention (<see cref="ModbusDriverFactoryExtensions"/>);
-    /// an unrecognized value is reported as a probe-target error rather than silently falling back.</summary>
+    /// omits <c>timeoutMs</c> the caller's <paramref name="fallbackTimeout"/> is used.</summary>
     /// <param name="configJson">The driver config JSON (factory DTO shape).</param>
     /// <param name="fallbackTimeout">The timeout used when the config omits <c>timeoutMs</c>.</param>
     /// <returns>The parsed target, or a null target with an error string.</returns>
@@ -56,15 +52,8 @@ public sealed class ModbusDriverProbe : IDriverProbe
         if (string.IsNullOrWhiteSpace(dto.Host) || port <= 0)
             return (null, "Config has no host/port to probe.");
 
-        var transportMode = ModbusTransportMode.Tcp;
-        if (dto.Transport is not null && !Enum.TryParse(dto.Transport, ignoreCase: true, out transportMode))
-        {
-            return (null, $"Config has unknown Transport '{dto.Transport}'. " +
-                $"Expected one of {string.Join(", ", Enum.GetNames<ModbusTransportMode>())}");
-        }
-
         var timeout = dto.TimeoutMs is { } ms && ms > 0 ? TimeSpan.FromMilliseconds(ms) : fallbackTimeout;
-        return (new ProbeTarget(dto.Host!, port, dto.UnitId ?? 1, timeout, transportMode), null);
+        return (new ProbeTarget(dto.Host!, port, dto.UnitId ?? 1, timeout), null);
     }
 
     /// <inheritdoc />
@@ -83,17 +72,9 @@ public sealed class ModbusDriverProbe : IDriverProbe
         using var cts = CancellationTokenSource.CreateLinkedTokenSource(ct);
         cts.CancelAfter(timeout);
 
-        // Phase 1 — TCP connect, over whichever transport the config's Transport mode selects
-        // (ModbusTransportFactory is the single mapping point — same switch the live driver uses).
+        // Phase 1 — TCP connect (using ModbusTcpTransport which handles IPv4 preference).
         // autoReconnect=false: this is a one-shot probe, no retry loops.
-        var transport = ModbusTransportFactory.Create(new ModbusDriverOptions
-        {
-            Host = host,
-            Port = port,
-            Timeout = timeout,
-            Transport = t.Transport,
-            AutoReconnect = false,
-        });
+        var transport = new ModbusTcpTransport(host, port, timeout, autoReconnect: false);
         await using (transport.ConfigureAwait(false))
         {
             try

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus/ModbusRtuFraming.cs

@@ -1,187 +0,0 @@
-namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus;
-
-/// <summary>
-///     Modbus RTU framing: builds a request ADU (<c>[unitId] + PDU + CRC</c>) and deframes a
-///     response back to its bare PDU. Byte-stream-agnostic — it operates on a <see cref="Stream"/>
-///     and knows nothing about sockets or serial ports, so a future serial transport can reuse it.
-/// </summary>
-/// <remarks>
-///     <para>
-///         The single genuinely-new correctness risk of the RTU path: an RTU frame carries <b>no
-///         length field</b> (unlike TCP's MBAP header), so the response size must be derived from
-///         the function code. After reading <c>addr(1)</c> + <c>fc(1)</c>, the remaining byte count
-///         is one of three shapes:
-///     </para>
-///     <list type="table">
-///         <listheader><term>Shape</term><description>Trailing bytes after <c>addr,fc</c></description></listheader>
-///         <item>
-///             <term>Exception (<c>fc &amp; 0x80</c>)</term>
-///             <description><c>excCode(1)</c> + <c>CRC(2)</c></description>
-///         </item>
-///         <item>
-///             <term>Read (FC 01/02/03/04)</term>
-///             <description><c>byteCount(1)</c> then <c>byteCount</c> data bytes + <c>CRC(2)</c></description>
-///         </item>
-///         <item>
-///             <term>Write echo (FC 05/06/15/16)</term>
-///             <description>fixed <c>4</c> bytes + <c>CRC(2)</c></description>
-///         </item>
-///     </list>
-///     <para>
-///         The trailing CRC is validated over <c>[addr, ...pdu]</c> (everything except the two CRC
-///         bytes) <b>before</b> the frame is interpreted — so a corrupt exception frame surfaces as a
-///         desync, never as a bogus <see cref="ModbusException"/>. A CRC mismatch or a short read
-///         (truncation / stream closed mid-frame) throws <see cref="ModbusTransportDesyncException"/>;
-///         a CRC-valid exception PDU throws <see cref="ModbusException"/> carrying the original
-///         function code (<c>fc &amp; 0x7F</c>) and exception code.
-///     </para>
-///     <para>
-///         Once the CRC passes, the response's address byte is validated against the addressed unit.
-///         On an RS-485 multi-drop bus a CRC-valid reply from the <b>wrong</b> slave would otherwise be
-///         silently accepted as the addressed unit's data; such a frame is a unit-mismatch
-///         <see cref="ModbusTransportDesyncException"/>. This ordering is deliberate — a corrupt frame
-///         stays a CRC/desync failure, and only a coherent-but-mis-addressed frame becomes a
-///         unit-mismatch desync.
-///     </para>
-/// </remarks>
-public static class ModbusRtuFraming
-{
-    /// <summary>
-    ///     Builds an RTU request ADU: the unit id, the PDU, and the trailing CRC-16/MODBUS
-    ///     (appended low byte first).
-    /// </summary>
-    /// <param name="unitId">The RTU slave/unit address.</param>
-    /// <param name="pdu">The bare PDU (function code + data).</param>
-    /// <returns>A new array: <c>[unitId, ...pdu, crcLo, crcHi]</c>.</returns>
-    public static byte[] BuildAdu(byte unitId, ReadOnlySpan<byte> pdu)
-    {
-        var frame = new byte[1 + pdu.Length];
-        frame[0] = unitId;
-        pdu.CopyTo(frame.AsSpan(1));
-        return ModbusCrc.Append(frame);
-    }
-
-    /// <summary>
-    ///     Reads a single RTU response frame from <paramref name="stream"/> and returns its bare PDU
-    ///     (<c>[fc, ...data]</c>), with the leading unit-id and trailing CRC stripped.
-    /// </summary>
-    /// <param name="stream">The byte stream to read the response from.</param>
-    /// <param name="expectedUnit">
-    ///     The unit id the request was addressed to. The response's address byte is validated against
-    ///     it after the CRC passes; a mismatch is a unit-mismatch desync.
-    /// </param>
-    /// <param name="ct">A token to cancel the read.</param>
-    /// <returns>The bare response PDU (function code followed by its data).</returns>
-    /// <exception cref="ModbusTransportDesyncException">
-    ///     The frame was truncated (stream closed mid-frame), its trailing CRC did not validate, or its
-    ///     address byte did not match <paramref name="expectedUnit"/>.
-    /// </exception>
-    /// <exception cref="ModbusException">
-    ///     The frame was a CRC-valid Modbus exception PDU (high bit set on the function code).
-    /// </exception>
-    public static async Task<byte[]> ReadResponsePduAsync(
-        Stream stream, byte expectedUnit, CancellationToken ct)
-    {
-        // Header: addr(1) + fc(1). The function code selects how many more bytes to read.
-        var header = new byte[2];
-        await ReadExactlyAsync(stream, header, ct).ConfigureAwait(false);
-        var fc = header[1];
-
-        int trailing; // bytes after addr+fc, up to and including the 2 CRC bytes.
-        if ((fc & 0x80) != 0)
-        {
-            // Exception frame: excCode(1) + CRC(2).
-            trailing = 1 + 2;
-        }
-        else if (fc is 0x01 or 0x02 or 0x03 or 0x04)
-        {
-            // Read response: byteCount(1) then byteCount data bytes + CRC(2).
-            var bc = new byte[1];
-            await ReadExactlyAsync(stream, bc, ct).ConfigureAwait(false);
-            var byteCount = bc[0];
-            var rest = new byte[byteCount + 2];
-            await ReadExactlyAsync(stream, rest, ct).ConfigureAwait(false);
-            return ValidateAndStrip(expectedUnit, header, bc, rest);
-        }
-        else
-        {
-            // Fixed 4-byte echo: correct for the write FCs this driver emits (05/06/0F/10). A future
-            // variable-length response FC outside 01-04 (e.g. FC23) would be mis-sized here and
-            // surface as a desync — revisit the FC-shape table if the driver starts emitting one.
-            trailing = 4 + 2;
-        }
-
-        var tail = new byte[trailing];
-        await ReadExactlyAsync(stream, tail, ct).ConfigureAwait(false);
-        return ValidateAndStrip(expectedUnit, header, ReadOnlySpan<byte>.Empty, tail);
-    }
-
-    /// <summary>
-    ///     Assembles the full frame from its pieces, validates the trailing CRC over everything
-    ///     except the CRC bytes, then validates the response address against
-    ///     <paramref name="expectedUnit"/> and strips <c>addr</c> + <c>CRC</c> to return the bare PDU.
-    ///     A CRC-valid exception PDU throws <see cref="ModbusException"/>.
-    /// </summary>
-    private static byte[] ValidateAndStrip(
-        byte expectedUnit, ReadOnlySpan<byte> header, ReadOnlySpan<byte> middle, ReadOnlySpan<byte> tail)
-    {
-        // Reassemble the whole frame: header(addr,fc) + middle(optional byteCount) + tail.
-        var frame = new byte[header.Length + middle.Length + tail.Length];
-        header.CopyTo(frame);
-        middle.CopyTo(frame.AsSpan(header.Length));
-        tail.CopyTo(frame.AsSpan(header.Length + middle.Length));
-
-        // CRC covers everything except the trailing 2 CRC bytes.
-        var body = frame.AsSpan(0, frame.Length - 2);
-        var expected = ModbusCrc.Compute(body);
-        var actual = (ushort)(frame[^2] | (frame[^1] << 8));
-        if (actual != expected)
-            throw new ModbusTransportDesyncException(
-                ModbusTransportDesyncException.DesyncReason.CrcMismatch,
-                $"Modbus RTU CRC mismatch: computed {expected:X4} got {actual:X4}");
-
-        // Unit-address validation runs only AFTER the CRC passes: a corrupt frame is a CRC/desync
-        // failure, and only a coherent-but-mis-addressed frame (a CRC-valid reply from the wrong
-        // RS-485 slave) is a unit-mismatch desync. Never silently accept another unit's data.
-        var addr = frame[0];
-        if (addr != expectedUnit)
-            throw new ModbusTransportDesyncException(
-                ModbusTransportDesyncException.DesyncReason.UnitMismatch,
-                $"Modbus RTU unit mismatch: expected {expectedUnit} got {addr}");
-
-        // Bare PDU = frame minus leading addr and trailing CRC.
-        var pdu = body[1..].ToArray();
-
-        // Exception PDU: high bit set on the function code. The CRC already validated, so this is a
-        // coherent protocol-level error — surface the ORIGINAL function code (fc & 0x7F).
-        if ((pdu[0] & 0x80) != 0)
-        {
-            var fc = (byte)(pdu[0] & 0x7F);
-            var exCode = pdu[1];
-            throw new ModbusException(fc, exCode, $"Modbus exception fc={fc} code={exCode}");
-        }
-
-        return pdu;
-    }
-
-    /// <summary>
-    ///     Fills <paramref name="buf"/> completely from <paramref name="stream"/>, throwing a
-    ///     truncation desync if the stream ends first. Mirrors
-    ///     <c>ModbusTcpTransport.ReadExactlyAsync</c>, but normalises the end-of-stream to a
-    ///     <see cref="ModbusTransportDesyncException"/> so a length-less RTU frame that arrives
-    ///     short is classified as a desync rather than a bare <see cref="EndOfStreamException"/>.
-    /// </summary>
-    private static async Task ReadExactlyAsync(Stream stream, byte[] buf, CancellationToken ct)
-    {
-        var read = 0;
-        while (read < buf.Length)
-        {
-            var n = await stream.ReadAsync(buf.AsMemory(read), ct).ConfigureAwait(false);
-            if (n == 0)
-                throw new ModbusTransportDesyncException(
-                    ModbusTransportDesyncException.DesyncReason.TruncatedFrame,
-                    $"Modbus RTU frame truncated: expected {buf.Length} bytes, got {read}");
-            read += n;
-        }
-    }
-}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus/ModbusRtuOverTcpTransport.cs

@@ -1,190 +0,0 @@
-using System.Net.Sockets;
-
-namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus;
-
-/// <summary>
-///     Concrete Modbus RTU-over-TCP transport. Composes <see cref="ModbusSocketLifecycle"/> for the
-///     connect / reconnect / keep-alive / idle machinery and <see cref="ModbusRtuFraming"/> for the
-///     wire layout — the same lifecycle <see cref="ModbusTcpTransport"/> uses, but with CRC framing
-///     instead of MBAP.
-/// </summary>
-/// <remarks>
-///     <para>
-///         Delta from <see cref="ModbusTcpTransport"/>: an RTU ADU is <c>[unitId][PDU][CRC]</c> with
-///         <b>no MBAP header and no transaction id</b>. Because there is no TxId to correlate
-///         interleaved responses, at most one transaction may be on the bus at a time — the
-///         <see cref="_gate"/> single-flight is therefore <b>mandatory</b>, not merely a
-///         diagnostics convenience.
-///     </para>
-///     <para>
-///         Survives mid-transaction socket drops the same way the TCP transport does: a socket-level
-///         failure (<see cref="IOException"/> / <see cref="SocketException"/> /
-///         <see cref="EndOfStreamException"/>, and the <see cref="ModbusTransportDesyncException"/>
-///         that derives from <see cref="IOException"/>) triggers a single reconnect-then-retry; a
-///         second failure bubbles up so the driver's health surface reflects the real state.
-///     </para>
-///     <para>
-///         Every transaction runs under a per-op deadline (a linked
-///         <see cref="CancellationTokenSource.CancelAfter(TimeSpan)"/>, design §7 / R2-01) so a
-///         frozen gateway can never wedge a poll: the deadline firing is normalised to a
-///         <see cref="ModbusTransportDesyncException"/> and tears the socket down so the next attempt
-///         reconnects. A <b>caller</b> cancellation is distinguished from that timeout and propagates
-///         as a plain <see cref="OperationCanceledException"/> with no teardown.
-///     </para>
-///     <para>
-///         The constructor is connection-free; all socket I/O happens in <see cref="ConnectAsync"/> /
-///         <see cref="SendAsync"/>. The <see cref="ForTest"/> seam injects a pre-connected
-///         <see cref="Stream"/> (an in-memory duplex fake) so the send/receive orchestration,
-///         single-flight, and deadline can be exercised with no socket — in that path
-///         <see cref="_life"/> is <see langword="null"/> and the idle / reconnect machinery is
-///         skipped (a raw injected stream cannot reconnect).
-///     </para>
-/// </remarks>
-public sealed class ModbusRtuOverTcpTransport : IModbusTransport
-{
-    private readonly ModbusSocketLifecycle? _life;
-    private readonly Stream? _testStream;
-    private readonly TimeSpan _timeout;
-    private readonly SemaphoreSlim _gate = new(1, 1);
-    private bool _disposed;
-
-    /// <summary>Initializes a new instance of the <see cref="ModbusRtuOverTcpTransport"/> class.</summary>
-    /// <param name="host">The host address or hostname of the Modbus gateway.</param>
-    /// <param name="port">The TCP port of the Modbus gateway.</param>
-    /// <param name="timeout">The timeout for socket operations and the per-op response deadline.</param>
-    /// <param name="autoReconnect">Whether to automatically reconnect on socket failures.</param>
-    /// <param name="keepAlive">Optional keep-alive configuration for the socket.</param>
-    /// <param name="idleDisconnect">Optional duration after which an idle socket is disconnected.</param>
-    /// <param name="reconnect">Optional reconnect backoff configuration.</param>
-    public ModbusRtuOverTcpTransport(
-        string host, int port, TimeSpan timeout, bool autoReconnect = true,
-        ModbusKeepAliveOptions? keepAlive = null,
-        TimeSpan? idleDisconnect = null,
-        ModbusReconnectOptions? reconnect = null)
-    {
-        _timeout = timeout;
-        _life = new ModbusSocketLifecycle(host, port, timeout, autoReconnect, keepAlive, idleDisconnect, reconnect);
-    }
-
-    private ModbusRtuOverTcpTransport(Stream testStream, TimeSpan timeout)
-    {
-        _timeout = timeout;
-        _testStream = testStream;
-    }
-
-    /// <summary>
-    ///     Test seam: builds a transport over a pre-connected, in-memory duplex <paramref name="stream"/>,
-    ///     bypassing <see cref="ConnectAsync"/> and the idle / reconnect machinery so the send/receive
-    ///     orchestration, single-flight, and per-op deadline can be exercised with no real socket.
-    /// </summary>
-    /// <param name="stream">A pre-connected duplex stream standing in for the socket.</param>
-    /// <param name="timeout">The per-op response deadline.</param>
-    /// <returns>A transport driving <paramref name="stream"/> directly.</returns>
-    internal static ModbusRtuOverTcpTransport ForTest(Stream stream, TimeSpan timeout) => new(stream, timeout);
-
-    /// <inheritdoc />
-    public Task ConnectAsync(CancellationToken ct) =>
-        // The ForTest seam is handed a pre-connected stream — nothing to dial.
-        _life is null ? Task.CompletedTask : _life.ConnectAsync(ct);
-
-    /// <inheritdoc />
-    public async Task<byte[]> SendAsync(byte unitId, byte[] pdu, CancellationToken ct)
-    {
-        if (_disposed) throw new ObjectDisposedException(nameof(ModbusRtuOverTcpTransport));
-        if (CurrentStream is null) throw new InvalidOperationException("Transport not connected");
-
-        // Single-flight: RTU carries no transaction id, so at most one transaction may be on the bus
-        // at a time — serialise every send/receive under the gate.
-        await _gate.WaitAsync(ct).ConfigureAwait(false);
-        try
-        {
-            // Proactive idle-disconnect (real socket only): if the socket has been quiet longer than
-            // the configured threshold, tear it down + reconnect before this PDU lands. Defends
-            // against silent NAT / firewall reaping.
-            if (_life is not null && _life.ShouldReconnectForIdle())
-            {
-                await _life.TearDownAsync().ConfigureAwait(false);
-                await _life.ConnectWithBackoffAsync(ct).ConfigureAwait(false);
-            }
-
-            try
-            {
-                var result = await SendOnceAsync(unitId, pdu, ct).ConfigureAwait(false);
-                _life?.MarkSuccess();
-                return result;
-            }
-            catch (Exception ex) when (_life is not null && _life.AutoReconnect && ModbusSocketLifecycle.IsSocketLevelFailure(ex))
-            {
-                // Mid-transaction drop: tear down the dead socket, reconnect (with backoff if
-                // configured), resend. Single retry — a second failure propagates so health/status
-                // reflect reality. Never reached in the ForTest seam (a raw injected stream has no
-                // lifecycle to reconnect).
-                await _life.TearDownAsync().ConfigureAwait(false);
-                await _life.ConnectWithBackoffAsync(ct).ConfigureAwait(false);
-                var result = await SendOnceAsync(unitId, pdu, ct).ConfigureAwait(false);
-                _life.MarkSuccess();
-                return result;
-            }
-        }
-        finally
-        {
-            _gate.Release();
-        }
-    }
-
-    /// <summary>The live stream: the lifecycle's <see cref="NetworkStream"/>, or the injected test stream.</summary>
-    private Stream? CurrentStream => _life?.Stream ?? _testStream;
-
-    /// <summary>
-    ///     Executes exactly one RTU transaction on the current stream: build the ADU, write + flush,
-    ///     read back one deframed response PDU. See the class remarks for the desync / timeout /
-    ///     caller-cancel handling.
-    /// </summary>
-    private async Task<byte[]> SendOnceAsync(byte unitId, byte[] pdu, CancellationToken ct)
-    {
-        var stream = CurrentStream;
-        if (stream is null) throw new InvalidOperationException("Transport not connected");
-
-        // RTU ADU: [unitId] + PDU + CRC — no MBAP header, no TxId.
-        var adu = ModbusRtuFraming.BuildAdu(unitId, pdu);
-
-        using var cts = CancellationTokenSource.CreateLinkedTokenSource(ct);
-        cts.CancelAfter(_timeout);
-        try
-        {
-            await stream.WriteAsync(adu.AsMemory(), cts.Token).ConfigureAwait(false);
-            await stream.FlushAsync(cts.Token).ConfigureAwait(false);
-
-            // Framing owns the length-less RTU deframe + CRC + unit-address validation. A CRC-valid
-            // exception PDU throws ModbusException (socket still coherent — propagates, no teardown);
-            // truncation / CRC / unit-mismatch throw ModbusTransportDesyncException.
-            return await ModbusRtuFraming.ReadResponsePduAsync(stream, unitId, cts.Token).ConfigureAwait(false);
-        }
-        catch (ModbusTransportDesyncException)
-        {
-            // Framing violation: the stream is desynchronized — never reuse it.
-            if (_life is not null) await _life.TearDownAsync().ConfigureAwait(false);
-            throw;
-        }
-        catch (OperationCanceledException) when (!ct.IsCancellationRequested)
-        {
-            // Per-op timeout fired (NOT the caller). The response is unknown / may still land later
-            // and corrupt the next read — tear the socket down and normalise as a desync so the
-            // reconnect retry / status mapping engages.
-            if (_life is not null) await _life.TearDownAsync().ConfigureAwait(false);
-            throw new ModbusTransportDesyncException(
-                ModbusTransportDesyncException.DesyncReason.Timeout,
-                $"Modbus per-op response timeout after {_timeout.TotalMilliseconds:0}ms");
-        }
-    }
-
-    /// <summary>Asynchronously disposes the transport and underlying socket resources.</summary>
-    /// <returns>A task that represents the asynchronous operation.</returns>
-    public async ValueTask DisposeAsync()
-    {
-        if (_disposed) return;
-        _disposed = true;
-        if (_life is not null) await _life.DisposeAsync().ConfigureAwait(false);
-        _gate.Dispose();
-    }
-}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus/ModbusSocketLifecycle.cs

@@ -1,221 +0,0 @@
-using System.Net.Sockets;
-
-namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus;
-
-/// <summary>
-///     Owns the raw TCP socket lifecycle shared by every Modbus-over-TCP transport (MBAP and
-///     RTU-over-TCP alike): the IPv4-preference connect, OS-level keep-alive, geometric-backoff
-///     reconnect, idle-disconnect tracking, and teardown. It exposes the current
-///     <see cref="NetworkStream"/> so the composing transport can drive its own framing on top —
-///     the lifecycle knows nothing about MBAP / RTU wire layout.
-/// </summary>
-/// <remarks>
-///     <para>
-///         Extracted verbatim from <see cref="ModbusTcpTransport"/> so the connect / reconnect /
-///         keep-alive / idle behaviour is written once and composed by both transports. The
-///         constructor is connection-free — all socket I/O happens in <see cref="ConnectAsync"/> /
-///         <see cref="ConnectWithBackoffAsync"/>.
-///     </para>
-///     <para>
-///         Why keep-alive matters for DL205/DL260: the AutomationDirect H2-ECOM100 does NOT send
-///         TCP keepalives per <c>docs/v2/dl205.md</c> §behavioral-oddities, so any NAT/firewall
-///         between the gateway and PLC can silently close an idle socket after 2-5 minutes.
-///         Enabling OS-level <c>SO_KEEPALIVE</c> lets the driver's own side detect a stuck socket
-///         in reasonable time even when the application is mostly idle.
-///     </para>
-/// </remarks>
-public sealed class ModbusSocketLifecycle : IAsyncDisposable
-{
-    private readonly string _host;
-    private readonly int _port;
-    private readonly TimeSpan _timeout;
-    private readonly bool _autoReconnect;
-    private readonly ModbusKeepAliveOptions _keepAlive;
-    private readonly TimeSpan? _idleDisconnect;
-    private readonly ModbusReconnectOptions _reconnect;
-    private TcpClient? _client;
-    private NetworkStream? _stream;
-    private DateTime _lastSuccessUtc = DateTime.UtcNow;
-
-    /// <summary>Initializes a new instance of the <see cref="ModbusSocketLifecycle"/> class.</summary>
-    /// <param name="host">The host address or hostname of the Modbus server.</param>
-    /// <param name="port">The TCP port of the Modbus server.</param>
-    /// <param name="timeout">The timeout for socket operations.</param>
-    /// <param name="autoReconnect">Whether to automatically reconnect on socket failures.</param>
-    /// <param name="keepAlive">Optional keep-alive configuration for the socket.</param>
-    /// <param name="idleDisconnect">Optional duration after which an idle socket is disconnected.</param>
-    /// <param name="reconnect">Optional reconnect backoff configuration.</param>
-    public ModbusSocketLifecycle(
-        string host, int port, TimeSpan timeout, bool autoReconnect = true,
-        ModbusKeepAliveOptions? keepAlive = null,
-        TimeSpan? idleDisconnect = null,
-        ModbusReconnectOptions? reconnect = null)
-    {
-        _host = host;
-        _port = port;
-        _timeout = timeout;
-        _autoReconnect = autoReconnect;
-        _keepAlive = keepAlive ?? new ModbusKeepAliveOptions();
-        _idleDisconnect = idleDisconnect;
-        _reconnect = reconnect ?? new ModbusReconnectOptions();
-    }
-
-    /// <summary>Gets the current live <see cref="NetworkStream"/>, or <see langword="null"/> when not connected.</summary>
-    public NetworkStream? Stream => _stream;
-
-    /// <summary>Gets a value indicating whether auto-reconnect on socket failures is enabled.</summary>
-    public bool AutoReconnect => _autoReconnect;
-
-    /// <summary>Establishes a connection to the Modbus server, preferring IPv4.</summary>
-    /// <param name="ct">A cancellation token to observe for cancellation.</param>
-    /// <returns>A task representing the asynchronous connection operation.</returns>
-    public async Task ConnectAsync(CancellationToken ct)
-    {
-        // Resolve the host explicitly + prefer IPv4. .NET's TcpClient default-constructor is
-        // dual-stack (IPv6 first, fallback to IPv4) — but most Modbus TCP devices (PLCs and
-        // simulators like pymodbus) bind 0.0.0.0 only, so the IPv6 attempt times out and we
-        // burn the entire ConnectAsync budget before even trying IPv4. Resolving first +
-        // dialing the IPv4 address directly sidesteps that.
-        var addresses = await System.Net.Dns.GetHostAddressesAsync(_host, ct).ConfigureAwait(false);
-        var ipv4 = System.Linq.Enumerable.FirstOrDefault(addresses,
-            a => a.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork);
-        var target = ipv4 ?? (addresses.Length > 0 ? addresses[0] : System.Net.IPAddress.Loopback);
-
-        _client = new TcpClient(target.AddressFamily);
-        EnableKeepAlive(_client, _keepAlive);
-
-        using var cts = CancellationTokenSource.CreateLinkedTokenSource(ct);
-        cts.CancelAfter(_timeout);
-        await _client.ConnectAsync(target, _port, cts.Token).ConfigureAwait(false);
-        _stream = _client.GetStream();
-        _lastSuccessUtc = DateTime.UtcNow;
-    }
-
-    /// <summary>
-    ///     Connect attempt with the configured geometric backoff. The first attempt fires after
-    ///     <see cref="ModbusReconnectOptions.InitialDelay"/> (default zero — immediate); each
-    ///     subsequent attempt sleeps for the previous delay times <c>BackoffMultiplier</c>,
-    ///     capped at <c>MaxDelay</c>. Caller's cancellation token aborts the loop.
-    /// </summary>
-    /// <param name="ct">A cancellation token to observe for cancellation.</param>
-    /// <returns>A task representing the asynchronous reconnect operation.</returns>
-    public async Task ConnectWithBackoffAsync(CancellationToken ct)
-    {
-        var delay = _reconnect.InitialDelay;
-        var attempt = 0;
-        while (true)
-        {
-            if (delay > TimeSpan.Zero)
-                await Task.Delay(delay, ct).ConfigureAwait(false);
-            try
-            {
-                await ConnectAsync(ct).ConfigureAwait(false);
-                return;
-            }
-            catch (Exception ex) when (IsSocketLevelFailure(ex) && _autoReconnect)
-            {
-                attempt++;
-                // Geometric growth, capped. Use Math.Min on ticks so we don't overflow with
-                // pathological multipliers / long deployments.
-                var nextTicks = (long)(Math.Max(delay.Ticks, TimeSpan.FromMilliseconds(100).Ticks) * _reconnect.BackoffMultiplier);
-                delay = TimeSpan.FromTicks(Math.Min(nextTicks, _reconnect.MaxDelay.Ticks));
-                if (attempt >= 10)
-                {
-                    // Bail after 10 attempts to surface persistent failure to the caller. With
-                    // the default backoff (1s base, 2.0x mult, 30s cap) this is roughly 4 minutes
-                    // of attempts; with InitialDelay=0 it's immediate up to the same cap.
-                    throw;
-                }
-            }
-        }
-    }
-
-    /// <summary>
-    ///     Reports whether the socket has been idle longer than the configured idle-disconnect
-    ///     threshold and should be proactively torn down + reconnected before the next transaction.
-    ///     Always <see langword="false"/> when no idle-disconnect timeout is configured.
-    /// </summary>
-    /// <returns><see langword="true"/> when the idle threshold has been exceeded.</returns>
-    public bool ShouldReconnectForIdle() =>
-        _idleDisconnect.HasValue && DateTime.UtcNow - _lastSuccessUtc > _idleDisconnect.Value;
-
-    /// <summary>Records that a transaction just succeeded, resetting the idle-disconnect clock.</summary>
-    public void MarkSuccess() => _lastSuccessUtc = DateTime.UtcNow;
-
-    /// <summary>Tears down the current socket + stream, leaving the lifecycle ready to reconnect.</summary>
-    /// <returns>A task representing the asynchronous teardown operation.</returns>
-    public async Task TearDownAsync()
-    {
-        try { if (_stream is not null) await _stream.DisposeAsync().ConfigureAwait(false); }
-        catch { /* best-effort */ }
-        _stream = null;
-        try { _client?.Dispose(); } catch { }
-        _client = null;
-    }
-
-    /// <summary>
-    ///     Enable SO_KEEPALIVE with aggressive probe timing. DL205/DL260 doesn't send keepalives
-    ///     itself; having the OS probe the socket every ~30s lets the driver notice a dead PLC
-    ///     or broken NAT path long before the default 2-hour Windows idle timeout fires.
-    ///     Non-fatal if the underlying OS rejects the option (some older Linux / container
-    ///     sandboxes don't expose the fine-grained timing levers — the driver still works,
-    ///     application-level probe still detects problems).
-    /// </summary>
-    private static void EnableKeepAlive(TcpClient client, ModbusKeepAliveOptions opts)
-    {
-        if (!opts.Enabled) return;
-        try
-        {
-            client.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.KeepAlive, true);
-            // A TimeSpan < 1s previously truncated to 0 via the int cast,
-            // which Windows / Linux interpret as "use the default" — silently defeating the
-            // configured keep-alive timing. Round up to at least 1 second so a sub-second
-            // configuration still produces a real keep-alive cadence. Negative values are
-            // also clamped to 1 to avoid surfacing as OS errors.
-            client.Client.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveTime,
-                ClampToWholeSeconds(opts.Time));
-            client.Client.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveInterval,
-                ClampToWholeSeconds(opts.Interval));
-            client.Client.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveRetryCount, opts.RetryCount);
-        }
-        catch { /* best-effort; older OSes may not expose the granular knobs */ }
-    }
-
-    /// <summary>
-    ///     Cast a <see cref="TimeSpan"/> to a whole number of seconds with a
-    ///     minimum of 1 — protects callers from the int-cast truncation that turned 500 ms
-    ///     keep-alive timing into "use the default" on most OSes.
-    /// </summary>
-    /// <param name="ts">The timespan to clamp to whole seconds.</param>
-    /// <returns>The clamped duration expressed as a whole number of seconds, never less than 1.</returns>
-    internal static int ClampToWholeSeconds(TimeSpan ts)
-    {
-        var seconds = (int)Math.Ceiling(ts.TotalSeconds);
-        return seconds < 1 ? 1 : seconds;
-    }
-
-    /// <summary>
-    ///     Distinguish socket-layer failures (eligible for reconnect-and-retry) from
-    ///     protocol-layer failures (must propagate — retrying the same PDU won't help if the
-    ///     PLC just returned exception 02 Illegal Data Address).
-    /// </summary>
-    /// <param name="ex">The exception to classify.</param>
-    /// <returns><see langword="true"/> when the exception is a socket-level failure.</returns>
-    internal static bool IsSocketLevelFailure(Exception ex) =>
-        ex is EndOfStreamException
-        || ex is IOException
-        || ex is SocketException
-        || ex is ObjectDisposedException;
-
-    /// <summary>Asynchronously disposes the underlying socket + stream resources.</summary>
-    /// <returns>A task that represents the asynchronous operation.</returns>
-    public async ValueTask DisposeAsync()
-    {
-        try
-        {
-            if (_stream is not null) await _stream.DisposeAsync().ConfigureAwait(false);
-        }
-        catch { /* best-effort */ }
-        _client?.Dispose();
-    }
-}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus/ModbusTcpTransport.cs

@@ -3,19 +3,13 @@ using System.Net.Sockets;
 namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus;
 
 /// <summary>
-///     Concrete Modbus TCP transport. Wraps a single socket (owned by <see cref="ModbusSocketLifecycle"/>)
-///     and serializes requests so at most one transaction is in-flight at a time — Modbus servers
-///     typically support concurrent transactions, but the single-flight model keeps the wire trace
+///     Concrete Modbus TCP transport. Wraps a single <see cref="TcpClient"/> and serializes
+///     requests so at most one transaction is in-flight at a time — Modbus servers typically
+///     support concurrent transactions, but the single-flight model keeps the wire trace
 ///     easy to diagnose and avoids interleaved-response correlation bugs.
 /// </summary>
 /// <remarks>
 ///     <para>
-///         Owns the MBAP framing (<see cref="SendOnceAsync"/>: 7-byte header + transaction-id
-///         pairing) and composes <see cref="ModbusSocketLifecycle"/> for the connect / reconnect /
-///         keep-alive / idle-disconnect machinery — the same lifecycle the RTU-over-TCP transport
-///         reuses with different framing.
-///     </para>
-///     <para>
 ///         Survives mid-transaction socket drops: when a send/read fails with a socket-level
 ///         error (<see cref="IOException"/>, <see cref="SocketException"/>, <see cref="EndOfStreamException"/>)
 ///         the transport disposes the dead socket, reconnects, and retries the PDU exactly
@@ -32,11 +26,19 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus;
 /// </remarks>
 public sealed class ModbusTcpTransport : IModbusTransport
 {
-    private readonly ModbusSocketLifecycle _life;
+    private readonly string _host;
+    private readonly int _port;
     private readonly TimeSpan _timeout;
+    private readonly bool _autoReconnect;
+    private readonly ModbusKeepAliveOptions _keepAlive;
+    private readonly TimeSpan? _idleDisconnect;
+    private readonly ModbusReconnectOptions _reconnect;
     private readonly SemaphoreSlim _gate = new(1, 1);
+    private TcpClient? _client;
+    private NetworkStream? _stream;
     private ushort _nextTx;
     private bool _disposed;
+    private DateTime _lastSuccessUtc = DateTime.UtcNow;
 
     /// <summary>Initializes a new instance of the <see cref="ModbusTcpTransport"/> class.</summary>
     /// <param name="host">The host address or hostname of the Modbus server.</param>
@@ -52,18 +54,84 @@ public sealed class ModbusTcpTransport : IModbusTransport
         TimeSpan? idleDisconnect = null,
         ModbusReconnectOptions? reconnect = null)
     {
+        _host = host;
+        _port = port;
         _timeout = timeout;
-        _life = new ModbusSocketLifecycle(host, port, timeout, autoReconnect, keepAlive, idleDisconnect, reconnect);
+        _autoReconnect = autoReconnect;
+        _keepAlive = keepAlive ?? new ModbusKeepAliveOptions();
+        _idleDisconnect = idleDisconnect;
+        _reconnect = reconnect ?? new ModbusReconnectOptions();
     }
 
     /// <inheritdoc />
-    public Task ConnectAsync(CancellationToken ct) => _life.ConnectAsync(ct);
+    public async Task ConnectAsync(CancellationToken ct)
+    {
+        // Resolve the host explicitly + prefer IPv4. .NET's TcpClient default-constructor is
+        // dual-stack (IPv6 first, fallback to IPv4) — but most Modbus TCP devices (PLCs and
+        // simulators like pymodbus) bind 0.0.0.0 only, so the IPv6 attempt times out and we
+        // burn the entire ConnectAsync budget before even trying IPv4. Resolving first +
+        // dialing the IPv4 address directly sidesteps that.
+        var addresses = await System.Net.Dns.GetHostAddressesAsync(_host, ct).ConfigureAwait(false);
+        var ipv4 = System.Linq.Enumerable.FirstOrDefault(addresses,
+            a => a.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork);
+        var target = ipv4 ?? (addresses.Length > 0 ? addresses[0] : System.Net.IPAddress.Loopback);
+
+        _client = new TcpClient(target.AddressFamily);
+        EnableKeepAlive(_client, _keepAlive);
+
+        using var cts = CancellationTokenSource.CreateLinkedTokenSource(ct);
+        cts.CancelAfter(_timeout);
+        await _client.ConnectAsync(target, _port, cts.Token).ConfigureAwait(false);
+        _stream = _client.GetStream();
+        _lastSuccessUtc = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    ///     Enable SO_KEEPALIVE with aggressive probe timing. DL205/DL260 doesn't send keepalives
+    ///     itself; having the OS probe the socket every ~30s lets the driver notice a dead PLC
+    ///     or broken NAT path long before the default 2-hour Windows idle timeout fires.
+    ///     Non-fatal if the underlying OS rejects the option (some older Linux / container
+    ///     sandboxes don't expose the fine-grained timing levers — the driver still works,
+    ///     application-level probe still detects problems).
+    /// </summary>
+    private static void EnableKeepAlive(TcpClient client, ModbusKeepAliveOptions opts)
+    {
+        if (!opts.Enabled) return;
+        try
+        {
+            client.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.KeepAlive, true);
+            // A TimeSpan < 1s previously truncated to 0 via the int cast,
+            // which Windows / Linux interpret as "use the default" — silently defeating the
+            // configured keep-alive timing. Round up to at least 1 second so a sub-second
+            // configuration still produces a real keep-alive cadence. Negative values are
+            // also clamped to 1 to avoid surfacing as OS errors.
+            client.Client.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveTime,
+                ClampToWholeSeconds(opts.Time));
+            client.Client.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveInterval,
+                ClampToWholeSeconds(opts.Interval));
+            client.Client.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveRetryCount, opts.RetryCount);
+        }
+        catch { /* best-effort; older OSes may not expose the granular knobs */ }
+    }
+
+    /// <summary>
+    ///     Cast a <see cref="TimeSpan"/> to a whole number of seconds with a
+    ///     minimum of 1 — protects callers from the int-cast truncation that turned 500 ms
+    ///     keep-alive timing into "use the default" on most OSes.
+    /// </summary>
+    /// <param name="ts">The timespan to clamp to whole seconds.</param>
+    /// <returns>The clamped duration expressed as a whole number of seconds, never less than 1.</returns>
+    internal static int ClampToWholeSeconds(TimeSpan ts)
+    {
+        var seconds = (int)Math.Ceiling(ts.TotalSeconds);
+        return seconds < 1 ? 1 : seconds;
+    }
 
     /// <inheritdoc />
     public async Task<byte[]> SendAsync(byte unitId, byte[] pdu, CancellationToken ct)
     {
         if (_disposed) throw new ObjectDisposedException(nameof(ModbusTcpTransport));
-        if (_life.Stream is null) throw new InvalidOperationException("Transport not connected");
+        if (_stream is null) throw new InvalidOperationException("Transport not connected");
 
         await _gate.WaitAsync(ct).ConfigureAwait(false);
         try
@@ -72,27 +140,27 @@ public sealed class ModbusTcpTransport : IModbusTransport
             // threshold, tear it down + reconnect before this PDU lands. Defends against silent
             // NAT / firewall reaping where the socket looks alive locally but the upstream side
             // dropped it minutes ago.
-            if (_life.ShouldReconnectForIdle())
+            if (_idleDisconnect.HasValue && DateTime.UtcNow - _lastSuccessUtc > _idleDisconnect.Value)
             {
-                await _life.TearDownAsync().ConfigureAwait(false);
-                await _life.ConnectWithBackoffAsync(ct).ConfigureAwait(false);
+                await TearDownAsync().ConfigureAwait(false);
+                await ConnectWithBackoffAsync(ct).ConfigureAwait(false);
             }
 
             try
             {
                 var result = await SendOnceAsync(unitId, pdu, ct).ConfigureAwait(false);
-                _life.MarkSuccess();
+                _lastSuccessUtc = DateTime.UtcNow;
                 return result;
             }
-            catch (Exception ex) when (_life.AutoReconnect && ModbusSocketLifecycle.IsSocketLevelFailure(ex))
+            catch (Exception ex) when (_autoReconnect && IsSocketLevelFailure(ex))
             {
                 // Mid-transaction drop: tear down the dead socket, reconnect (with backoff if
                 // configured), resend. Single retry — if it fails again, let it propagate so
                 // health/status reflect reality.
-                await _life.TearDownAsync().ConfigureAwait(false);
-                await _life.ConnectWithBackoffAsync(ct).ConfigureAwait(false);
+                await TearDownAsync().ConfigureAwait(false);
+                await ConnectWithBackoffAsync(ct).ConfigureAwait(false);
                 var result = await SendOnceAsync(unitId, pdu, ct).ConfigureAwait(false);
-                _life.MarkSuccess();
+                _lastSuccessUtc = DateTime.UtcNow;
                 return result;
             }
         }
@@ -102,6 +170,43 @@ public sealed class ModbusTcpTransport : IModbusTransport
         }
     }
 
+    /// <summary>
+    ///     Connect attempt with the configured geometric backoff. The first attempt fires after
+    ///     <see cref="ModbusReconnectOptions.InitialDelay"/> (default zero — immediate); each
+    ///     subsequent attempt sleeps for the previous delay times <c>BackoffMultiplier</c>,
+    ///     capped at <c>MaxDelay</c>. Caller's cancellation token aborts the loop.
+    /// </summary>
+    private async Task ConnectWithBackoffAsync(CancellationToken ct)
+    {
+        var delay = _reconnect.InitialDelay;
+        var attempt = 0;
+        while (true)
+        {
+            if (delay > TimeSpan.Zero)
+                await Task.Delay(delay, ct).ConfigureAwait(false);
+            try
+            {
+                await ConnectAsync(ct).ConfigureAwait(false);
+                return;
+            }
+            catch (Exception ex) when (IsSocketLevelFailure(ex) && _autoReconnect)
+            {
+                attempt++;
+                // Geometric growth, capped. Use Math.Min on ticks so we don't overflow with
+                // pathological multipliers / long deployments.
+                var nextTicks = (long)(Math.Max(delay.Ticks, TimeSpan.FromMilliseconds(100).Ticks) * _reconnect.BackoffMultiplier);
+                delay = TimeSpan.FromTicks(Math.Min(nextTicks, _reconnect.MaxDelay.Ticks));
+                if (attempt >= 10)
+                {
+                    // Bail after 10 attempts to surface persistent failure to the caller. With
+                    // the default backoff (1s base, 2.0x mult, 30s cap) this is roughly 4 minutes
+                    // of attempts; with InitialDelay=0 it's immediate up to the same cap.
+                    throw;
+                }
+            }
+        }
+    }
+
     /// <summary>
     ///     Executes exactly one Modbus transaction on the current socket.
     /// </summary>
@@ -125,8 +230,7 @@ public sealed class ModbusTcpTransport : IModbusTransport
     /// </remarks>
     private async Task<byte[]> SendOnceAsync(byte unitId, byte[] pdu, CancellationToken ct)
     {
-        var stream = _life.Stream;
-        if (stream is null) throw new InvalidOperationException("Transport not connected");
+        if (_stream is null) throw new InvalidOperationException("Transport not connected");
         var txId = ++_nextTx;
 
         // MBAP: [TxId(2)][Proto=0(2)][Length(2)][UnitId(1)] + PDU
@@ -144,11 +248,11 @@ public sealed class ModbusTcpTransport : IModbusTransport
         cts.CancelAfter(_timeout);
         try
         {
-            await stream.WriteAsync(adu.AsMemory(), cts.Token).ConfigureAwait(false);
-            await stream.FlushAsync(cts.Token).ConfigureAwait(false);
+            await _stream.WriteAsync(adu.AsMemory(), cts.Token).ConfigureAwait(false);
+            await _stream.FlushAsync(cts.Token).ConfigureAwait(false);
 
             var header = new byte[7];
-            await ReadExactlyAsync(stream, header, cts.Token).ConfigureAwait(false);
+            await ReadExactlyAsync(_stream, header, cts.Token).ConfigureAwait(false);
             var respTxId = (ushort)((header[0] << 8) | header[1]);
             if (respTxId != txId)
                 throw new ModbusTransportDesyncException(
@@ -160,7 +264,7 @@ public sealed class ModbusTcpTransport : IModbusTransport
                     ModbusTransportDesyncException.DesyncReason.TruncatedFrame,
                     $"Modbus response length too small: {respLen}");
             var respPdu = new byte[respLen - 1];
-            await ReadExactlyAsync(stream, respPdu, cts.Token).ConfigureAwait(false);
+            await ReadExactlyAsync(_stream, respPdu, cts.Token).ConfigureAwait(false);
 
             // Exception PDU: function code has high bit set. This is a well-formed protocol-level
             // error — the socket is still coherent, so it MUST propagate without teardown.
@@ -176,7 +280,7 @@ public sealed class ModbusTcpTransport : IModbusTransport
         catch (ModbusTransportDesyncException)
         {
             // Framing violation: the socket is desynchronized — never reuse it.
-            await _life.TearDownAsync().ConfigureAwait(false);
+            await TearDownAsync().ConfigureAwait(false);
             throw;
         }
         catch (OperationCanceledException) when (!ct.IsCancellationRequested)
@@ -184,13 +288,33 @@ public sealed class ModbusTcpTransport : IModbusTransport
             // Per-op timeout fired (NOT the caller). The response is unknown / may still land later
             // and corrupt the next read — tear the socket down and normalize as a desync so the
             // reconnect retry / status mapping engages.
-            await _life.TearDownAsync().ConfigureAwait(false);
+            await TearDownAsync().ConfigureAwait(false);
             throw new ModbusTransportDesyncException(
                 ModbusTransportDesyncException.DesyncReason.Timeout,
                 $"Modbus per-op response timeout after {_timeout.TotalMilliseconds:0}ms");
         }
     }
 
+    /// <summary>
+    ///     Distinguish socket-layer failures (eligible for reconnect-and-retry) from
+    ///     protocol-layer failures (must propagate — retrying the same PDU won't help if the
+    ///     PLC just returned exception 02 Illegal Data Address).
+    /// </summary>
+    private static bool IsSocketLevelFailure(Exception ex) =>
+        ex is EndOfStreamException
+        || ex is IOException
+        || ex is SocketException
+        || ex is ObjectDisposedException;
+
+    private async Task TearDownAsync()
+    {
+        try { if (_stream is not null) await _stream.DisposeAsync().ConfigureAwait(false); }
+        catch { /* best-effort */ }
+        _stream = null;
+        try { _client?.Dispose(); } catch { }
+        _client = null;
+    }
+
     private static async Task ReadExactlyAsync(Stream s, byte[] buf, CancellationToken ct)
     {
         var read = 0;
@@ -208,7 +332,12 @@ public sealed class ModbusTcpTransport : IModbusTransport
     {
         if (_disposed) return;
         _disposed = true;
-        await _life.DisposeAsync().ConfigureAwait(false);
+        try
+        {
+            if (_stream is not null) await _stream.DisposeAsync().ConfigureAwait(false);
+        }
+        catch { /* best-effort */ }
+        _client?.Dispose();
         _gate.Dispose();
     }
 }

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus/ModbusTransportDesyncException.cs

@@ -1,10 +1,9 @@
 namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus;
 
 /// <summary>
-///     Raised when a Modbus transaction leaves the single-flight socket in an unknown /
+///     Raised when a Modbus TCP transaction leaves the single-flight socket in an unknown /
 ///     desynchronized state — a per-op response timeout, or a framing violation (transaction-id
-///     mismatch, truncated frame, RTU CRC mismatch, or RTU unit-address mismatch). Unlike a Modbus
-///     <em>exception PDU</em> (a well-formed
+///     mismatch or truncated MBAP length). Unlike a Modbus <em>exception PDU</em> (a well-formed
 ///     protocol-level error where the socket is still coherent and the request must simply
 ///     propagate), a desync means bytes may still be in flight or half-read, so the socket is
 ///     unusable and MUST be torn down before this is thrown.
@@ -28,20 +27,8 @@ public sealed class ModbusTransportDesyncException : IOException
         /// <summary>The response MBAP transaction id did not match the request's.</summary>
         TxIdMismatch,
 
-        /// <summary>
-        ///     The frame ended before it was complete — the MBAP length field was below the mandatory
-        ///     minimum (TCP), or the stream closed mid-frame while reading a length-less RTU frame.
-        /// </summary>
+        /// <summary>The response MBAP length field was below the mandatory minimum (truncated frame).</summary>
         TruncatedFrame,
-
-        /// <summary>The RTU frame's trailing CRC-16 did not validate over the received bytes.</summary>
-        CrcMismatch,
-
-        /// <summary>
-        ///     A CRC-valid RTU frame carried a slave/unit address other than the one addressed — on an
-        ///     RS-485 multi-drop bus, a reply from the wrong slave.
-        /// </summary>
-        UnitMismatch,
     }
 
     /// <summary>Gets the reason the socket was classified desynchronized.</summary>

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus/ModbusTransportFactory.cs

@@ -1,43 +0,0 @@
-namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus;
-
-/// <summary>
-///     Single mapping point from <see cref="ModbusDriverOptions"/> to the concrete
-///     <see cref="IModbusTransport"/> its <see cref="ModbusDriverOptions.Transport"/> selects.
-///     Consumed by both <see cref="ModbusDriver"/>'s default transport-factory closure and the
-///     AdminUI Test-Connect probe, so the <see cref="ModbusTransportMode"/> switch lives in
-///     exactly one place.
-/// </summary>
-public static class ModbusTransportFactory
-{
-    /// <summary>
-    ///     Builds the transport <paramref name="options"/>.<see cref="ModbusDriverOptions.Transport"/>
-    ///     selects, threading every shared connection setting (Host/Port/Timeout/AutoReconnect/
-    ///     KeepAlive/IdleDisconnectTimeout/Reconnect) through to whichever concrete transport is built.
-    /// </summary>
-    /// <param name="options">Driver configuration options.</param>
-    /// <returns>A <see cref="ModbusRtuOverTcpTransport"/> when <see cref="ModbusTransportMode.RtuOverTcp"/>
-    /// is selected; a <see cref="ModbusTcpTransport"/> when <see cref="ModbusTransportMode.Tcp"/> is selected.</returns>
-    /// <exception cref="ArgumentOutOfRangeException">
-    /// <paramref name="options"/>.<see cref="ModbusDriverOptions.Transport"/> is not a recognized
-    /// <see cref="ModbusTransportMode"/> member — fail loudly rather than silently falling back to TCP/MBAP.
-    /// </exception>
-    public static IModbusTransport Create(ModbusDriverOptions options)
-    {
-        ArgumentNullException.ThrowIfNull(options);
-        return options.Transport switch
-        {
-            ModbusTransportMode.RtuOverTcp => new ModbusRtuOverTcpTransport(
-                options.Host, options.Port, options.Timeout, options.AutoReconnect,
-                keepAlive: options.KeepAlive,
-                idleDisconnect: options.IdleDisconnectTimeout,
-                reconnect: options.Reconnect),
-            ModbusTransportMode.Tcp => new ModbusTcpTransport(
-                options.Host, options.Port, options.Timeout, options.AutoReconnect,
-                keepAlive: options.KeepAlive,
-                idleDisconnect: options.IdleDisconnectTimeout,
-                reconnect: options.Reconnect),
-            _ => throw new ArgumentOutOfRangeException(
-                nameof(options), options.Transport, "Unknown Modbus transport mode."),
-        };
-    }
-}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser/SqlBrowseNodeId.cs

@@ -0,0 +1,201 @@
+using System.Text;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser;
+
+/// <summary>Which catalog level a browse <c>NodeId</c> addresses.</summary>
+public enum SqlBrowseNodeKind
+{
+    /// <summary>A schema — the browse root level.</summary>
+    Schema,
+
+    /// <summary>A table or view inside a schema.</summary>
+    Table,
+
+    /// <summary>A column of a table or view — the terminal (leaf) level.</summary>
+    Column,
+}
+
+/// <summary>A decoded browse <c>NodeId</c>.</summary>
+/// <param name="Kind">Which catalog level this reference addresses.</param>
+/// <param name="Schema">The schema name. Always present.</param>
+/// <param name="Table">The table/view name; <c>null</c> for <see cref="SqlBrowseNodeKind.Schema"/>.</param>
+/// <param name="Column">The column name; <c>null</c> unless <see cref="SqlBrowseNodeKind.Column"/>.</param>
+public readonly record struct SqlBrowseNodeRef(
+    SqlBrowseNodeKind Kind,
+    string Schema,
+    string? Table,
+    string? Column);
+
+/// <summary>
+///     Codec for the browse <c>NodeId</c>s the SQL schema browser hands the picker, and the picker hands back
+///     on expand / attribute fetch / column commit.
+///     <para><b>Why not the design's literal <c>schema.table|column</c>.</b> That sketch assumes <c>.</c> and
+///     <c>|</c> cannot occur inside an identifier. They can: SQL Server permits essentially any character
+///     inside a quoted (bracketed) identifier, and <c>SqlServerDialect.QuoteIdentifier</c> deliberately passes
+///     both through — only <c>]</c>, control characters and Unicode format characters are special to it. So
+///     <c>main.a.b|c</c> decodes equally as schema <c>main</c> + table <c>a.b</c> and as schema <c>main.a</c>
+///     + table <c>b</c>, and a table named <c>x|y</c> loses its second half entirely. That is not a cosmetic
+///     bug: the operator clicks one column, the NodeId decodes to a different one, and the tag they author
+///     polls the wrong data forever — silently, because the wrong column usually exists and usually reads.
+///     </para>
+///     <para><b>The encoding.</b> <c>&lt;kind&gt;:&lt;part&gt;[|&lt;part&gt;…]</c>, where <c>kind</c> is one
+///     of <c>schema</c> / <c>table</c> / <c>column</c> and every part is escaped so no identifier character
+///     can be mistaken for structure: a literal <c>\</c> becomes <c>\\</c> and a literal <c>|</c> becomes
+///     <c>\|</c>. <c>.</c> needs no escape at all — it is not structural here — so the common case stays
+///     readable (<c>column:dbo|TagValues|num_value</c>). The kind prefix carries the arity, so decoding never
+///     has to guess how many parts a name "should" have; a part count that disagrees with the kind is
+///     rejected rather than truncated or padded.</para>
+///     <para><b>Public on purpose</b>, unlike the session itself: the AdminUI picker body decodes a committed
+///     column NodeId back into schema/table/column to compose the tag's <c>TagConfig</c>. Encode and decode
+///     must stay in one place — a second, hand-rolled split in the picker is exactly the defect this type
+///     exists to prevent.</para>
+/// </summary>
+public static class SqlBrowseNodeId
+{
+    private const char Separator = '|';
+    private const char Escape = '\\';
+    private const char KindTerminator = ':';
+
+    private const string SchemaKind = "schema";
+    private const string TableKind = "table";
+    private const string ColumnKind = "column";
+
+    /// <summary>Encodes a schema-level NodeId.</summary>
+    /// <param name="schema">The schema name, exactly as the catalog reports it.</param>
+    /// <returns>The encoded NodeId.</returns>
+    /// <exception cref="ArgumentException"><paramref name="schema"/> is null, empty or whitespace.</exception>
+    public static string ForSchema(string schema) => Encode(SchemaKind, schema);
+
+    /// <summary>Encodes a table-level NodeId.</summary>
+    /// <param name="schema">The schema name, exactly as the catalog reports it.</param>
+    /// <param name="table">The table or view name, exactly as the catalog reports it.</param>
+    /// <returns>The encoded NodeId.</returns>
+    /// <exception cref="ArgumentException">Either name is null, empty or whitespace.</exception>
+    public static string ForTable(string schema, string table) => Encode(TableKind, schema, table);
+
+    /// <summary>Encodes a column-level (leaf) NodeId.</summary>
+    /// <param name="schema">The schema name, exactly as the catalog reports it.</param>
+    /// <param name="table">The table or view name, exactly as the catalog reports it.</param>
+    /// <param name="column">The column name, exactly as the catalog reports it.</param>
+    /// <returns>The encoded NodeId.</returns>
+    /// <exception cref="ArgumentException">Any name is null, empty or whitespace.</exception>
+    public static string ForColumn(string schema, string table, string column) =>
+        Encode(ColumnKind, schema, table, column);
+
+    /// <summary>Attempts to decode a NodeId.</summary>
+    /// <param name="nodeId">The NodeId to decode.</param>
+    /// <param name="reference">The decoded reference on success; <c>default</c> otherwise.</param>
+    /// <returns><c>true</c> when <paramref name="nodeId"/> is a well-formed SQL browse NodeId.</returns>
+    public static bool TryParse(string? nodeId, out SqlBrowseNodeRef reference)
+    {
+        reference = default;
+        if (string.IsNullOrWhiteSpace(nodeId)) return false;
+
+        var terminator = nodeId.IndexOf(KindTerminator, StringComparison.Ordinal);
+        if (terminator <= 0) return false;
+
+        var kind = nodeId[..terminator];
+        if (!TrySplit(nodeId[(terminator + 1)..], out var parts)) return false;
+        if (parts.Exists(string.IsNullOrWhiteSpace)) return false;
+
+        switch (kind)
+        {
+            case SchemaKind when parts.Count == 1:
+                reference = new SqlBrowseNodeRef(SqlBrowseNodeKind.Schema, parts[0], null, null);
+                return true;
+            case TableKind when parts.Count == 2:
+                reference = new SqlBrowseNodeRef(SqlBrowseNodeKind.Table, parts[0], parts[1], null);
+                return true;
+            case ColumnKind when parts.Count == 3:
+                reference = new SqlBrowseNodeRef(SqlBrowseNodeKind.Column, parts[0], parts[1], parts[2]);
+                return true;
+            default:
+                return false;
+        }
+    }
+
+    /// <summary>
+    ///     Decodes a NodeId, throwing when it is malformed.
+    ///     <para>The message deliberately does <b>not</b> echo the offending value: a NodeId can carry an
+    ///     arbitrary authored identifier and this text reaches the AdminUI's inline error and the log.</para>
+    /// </summary>
+    /// <param name="nodeId">The NodeId to decode.</param>
+    /// <returns>The decoded reference.</returns>
+    /// <exception cref="ArgumentException">The value is not a well-formed SQL browse NodeId.</exception>
+    public static SqlBrowseNodeRef Parse(string? nodeId)
+    {
+        if (TryParse(nodeId, out var reference)) return reference;
+        throw new ArgumentException(
+            "Not a SQL schema-browse node. Expected 'schema:<schema>', 'table:<schema>|<table>' or " +
+            "'column:<schema>|<table>|<column>'. Re-open the browser and expand from the root.",
+            nameof(nodeId));
+    }
+
+    private static string Encode(string kind, params string[] parts)
+    {
+        var builder = new StringBuilder(kind.Length + 1 + (parts.Length * 16));
+        builder.Append(kind).Append(KindTerminator);
+        for (var i = 0; i < parts.Length; i++)
+        {
+            if (string.IsNullOrWhiteSpace(parts[i]))
+            {
+                throw new ArgumentException(
+                    "A SQL catalog name in a browse node may not be empty or whitespace.", nameof(parts));
+            }
+
+            if (i > 0) builder.Append(Separator);
+            AppendEscaped(builder, parts[i]);
+        }
+
+        return builder.ToString();
+    }
+
+    private static void AppendEscaped(StringBuilder builder, string part)
+    {
+        foreach (var ch in part)
+        {
+            if (ch is Separator or Escape) builder.Append(Escape);
+            builder.Append(ch);
+        }
+    }
+
+    /// <summary>
+    ///     Splits an encoded payload on <b>unescaped</b> separators, unescaping as it goes. Returns
+    ///     <c>false</c> on a dangling trailing escape, which cannot be produced by
+    ///     <see cref="AppendEscaped"/> and therefore means the value was hand-made or truncated.
+    /// </summary>
+    private static bool TrySplit(string payload, out List<string> parts)
+    {
+        parts = [];
+        var current = new StringBuilder(payload.Length);
+        var escaped = false;
+
+        foreach (var ch in payload)
+        {
+            if (escaped)
+            {
+                current.Append(ch);
+                escaped = false;
+                continue;
+            }
+
+            switch (ch)
+            {
+                case Escape:
+                    escaped = true;
+                    break;
+                case Separator:
+                    parts.Add(current.ToString());
+                    current.Clear();
+                    break;
+                default:
+                    current.Append(ch);
+                    break;
+            }
+        }
+
+        if (escaped) return false;
+        parts.Add(current.ToString());
+        return true;
+    }
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser/SqlBrowseSession.cs

@@ -0,0 +1,304 @@
+using System.Data;
+using System.Data.Common;
+using ZB.MOM.WW.OtOpcUa.Commons.Browsing;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser;
+
+/// <summary>
+///     Live, one-level-per-call walk of a relational catalog: schemas → tables/views → columns, with the
+///     column's mapped <c>DriverDataType</c> in the attribute side-panel (design §4.1, mirroring Galaxy's
+///     two-stage object-then-attribute pick). Created by <c>SqlDriverBrowser</c> on picker open and owned by
+///     the AdminUI's <c>BrowseSessionRegistry</c>, whose TTL reaper disposes idle sessions.
+///     <para><b>Every level is the dialect's catalog SQL</b> (<see cref="ISqlDialect.ListSchemasSql"/> /
+///     <see cref="ISqlDialect.ListTablesSql"/> / <see cref="ISqlDialect.ListColumnsSql"/>) — nothing here
+///     knows what <c>INFORMATION_SCHEMA</c> is, because Oracle and SQLite do not have it. The catalog SQL is
+///     read verbatim and <c>@schema</c> / <c>@table</c> are <b>bound as parameters</b>; no name from a NodeId
+///     is ever concatenated into a command text, so a hostile or merely awkward catalog name is inert here.
+///     <see cref="ISqlDialect.QuoteIdentifier"/> is deliberately <em>not</em> used on this path — the browse
+///     never needs an identifier in text.</para>
+///     <para><b>Connection ownership: this session owns the connection it is handed and closes it on
+///     <see cref="DisposeAsync"/>.</b> It does not open one, and it never re-opens a closed one. The handoff
+///     is the same as the Galaxy and OPC UA client sessions': the browser owns the connection only until
+///     construction succeeds, after which the registry-held session is the sole thing with a lifetime hook —
+///     if the session did not close it, nothing would, and every reaped picker would leak a pooled
+///     connection.</para>
+///     <para><b>No timeout of its own.</b> The AdminUI already bounds each root/expand/attributes call with a
+///     20-second linked CTS (<c>BrowserSessionService.PerCallTimeout</c>); this session's job is simply to
+///     honour the token it is handed, into the gate wait and into every ADO.NET call. Adding a second
+///     independent deadline here would only produce two competing, differently-worded failures.</para>
+/// </summary>
+internal sealed class SqlBrowseSession : IBrowseSession
+{
+    /// <summary>Column alias every dialect's <see cref="ISqlDialect.ListSchemasSql"/> projects.</summary>
+    private const string SchemaColumn = "TABLE_SCHEMA";
+
+    /// <summary>Column alias every dialect's <see cref="ISqlDialect.ListTablesSql"/> projects.</summary>
+    private const string TableNameColumn = "TABLE_NAME";
+
+    /// <summary>Column alias carrying <c>BASE TABLE</c> / <c>VIEW</c>.</summary>
+    private const string TableTypeColumn = "TABLE_TYPE";
+
+    /// <summary>Column alias every dialect's <see cref="ISqlDialect.ListColumnsSql"/> projects.</summary>
+    private const string ColumnNameColumn = "COLUMN_NAME";
+
+    /// <summary>Column alias carrying the SQL type family name.</summary>
+    private const string DataTypeColumn = "DATA_TYPE";
+
+    /// <summary>The <c>TABLE_TYPE</c> value marking a view rather than a base table.</summary>
+    private const string ViewTableType = "VIEW";
+
+    /// <summary>
+    ///     The security class every browsed column reports. The <c>Sql</c> driver is read-only in v1
+    ///     (design §4.3), so there is nothing else a picked column could be.
+    /// </summary>
+    private const string ReadOnlySecurityClass = "ViewOnly";
+
+    private readonly DbConnection _connection;
+    private readonly ISqlDialect _dialect;
+
+    /// <summary>
+    ///     Serializes catalog calls. One ADO.NET connection carries at most one active command/reader, and
+    ///     the AdminUI tree happily fires several expands at once when an operator clicks quickly.
+    /// </summary>
+    private readonly SemaphoreSlim _gate = new(1, 1);
+
+    private volatile bool _disposed;
+
+    /// <summary>Constructs a session over an already-open connection, which it takes ownership of.</summary>
+    /// <param name="connection">The open connection to browse. Closed by <see cref="DisposeAsync"/>.</param>
+    /// <param name="dialect">The dialect supplying the catalog SQL and the column-type map.</param>
+    internal SqlBrowseSession(DbConnection connection, ISqlDialect dialect)
+    {
+        _connection = connection ?? throw new ArgumentNullException(nameof(connection));
+        _dialect = dialect ?? throw new ArgumentNullException(nameof(dialect));
+    }
+
+    /// <inheritdoc />
+    public Guid Token { get; } = Guid.NewGuid();
+
+    /// <inheritdoc />
+    public DateTime LastUsedUtc { get; private set; } = DateTime.UtcNow;
+
+    /// <inheritdoc />
+    public async Task<IReadOnlyList<BrowseNode>> RootAsync(CancellationToken cancellationToken)
+    {
+        var schemas = await QueryAsync(
+            _dialect.ListSchemasSql,
+            static _ => { },
+            static reader => ReadString(reader, SchemaColumn),
+            cancellationToken).ConfigureAwait(false);
+
+        var nodes = new List<BrowseNode>(schemas.Count);
+        foreach (var schema in schemas)
+        {
+            if (string.IsNullOrWhiteSpace(schema)) continue;
+            nodes.Add(new BrowseNode(
+                NodeId: SqlBrowseNodeId.ForSchema(schema),
+                DisplayName: schema,
+                Kind: BrowseNodeKind.Folder,
+                HasChildrenHint: true));
+        }
+
+        return nodes;
+    }
+
+    /// <inheritdoc />
+    /// <exception cref="ArgumentException"><paramref name="nodeId"/> is not a SQL schema-browse node.</exception>
+    public async Task<IReadOnlyList<BrowseNode>> ExpandAsync(string nodeId, CancellationToken cancellationToken)
+    {
+        ObjectDisposedException.ThrowIf(_disposed, this);
+        var reference = SqlBrowseNodeId.Parse(nodeId);
+        switch (reference.Kind)
+        {
+            case SqlBrowseNodeKind.Schema:
+                return await ExpandSchemaAsync(reference.Schema, cancellationToken).ConfigureAwait(false);
+            case SqlBrowseNodeKind.Table:
+                return await ExpandTableAsync(reference.Schema, reference.Table!, cancellationToken)
+                    .ConfigureAwait(false);
+            default:
+                // A column is terminal. Expanding one is a UI no-op, never an error — the tree may ask before
+                // it has re-read the node's Kind.
+                LastUsedUtc = DateTime.UtcNow;
+                return Array.Empty<BrowseNode>();
+        }
+    }
+
+    /// <inheritdoc />
+    /// <exception cref="ArgumentException"><paramref name="nodeId"/> is not a SQL schema-browse node.</exception>
+    public async Task<IReadOnlyList<AttributeInfo>> AttributesAsync(
+        string nodeId, CancellationToken cancellationToken)
+    {
+        ObjectDisposedException.ThrowIf(_disposed, this);
+        var reference = SqlBrowseNodeId.Parse(nodeId);
+        if (reference.Kind != SqlBrowseNodeKind.Column)
+        {
+            // Schemas and tables have no side-panel — same shape as the OPC UA client browser, whose tree is
+            // uniform and returns empty for every node.
+            LastUsedUtc = DateTime.UtcNow;
+            return Array.Empty<AttributeInfo>();
+        }
+
+        var columns = await ReadColumnsAsync(
+            reference.Schema, reference.Table!, cancellationToken).ConfigureAwait(false);
+
+        // Ordinal: a column NodeId is only ever minted from this same catalog output, so its case is the
+        // catalog's own. A case-insensitive match would pick the wrong column on a case-sensitive collation
+        // that legitimately carries both "Value" and "value".
+        foreach (var column in columns)
+        {
+            if (!string.Equals(column.Name, reference.Column, StringComparison.Ordinal)) continue;
+            return
+            [
+                new AttributeInfo(
+                    Name: column.Name,
+                    DriverDataType: _dialect.MapColumnType(column.DataType).ToString(),
+                    IsArray: false,
+                    SecurityClass: ReadOnlySecurityClass),
+            ];
+        }
+
+        // The column is gone (dropped since the expand, or the NodeId was hand-made). An empty side-panel is
+        // the honest answer; the picker simply has nothing to prefill.
+        return Array.Empty<AttributeInfo>();
+    }
+
+    /// <summary>
+    ///     Idempotently closes the owned connection and the gate. Errors are swallowed: the registry's reaper
+    ///     may be racing a server-side disconnect, and a failed close must never surface in the AdminUI.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    public async ValueTask DisposeAsync()
+    {
+        if (_disposed) return;
+        _disposed = true;
+
+        try { await _connection.DisposeAsync().ConfigureAwait(false); }
+        catch { /* best-effort: the connection may already be broken or closed. */ }
+
+        try { _gate.Dispose(); }
+        catch { /* best-effort: a concurrent second dispose already tore it down. */ }
+    }
+
+    private async Task<IReadOnlyList<BrowseNode>> ExpandSchemaAsync(string schema, CancellationToken ct)
+    {
+        var rows = await QueryAsync(
+            _dialect.ListTablesSql,
+            command => Bind(command, "@schema", schema),
+            static reader => (
+                Name: ReadString(reader, TableNameColumn),
+                Type: ReadOptionalString(reader, TableTypeColumn)),
+            ct).ConfigureAwait(false);
+
+        var nodes = new List<BrowseNode>(rows.Count);
+        foreach (var (name, type) in rows)
+        {
+            if (string.IsNullOrWhiteSpace(name)) continue;
+            var isView = string.Equals(type, ViewTableType, StringComparison.OrdinalIgnoreCase);
+            nodes.Add(new BrowseNode(
+                NodeId: SqlBrowseNodeId.ForTable(schema, name),
+                // The label is decorated, never the NodeId — a view and a table of the same name in the same
+                // schema cannot exist, so the suffix is presentation only.
+                DisplayName: isView ? $"{name} (view)" : name,
+                Kind: BrowseNodeKind.Folder,
+                HasChildrenHint: true));
+        }
+
+        return nodes;
+    }
+
+    private async Task<IReadOnlyList<BrowseNode>> ExpandTableAsync(
+        string schema, string table, CancellationToken ct)
+    {
+        var columns = await ReadColumnsAsync(schema, table, ct).ConfigureAwait(false);
+
+        var nodes = new List<BrowseNode>(columns.Count);
+        foreach (var column in columns)
+        {
+            if (string.IsNullOrWhiteSpace(column.Name)) continue;
+            nodes.Add(new BrowseNode(
+                NodeId: SqlBrowseNodeId.ForColumn(schema, table, column.Name),
+                DisplayName: column.Name,
+                Kind: BrowseNodeKind.Leaf,
+                HasChildrenHint: false));
+        }
+
+        return nodes;
+    }
+
+    /// <summary>
+    ///     Reads one table's columns. A table that no longer exists (or never did) yields an empty list rather
+    ///     than an error: the catalog answering "no rows" is indistinguishable from a genuinely column-less
+    ///     relation, and neither is a reason to fail an operator's click.
+    /// </summary>
+    private Task<List<(string Name, string DataType)>> ReadColumnsAsync(
+        string schema, string table, CancellationToken ct) =>
+        QueryAsync(
+            _dialect.ListColumnsSql,
+            command =>
+            {
+                Bind(command, "@schema", schema);
+                Bind(command, "@table", table);
+            },
+            static reader => (
+                Name: ReadString(reader, ColumnNameColumn),
+                DataType: ReadOptionalString(reader, DataTypeColumn) ?? string.Empty),
+            ct);
+
+    /// <summary>
+    ///     Runs one catalog query under the gate and projects every row. The disposed check happens
+    ///     <em>inside</em> the gate wait so a dispose racing an in-flight call cannot be missed, and
+    ///     <see cref="LastUsedUtc"/> only advances on a call that actually completed.
+    /// </summary>
+    private async Task<List<T>> QueryAsync<T>(
+        string sql,
+        Action<DbCommand> bind,
+        Func<DbDataReader, T> project,
+        CancellationToken cancellationToken)
+    {
+        ObjectDisposedException.ThrowIf(_disposed, this);
+        await _gate.WaitAsync(cancellationToken).ConfigureAwait(false);
+        try
+        {
+            ObjectDisposedException.ThrowIf(_disposed, this);
+
+            var results = new List<T>();
+            await using var command = _connection.CreateCommand();
+            command.CommandText = sql;
+            bind(command);
+
+            await using var reader = await command
+                .ExecuteReaderAsync(CommandBehavior.SingleResult, cancellationToken).ConfigureAwait(false);
+            while (await reader.ReadAsync(cancellationToken).ConfigureAwait(false))
+                results.Add(project(reader));
+
+            LastUsedUtc = DateTime.UtcNow;
+            return results;
+        }
+        finally
+        {
+            // A dispose that raced this call has already disposed the gate; releasing it then is harmless to
+            // ignore and must not mask the real result.
+            try { _gate.Release(); }
+            catch (ObjectDisposedException) { }
+        }
+    }
+
+    /// <summary>Binds one catalog-query parameter. The only way a name reaches the database.</summary>
+    private static void Bind(DbCommand command, string name, string value)
+    {
+        var parameter = command.CreateParameter();
+        parameter.ParameterName = name;
+        parameter.DbType = DbType.String;
+        parameter.Value = value;
+        command.Parameters.Add(parameter);
+    }
+
+    private static string ReadString(DbDataReader reader, string columnName) =>
+        ReadOptionalString(reader, columnName) ?? string.Empty;
+
+    private static string? ReadOptionalString(DbDataReader reader, string columnName)
+    {
+        var ordinal = reader.GetOrdinal(columnName);
+        return reader.IsDBNull(ordinal) ? null : reader.GetValue(ordinal)?.ToString();
+    }
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser/SqlDriverBrowser.cs

@@ -0,0 +1,401 @@
+using System.Data.Common;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Commons.Browsing;
+using ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser;
+
+/// <summary>
+///     Opens a <b>transient</b> database connection from form-supplied JSON for the AdminUI schema picker,
+///     and hands it to a <see cref="SqlBrowseSession"/>. The AdminUI's <c>BrowseSessionRegistry</c> (its idle
+///     TTL reaper included) owns the returned session unchanged — nothing about the SQL browse needs a
+///     registry of its own.
+///     <para><b>Two ways to name the database, and only one of them is persisted.</b>
+///     <c>connectionStringRef</c> is the deployed form: a name resolved <em>in the AdminUI process</em> from
+///     the environment as <c>Sql__ConnectionStrings__&lt;ref&gt;</c> (design §4.4), so a deployed artifact
+///     never carries credentials. <c>connectionString</c> is an ad-hoc, <b>session-only</b> literal an
+///     operator may paste to browse a database that has no ref yet; it is used for this one connection and
+///     then forgotten — there is deliberately no cached-config field on this type, and nothing writes it
+///     anywhere.</para>
+///     <para><b>Precedence: a pasted literal wins over a ref</b>, and the ref is then not even read. The
+///     literal cannot arrive from a persisted blob — <see cref="SqlDriverConfigDto"/> has no such property, so
+///     the driver factory would drop it — which makes its presence proof that an operator typed it just now.
+///     A config carrying both logs a warning (naming the shadowed <em>ref</em>, never any connection text) so
+///     the override is visible rather than silent.</para>
+///     <para><b>Credential hygiene is the point of this type.</b> A connection string is a secret. It is
+///     passed to the provider and to nothing else: it never reaches a log line, an exception message, a field,
+///     or anything persisted. Because ADO.NET providers are free to echo connection-string content in their
+///     own errors, every failure on the open path goes through <see cref="Sanitize"/> before it leaves this
+///     class.</para>
+/// </summary>
+public sealed class SqlDriverBrowser : IDriverBrowser
+{
+    /// <summary>
+    ///     Prefix of the environment variable a <c>connectionStringRef</c> resolves through — the
+    ///     double-underscore form .NET configuration uses for the <c>Sql:ConnectionStrings:&lt;ref&gt;</c>
+    ///     key path.
+    /// </summary>
+    public const string ConnectionStringEnvironmentPrefix = "Sql__ConnectionStrings__";
+
+    /// <summary>
+    ///     Hard cap on the connect phase, layered on the caller's token. The AdminUI already bounds each
+    ///     browse call at 20 s; this only stops a pathological provider-side connect from outliving the
+    ///     picker entirely.
+    /// </summary>
+    private static readonly TimeSpan ConnectBudget = TimeSpan.FromSeconds(30);
+
+    /// <summary>
+    ///     Connection-string keys whose <em>values</em> are redacted out of any provider error text. The
+    ///     whole connection string is redacted unconditionally; these are the parts that could survive as a
+    ///     fragment. Server / database names are deliberately <b>not</b> redacted — "server X was not found"
+    ///     is the diagnostic the operator needs, and a hostname is not a credential.
+    /// </summary>
+    private static readonly string[] CredentialKeys =
+    [
+        "password", "pwd", "user id", "uid", "user", "username", "accesstoken", "access token",
+    ];
+
+    /// <summary>
+    ///     Kept deliberately identical in shape to the driver factory's options (design §5.1): enum-valued
+    ///     knobs are authored as their <em>names</em>, so the browser parses a given <c>DriverConfig</c> blob
+    ///     exactly as the runtime factory does. <see cref="JsonStringEnumConverter"/> also accepts ordinals,
+    ///     so a numeric config still binds.
+    /// </summary>
+    private static readonly JsonSerializerOptions JsonOpts = new()
+    {
+        UnmappedMemberHandling = JsonUnmappedMemberHandling.Skip,
+        PropertyNameCaseInsensitive = true,
+        Converters = { new JsonStringEnumConverter() },
+    };
+
+    private readonly Func<SqlProvider, ISqlDialect?> _dialectSelector;
+    private readonly Func<string, string?> _environmentReader;
+    private readonly ILogger<SqlDriverBrowser> _logger;
+
+    /// <summary>Creates a browser. Every dependency has a production default, so DI may construct it bare.</summary>
+    /// <param name="dialectSelector">
+    ///     Maps an authored <see cref="SqlProvider"/> onto the dialect that browses it, or <see langword="null"/>
+    ///     for a provider this build does not carry. Defaults to <see cref="DefaultDialectSelector"/>
+    ///     (SqlServer only, in v1). A constructor parameter rather than a test hatch: it is also how a P2
+    ///     provider gets added without touching this class.
+    /// </param>
+    /// <param name="environmentReader">
+    ///     Reads one environment variable. Defaults to <see cref="Environment.GetEnvironmentVariable(string)"/>.
+    ///     Injectable because environment variables are process-global, and a test that sets one races every
+    ///     other test in the assembly.
+    /// </param>
+    /// <param name="logger">Optional; defaults to <see cref="NullLogger{T}"/>.</param>
+    public SqlDriverBrowser(
+        Func<SqlProvider, ISqlDialect?>? dialectSelector = null,
+        Func<string, string?>? environmentReader = null,
+        ILogger<SqlDriverBrowser>? logger = null)
+    {
+        _dialectSelector = dialectSelector ?? DefaultDialectSelector;
+        _environmentReader = environmentReader ?? Environment.GetEnvironmentVariable;
+        _logger = logger ?? NullLogger<SqlDriverBrowser>.Instance;
+    }
+
+    /// <inheritdoc />
+    /// <remarks>
+    ///     Sourced from <see cref="SqlDriver.DriverTypeName"/>, the driver's interim local constant, rather
+    ///     than from <c>DriverTypeNames</c> — the shared constant set is added by the driver-factory task,
+    ///     because adding a member there reddens <c>DriverTypeNamesGuardTests</c> until a factory is
+    ///     registered against it. Repointing that one constant repoints this too.
+    /// </remarks>
+    public string DriverType => SqlDriver.DriverTypeName;
+
+    /// <summary>The environment variable a <c>connectionStringRef</c> resolves through.</summary>
+    /// <param name="connectionStringRef">The authored reference name.</param>
+    /// <returns>The full environment-variable name, e.g. <c>Sql__ConnectionStrings__MesStaging</c>.</returns>
+    public static string EnvironmentVariableFor(string connectionStringRef) =>
+        ConnectionStringEnvironmentPrefix + connectionStringRef;
+
+    /// <summary>
+    ///     The providers this build can browse. v1 constructs SQL Server only; every other
+    ///     <see cref="SqlProvider"/> member is a reserved name, so it resolves to <see langword="null"/> and
+    ///     the caller reports it as unavailable rather than crashing on a null dialect.
+    /// </summary>
+    /// <param name="provider">The authored provider.</param>
+    /// <returns>The dialect, or <see langword="null"/> when this build does not carry the provider.</returns>
+    public static ISqlDialect? DefaultDialectSelector(SqlProvider provider) =>
+        provider == SqlProvider.SqlServer ? new SqlServerDialect() : null;
+
+    /// <inheritdoc />
+    /// <exception cref="InvalidOperationException">
+    ///     The configuration is absent / malformed, names a provider this build does not carry, names neither
+    ///     a <c>connectionStringRef</c> nor a literal, resolves a ref that is not set in the environment, or
+    ///     the connection could not be opened.
+    /// </exception>
+    public async Task<IBrowseSession> OpenAsync(string configJson, CancellationToken cancellationToken)
+    {
+        if (string.IsNullOrWhiteSpace(configJson))
+        {
+            throw new InvalidOperationException(
+                "The Sql browser requires a driver configuration; none was supplied.");
+        }
+
+        var literal = ReadPastedConnectionString(configJson);
+        var config = Deserialize(configJson, literal);
+
+        // Provider first: "this build cannot browse Postgres" is true regardless of how the database is
+        // named, and answering it before touching the environment keeps the two failures from masking.
+        var dialect = _dialectSelector(config.Provider)
+            ?? throw new InvalidOperationException(
+                $"Sql provider '{config.Provider}' is not available in this build; v1 browses "
+                + $"'{SqlProvider.SqlServer}' only.");
+
+        var reference = config.ConnectionStringRef;
+        var connectionString = ResolveConnectionString(literal, reference);
+
+        _logger.LogInformation(
+            "AdminUI Sql browse session opening (provider {Provider}, connection from {Source})",
+            config.Provider,
+            DescribeSource(literal, reference));
+
+        return await OpenSessionAsync(dialect, connectionString, cancellationToken).ConfigureAwait(false);
+    }
+
+    /// <summary>
+    ///     Opens one transient connection and hands ownership to the session. <b>The session closes the
+    ///     connection on its own disposal</b>, so the only disposal this method owns is the failure path —
+    ///     disposing on success would double-close and leave the picker with a dead session.
+    /// </summary>
+    private static async Task<IBrowseSession> OpenSessionAsync(
+        ISqlDialect dialect, string connectionString, CancellationToken cancellationToken)
+    {
+        var connection = dialect.Factory.CreateConnection()
+            ?? throw new InvalidOperationException(
+                $"The ADO.NET provider for '{dialect.Provider}' returned no connection object.");
+
+        try
+        {
+            connection.ConnectionString = connectionString;
+
+            using var connectCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
+            connectCts.CancelAfter(ConnectBudget);
+            await connection.OpenAsync(connectCts.Token).ConfigureAwait(false);
+
+            return new SqlBrowseSession(connection, dialect);
+        }
+        catch (Exception ex)
+        {
+            try { await connection.DisposeAsync().ConfigureAwait(false); }
+            catch { /* best-effort: the original failure is the useful one. */ }
+
+            if (ex is OperationCanceledException) throw;
+            throw Sanitize(ex, connectionString);
+        }
+    }
+
+    /// <summary>
+    ///     Picks the connection string, literal first. A blank literal is treated as absent (an untouched
+    ///     form field), never as an empty connection string.
+    /// </summary>
+    private string ResolveConnectionString(string? literal, string? reference)
+    {
+        if (!string.IsNullOrWhiteSpace(literal))
+        {
+            if (!string.IsNullOrWhiteSpace(reference))
+            {
+                _logger.LogWarning(
+                    "Sql browse: a pasted connection string was supplied alongside connectionStringRef "
+                    + "'{Ref}'. The pasted value wins for this session only and is not persisted.",
+                    reference);
+            }
+
+            return literal;
+        }
+
+        if (string.IsNullOrWhiteSpace(reference))
+        {
+            throw new InvalidOperationException(
+                "The Sql browser needs a database to browse: set 'connectionStringRef' to a name resolved "
+                + $"from the environment as '{ConnectionStringEnvironmentPrefix}<ref>', or paste a "
+                + "connection string into 'connectionString' for an ad-hoc browse.");
+        }
+
+        var variable = EnvironmentVariableFor(reference);
+        var resolved = _environmentReader(variable);
+        if (string.IsNullOrWhiteSpace(resolved))
+        {
+            // Name the exact variable: "the ref did not resolve" is unactionable, and the operator's next
+            // move is to set this one name on the AdminUI host.
+            throw new InvalidOperationException(
+                $"connectionStringRef '{reference}' does not resolve: environment variable "
+                + $"'{variable}' is not set on the AdminUI host. Set it there (the AdminUI resolves browse "
+                + "connection strings in its own process), or paste a connection string for an ad-hoc "
+                + "browse.");
+        }
+
+        return resolved;
+    }
+
+    /// <summary>How the connection string was obtained, for the log. Carries no connection text.</summary>
+    private static string DescribeSource(string? literal, string? reference) =>
+        !string.IsNullOrWhiteSpace(literal)
+            ? "a pasted literal (session-only, not persisted)"
+            : $"connectionStringRef '{reference}'";
+
+    /// <summary>
+    ///     Pulls the ad-hoc <c>connectionString</c> literal out of the raw JSON. It is read here rather than
+    ///     off the DTO because <see cref="SqlDriverConfigDto"/> deliberately has no such property — the
+    ///     persisted contract must not be able to carry a credential — and the DTO's
+    ///     <see cref="JsonUnmappedMemberHandling.Skip"/> would silently drop it.
+    /// </summary>
+    /// <returns>The literal, or <see langword="null"/> when absent, blank, or not a JSON string.</returns>
+    private static string? ReadPastedConnectionString(string configJson)
+    {
+        using var document = ParseDocument(configJson);
+        if (document.RootElement.ValueKind != JsonValueKind.Object)
+        {
+            throw new InvalidOperationException(
+                "The Sql browser's driver configuration must be a JSON object.");
+        }
+
+        foreach (var property in document.RootElement.EnumerateObject())
+        {
+            if (!string.Equals(property.Name, "connectionString", StringComparison.OrdinalIgnoreCase))
+                continue;
+
+            if (property.Value.ValueKind != JsonValueKind.String) return null;
+            var value = property.Value.GetString();
+            return string.IsNullOrWhiteSpace(value) ? null : value;
+        }
+
+        return null;
+    }
+
+    /// <summary>
+    ///     Parses the raw configuration. The <see cref="JsonException"/> is <b>not</b> attached or echoed:
+    ///     at this point nothing has been extracted, so there is no known secret to redact against, and the
+    ///     malformed text may itself be a pasted connection string.
+    /// </summary>
+    private static JsonDocument ParseDocument(string configJson)
+    {
+        try
+        {
+            return JsonDocument.Parse(configJson);
+        }
+        catch (JsonException)
+        {
+            throw new InvalidOperationException(
+                "The Sql browser's driver configuration is not valid JSON. (The parser's message is "
+                + "withheld because the malformed text may carry a connection string.)");
+        }
+    }
+
+    /// <summary>
+    ///     Binds the typed configuration. A bind failure (e.g. an unknown <c>provider</c> name) is reported
+    ///     with the parser's own message redacted against the literal, which is known by now.
+    /// </summary>
+    private static SqlDriverConfigDto Deserialize(string configJson, string? literal)
+    {
+        try
+        {
+            return JsonSerializer.Deserialize<SqlDriverConfigDto>(configJson, JsonOpts)
+                ?? throw new InvalidOperationException(
+                    "The Sql browser's driver configuration deserialized to null.");
+        }
+        catch (JsonException ex)
+        {
+            throw new InvalidOperationException(
+                "The Sql browser's driver configuration could not be bound: "
+                + Redact(ex.Message, CollectSecrets(literal)));
+        }
+    }
+
+    /// <summary>
+    ///     Turns a provider-side open failure into an exception that cannot carry the connection string.
+    ///     <para><b>Live-probed, not assumed.</b> <c>Microsoft.Data.SqlClient</c> and
+    ///     <c>Microsoft.Data.Sqlite</c> keep connection-string <em>values</em> out of their
+    ///     <c>SqlException</c>/<c>SqliteException</c> text (a failed connect says "the server was not found",
+    ///     never what it was handed). Their connection-string <b>parser</b> is the exception: it reports an
+    ///     unrecognised keyword by quoting it, and a value carrying an unquoted <c>;</c> — legal inside a
+    ///     password, which ADO.NET expects you to quote — splits, so the tail of the password is parsed as a
+    ///     keyword and echoed verbatim. <c>Password=Sup3r;SecretTail</c> yields
+    ///     <c>Keyword not supported: 'secrettail;connect timeout'.</c> — the credential, in the message,
+    ///     lower-cased and therefore invisible to a naive ordinal search for the value.</para>
+    ///     <para>So the parser's message (an <see cref="ArgumentException"/>) is <b>never</b> surfaced. Every
+    ///     other failure is additionally passed through the substring redactor as a backstop, and when that
+    ///     fires anywhere in the exception <em>chain</em> the inner exception is dropped too — keeping it
+    ///     would re-expose through <c>ToString()</c> exactly what the message just removed.</para>
+    /// </summary>
+    private static InvalidOperationException Sanitize(Exception ex, string connectionString)
+    {
+        if (ex is ArgumentException)
+        {
+            return new InvalidOperationException(
+                "The Sql browser could not open a connection: the connection string is malformed, or "
+                + "carries a keyword this provider does not support. (The provider's own message is "
+                + "withheld because it quotes connection-string text verbatim; check for an unquoted ';' "
+                + "or '=' inside a value such as the password.)");
+        }
+
+        var secrets = CollectSecrets(connectionString);
+        var leaked = ContainsAny(ex.ToString(), secrets);
+        var reason = Redact(ex.Message, secrets);
+
+        var message = leaked
+            ? "The Sql browser could not open a connection: " + reason
+                + " (the provider's error echoed the connection string, so it was redacted and the inner "
+                + "exception withheld)"
+            : "The Sql browser could not open a connection: " + reason;
+
+        return new InvalidOperationException(message, leaked ? null : ex);
+    }
+
+    /// <summary>
+    ///     The substrings that must never leave this class: the whole connection string, and the values of
+    ///     its credential-bearing keys (which could surface on their own).
+    /// </summary>
+    private static List<string> CollectSecrets(string? connectionString)
+    {
+        var secrets = new List<string>();
+        if (string.IsNullOrWhiteSpace(connectionString)) return secrets;
+
+        secrets.Add(connectionString);
+
+        try
+        {
+            var builder = new DbConnectionStringBuilder { ConnectionString = connectionString };
+            foreach (var key in CredentialKeys)
+            {
+                if (!builder.TryGetValue(key, out var value)) continue;
+                var text = value?.ToString();
+                if (!string.IsNullOrWhiteSpace(text)) secrets.Add(text);
+            }
+        }
+        catch (ArgumentException)
+        {
+            // A malformed connection string has no parseable parts; the whole-string entry still stands.
+        }
+
+        // Longest first, so redacting a short credential value cannot chop a longer secret into
+        // unredactable halves.
+        secrets.Sort(static (left, right) => right.Length.CompareTo(left.Length));
+        return secrets;
+    }
+
+    private static bool ContainsAny(string text, List<string> secrets)
+    {
+        foreach (var secret in secrets)
+        {
+            if (text.Contains(secret, StringComparison.OrdinalIgnoreCase)) return true;
+        }
+
+        return false;
+    }
+
+    private static string Redact(string text, List<string> secrets)
+    {
+        foreach (var secret in secrets)
+        {
+            text = text.Replace(secret, "[redacted]", StringComparison.OrdinalIgnoreCase);
+        }
+
+        return text;
+    }
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser/ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser.csproj

@@ -0,0 +1,27 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+    <GenerateDocumentationFile>true</GenerateDocumentationFile>
+    <NoWarn>$(NoWarn);CS1591</NoWarn>
+    <RootNamespace>ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser</RootNamespace>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\..\Core\ZB.MOM.WW.OtOpcUa.Commons\ZB.MOM.WW.OtOpcUa.Commons.csproj" />
+    <ProjectReference Include="..\ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts\ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts.csproj" />
+    <!-- Deliberate deviation from the OpcUaClient.Browser house style (which refs only its
+         Contracts project and owns its own transport packages): the dialect's catalog SQL
+         (ISqlDialect / SqlServerDialect, in Driver.Sql) *is* the browse engine, so it must be
+         shared here rather than duplicated. Microsoft.Data.SqlClient comes in transitively.
+         The resulting transitive SqlClient reference on AdminUI is reviewed and accepted —
+         AdminUI already carries SqlClient for ConfigDb. See design doc §2, table row for this
+         project: docs/plans/2026-07-15-sql-poll-driver-design.md. Do not "fix" this to a
+         Contracts-only reference without reading that context first. -->
+    <ProjectReference Include="..\ZB.MOM.WW.OtOpcUa.Driver.Sql\ZB.MOM.WW.OtOpcUa.Driver.Sql.csproj" />
+  </ItemGroup>
+  <ItemGroup>
+    <InternalsVisibleTo Include="ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser.Tests"/>
+  </ItemGroup>
+</Project>

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts/SqlDriverConfigDto.cs

@@ -0,0 +1,64 @@
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
+
+/// <summary>
+///     The <c>DriverConfig</c> blob shape for a <c>Sql</c> driver instance (design §5.1). Deserialised by the
+///     driver factory, which applies the documented defaults for every absent (null) field and maps the result
+///     onto the driver's typed options.
+///     <para><b>No connection string lives here.</b> Only <see cref="ConnectionStringRef"/> — a name resolved at
+///     Initialize from the environment / secret store (e.g. <c>Sql__ConnectionStrings__MesStaging</c>) — so a
+///     deployed artifact never carries database credentials.</para>
+///     <para>Enum-valued fields are enum-typed (not strings) so a <c>JsonStringEnumConverter</c> round-trips
+///     their <em>names</em> rather than their ordinals. The converter is applied by the factory's
+///     <c>JsonSerializerOptions</c> (Task 9), not by an attribute on this DTO — mirroring the driver
+///     enum-serialization trap that bit the AdminUI driver pages.</para>
+/// </summary>
+public sealed class SqlDriverConfigDto
+{
+    /// <summary>Which ADO.NET provider/dialect backs this instance. Defaults to <see cref="SqlProvider.SqlServer"/> — the only provider v1 constructs.</summary>
+    public SqlProvider Provider { get; init; } = SqlProvider.SqlServer;
+
+    /// <summary>
+    ///     Name of the connection string to resolve from the environment / secret store at Initialize —
+    ///     <b>never</b> the connection string itself.
+    /// </summary>
+    public string? ConnectionStringRef { get; init; }
+
+    /// <summary>Poll interval applied to groups that do not carry their own. Absent ⇒ the factory default.</summary>
+    public TimeSpan? DefaultPollInterval { get; init; }
+
+    /// <summary>
+    ///     Per-query wall-clock deadline enforced client-side (a breach surfaces <c>BadTimeout</c>). Must be
+    ///     greater than <see cref="CommandTimeout"/>, which is only the server-side backstop (design §8.3).
+    /// </summary>
+    public TimeSpan? OperationTimeout { get; init; }
+
+    /// <summary>ADO.NET <c>CommandTimeout</c> backstop (seconds granularity server-side).</summary>
+    public TimeSpan? CommandTimeout { get; init; }
+
+    /// <summary>Cap on concurrently executing group queries — the connection-pool guard.</summary>
+    public int? MaxConcurrentGroups { get; init; }
+
+    /// <summary>When <see langword="true"/>, a NULL cell publishes Bad rather than the default Uncertain.</summary>
+    public bool? NullIsBad { get; init; }
+
+    /// <summary>
+    ///     Master write kill-switch. <b>v1 is read-only and this field is inert</b> — the driver does not
+    ///     implement <c>IWritable</c>, so no value here can produce a write. The factory <em>warns</em> when it
+    ///     is authored <see langword="true"/> rather than failing the driver, since the flag cannot do harm but
+    ///     an operator who believes writes are enabled can.
+    /// </summary>
+    public bool? AllowWrites { get; init; }
+
+    /// <summary>
+    ///     The authored raw tags the deploy artifact delivers for this driver instance — RawPath identity plus
+    ///     the driver <c>TagConfig</c> blob, the same shape every other driver receives. The factory copies
+    ///     these onto the driver's options and the driver maps each through
+    ///     <see cref="SqlEquipmentTagParser.TryParse"/> at Initialize.
+    ///     <para>A SQL source has no tag-discovery protocol, so this list is the complete set of tags the
+    ///     instance serves — an absent or empty list is a driver with nothing to poll, not a driver that will
+    ///     find its tags later.</para>
+    /// </summary>
+    public List<RawTagEntry>? RawTags { get; init; }
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts/SqlEquipmentTagParser.cs

@@ -0,0 +1,131 @@
+using System.Text.Json;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
+
+/// <summary>
+///     Pure mapper from an authored raw tag's <c>TagConfig</c> JSON (design §5.2 / §5.3) to a
+///     <see cref="SqlTagDefinition"/>, mirroring <c>ModbusTagDefinitionFactory.FromTagConfig</c>. The blob is
+///     recognised by a leading <c>{</c> plus a <c>"driver":"Sql"</c> marker or a <c>"model"</c> discriminator;
+///     the <c>model</c> and <c>type</c> enums are read with
+///     <see cref="TagConfigJson.TryReadEnumStrict{TEnum}"/>, so a present-but-invalid (typo'd) value rejects
+///     the whole tag — the driver then surfaces <c>BadNodeIdUnknown</c> instead of silently defaulting to a
+///     different model and publishing a misleading <c>Good</c> (R2-11).
+///     <para><b>No SQL is built here.</b> The parser only captures strings; the reader binds value fields as
+///     <c>DbParameter</c>s and validates + quotes identifier fields. Tag input is never concatenated into a
+///     command text, so a hostile <c>keyValue</c> is stored — and must be stored — verbatim.</para>
+/// </summary>
+public static class SqlEquipmentTagParser
+{
+    /// <summary>
+    ///     Maps an authored <c>TagConfig</c> blob to a typed definition keyed by <paramref name="rawPath"/>.
+    ///     Returns <see langword="false"/> — never throws — for anything the driver must not serve: a
+    ///     non-object / unparseable blob, a blob belonging to another driver, a typo'd <c>model</c> or
+    ///     <c>type</c> enum, a missing model-required field, or the P3-deferred
+    ///     <see cref="SqlTagModel.Query"/> model.
+    /// </summary>
+    /// <param name="reference">The authored equipment-tag TagConfig JSON.</param>
+    /// <param name="rawPath">The tag's RawPath — becomes the definition's identity (<c>Name</c>).</param>
+    /// <param name="def">The mapped definition when this returns <see langword="true"/>.</param>
+    /// <returns><see langword="true"/> when <paramref name="reference"/> is a valid Sql tag blob.</returns>
+    public static bool TryParse(string reference, string rawPath, out SqlTagDefinition def)
+    {
+        def = null!;
+        if (string.IsNullOrWhiteSpace(reference)) return false;
+        if (reference.TrimStart().FirstOrDefault() != '{') return false;
+        try
+        {
+            using var doc = JsonDocument.Parse(reference);
+            var root = doc.RootElement;
+            if (root.ValueKind != JsonValueKind.Object) return false;
+
+            // Recognition: either the explicit driver marker or the model discriminator must be present,
+            // so another driver's TagConfig blob is not mistaken for a Sql one.
+            var driver = ReadString(root, "driver");
+            var hasModel = root.TryGetProperty("model", out _);
+            if (!hasModel && !string.Equals(driver, "Sql", StringComparison.OrdinalIgnoreCase)) return false;
+
+            // Strict enum reads: absent ⇒ the fallback, present-but-invalid ⇒ reject the tag.
+            if (!TagConfigJson.TryReadEnumStrict(root, "model", SqlTagModel.KeyValue, out var model)) return false;
+            if (!TagConfigJson.TryReadEnumStrict(root, "type", default(DriverDataType), out var type)) return false;
+            DriverDataType? declaredType =
+                root.TryGetProperty("type", out var typeEl) && typeEl.ValueKind == JsonValueKind.String
+                    ? type
+                    : null;
+
+            var table = ReadString(root, "table");
+            if (string.IsNullOrWhiteSpace(table)) return false;
+            var timestampColumn = ReadString(root, "timestampColumn");
+
+            switch (model)
+            {
+                case SqlTagModel.KeyValue:
+                {
+                    var keyColumn = ReadString(root, "keyColumn");
+                    var keyValue = ReadString(root, "keyValue");
+                    var valueColumn = ReadString(root, "valueColumn");
+                    if (string.IsNullOrWhiteSpace(keyColumn)
+                        || string.IsNullOrWhiteSpace(valueColumn)
+                        || keyValue is null)
+                        return false;
+                    def = new SqlTagDefinition(
+                        Name: rawPath, Model: model, Table: table!,
+                        KeyColumn: keyColumn, KeyValue: keyValue, ValueColumn: valueColumn,
+                        TimestampColumn: timestampColumn, DeclaredType: declaredType);
+                    return true;
+                }
+
+                case SqlTagModel.WideRow:
+                {
+                    var columnName = ReadString(root, "columnName");
+                    if (string.IsNullOrWhiteSpace(columnName)) return false;
+                    string? selectorColumn = null, selectorValue = null, topByTimestamp = null;
+                    if (root.TryGetProperty("rowSelector", out var sel) && sel.ValueKind == JsonValueKind.Object)
+                    {
+                        selectorColumn = ReadString(sel, "whereColumn");
+                        selectorValue = ReadScalar(sel, "whereValue");
+                        topByTimestamp = ReadString(sel, "topByTimestamp");
+                    }
+                    // A wide-row tag must say WHICH row it reads — either a where-pair or newest-by-timestamp.
+                    var hasWherePair = !string.IsNullOrWhiteSpace(selectorColumn) && selectorValue is not null;
+                    if (!hasWherePair && string.IsNullOrWhiteSpace(topByTimestamp)) return false;
+                    def = new SqlTagDefinition(
+                        Name: rawPath, Model: model, Table: table!,
+                        TimestampColumn: timestampColumn, ColumnName: columnName,
+                        RowSelectorColumn: hasWherePair ? selectorColumn : null,
+                        RowSelectorValue: hasWherePair ? selectorValue : null,
+                        RowSelectorTopByTimestamp: hasWherePair ? null : topByTimestamp,
+                        DeclaredType: declaredType);
+                    return true;
+                }
+
+                default:
+                    // SqlTagModel.Query is design §5.4 / P3 — deferred. Reject rather than serve a model
+                    // the runtime cannot read.
+                    return false;
+            }
+        }
+        catch (JsonException) { return false; }
+        catch (FormatException) { return false; }
+    }
+
+    /// <summary>Reads a string-valued property; null when absent or not a JSON string.</summary>
+    private static string? ReadString(JsonElement o, string name)
+        => o.TryGetProperty(name, out var e) && e.ValueKind == JsonValueKind.String ? e.GetString() : null;
+
+    /// <summary>
+    ///     Reads a scalar property as its textual form — a JSON string yields its contents, a number or
+    ///     boolean yields its raw token — so an authored <c>whereValue</c> of either shape is captured
+    ///     verbatim for later parameter binding. Null when absent or not a scalar.
+    /// </summary>
+    private static string? ReadScalar(JsonElement o, string name)
+    {
+        if (!o.TryGetProperty(name, out var e)) return null;
+        return e.ValueKind switch
+        {
+            JsonValueKind.String => e.GetString(),
+            JsonValueKind.Number or JsonValueKind.True or JsonValueKind.False => e.GetRawText(),
+            _ => null,
+        };
+    }
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts/SqlProvider.cs

@@ -0,0 +1,39 @@
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
+
+/// <summary>Which ADO.NET provider/dialect backs a Sql driver instance. v1 constructs only SqlServer.</summary>
+public enum SqlProvider
+{
+    /// <summary>Microsoft SQL Server via <c>Microsoft.Data.SqlClient</c> — the only provider v1 constructs.</summary>
+    SqlServer,
+
+    /// <summary>PostgreSQL (Npgsql) — reserved for P2; not constructed in v1.</summary>
+    Postgres,
+
+    /// <summary>MySQL / MariaDB — reserved; not constructed in v1.</summary>
+    MySql,
+
+    /// <summary>Generic ODBC — reserved for P2; not constructed in v1.</summary>
+    Odbc,
+
+    /// <summary>Oracle — reserved; not constructed in v1.</summary>
+    Oracle,
+}
+
+/// <summary>Tag→value mapping model. v1 ships KeyValue + WideRow; Query is deferred (design §5.4 / P3).</summary>
+public enum SqlTagModel
+{
+    /// <summary>
+    ///     Key-value (EAV) table: one row per tag, selected by <c>keyColumn = keyValue</c>, value read from
+    ///     <c>valueColumn</c>.
+    /// </summary>
+    KeyValue,
+
+    /// <summary>
+    ///     Wide row: one row holds many signals as columns; the tag names its <c>columnName</c> and the row is
+    ///     picked by a row selector (a <c>whereColumn</c>/<c>whereValue</c> pair, or newest-by-timestamp).
+    /// </summary>
+    WideRow,
+
+    /// <summary>Named arbitrary-SELECT query (design §5.4). <b>Deferred to P3 — not accepted by v1's parser.</b></summary>
+    Query,
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts/SqlTagDefinition.cs

@@ -0,0 +1,47 @@
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
+
+/// <summary>
+///     One SQL-backed OPC UA variable — the typed form of an authored raw tag's <c>TagConfig</c> blob
+///     (design §5.2 / §5.3), produced by <see cref="SqlEquipmentTagParser.TryParse"/>.
+///     <para><b>Every string here is captured verbatim from the authored blob and is NEVER concatenated
+///     into SQL.</b> Value-bearing fields (<see cref="KeyValue"/>, <see cref="RowSelectorValue"/>) are bound
+///     as <c>DbParameter</c>s by the reader; identifier-bearing fields (<see cref="Table"/>,
+///     <see cref="KeyColumn"/>, <see cref="ValueColumn"/>, <see cref="TimestampColumn"/>,
+///     <see cref="ColumnName"/>, <see cref="RowSelectorColumn"/>,
+///     <see cref="RowSelectorTopByTimestamp"/>) must be validated against <c>INFORMATION_SCHEMA</c> and
+///     dialect-quoted by the reader before they reach a command text. Sanitising here would corrupt
+///     legitimate values, so the parser deliberately does not.</para>
+/// </summary>
+/// <param name="Name">
+///     The tag's identity — its <b>RawPath</b>, exactly as handed to the parser. The driver's forward
+///     router keys published values on this, so it must never be derived from the blob's contents.
+/// </param>
+/// <param name="Model">Which tag→value mapping this tag uses. v1 accepts KeyValue and WideRow only.</param>
+/// <param name="Table">The table or view to read (e.g. <c>dbo.TagValues</c>).</param>
+/// <param name="KeyColumn"><see cref="SqlTagModel.KeyValue"/>: the column matched against <see cref="KeyValue"/>.</param>
+/// <param name="KeyValue"><see cref="SqlTagModel.KeyValue"/>: this tag's key — <b>bound</b>, never interpolated.</param>
+/// <param name="ValueColumn"><see cref="SqlTagModel.KeyValue"/>: the column the value is read from.</param>
+/// <param name="TimestampColumn">Optional source-timestamp column; absent ⇒ the driver stamps the poll time.</param>
+/// <param name="ColumnName"><see cref="SqlTagModel.WideRow"/>: the column this tag reads from the selected row.</param>
+/// <param name="RowSelectorColumn"><see cref="SqlTagModel.WideRow"/>: the <c>whereColumn</c> that picks the row.</param>
+/// <param name="RowSelectorValue"><see cref="SqlTagModel.WideRow"/>: the <c>whereValue</c> — <b>bound</b>, never interpolated.</param>
+/// <param name="RowSelectorTopByTimestamp"><see cref="SqlTagModel.WideRow"/>: newest-row selector — the timestamp column to order by, when no where-pair is authored.</param>
+/// <param name="DeclaredType">
+///     Optional explicit type override from the blob's <c>type</c> field. <see langword="null"/> ⇒ the
+///     driver infers the type from the result set's column metadata.
+/// </param>
+public sealed record SqlTagDefinition(
+    string Name,
+    SqlTagModel Model,
+    string Table,
+    string? KeyColumn = null,
+    string? KeyValue = null,
+    string? ValueColumn = null,
+    string? TimestampColumn = null,
+    string? ColumnName = null,
+    string? RowSelectorColumn = null,
+    string? RowSelectorValue = null,
+    string? RowSelectorTopByTimestamp = null,
+    DriverDataType? DeclaredType = null);

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts/ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+    <GenerateDocumentationFile>true</GenerateDocumentationFile>
+    <NoWarn>$(NoWarn);CS1591</NoWarn>
+    <RootNamespace>ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts</RootNamespace>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\..\Core\ZB.MOM.WW.OtOpcUa.Core.Abstractions\ZB.MOM.WW.OtOpcUa.Core.Abstractions.csproj" />
+  </ItemGroup>
+</Project>

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql/ISqlDialect.cs

@@ -0,0 +1,123 @@
+using System.Data.Common;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql;
+
+/// <summary>
+///     The provider seam (design §2.2). ADO.NET's <see cref="System.Data.Common"/> base types abstract
+///     connections, commands, parameters and readers; they do <b>not</b> abstract the three things that differ
+///     per backend — <b>identifier quoting</b>, the <b>metadata-catalog SQL</b>, and <b>row-limit syntax</b>.
+///     Those live here, so no dialect assumption leaks into the reader, the poll planner, or the schema browser.
+///     <para><b>This interface is the driver's SQL-injection boundary.</b> Every runtime <em>value</em> is
+///     bound as a <see cref="DbParameter"/> and never reaches a command text. Identifiers cannot be
+///     parameterized in SQL, so the few that must appear as text are emitted through
+///     <see cref="QuoteIdentifier"/>. Any code path that builds SQL by concatenating an authored tag field
+///     <em>without</em> going through <see cref="QuoteIdentifier"/> is a defect (design §8.1).</para>
+///     <para><b>Quoting is the backstop, not the only defence.</b> Design §8.1's catalog gate is
+///     implemented: <see cref="SqlCatalogGate"/> resolves every authored table/column against the live
+///     catalog at Initialize and <b>replaces it with the catalog's own spelling</b>, so an identifier
+///     reaching <see cref="QuoteIdentifier"/> on the poll path is a string this driver read back out of
+///     <see cref="ListSchemasSql"/> / <see cref="ListTablesSql"/> / <see cref="ListColumnsSql"/> — not
+///     operator input. An identifier that resolves to nothing rejects its tag (which then publishes
+///     <c>BadNodeIdUnknown</c>) rather than being quoted into a query against a nonexistent object.</para>
+///     <para>Public because <c>Driver.Sql.Browser</c> consumes it — the catalog SQL <em>is</em> the browse
+///     engine, so it is shared rather than duplicated. Implementations own their provider package;
+///     <b>no provider-specific type appears in this signature</b> (<see cref="Factory"/> is the abstract
+///     <see cref="DbProviderFactory"/>).</para>
+/// </summary>
+public interface ISqlDialect
+{
+    /// <summary>Which backend this dialect speaks. v1 constructs <see cref="SqlProvider.SqlServer"/> only.</summary>
+    SqlProvider Provider { get; }
+
+    /// <summary>
+    ///     The provider's factory singleton, used to create connections/commands/parameters. Deliberately the
+    ///     abstract base type so consumers never bind to a concrete provider package.
+    /// </summary>
+    DbProviderFactory Factory { get; }
+
+    /// <summary>
+    ///     Quotes <b>one</b> identifier part so it can be safely embedded in a command text, escaping the
+    ///     dialect's own quote character. Rejects anything that cannot be a real catalog identifier rather
+    ///     than emitting it.
+    ///     <para><b>One part only.</b> A multi-part name such as <c>dbo.TagValues</c> must be split by the
+    ///     caller and each part quoted separately; passing the dotted form yields a single (nonexistent)
+    ///     identifier — safe, but not what the caller meant.</para>
+    /// </summary>
+    /// <param name="ident">The bare, unquoted identifier — as returned by the catalog, not pre-quoted.</param>
+    /// <returns>The quoted identifier, ready to concatenate into a command text.</returns>
+    /// <exception cref="ArgumentException">The value cannot be a valid catalog identifier.</exception>
+    string QuoteIdentifier(string ident);
+
+    /// <summary>Cheapest statement that proves the connection is alive (<c>SELECT 1</c>; Oracle needs <c>FROM DUAL</c>).</summary>
+    string LivenessSql { get; }
+
+    /// <summary>
+    ///     The fragment that goes <b>immediately after <c>SELECT</c></b> to limit a statement to one row —
+    ///     T-SQL's <c>"TOP 1 "</c>. Empty for a dialect that spells the limit at the end of the statement (see
+    ///     <see cref="SingleRowLimitSuffix"/>).
+    ///     <para><b>Include the trailing space</b> when non-empty: the planner concatenates
+    ///     <c>"SELECT " + SingleRowLimitPrefix + columns</c> with no separator of its own, so an empty fragment
+    ///     must leave the statement byte-identical to an unlimited one.</para>
+    /// </summary>
+    /// <remarks>
+    ///     <para><b>Why a prefix/suffix pair rather than one <c>ApplyRowLimit(sql, n)</c> method.</b> The two
+    ///     spellings sit at opposite ends of the statement — SQL Server writes
+    ///     <c>SELECT TOP 1 … ORDER BY … DESC</c>, while SQLite/Postgres/MySQL write
+    ///     <c>SELECT … ORDER BY … DESC LIMIT 1</c>. A single method taking the SELECT list could only serve the
+    ///     prefix position; a single method taking the whole statement would move statement assembly out of the
+    ///     planner and into every dialect. Two fragments keep the planner the sole author of statement shape
+    ///     and let each dialect fill in the end it uses.</para>
+    ///     <para><b>Why "single row" rather than a row count.</b> The only limit v1 emits is the wide-row
+    ///     <c>topByTimestamp</c> selector's newest-row pick. Modelling an arbitrary <c>n</c> would be untested
+    ///     surface, and <c>FETCH FIRST</c>/<c>ROWNUM</c> dialects need more than a substituted number anyway.
+    ///     Widen this to a method when a feature actually needs <c>n &gt; 1</c>.</para>
+    /// </remarks>
+    string SingleRowLimitPrefix { get; }
+
+    /// <summary>
+    ///     The fragment appended to the <b>very end</b> of a statement to limit it to one row —
+    ///     <c>" LIMIT 1"</c> for SQLite/Postgres/MySQL. Empty for a dialect that limits after <c>SELECT</c>
+    ///     (see <see cref="SingleRowLimitPrefix"/>).
+    ///     <para><b>Include the leading space</b> when non-empty, for the same reason the prefix carries a
+    ///     trailing one: the planner appends it directly to the finished statement.</para>
+    ///     <para>Exactly one of the two fragments is non-empty in every dialect modelled so far, but the planner
+    ///     emits <b>both</b> unconditionally — a dialect needing both ends (or neither) is expressible without
+    ///     touching the call site.</para>
+    /// </summary>
+    string SingleRowLimitSuffix { get; }
+
+    /// <summary>Catalog query listing schemas — the browser's <c>RootAsync</c> level. Takes no parameters.</summary>
+    string ListSchemasSql { get; }
+
+    /// <summary>
+    ///     Scalar query returning the schema an <b>unqualified</b> object name resolves to for the connecting
+    ///     principal — T-SQL's <c>SELECT SCHEMA_NAME()</c>. Takes no parameters.
+    /// </summary>
+    /// <remarks>
+    ///     <para>Needed by <see cref="SqlCatalogGate"/>: a tag authored as <c>TagValues</c> rather than
+    ///     <c>dbo.TagValues</c> has to be looked up in <em>some</em> schema, and guessing <c>dbo</c> would be a
+    ///     silent lie on any estate that maps its service accounts to their own default schema. Asking the
+    ///     server is the only answer that matches how the poll query itself will resolve the name.</para>
+    ///     <para>It is a <em>query</em> rather than a name because the answer is per-connection, not per-dialect
+    ///     — the same dialect resolves differently for two different logins.</para>
+    /// </remarks>
+    string DefaultSchemaSql { get; }
+
+    /// <summary>Catalog query listing tables + views in one schema — the browser's schema-expand level. Bind <c>@schema</c>.</summary>
+    string ListTablesSql { get; }
+
+    /// <summary>Catalog query listing columns of one table — the browser's table-expand / attributes level. Bind <c>@schema</c> and <c>@table</c>.</summary>
+    string ListColumnsSql { get; }
+
+    /// <summary>
+    ///     Folds a catalog data-type family name (as <c>INFORMATION_SCHEMA.COLUMNS.DATA_TYPE</c> reports it —
+    ///     e.g. <c>nvarchar</c>, never <c>nvarchar(50)</c>) onto a <see cref="DriverDataType"/>.
+    ///     <para>Must <b>never throw</b>: a browse over a table holding one exotic column must still render.
+    ///     An unrecognised family falls back to <see cref="DriverDataType.String"/>.</para>
+    /// </summary>
+    /// <param name="sqlDataType">The bare SQL type family name; matched case-insensitively.</param>
+    /// <returns>The mapped driver data type, or <see cref="DriverDataType.String"/> when unrecognised.</returns>
+    DriverDataType MapColumnType(string sqlDataType);
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql/SqlCatalog.cs

@@ -0,0 +1,137 @@
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql;
+
+/// <summary>
+///     An immutable snapshot of the parts of a database's catalog the authored tags actually name — the
+///     allow-list design §8.1 requires identifiers to come from.
+///     <para><b>This type holds catalog strings only.</b> Every name in it was read back out of
+///     <see cref="ISqlDialect.ListSchemasSql"/> / <see cref="ISqlDialect.ListTablesSql"/> /
+///     <see cref="ISqlDialect.ListColumnsSql"/>; nothing an operator typed is ever stored here. That is what
+///     lets <see cref="SqlCatalogGate"/> hand the planner catalog spellings rather than authored ones, so the
+///     identifier text in an emitted query is a string the database gave us.</para>
+///     <para><b>Deliberately partial.</b> Only the schemas/tables the authored tags name are loaded — a
+///     driver polling three tables must not enumerate a warehouse's ten thousand. A name absent from this
+///     snapshot therefore means "not found <em>when we looked</em>", which is exactly the question the gate
+///     asks.</para>
+/// </summary>
+public sealed class SqlCatalog
+{
+    private readonly IReadOnlyList<string> _schemas;
+
+    /// <summary>Canonical schema → canonical table names in it.</summary>
+    private readonly IReadOnlyDictionary<string, IReadOnlyList<string>> _tablesBySchema;
+
+    /// <summary>Canonical <c>schema.table</c> → that relation's canonical column names.</summary>
+    private readonly IReadOnlyDictionary<string, IReadOnlyList<string>> _columnsByTable;
+
+    /// <summary>Constructs a catalog snapshot.</summary>
+    /// <param name="defaultSchema">The schema an unqualified object name resolves to for this connection.</param>
+    /// <param name="schemas">Every schema the connection can see.</param>
+    /// <param name="tablesBySchema">Canonical schema → its tables/views.</param>
+    /// <param name="columnsByTable">Canonical <c>schema.table</c> → its columns.</param>
+    internal SqlCatalog(
+        string defaultSchema,
+        IReadOnlyList<string> schemas,
+        IReadOnlyDictionary<string, IReadOnlyList<string>> tablesBySchema,
+        IReadOnlyDictionary<string, IReadOnlyList<string>> columnsByTable)
+    {
+        DefaultSchema = defaultSchema;
+        _schemas = schemas;
+        _tablesBySchema = tablesBySchema;
+        _columnsByTable = columnsByTable;
+    }
+
+    /// <summary>The schema an unqualified authored object name is resolved in.</summary>
+    public string DefaultSchema { get; }
+
+    /// <summary>Resolves an authored schema name to the catalog's own spelling.</summary>
+    /// <param name="authored">The authored schema, or null/blank for the default schema.</param>
+    /// <param name="canonical">The catalog's spelling, when resolved.</param>
+    /// <returns><see langword="true"/> when the schema exists (or the default schema is used).</returns>
+    public bool TryResolveSchema(string? authored, out string canonical)
+    {
+        if (string.IsNullOrWhiteSpace(authored))
+        {
+            canonical = DefaultSchema;
+            return true;
+        }
+
+        return TryMatch(_schemas, authored, out canonical);
+    }
+
+    /// <summary>Resolves an authored table/view name within a canonical schema.</summary>
+    /// <param name="canonicalSchema">The schema, already resolved through <see cref="TryResolveSchema"/>.</param>
+    /// <param name="authored">The authored table or view name.</param>
+    /// <param name="canonical">The catalog's spelling, when resolved.</param>
+    /// <returns><see langword="true"/> when the relation exists in that schema.</returns>
+    public bool TryResolveTable(string canonicalSchema, string authored, out string canonical)
+    {
+        canonical = string.Empty;
+        return _tablesBySchema.TryGetValue(canonicalSchema, out var tables)
+               && TryMatch(tables, authored, out canonical);
+    }
+
+    /// <summary>Resolves an authored column name within a canonical relation.</summary>
+    /// <param name="canonicalSchema">The resolved schema.</param>
+    /// <param name="canonicalTable">The resolved table or view.</param>
+    /// <param name="authored">The authored column name.</param>
+    /// <param name="canonical">The catalog's spelling, when resolved.</param>
+    /// <returns><see langword="true"/> when the column exists on that relation.</returns>
+    public bool TryResolveColumn(
+        string canonicalSchema, string canonicalTable, string authored, out string canonical)
+    {
+        canonical = string.Empty;
+        return _columnsByTable.TryGetValue(QualifiedKey(canonicalSchema, canonicalTable), out var columns)
+               && TryMatch(columns, authored, out canonical);
+    }
+
+    /// <summary>The dictionary key for a canonical relation.</summary>
+    /// <param name="schema">The canonical schema.</param>
+    /// <param name="table">The canonical table.</param>
+    /// <returns>The composite key.</returns>
+    internal static string QualifiedKey(string schema, string table) => schema + "." + table;
+
+    /// <summary>
+    ///     Matches an authored name against catalog spellings: an exact (ordinal) hit wins, otherwise a
+    ///     <b>unique</b> case-insensitive hit is accepted and its catalog spelling returned.
+    /// </summary>
+    /// <remarks>
+    ///     <para><b>Why case-insensitive at all.</b> SQL Server's default collation is case-insensitive, so
+    ///     <c>num_value</c> and <c>NUM_VALUE</c> genuinely name the same column and both work today. Matching
+    ///     ordinally would reject configurations that have always been valid — a gate that breaks working
+    ///     deployments is not defence in depth.</para>
+    ///     <para><b>Why exact-first, and why ambiguity fails.</b> On a case-<em>sensitive</em> collation a
+    ///     relation may legitimately carry both <c>Value</c> and <c>value</c>. Preferring the exact match keeps
+    ///     such a config resolving to what the operator wrote, and refusing to choose between two
+    ///     case-insensitive candidates is the only safe answer — silently picking one would publish a different
+    ///     column's data under the operator's node, which is worse than rejecting the tag.</para>
+    /// </remarks>
+    /// <param name="candidates">The catalog spellings to match against.</param>
+    /// <param name="authored">The authored name.</param>
+    /// <param name="canonical">The catalog's spelling, when matched.</param>
+    /// <returns><see langword="true"/> on an unambiguous match.</returns>
+    internal static bool TryMatch(IReadOnlyList<string> candidates, string authored, out string canonical)
+    {
+        foreach (var candidate in candidates)
+        {
+            if (!string.Equals(candidate, authored, StringComparison.Ordinal)) continue;
+            canonical = candidate;
+            return true;
+        }
+
+        canonical = string.Empty;
+        var matches = 0;
+        foreach (var candidate in candidates)
+        {
+            if (!string.Equals(candidate, authored, StringComparison.OrdinalIgnoreCase)) continue;
+            if (++matches > 1)
+            {
+                canonical = string.Empty;
+                return false;
+            }
+
+            canonical = candidate;
+        }
+
+        return matches == 1;
+    }
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql/SqlCatalogGate.cs

@@ -0,0 +1,241 @@
+using ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql;
+
+/// <summary>
+///     One tag the gate refused, and why. Carried rather than logged in place so the caller decides the log
+///     shape and the caller's tests can assert on the reason.
+/// </summary>
+/// <param name="RawPath">The rejected tag's identity — its RawPath, which is trusted structure, not blob content.</param>
+/// <param name="Field">The <see cref="SqlTagDefinition"/> field that failed (e.g. <c>ValueColumn</c>).</param>
+/// <param name="Reason">An operator-actionable explanation, safe to log.</param>
+public sealed record SqlCatalogRejection(string RawPath, string Field, string Reason);
+
+/// <summary>The outcome of applying a <see cref="SqlCatalog"/> to a set of authored tags.</summary>
+/// <param name="Accepted">
+///     The surviving definitions, <b>rewritten to catalog spellings</b>. Safe to hand to
+///     <see cref="SqlGroupPlanner"/>.
+/// </param>
+/// <param name="Rejected">Every tag the gate refused, in input order.</param>
+public sealed record SqlCatalogGateResult(
+    IReadOnlyList<SqlTagDefinition> Accepted,
+    IReadOnlyList<SqlCatalogRejection> Rejected);
+
+/// <summary>
+///     Design §8.1's identifier gate: validates every authored table/column against the live catalog
+///     <b>before</b> it can be quoted into SQL text, and replaces it with the catalog's own spelling.
+/// </summary>
+/// <remarks>
+///     <para><b>What this closes.</b> Until this existed, <see cref="ISqlDialect.QuoteIdentifier"/> was the
+///     sole defence: an identifier went from the authored <c>TagConfig</c> blob straight into a command text,
+///     bracket-quoted. The residual risk was bounded — a hostile name is quoted into one nonexistent object,
+///     the query fails after the connection opens, and the tag Bad-codes — but "bounded" is not "filtered",
+///     and the design promised a filter. With the gate in place the identifier text in an emitted query is a
+///     string this driver read back out of the catalog, so quoting is a backstop behind an allow-list rather
+///     than the whole story.</para>
+///     <para><b>Charset first, catalog second.</b> Each identifier is passed through
+///     <see cref="ISqlDialect.QuoteIdentifier"/> before it is looked up, purely for its rejection rules
+///     (control characters, Unicode format characters, over-length). That ordering is deliberate: a name that
+///     fails the charset check is rejected <em>without its value being echoed</em>, so nothing carrying a bidi
+///     override or a NUL can reach a log line through this type's rejection messages. A name that passes has
+///     been proven safe to render, which is why the catalog-miss messages can afford to name it — and they
+///     must, or an operator has no way to find the typo.</para>
+///     <para><b>Rejection is per-tag, never driver-wide.</b> A tag naming a dropped column is dropped from the
+///     driver's table, so its RawPath resolves to nothing and it publishes
+///     <see cref="SqlStatusCodes.BadNodeIdUnknown"/> — design §8.1's specified outcome — while every other tag
+///     on that database keeps polling. This mirrors the "one malformed blob must not take the whole driver
+///     down" rule the tag-table build already follows.</para>
+/// </remarks>
+public static class SqlCatalogGate
+{
+    /// <summary>
+    ///     The most name parts this gate can validate. A three-part <c>db.schema.table</c> (or a
+    ///     four-part linked-server name) addresses a catalog this connection's <c>INFORMATION_SCHEMA</c>
+    ///     cannot see, so it cannot be allow-listed.
+    /// </summary>
+    private const int MaxNameParts = 2;
+
+    /// <summary>
+    ///     Applies <paramref name="catalog"/> to <paramref name="definitions"/>, returning the accepted tags
+    ///     with catalog-spelled identifiers and the rejected ones with reasons.
+    /// </summary>
+    /// <param name="definitions">The authored definitions, as parsed from their <c>TagConfig</c> blobs.</param>
+    /// <param name="catalog">The catalog snapshot to validate against.</param>
+    /// <param name="dialect">Supplies the identifier charset rules via <see cref="ISqlDialect.QuoteIdentifier"/>.</param>
+    /// <returns>The accepted and rejected sets.</returns>
+    /// <exception cref="ArgumentNullException">A required argument is null.</exception>
+    public static SqlCatalogGateResult Apply(
+        IEnumerable<SqlTagDefinition> definitions, SqlCatalog catalog, ISqlDialect dialect)
+    {
+        ArgumentNullException.ThrowIfNull(definitions);
+        ArgumentNullException.ThrowIfNull(catalog);
+        ArgumentNullException.ThrowIfNull(dialect);
+
+        var accepted = new List<SqlTagDefinition>();
+        var rejected = new List<SqlCatalogRejection>();
+
+        foreach (var definition in definitions)
+        {
+            ArgumentNullException.ThrowIfNull(definition);
+            if (TryCanonicalize(definition, catalog, dialect, out var canonical, out var rejection))
+                accepted.Add(canonical!);
+            else
+                rejected.Add(rejection!);
+        }
+
+        return new SqlCatalogGateResult(accepted, rejected);
+    }
+
+    /// <summary>Resolves one definition's identifiers, or explains the first failure.</summary>
+    private static bool TryCanonicalize(
+        SqlTagDefinition definition,
+        SqlCatalog catalog,
+        ISqlDialect dialect,
+        out SqlTagDefinition? canonical,
+        out SqlCatalogRejection? rejection)
+    {
+        canonical = null;
+        rejection = null;
+
+        if (!TryResolveRelation(definition, catalog, dialect, out var schema, out var table, out rejection))
+            return false;
+
+        // Every identifier-bearing field, paired with its name for the rejection message. A field the tag's
+        // model does not use is null and simply skipped — the planner enforces which are required.
+        var resolved = new Dictionary<string, string?>(StringComparer.Ordinal);
+        foreach (var (field, authored) in new (string Field, string? Authored)[]
+                 {
+                     (nameof(SqlTagDefinition.KeyColumn), definition.KeyColumn),
+                     (nameof(SqlTagDefinition.ValueColumn), definition.ValueColumn),
+                     (nameof(SqlTagDefinition.TimestampColumn), definition.TimestampColumn),
+                     (nameof(SqlTagDefinition.ColumnName), definition.ColumnName),
+                     (nameof(SqlTagDefinition.RowSelectorColumn), definition.RowSelectorColumn),
+                     (nameof(SqlTagDefinition.RowSelectorTopByTimestamp), definition.RowSelectorTopByTimestamp),
+                 })
+        {
+            if (string.IsNullOrWhiteSpace(authored))
+            {
+                resolved[field] = authored;
+                continue;
+            }
+
+            if (!IsRenderableIdentifier(authored, dialect))
+            {
+                rejection = new SqlCatalogRejection(definition.Name, field,
+                    $"the authored {field} is not a usable identifier (it is over-long, or contains control " +
+                    "or Unicode format characters); the value is withheld from this message because it " +
+                    "cannot be safely rendered");
+                return false;
+            }
+
+            if (!catalog.TryResolveColumn(schema, table, authored, out var column))
+            {
+                rejection = new SqlCatalogRejection(definition.Name, field,
+                    $"column '{authored}' does not exist on '{schema}.{table}' (or matches more than one " +
+                    "column under a case-sensitive collation)");
+                return false;
+            }
+
+            resolved[field] = column;
+        }
+
+        canonical = definition with
+        {
+            Table = SqlCatalog.QualifiedKey(schema, table),
+            KeyColumn = resolved[nameof(SqlTagDefinition.KeyColumn)],
+            ValueColumn = resolved[nameof(SqlTagDefinition.ValueColumn)],
+            TimestampColumn = resolved[nameof(SqlTagDefinition.TimestampColumn)],
+            ColumnName = resolved[nameof(SqlTagDefinition.ColumnName)],
+            RowSelectorColumn = resolved[nameof(SqlTagDefinition.RowSelectorColumn)],
+            RowSelectorTopByTimestamp = resolved[nameof(SqlTagDefinition.RowSelectorTopByTimestamp)],
+        };
+        return true;
+    }
+
+    /// <summary>Splits and resolves the authored <c>table</c> to a canonical schema + relation.</summary>
+    private static bool TryResolveRelation(
+        SqlTagDefinition definition,
+        SqlCatalog catalog,
+        ISqlDialect dialect,
+        out string schema,
+        out string table,
+        out SqlCatalogRejection? rejection)
+    {
+        schema = string.Empty;
+        table = string.Empty;
+        rejection = null;
+        const string Field = nameof(SqlTagDefinition.Table);
+
+        if (string.IsNullOrWhiteSpace(definition.Table))
+        {
+            rejection = new SqlCatalogRejection(definition.Name, Field,
+                "the tag has no 'table'; author the table or view to read");
+            return false;
+        }
+
+        var parts = definition.Table.Split('.');
+        if (parts.Length > MaxNameParts)
+        {
+            rejection = new SqlCatalogRejection(definition.Name, Field,
+                $"'{definition.Table}' is a {parts.Length}-part name. Only 'table' and 'schema.table' can be " +
+                "validated against this connection's catalog, so a cross-database or linked-server name " +
+                "cannot be allow-listed; expose the data through a view in this database instead");
+            return false;
+        }
+
+        var authoredSchema = parts.Length == MaxNameParts ? parts[0] : null;
+        var authoredTable = parts[^1];
+
+        foreach (var part in parts)
+        {
+            if (IsRenderableIdentifier(part, dialect)) continue;
+            rejection = new SqlCatalogRejection(definition.Name, Field,
+                "the authored table name has a part that is not a usable identifier (empty, over-long, or " +
+                "containing control or Unicode format characters); the value is withheld from this message " +
+                "because it cannot be safely rendered");
+            return false;
+        }
+
+        if (!catalog.TryResolveSchema(authoredSchema, out schema))
+        {
+            rejection = new SqlCatalogRejection(definition.Name, Field,
+                $"schema '{authoredSchema}' does not exist (or matches more than one schema under a " +
+                "case-sensitive collation)");
+            return false;
+        }
+
+        if (!catalog.TryResolveTable(schema, authoredTable, out table))
+        {
+            rejection = new SqlCatalogRejection(definition.Name, Field,
+                $"table or view '{authoredTable}' does not exist in schema '{schema}'" +
+                (authoredSchema is null
+                    ? $" (the connection's default schema — qualify the name as 'schema.{authoredTable}' if it lives elsewhere)"
+                    : string.Empty));
+            return false;
+        }
+
+        return true;
+    }
+
+    /// <summary>
+    ///     True when the dialect's quoting rules accept <paramref name="identifier"/> — i.e. it is safe both to
+    ///     embed in SQL and to render into a log line or an AdminUI label.
+    /// </summary>
+    /// <remarks>
+    ///     Uses <see cref="ISqlDialect.QuoteIdentifier"/> as the charset authority rather than duplicating its
+    ///     rules, so the two can never disagree about what a legal identifier is. The quoted result is
+    ///     discarded: only whether it threw is interesting here.
+    /// </remarks>
+    private static bool IsRenderableIdentifier(string identifier, ISqlDialect dialect)
+    {
+        try
+        {
+            dialect.QuoteIdentifier(identifier);
+            return true;
+        }
+        catch (ArgumentException)
+        {
+            return false;
+        }
+    }
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql/SqlCatalogLoader.cs

@@ -0,0 +1,189 @@
+using System.Data;
+using System.Data.Common;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql;
+
+/// <summary>
+///     Loads the <see cref="SqlCatalog"/> slice the authored tags need, over one connection, using only the
+///     dialect's catalog SQL (design §8.1).
+/// </summary>
+/// <remarks>
+///     <para><b>Bounded by what is authored, not by what exists.</b> One query for the schema list, one for
+///     the default schema, then one <see cref="ISqlDialect.ListTablesSql"/> per distinct authored schema and
+///     one <see cref="ISqlDialect.ListColumnsSql"/> per distinct authored relation. A driver polling three
+///     tables issues a handful of round-trips at Initialize and none thereafter; it never enumerates a
+///     warehouse.</para>
+///     <para><b>Every parameter is bound.</b> Authored names reach the catalog queries as
+///     <c>@schema</c>/<c>@table</c> parameters — the same discipline the schema browser follows — so loading
+///     the allow-list cannot itself be an injection vector. No identifier is quoted into text on this path.</para>
+///     <para><b>Failures throw; they do not degrade to an empty catalog.</b> An empty catalog would reject
+///     every tag, which is indistinguishable at the OPC UA surface from a database whose objects were all
+///     dropped. A caller that cannot read the catalog has not learned that the tags are invalid — it has
+///     learned nothing — and must fail its Initialize so the driver retries rather than serving a
+///     confidently-empty address space.</para>
+/// </remarks>
+internal static class SqlCatalogLoader
+{
+    /// <summary>Column alias <see cref="ISqlDialect.ListSchemasSql"/> projects.</summary>
+    private const string SchemaColumn = "TABLE_SCHEMA";
+
+    /// <summary>Column alias <see cref="ISqlDialect.ListTablesSql"/> projects.</summary>
+    private const string TableNameColumn = "TABLE_NAME";
+
+    /// <summary>Column alias <see cref="ISqlDialect.ListColumnsSql"/> projects.</summary>
+    private const string ColumnNameColumn = "COLUMN_NAME";
+
+    /// <summary>
+    ///     Reads the catalog slice covering <paramref name="authoredTables"/>.
+    /// </summary>
+    /// <param name="connection">An <b>already-open</b> connection. Not disposed here; the caller owns it.</param>
+    /// <param name="dialect">Supplies the catalog SQL.</param>
+    /// <param name="authoredTables">The distinct authored <c>table</c> strings, as written in the blobs.</param>
+    /// <param name="commandTimeout">Per-command server-side backstop.</param>
+    /// <param name="cancellationToken">Cancellation token for the operation.</param>
+    /// <returns>The loaded catalog.</returns>
+    /// <exception cref="InvalidOperationException">The connection can see no schemas at all.</exception>
+    internal static async Task<SqlCatalog> LoadAsync(
+        DbConnection connection,
+        ISqlDialect dialect,
+        IReadOnlyCollection<string> authoredTables,
+        TimeSpan commandTimeout,
+        CancellationToken cancellationToken)
+    {
+        var timeoutSeconds = Math.Max(1, (int)Math.Ceiling(commandTimeout.TotalSeconds));
+
+        var schemas = await QueryColumnAsync(
+            connection, dialect.ListSchemasSql, SchemaColumn,
+            static _ => { }, timeoutSeconds, cancellationToken).ConfigureAwait(false);
+
+        // Zero schemas is a permissions or visibility symptom, never a real database. Rejecting every tag on
+        // that basis would report an authoring fault for what is actually a grant problem, and would send the
+        // operator to the wrong system — the same misdiagnosis the driver's health classification avoids.
+        if (schemas.Count == 0)
+            throw new InvalidOperationException(
+                "the catalog returned no schemas at all; the connecting principal most likely cannot read " +
+                "the catalog views, which is a grant problem rather than a tag-authoring one");
+
+        var defaultSchema = await ReadDefaultSchemaAsync(
+            connection, dialect, timeoutSeconds, cancellationToken).ConfigureAwait(false);
+
+        var tablesBySchema = new Dictionary<string, IReadOnlyList<string>>(StringComparer.Ordinal);
+        var columnsByTable = new Dictionary<string, IReadOnlyList<string>>(StringComparer.Ordinal);
+
+        // Resolving here goes through SqlCatalog.TryMatch — the SAME matcher the gate will use — so the
+        // loader and the gate can never disagree about which relation an authored name resolved to. Loading
+        // one table and validating against another would be a silent wrong-column defect.
+        foreach (var authored in authoredTables)
+        {
+            if (string.IsNullOrWhiteSpace(authored)) continue;
+
+            var parts = authored.Split('.');
+            if (parts.Length > 2) continue;   // the gate rejects these by name; nothing to load.
+
+            var authoredTable = parts[^1];
+            string schema;
+            if (parts.Length == 2)
+            {
+                if (!SqlCatalog.TryMatch(schemas, parts[0], out schema)) continue;
+            }
+            else
+            {
+                schema = defaultSchema;
+            }
+
+            if (!tablesBySchema.TryGetValue(schema, out var tables))
+            {
+                tables = await QueryColumnAsync(
+                    connection, dialect.ListTablesSql, TableNameColumn,
+                    command => Bind(command, "@schema", schema),
+                    timeoutSeconds, cancellationToken).ConfigureAwait(false);
+                tablesBySchema[schema] = tables;
+            }
+
+            if (!SqlCatalog.TryMatch(tables, authoredTable, out var table)) continue;
+
+            var key = SqlCatalog.QualifiedKey(schema, table);
+            if (columnsByTable.ContainsKey(key)) continue;
+
+            columnsByTable[key] = await QueryColumnAsync(
+                connection, dialect.ListColumnsSql, ColumnNameColumn,
+                command =>
+                {
+                    Bind(command, "@schema", schema);
+                    Bind(command, "@table", table);
+                },
+                timeoutSeconds, cancellationToken).ConfigureAwait(false);
+        }
+
+        return new SqlCatalog(defaultSchema, schemas, tablesBySchema, columnsByTable);
+    }
+
+    /// <summary>
+    ///     Reads the connection's default schema, falling back to the sole visible schema when the dialect's
+    ///     query answers null/blank.
+    /// </summary>
+    /// <remarks>
+    ///     A null answer is possible (a login with no default schema mapped). Falling back to the single
+    ///     visible schema keeps the common one-schema database working; with several visible schemas there is
+    ///     no defensible guess, so unqualified names simply will not resolve and the gate says so by name.
+    /// </remarks>
+    private static async Task<string> ReadDefaultSchemaAsync(
+        DbConnection connection, ISqlDialect dialect, int timeoutSeconds, CancellationToken cancellationToken)
+    {
+        var command = connection.CreateCommand();
+        await using (command.ConfigureAwait(false))
+        {
+            command.CommandText = dialect.DefaultSchemaSql;
+            command.CommandTimeout = timeoutSeconds;
+            var value = await command.ExecuteScalarAsync(cancellationToken).ConfigureAwait(false);
+            var schema = value is null or DBNull ? null : value.ToString();
+            return string.IsNullOrWhiteSpace(schema) ? string.Empty : schema;
+        }
+    }
+
+    /// <summary>Runs one catalog query and projects a single string column from every row.</summary>
+    private static async Task<IReadOnlyList<string>> QueryColumnAsync(
+        DbConnection connection,
+        string sql,
+        string columnName,
+        Action<DbCommand> bind,
+        int timeoutSeconds,
+        CancellationToken cancellationToken)
+    {
+        var results = new List<string>();
+
+        var command = connection.CreateCommand();
+        await using (command.ConfigureAwait(false))
+        {
+            command.CommandText = sql;
+            command.CommandTimeout = timeoutSeconds;
+            bind(command);
+
+            var reader = await command
+                .ExecuteReaderAsync(CommandBehavior.SingleResult, cancellationToken).ConfigureAwait(false);
+            await using (reader.ConfigureAwait(false))
+            {
+                var ordinal = -1;
+                while (await reader.ReadAsync(cancellationToken).ConfigureAwait(false))
+                {
+                    if (ordinal < 0) ordinal = reader.GetOrdinal(columnName);
+                    if (reader.IsDBNull(ordinal)) continue;
+                    var value = reader.GetValue(ordinal)?.ToString();
+                    if (!string.IsNullOrWhiteSpace(value)) results.Add(value);
+                }
+            }
+        }
+
+        return results;
+    }
+
+    /// <summary>Binds one catalog-query parameter — the only way an authored name reaches the database here.</summary>
+    private static void Bind(DbCommand command, string name, string value)
+    {
+        var parameter = command.CreateParameter();
+        parameter.ParameterName = name;
+        parameter.DbType = DbType.String;
+        parameter.Value = value;
+        command.Parameters.Add(parameter);
+    }
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql/SqlConnectionStringResolver.cs

@@ -0,0 +1,62 @@
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql;
+
+/// <summary>
+///     Resolves a <c>Sql</c> driver config's <c>connectionStringRef</c> — a NAME — into the connection string
+///     it stands for (design §8.2). The deployed artifact carries only the name, so database credentials never
+///     ride in a config blob, never land in the central config DB, and never appear in a deployment diff.
+///     <para><b>The environment is read directly, on purpose.</b> A driver factory is invoked through
+///     <c>DriverFactoryRegistry</c>'s <c>(driverInstanceId, driverConfigJson)</c> closure — there is no
+///     <c>IConfiguration</c>, no <c>IServiceProvider</c> and no ambient scope at that seam, and widening the
+///     registry's signature for one driver would change every driver in the tree. The
+///     <c>Sql__ConnectionStrings__&lt;ref&gt;</c> spelling is exactly the key .NET's environment-variable
+///     configuration provider would bind to <c>Sql:ConnectionStrings:&lt;ref&gt;</c>, so an operator can set it
+///     the same way they set every other secret and a later move onto <c>IConfiguration</c> needs no
+///     re-provisioning.</para>
+///     <para><b>Nothing here ever emits the resolved value.</b> Messages name the environment
+///     <em>variable</em>, which is not a secret and is the operator's next action; the value itself is returned
+///     to exactly one caller and is otherwise unmentioned.</para>
+/// </summary>
+public static class SqlConnectionStringResolver
+{
+    /// <summary>
+    ///     The environment-variable prefix a <c>connectionStringRef</c> is appended to. The double underscore
+    ///     is .NET's configuration hierarchy separator, so this is the environment spelling of
+    ///     <c>Sql:ConnectionStrings:&lt;ref&gt;</c>.
+    /// </summary>
+    public const string EnvironmentVariablePrefix = "Sql__ConnectionStrings__";
+
+    /// <summary>The environment variable a given <c>connectionStringRef</c> is read from.</summary>
+    /// <param name="connectionStringRef">The authored reference name.</param>
+    /// <returns>The full environment-variable name.</returns>
+    /// <exception cref="ArgumentException"><paramref name="connectionStringRef"/> is null, empty or whitespace.</exception>
+    public static string EnvironmentVariableFor(string connectionStringRef)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(connectionStringRef);
+        return string.Concat(EnvironmentVariablePrefix, connectionStringRef);
+    }
+
+    /// <summary>
+    ///     Resolves <paramref name="connectionStringRef"/> to its connection string.
+    ///     <para>An absent <b>or blank</b> variable is a half-provisioned deployment and throws: handing an
+    ///     empty string to the provider would surface as an unintelligible ADO.NET error at the first poll,
+    ///     far from the missing secret that actually caused it.</para>
+    /// </summary>
+    /// <param name="connectionStringRef">The authored reference name.</param>
+    /// <returns>The resolved connection string. <b>Treat as a secret</b> — never log it.</returns>
+    /// <exception cref="ArgumentException"><paramref name="connectionStringRef"/> is null, empty or whitespace.</exception>
+    /// <exception cref="InvalidOperationException">The environment variable is absent or blank.</exception>
+    public static string Resolve(string connectionStringRef)
+    {
+        var variable = EnvironmentVariableFor(connectionStringRef);
+        var value = Environment.GetEnvironmentVariable(variable);
+        if (string.IsNullOrWhiteSpace(value))
+        {
+            throw new InvalidOperationException(
+                $"Sql connection string '{connectionStringRef}' is not provisioned: set the environment " +
+                $"variable '{variable}' on every node that runs this driver. The connection string is " +
+                $"deliberately not carried in the deployed configuration.");
+        }
+
+        return value;
+    }
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql/SqlDriver.cs

@@ -0,0 +1,937 @@
+using System.Data.Common;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql;
+
+/// <summary>
+///     The <c>Sql</c> driver instance: a <b>read-only</b> Equipment-kind driver that polls SQL tables/views
+///     and publishes selected cells as OPC UA variables. Structurally the SQL analogue of
+///     <c>ModbusDriver</c> — this type owns lifecycle, the authored RawPath table, health, host
+///     connectivity, and the <see cref="PollGroupEngine"/> subscription overlay, while
+///     <see cref="SqlPollReader"/> owns the read path.
+///     <para><b>Read-only is structural, not configured.</b> <see cref="IWritable"/> is deliberately not
+///     implemented, so no amount of config (and no <c>WriteOperate</c> role) can produce a write; every
+///     discovered variable is <see cref="SecurityClassification.ViewOnly"/>. A future write feature is a
+///     new capability, not a flag flip.</para>
+///     <para><b>Health is classified here, because nothing below does it.</b> The reader honours
+///     <see cref="IReadable"/> literally: it throws only when the database cannot be reached, and turns
+///     every other failure — including a frozen database — into Bad-coded snapshots. Those return
+///     <em>successfully</em>, so <see cref="PollGroupEngine"/> sees a clean tick, does not back off, and does
+///     not call <see cref="HandlePollError"/>. Without <see cref="ObservePollOutcome"/> below, a driver whose
+///     every value is <see cref="SqlStatusCodes.BadTimeout"/> would keep reporting
+///     <see cref="DriverState.Healthy"/>. See that method for the exact rule and for why it does not
+///     manufacture an exception to force backoff.</para>
+/// </summary>
+public sealed class SqlDriver
+    : IDriver, ITagDiscovery, IReadable, ISubscribable, IHostConnectivityProbe, IAsyncDisposable
+{
+    /// <summary>
+    ///     The driver-type string this driver registers under — <see cref="DriverTypeNames.Sql"/>, the single
+    ///     source of truth the deploy pipeline stores in <c>DriverInstance.DriverType</c> and every dispatch
+    ///     map keys by. Chained off the shared constant (Task 11 wired the factory + probe, so
+    ///     <c>DriverTypeNamesGuardTests</c>' bidirectional-parity check is satisfied).
+    /// </summary>
+    public const string DriverTypeName = DriverTypeNames.Sql;
+
+    /// <summary>Shown for a connection string that names no recognisable server.</summary>
+    private const string UnknownEndpoint = "(unknown sql endpoint)";
+
+    /// <summary>Upper bound on the poll-loop failure backoff — the S7-proven 30 s cap adopted fleet-wide (05/STAB-8).</summary>
+    private static readonly TimeSpan PollBackoffCap = TimeSpan.FromSeconds(30);
+
+    /// <summary>Connection-string keys that name the server, in the order they are consulted.</summary>
+    private static readonly string[] ServerKeys =
+        ["server", "data source", "datasource", "host", "address", "addr", "network address"];
+
+    /// <summary>Connection-string keys that name the database.</summary>
+    private static readonly string[] DatabaseKeys = ["database", "initial catalog"];
+
+    // ---- instance fields (grouped at top for auditability) ----
+
+    private readonly SqlDriverOptions _options;
+    private readonly string _driverInstanceId;
+    private readonly ISqlDialect _dialect;
+    private readonly DbProviderFactory _factory;
+
+    /// <summary>
+    ///     The resolved connection string — a <b>secret</b>. It is passed to the provider and to nothing
+    ///     else: every log line, health message and host status carries <see cref="Endpoint"/> instead.
+    /// </summary>
+    private readonly string _connectionString;
+
+    private readonly ILogger<SqlDriver> _logger;
+
+    /// <summary>
+    ///     The authored RawPath → definition table, held as an <b>immutable snapshot swapped atomically</b>
+    ///     rather than as a mutated dictionary (the shape <c>ModbusDriver</c> uses).
+    ///     <see cref="ReinitializeAsync"/> rebuilds this table while poll loops are reading it; clearing and
+    ///     refilling a shared <see cref="Dictionary{TKey,TValue}"/> under that concurrency is a torn read at
+    ///     best and an <see cref="InvalidOperationException"/> inside a poll at worst.
+    /// </summary>
+    private IReadOnlyDictionary<string, SqlTagDefinition> _tagsByRawPath =
+        new Dictionary<string, SqlTagDefinition>(StringComparer.Ordinal);
+
+    /// <summary>
+    ///     The subset of <see cref="_tagsByRawPath"/> that survived the design §8.1 catalog gate, with every
+    ///     identifier rewritten to the catalog's own spelling. <b>This — not the authored table — is what a
+    ///     read or a poll resolves against</b>, so an identifier that never appeared in the catalog can never
+    ///     reach a query.
+    ///     <para><b>Why the two tables are separate.</b> A tag the gate rejected must still <em>exist</em> as a
+    ///     node: §8.1's specified outcome is that it publishes
+    ///     <see cref="SqlStatusCodes.BadNodeIdUnknown"/>, and a status code can only be published by a node
+    ///     that is there. Dropping rejected tags from the authored table too would delete the node instead,
+    ///     turning a diagnosable Bad quality into a silently missing address-space entry — a strictly worse
+    ///     failure for the operator trying to find their typo.</para>
+    ///     <para>Swapped atomically, for the same reason the authored table is.</para>
+    /// </summary>
+    private IReadOnlyDictionary<string, SqlTagDefinition> _polledByRawPath =
+        new Dictionary<string, SqlTagDefinition>(StringComparer.Ordinal);
+
+    /// <summary>Resolves a read/subscribe RawPath to its <b>catalog-validated</b> definition, or a miss.</summary>
+    private readonly EquipmentTagRefResolver<SqlTagDefinition> _resolver;
+
+    /// <summary>
+    ///     The read path. Built once, in the constructor, and <b>not</b> injected: its <c>resolve</c>
+    ///     delegate must read this driver's live authored table, which does not exist before the driver does.
+    /// </summary>
+    private readonly SqlPollReader _reader;
+
+    /// <summary>Polled subscriptions. The driver supplies the reader + change bridge; the engine owns the loop.</summary>
+    private readonly PollGroupEngine _poll;
+
+    // Single logical host: one driver instance dials one connection string. HostName is the endpoint
+    // description (server[/database]) so the Admin UI shows operators where to look.
+    private readonly object _probeLock = new();
+    private HostState _hostState = HostState.Unknown;
+    private DateTime _hostStateChangedUtc = DateTime.UtcNow;
+
+    private DriverHealth _health = new(DriverState.Unknown, null, null);
+
+    /// <summary>Occurs when a subscribed tag's value or quality changes.</summary>
+    public event EventHandler<DataChangeEventArgs>? OnDataChange;
+
+    /// <summary>Occurs when the database endpoint transitions between reachable and unreachable.</summary>
+    public event EventHandler<HostStatusChangedEventArgs>? OnHostStatusChanged;
+
+    // ---- ctor + identity ----
+
+    /// <summary>Initializes a new <c>Sql</c> driver instance.</summary>
+    /// <param name="options">The driver's typed configuration (the factory applies the documented defaults).</param>
+    /// <param name="driverInstanceId">The central config DB's identity for this driver instance.</param>
+    /// <param name="dialect">
+    ///     The provider seam — identifier quoting, liveness SQL, row-limit syntax and column-type mapping.
+    /// </param>
+    /// <param name="connectionString">
+    ///     The <b>already-resolved</b> connection string. The driver never resolves a
+    ///     <c>connectionStringRef</c> itself and never logs this value.
+    /// </param>
+    /// <param name="factory">
+    ///     Creates the provider's connections. Defaults to <paramref name="dialect"/>'s factory; passed
+    ///     explicitly by tests that need to observe or delay connection creation.
+    /// </param>
+    /// <param name="logger">Optional; defaults to a no-op logger.</param>
+    /// <exception cref="ArgumentNullException">A required reference argument is null.</exception>
+    /// <exception cref="ArgumentException"><paramref name="driverInstanceId"/> or <paramref name="connectionString"/> is blank.</exception>
+    public SqlDriver(
+        SqlDriverOptions options,
+        string driverInstanceId,
+        ISqlDialect dialect,
+        string connectionString,
+        DbProviderFactory? factory = null,
+        ILogger<SqlDriver>? logger = null)
+    {
+        ArgumentNullException.ThrowIfNull(options);
+        ArgumentNullException.ThrowIfNull(dialect);
+        ArgumentException.ThrowIfNullOrWhiteSpace(driverInstanceId);
+        if (string.IsNullOrWhiteSpace(connectionString))
+            throw new ArgumentException("A Sql driver needs a resolved connection string.", nameof(connectionString));
+
+        _options = options;
+        _driverInstanceId = driverInstanceId;
+        _dialect = dialect;
+        _factory = factory ?? dialect.Factory;
+        _connectionString = connectionString;
+        _logger = logger ?? NullLogger<SqlDriver>.Instance;
+        Endpoint = DescribeEndpoint(connectionString);
+
+        _resolver = new EquipmentTagRefResolver<SqlTagDefinition>(Lookup);
+        _reader = new SqlPollReader(
+            _factory,
+            connectionString,
+            dialect,
+            commandTimeout: options.CommandTimeout,
+            operationTimeout: options.OperationTimeout,
+            maxConcurrentGroups: options.MaxConcurrentGroups,
+            nullIsBad: options.NullIsBad,
+            resolve: rawPath => _resolver.TryResolve(rawPath, out var definition) ? definition : null,
+            logger: _logger);
+        _poll = new PollGroupEngine(
+            reader: ReadAsync,
+            onChange: (handle, tagRef, snapshot) =>
+                OnDataChange?.Invoke(this, new DataChangeEventArgs(handle, tagRef, snapshot)),
+            onError: HandlePollError,
+            backoffCap: PollBackoffCap);
+    }
+
+    /// <inheritdoc />
+    public string DriverInstanceId => _driverInstanceId;
+
+    /// <inheritdoc />
+    public string DriverType => DriverTypeName;
+
+    /// <summary>
+    ///     The credential-free description of the database this instance polls — <c>server/database</c> where
+    ///     the connection string names both. This is the only rendering of the connection string that may
+    ///     appear in a log, a health message, or the Admin UI.
+    /// </summary>
+    public string Endpoint { get; }
+
+    /// <summary>Host identifier surfaced through <see cref="IHostConnectivityProbe"/> — the endpoint description.</summary>
+    public string HostName => Endpoint;
+
+    /// <summary>Active polled-subscription count. Diagnostics + disposal assertions.</summary>
+    internal int ActiveSubscriptionCount => _poll.ActiveSubscriptionCount;
+
+    /// <summary>The current authored-tag snapshot. Read through a barrier — <see cref="BuildTagTable"/> swaps it.</summary>
+    private IReadOnlyDictionary<string, SqlTagDefinition> Tags => Volatile.Read(ref _tagsByRawPath);
+
+    /// <summary>
+    ///     The catalog-validated snapshot. Read through a barrier — <see cref="ApplyCatalogGateAsync"/> swaps it.
+    /// </summary>
+    private IReadOnlyDictionary<string, SqlTagDefinition> PolledTags => Volatile.Read(ref _polledByRawPath);
+
+    /// <summary>
+    ///     The resolver's lookup: RawPath → <b>catalog-validated</b> definition, or null on a miss.
+    ///     <para>Deliberately reads <see cref="PolledTags"/> rather than <see cref="Tags"/>: a tag the gate
+    ///     rejected must miss here so the reader publishes
+    ///     <see cref="SqlStatusCodes.BadNodeIdUnknown"/>, exactly as design §8.1 specifies.</para>
+    /// </summary>
+    private SqlTagDefinition? Lookup(string rawPath) => PolledTags.GetValueOrDefault(rawPath);
+
+    // ---- IDriver lifecycle ----
+
+    /// <summary>
+    ///     Builds the authored RawPath table and proves the database is reachable.
+    ///     <para><paramref name="driverConfigJson"/> is <b>not</b> re-parsed here: the driver serves the
+    ///     typed <see cref="SqlDriverOptions"/> it was constructed with, exactly as <c>ModbusDriver</c> does
+    ///     (config parsing belongs to the factory, which builds a fresh instance).</para>
+    ///     <para>The table is built first because it is pure and cannot fail; the liveness check is the only
+    ///     I/O, and on failure this method records <see cref="DriverState.Faulted"/> <b>and rethrows</b> —
+    ///     <c>DriverInstanceActor</c> reads a throw as InitializeFailed and lands in Reconnecting with its
+    ///     retry timer running, which is exactly the recovery a database that is merely down needs.</para>
+    ///     <para>The liveness check is then followed by the design §8.1 <b>catalog gate</b>
+    ///     (<see cref="ApplyCatalogGateAsync"/>), which is the second and last piece of I/O. It runs after
+    ///     liveness because it needs a working connection, and before the driver reports Healthy because the
+    ///     tag table it publishes must be the validated one — a poll must never see an unvalidated
+    ///     identifier.</para>
+    /// </summary>
+    /// <param name="driverConfigJson">The driver configuration JSON (unused; see remarks).</param>
+    /// <param name="cancellationToken">Cancellation token for the operation.</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    /// <exception cref="InvalidOperationException">The database could not be reached, or its catalog could not be read.</exception>
+    public async Task InitializeAsync(string driverConfigJson, CancellationToken cancellationToken)
+    {
+        WriteHealth(new DriverHealth(DriverState.Initializing, null, null));
+        BuildTagTable();
+
+        try
+        {
+            await VerifyLivenessAsync(cancellationToken).ConfigureAwait(false);
+        }
+        catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)
+        {
+            // The caller tore the initialization down; not a database verdict.
+            WriteHealth(new DriverHealth(DriverState.Unknown, null, null));
+            throw;
+        }
+        catch (Exception ex)
+        {
+            // Never interpolate _connectionString OR ex.Message onto the operator surface. The driver is
+            // dialect-agnostic over an arbitrary DbProviderFactory, so it cannot rely on any one provider's
+            // message discipline — Microsoft.Data.SqlClient's connection-string parser, for one, echoes an
+            // unrecognised keyword lower-cased, which a value-based password redactor misses entirely. Only
+            // the exception TYPE reaches LastError/host status; the full exception object goes to the log
+            // SINK via the structured logger's exception parameter (below), never into a rendered string.
+            var message =
+                $"Sql driver '{_driverInstanceId}' could not reach {Endpoint}: {ex.GetType().Name}. " +
+                $"Check the database is reachable and the connection string is valid.";
+            _logger.LogError(ex, "Sql driver {DriverInstanceId} liveness check against {Endpoint} failed.",
+                _driverInstanceId, Endpoint);
+            WriteHealth(new DriverHealth(DriverState.Faulted, null, message));
+            TransitionHostTo(HostState.Stopped);
+            throw new InvalidOperationException(message, ex);
+        }
+
+        // Separate try from liveness so the operator surface names the stage that actually failed: "could
+        // not reach the database" and "reached it but could not read its catalog" send an operator to
+        // different places, and the second is usually a GRANT rather than an outage.
+        try
+        {
+            await ApplyCatalogGateAsync(cancellationToken).ConfigureAwait(false);
+        }
+        catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)
+        {
+            WriteHealth(new DriverHealth(DriverState.Unknown, null, null));
+            throw;
+        }
+        catch (Exception ex)
+        {
+            // Same discipline as above: exception TYPE only on the operator surface, full exception to the
+            // log sink. A catalog read that fails is NOT evidence the tags are wrong — it is the absence of
+            // evidence — so this faults the driver (and retries) rather than rejecting every tag and serving
+            // a confidently-empty address space.
+            var message =
+                $"Sql driver '{_driverInstanceId}' reached {Endpoint} but could not read its catalog to " +
+                $"validate authored tables/columns: {ex.GetType().Name}. Check that the connecting principal " +
+                "can read the catalog views.";
+            _logger.LogError(ex,
+                "Sql driver {DriverInstanceId} catalog validation against {Endpoint} failed.",
+                _driverInstanceId, Endpoint);
+            WriteHealth(new DriverHealth(DriverState.Faulted, null, message));
+            TransitionHostTo(HostState.Stopped);
+            throw new InvalidOperationException(message, ex);
+        }
+
+        WriteHealth(new DriverHealth(DriverState.Healthy, DateTime.UtcNow, null));
+        TransitionHostTo(HostState.Running);
+        _logger.LogInformation(
+            "Sql driver {DriverInstanceId} initialized against {Endpoint} with {TagCount} authored tag(s).",
+            _driverInstanceId, Endpoint, Tags.Count);
+    }
+
+    /// <inheritdoc />
+    public async Task ReinitializeAsync(string driverConfigJson, CancellationToken cancellationToken)
+    {
+        await ShutdownAsync(cancellationToken).ConfigureAwait(false);
+        await InitializeAsync(driverConfigJson, cancellationToken).ConfigureAwait(false);
+    }
+
+    /// <inheritdoc />
+    public async Task ShutdownAsync(CancellationToken cancellationToken)
+    {
+        var lastRead = ReadHealth().LastSuccessfulRead;
+        await TeardownAsync().ConfigureAwait(false);
+        WriteHealth(new DriverHealth(DriverState.Unknown, lastRead, null));
+    }
+
+    /// <inheritdoc />
+    public DriverHealth GetHealth() => ReadHealth();
+
+    /// <summary>No caches, no symbol table, no connection between polls — the footprint is the tag table.</summary>
+    /// <returns>Always zero.</returns>
+    public long GetMemoryFootprint() => 0;
+
+    /// <summary>Nothing optional to flush: the authored table is required for correctness.</summary>
+    /// <param name="cancellationToken">Cancellation token for the operation.</param>
+    /// <returns>A completed task.</returns>
+    public Task FlushOptionalCachesAsync(CancellationToken cancellationToken) => Task.CompletedTask;
+
+    // ---- ITagDiscovery ----
+
+    /// <summary>
+    ///     Exactly one pass: the tag set is the authored one, fixed at Initialize, so re-running discovery
+    ///     could only produce the same nodes.
+    /// </summary>
+    public DiscoveryRediscoverPolicy RediscoverPolicy => DiscoveryRediscoverPolicy.Once;
+
+    /// <summary>
+    ///     False — <see cref="DiscoverAsync"/> replays authored tags rather than enumerating the backend, so
+    ///     the universal discovery browser must not treat this driver as browsable. (Live schema browsing is
+    ///     a separate surface: <c>Driver.Sql.Browser</c>.)
+    /// </summary>
+    public bool SupportsOnlineDiscovery => false;
+
+    /// <summary>
+    ///     Streams the authored tags as read-only variables.
+    ///     <para>An undeclared tag materialises as <see cref="DriverDataType.String"/> — the same fallback
+    ///     <see cref="ISqlDialect.MapColumnType"/> uses for an unrecognised column type — because a column's
+    ///     real type is only known once a poll has returned result-set metadata, which has not happened at
+    ///     discovery time. Author <c>"type"</c> on a numeric tag.</para>
+    /// </summary>
+    /// <param name="builder">The address-space builder to stream discovered nodes into.</param>
+    /// <param name="cancellationToken">Cancellation token for the operation.</param>
+    /// <returns>A completed task — discovery is synchronous over the authored table.</returns>
+    public Task DiscoverAsync(IAddressSpaceBuilder builder, CancellationToken cancellationToken)
+    {
+        ArgumentNullException.ThrowIfNull(builder);
+        var folder = builder.Folder(DriverTypeName, DriverTypeName);
+        foreach (var tag in Tags.Values)
+        {
+            if (tag.DeclaredType is null)
+            {
+                // Discovery cannot infer a column's real type — that needs live result-set metadata, which
+                // only a poll returns — so an omitted-type tag materialises as String (the same fallback
+                // ISqlDialect.MapColumnType uses) while the reader coerces and publishes the column's actual,
+                // possibly numeric, CLR value against that String node. Nothing else signals the operator to
+                // this declared-vs-published mismatch, so warn and point them at the fix.
+                _logger.LogWarning(
+                    "Sql tag '{Tag}' has no authored \"type\" and is discovered as String; a numeric column " +
+                    "will then publish numeric values against a String node. Author an explicit \"type\" on " +
+                    "numeric tags. Driver={DriverInstanceId}",
+                    tag.Name, _driverInstanceId);
+            }
+
+            folder.Variable(tag.Name, tag.Name, new DriverAttributeInfo(
+                FullName: tag.Name,
+                DriverDataType: tag.DeclaredType ?? DriverDataType.String,
+                IsArray: false,
+                ArrayDim: null,
+                // v1 is read-only: no tag, and no configuration, can widen this.
+                SecurityClass: SecurityClassification.ViewOnly,
+                IsHistorized: false,
+                IsAlarm: false,
+                WriteIdempotent: false));
+        }
+
+        return Task.CompletedTask;
+    }
+
+    // ---- IReadable ----
+
+    /// <summary>
+    ///     Reads a batch, delegating to <see cref="SqlPollReader"/> and classifying what came back
+    ///     (<see cref="ObservePollOutcome"/>).
+    /// </summary>
+    /// <param name="fullReferences">The RawPaths to read.</param>
+    /// <param name="cancellationToken">Cancellation token for the operation.</param>
+    /// <returns>One snapshot per reference, at the same index.</returns>
+    /// <exception cref="DbException">The database could not be reached — the engine backs off on this.</exception>
+    public async Task<IReadOnlyList<DataValueSnapshot>> ReadAsync(
+        IReadOnlyList<string> fullReferences, CancellationToken cancellationToken)
+    {
+        // Guarded here rather than inside the try, so a caller's bug cannot be misread as "the database is
+        // unreachable" and degrade a perfectly healthy driver.
+        ArgumentNullException.ThrowIfNull(fullReferences);
+
+        try
+        {
+            var snapshots = await _reader.ReadAsync(fullReferences, cancellationToken).ConfigureAwait(false);
+            ObservePollOutcome(snapshots);
+            return snapshots;
+        }
+        catch (OperationCanceledException)
+        {
+            // Teardown, not a database verdict — leave health and host state exactly as they were.
+            throw;
+        }
+        catch (Exception ex)
+        {
+            // The reader throws for one reason only: opening a connection failed (IReadable's contract).
+            _logger.LogWarning(ex, "Sql driver {DriverInstanceId} could not reach {Endpoint} during a read.",
+                _driverInstanceId, Endpoint);
+            // Type name only — never ex.Message (see InitializeAsync for why); the full exception is already
+            // on the log sink via the LogWarning exception parameter above.
+            Degrade($"Sql driver '{_driverInstanceId}' could not reach {Endpoint}: {ex.GetType().Name}.");
+            TransitionHostTo(HostState.Stopped);
+            throw;
+        }
+    }
+
+    // ---- ISubscribable (polling overlay via the shared engine) ----
+
+    /// <summary>
+    ///     Registers a polled subscription.
+    ///     <para>A non-positive <paramref name="publishingInterval"/> falls back to the configured
+    ///     <see cref="SqlDriverOptions.DefaultPollInterval"/>; anything faster than
+    ///     <see cref="PollGroupEngine.DefaultMinInterval"/> is floored by the engine.</para>
+    /// </summary>
+    /// <param name="fullReferences">The RawPaths to poll.</param>
+    /// <param name="publishingInterval">The requested publishing interval.</param>
+    /// <param name="cancellationToken">Cancellation token for the operation.</param>
+    /// <returns>The subscription handle.</returns>
+    public Task<ISubscriptionHandle> SubscribeAsync(
+        IReadOnlyList<string> fullReferences, TimeSpan publishingInterval, CancellationToken cancellationToken)
+    {
+        var interval = publishingInterval > TimeSpan.Zero ? publishingInterval : _options.DefaultPollInterval;
+        return Task.FromResult(_poll.Subscribe(fullReferences, interval));
+    }
+
+    /// <inheritdoc />
+    public Task UnsubscribeAsync(ISubscriptionHandle handle, CancellationToken cancellationToken)
+    {
+        _poll.Unsubscribe(handle);
+        return Task.CompletedTask;
+    }
+
+    // ---- IHostConnectivityProbe ----
+
+    /// <summary>
+    ///     The single logical host this instance dials. There is no background probe loop: the state is a
+    ///     by-product of the Initialize-time liveness check and of every poll, so the report is always a
+    ///     statement about traffic that actually happened rather than about a synthetic ping.
+    /// </summary>
+    /// <returns>A one-element list describing the configured database endpoint.</returns>
+    public IReadOnlyList<HostConnectivityStatus> GetHostStatuses()
+    {
+        lock (_probeLock)
+            return [new HostConnectivityStatus(HostName, _hostState, _hostStateChangedUtc)];
+    }
+
+    // ---- health + host-state classification ----
+
+    /// <summary>
+    ///     Classifies one poll's snapshots into a health verdict and a host state.
+    ///     <list type="bullet">
+    ///         <item>Any Good snapshot ⇒ the database answered: <c>LastSuccessfulRead</c> advances and the
+    ///         host is Running.</item>
+    ///         <item>Any <b>connection-class</b> Bad snapshot (<see cref="SqlStatusCodes.BadTimeout"/> /
+    ///         <see cref="SqlStatusCodes.BadCommunicationError"/>) ⇒ Degraded; when nothing at all was Good,
+    ///         the host is Stopped.</item>
+    ///         <item>Bad codes that are <b>authoring</b> facts — an unresolvable RawPath, an absent row, a
+    ///         type mismatch, a rejected definition — change nothing. A tag typo must never report the
+    ///         database as down and send an operator to the wrong system.</item>
+    ///     </list>
+    ///     <para><b>Why this does not throw to force poll-engine backoff.</b> Backoff would require turning
+    ///     an all-<c>BadTimeout</c> batch into an exception, and the engine's exception path publishes
+    ///     nothing — clients would lose the very BadTimeout quality the reader went out of its way to
+    ///     produce, and would sit on stale Good values instead. Nor is hammering a real risk: each group is
+    ///     already bounded by <c>operationTimeout</c> and the reader never holds more than
+    ///     <c>maxConcurrentGroups</c> connections however long the database stays frozen. So a frozen
+    ///     database is reported (Degraded + host Stopped + Bad-quality values) at the configured poll
+    ///     cadence rather than backed off from.</para>
+    /// </summary>
+    /// <param name="snapshots">The snapshots the reader returned for one poll.</param>
+    internal void ObservePollOutcome(IReadOnlyList<DataValueSnapshot> snapshots)
+    {
+        if (snapshots.Count == 0) return;
+
+        var good = 0;
+        var unreachable = 0;
+        foreach (var snapshot in snapshots)
+        {
+            if (SqlStatusCodes.IsGood(snapshot.StatusCode)) good++;
+            else if (IsConnectionClass(snapshot.StatusCode)) unreachable++;
+        }
+
+        if (unreachable > 0)
+        {
+            Degrade(
+                $"{unreachable} of {snapshots.Count} Sql tag(s) timed out or failed communication against " +
+                $"{Endpoint} on the last poll.");
+            if (good > 0)
+            {
+                // Partial: something answered, so the endpoint is up — but the driver is not healthy.
+                TouchLastSuccessfulRead();
+                TransitionHostTo(HostState.Running);
+            }
+            else
+            {
+                TransitionHostTo(HostState.Stopped);
+            }
+
+            return;
+        }
+
+        if (good == 0) return;   // authoring-class Bad only — not a statement about the database.
+
+        // Route through the Faulted guard, not a raw WriteHealth: a poll still in flight when a concurrent
+        // ReinitializeAsync has recorded Faulted (the engine's ~5 s teardown wait is shorter than the 15 s
+        // default operationTimeout, so a stale poll can still complete afterwards) must not flip Faulted back
+        // to Healthy with no real recovery. Only a successful (re)initialize clears Faulted.
+        SetHealthUnlessFaulted(new DriverHealth(DriverState.Healthy, DateTime.UtcNow, null));
+        TransitionHostTo(HostState.Running);
+    }
+
+    /// <summary>True for the status codes that mean "the database did not answer", as opposed to "the data is not there".</summary>
+    private static bool IsConnectionClass(uint statusCode)
+        => statusCode is SqlStatusCodes.BadTimeout or SqlStatusCodes.BadCommunicationError;
+
+    /// <summary>
+    ///     Routes a poll-loop reader failure to the health surface (05/STAB-9). Deliberately does <b>not</b>
+    ///     touch host state: the engine also reports its own contract violations here, which say nothing
+    ///     about connectivity — the unreachable-database transition is raised by <see cref="ReadAsync"/>,
+    ///     which knows the exception came from the reader.
+    /// </summary>
+    /// <param name="ex">The exception the poll engine caught.</param>
+    internal void HandlePollError(Exception ex)
+    {
+        // A subscribed-read outage surfaces as a DbException the reader threw, which ReadAsync has ALREADY
+        // classified — good, endpoint-bearing LastError + host Stopped — before rethrowing. The poll engine
+        // then routes that same exception here. Re-degrading would overwrite the good LastError with a worse,
+        // guidance-free one and log the outage a second time, so skip the connection class ReadAsync owns.
+        if (ex is DbException) return;
+
+        // Whatever reaches here — an engine contract-violation, or a non-DbException the provider raised
+        // (e.g. an ArgumentException from a malformed connection string, which the parser echoes with
+        // credential fragments) — the operator surface carries only the exception TYPE, never ex.Message.
+        // The full exception, with its text, still reaches the log SINK via the exception parameter. This is
+        // the same unconditional rule InitializeAsync/ReadAsync follow; do not weaken it to a type check.
+        _logger.LogWarning(ex, "Sql poll failed. Driver={DriverInstanceId} Endpoint={Endpoint}",
+            _driverInstanceId, Endpoint);
+        Degrade($"Sql driver '{_driverInstanceId}' poll failed: {ex.GetType().Name}.");
+    }
+
+    /// <summary>
+    ///     Degrades health, preserving <c>LastSuccessfulRead</c> and never downgrading
+    ///     <see cref="DriverState.Faulted"/> — a config-level verdict that only a successful read or an
+    ///     operator reinitialize may clear.
+    /// </summary>
+    /// <param name="reason">The operator-facing reason, which must never carry the connection string.</param>
+    private void Degrade(string reason)
+    {
+        var current = ReadHealth();
+        SetHealthUnlessFaulted(new DriverHealth(DriverState.Degraded, current.LastSuccessfulRead, reason));
+    }
+
+    /// <summary>
+    ///     Publishes <paramref name="value"/> unless the driver is already <see cref="DriverState.Faulted"/>
+    ///     — a liveness/config verdict that only a successful (re)initialize may clear. Every non-Initialize
+    ///     health write routes through here: <see cref="Degrade"/> and the poll's Healthy verdict in
+    ///     <see cref="ObservePollOutcome"/>, so a late in-flight poll cannot un-fault a driver a concurrent
+    ///     <see cref="ReinitializeAsync"/> just faulted.
+    /// </summary>
+    /// <param name="value">The health snapshot to publish when the driver is not Faulted.</param>
+    private void SetHealthUnlessFaulted(DriverHealth value)
+    {
+        if (ReadHealth().State == DriverState.Faulted) return;
+        WriteHealth(value);
+    }
+
+    /// <summary>Advances <c>LastSuccessfulRead</c> without changing the current state or error.</summary>
+    private void TouchLastSuccessfulRead()
+    {
+        var current = ReadHealth();
+        WriteHealth(current with { LastSuccessfulRead = DateTime.UtcNow });
+    }
+
+    /// <summary>Barrier-protected read of the multi-threaded health field.</summary>
+    private DriverHealth ReadHealth() => Volatile.Read(ref _health);
+
+    /// <summary>Barrier-protected publish of a new health snapshot.</summary>
+    private void WriteHealth(DriverHealth value) => Volatile.Write(ref _health, value);
+
+    /// <summary>Records a host-state change and raises <see cref="OnHostStatusChanged"/> — on transitions only.</summary>
+    private void TransitionHostTo(HostState newState)
+    {
+        HostState old;
+        lock (_probeLock)
+        {
+            old = _hostState;
+            if (old == newState) return;
+            _hostState = newState;
+            _hostStateChangedUtc = DateTime.UtcNow;
+        }
+
+        OnHostStatusChanged?.Invoke(this, new HostStatusChangedEventArgs(HostName, old, newState));
+    }
+
+    // ---- authored tag table ----
+
+    /// <summary>
+    ///     Maps every authored <see cref="RawTagEntry"/> through <see cref="SqlEquipmentTagParser.TryParse"/>
+    ///     and publishes the result as one atomic snapshot. A blob that does not map is <b>logged and
+    ///     skipped</b>, never thrown: one malformed tag must not take the whole driver — and therefore every
+    ///     other tag on that database — down with it. The skipped RawPath then resolves to nothing, so it
+    ///     publishes <see cref="SqlStatusCodes.BadNodeIdUnknown"/> rather than someone else's row.
+    /// </summary>
+    private void BuildTagTable()
+    {
+        var table = new Dictionary<string, SqlTagDefinition>(_options.RawTags.Count, StringComparer.Ordinal);
+        foreach (var entry in _options.RawTags)
+        {
+            try
+            {
+                if (SqlEquipmentTagParser.TryParse(entry.TagConfig, entry.RawPath, out var definition))
+                    table[entry.RawPath] = definition;
+                else
+                    _logger.LogWarning(
+                        "Sql tag config did not map to a definition; skipping. Driver={DriverInstanceId} RawPath={RawPath}",
+                        _driverInstanceId, entry.RawPath);
+            }
+            catch (Exception ex)
+            {
+                // TryParse is contracted never to throw, but BuildTagTable runs BEFORE InitializeAsync's
+                // try/catch, so a stray throw here (a parser bug on one blob) would escape Initialize and
+                // strand health at Initializing across every DriverInstanceActor retry. Skip the offending
+                // tag — the same "one bad tag must not take the whole driver down" rule the malformed-blob
+                // branch above follows — rather than fault the driver over a single entry.
+                _logger.LogError(
+                    ex, "Sql tag config threw while parsing; skipping. Driver={DriverInstanceId} RawPath={RawPath}",
+                    _driverInstanceId, entry.RawPath);
+            }
+        }
+
+        Volatile.Write(ref _tagsByRawPath, table);
+
+        // Nothing is pollable until the catalog gate has validated it. Clearing here (rather than leaving a
+        // previous generation's validated table in place) means a Reinitialize whose gate then fails cannot
+        // keep polling the OLD identifiers against a database whose schema may be exactly what changed.
+        Volatile.Write(ref _polledByRawPath, new Dictionary<string, SqlTagDefinition>(StringComparer.Ordinal));
+    }
+
+    // ---- catalog gate (design §8.1) ----
+
+    /// <summary>
+    ///     Validates every authored identifier against the live catalog and republishes the tag table with
+    ///     catalog spellings, dropping the tags that do not resolve (design §8.1).
+    /// </summary>
+    /// <remarks>
+    ///     <para><b>Why this must run before the driver reports Healthy.</b> The table this swaps in is what
+    ///     every poll resolves against. Running it later — or in the background — would leave a window in
+    ///     which an unvalidated identifier could be quoted into a query, which is the entire hole the gate
+    ///     exists to close.</para>
+    ///     <para><b>A dropped tag is not a driver fault.</b> It disappears from the table, so its RawPath
+    ///     resolves to nothing and it publishes <see cref="SqlStatusCodes.BadNodeIdUnknown"/> — one operator
+    ///     typo must not stop the other tags on that database, the same rule
+    ///     <see cref="BuildTagTable"/> follows for a malformed blob. Each drop is logged at Warning with the
+    ///     tag, the field and the reason, because a node that silently goes Bad with nothing in the log is
+    ///     unsupportable.</para>
+    ///     <para><b>No tags ⇒ no I/O.</b> A driver with nothing authored has nothing to validate, and issuing
+    ///     catalog queries to prove that would be a round-trip that can only fail.</para>
+    ///     <para>Bounded by the same wall-clock discipline as the liveness check (R2-01 / STAB-14): the work
+    ///     runs on the thread pool so a provider implementing the async path synchronously blocks a pool
+    ///     thread rather than wedging Initialize forever with no retry.</para>
+    /// </remarks>
+    /// <param name="cancellationToken">The caller's token.</param>
+    /// <returns>A task that completes when the tag table has been validated and republished.</returns>
+    private async Task ApplyCatalogGateAsync(CancellationToken cancellationToken)
+    {
+        var authored = Tags;
+        if (authored.Count == 0) return;
+
+        var tables = authored.Values
+            .Select(definition => definition.Table)
+            .Where(table => !string.IsNullOrWhiteSpace(table))
+            .Distinct(StringComparer.OrdinalIgnoreCase)
+            .ToArray();
+
+        var catalog = await RunBoundedAsync(
+            token => LoadCatalogAsync(tables, token),
+            _options.OperationTimeout,
+            "the catalog queries did not return",
+            cancellationToken).ConfigureAwait(false);
+
+        var result = SqlCatalogGate.Apply(authored.Values, catalog, _dialect);
+
+        foreach (var rejection in result.Rejected)
+        {
+            _logger.LogWarning(
+                "Sql tag '{Tag}' rejected by the catalog gate: {Field} — {Reason}. It will publish "
+                + "BadNodeIdUnknown until the tag or the database is corrected. Driver={DriverInstanceId}",
+                rejection.RawPath, rejection.Field, rejection.Reason, _driverInstanceId);
+        }
+
+        var validated = new Dictionary<string, SqlTagDefinition>(result.Accepted.Count, StringComparer.Ordinal);
+        foreach (var definition in result.Accepted) validated[definition.Name] = definition;
+
+        // Only the POLLED table is replaced. The authored table is left intact so every authored tag keeps
+        // its node and a rejected one publishes BadNodeIdUnknown rather than vanishing (see _polledByRawPath).
+        Volatile.Write(ref _polledByRawPath, validated);
+
+        _logger.LogInformation(
+            "Sql driver {DriverInstanceId} catalog gate accepted {Accepted} of {Total} authored tag(s) "
+            + "across {Tables} table(s) on {Endpoint}.",
+            _driverInstanceId, result.Accepted.Count, authored.Count, tables.Length, Endpoint);
+    }
+
+    /// <summary>Opens one connection and reads the catalog slice the authored tables need.</summary>
+    private async Task<SqlCatalog> LoadCatalogAsync(
+        IReadOnlyCollection<string> authoredTables, CancellationToken cancellationToken)
+    {
+        var connection = _factory.CreateConnection()
+                         ?? throw new InvalidOperationException(
+                             $"the {_dialect.Provider} provider factory returned no connection.");
+
+        await using (connection.ConfigureAwait(false))
+        {
+            connection.ConnectionString = _connectionString;
+            await connection.OpenAsync(cancellationToken).ConfigureAwait(false);
+            return await SqlCatalogLoader
+                .LoadAsync(connection, _dialect, authoredTables, _options.CommandTimeout, cancellationToken)
+                .ConfigureAwait(false);
+        }
+    }
+
+    // ---- liveness ----
+
+    /// <summary>
+    ///     Opens ONE connection, runs the dialect's liveness statement, and disposes it. No connection is
+    ///     held between this check and the first poll — the reader opens, uses and disposes per poll, so a
+    ///     long-lived connection here would only be a second thing to keep alive.
+    ///     <para><b>Bounded by wall-clock, not only by the token</b> (the R2-01 / STAB-14 lesson): some ADO.NET
+    ///     providers implement the async path synchronously, and a wedged socket can hang inside the
+    ///     provider's own cancellation handshake. If Initialize hung there, <c>DriverInstanceActor</c>'s init
+    ///     task would never complete and the driver would sit in Connecting forever with no retry. The work
+    ///     runs on the thread pool so a synchronous provider blocks a pool thread rather than the caller, and
+    ///     an abandoned attempt still owns and disposes its own connection.</para>
+    /// </summary>
+    /// <param name="cancellationToken">The caller's token.</param>
+    /// <returns>A task that completes when the database has answered.</returns>
+    private Task VerifyLivenessAsync(CancellationToken cancellationToken) =>
+        RunBoundedAsync(
+            async token => { await PingAsync(token).ConfigureAwait(false); return true; },
+            _options.CommandTimeout,
+            "the liveness statement did not return",
+            cancellationToken);
+
+    /// <summary>
+    ///     Runs <paramref name="work"/> under a hard wall-clock <paramref name="budget"/>, on the thread pool,
+    ///     converting a breach into a <see cref="TimeoutException"/> worded from <paramref name="what"/>.
+    /// </summary>
+    /// <remarks>
+    ///     <para>The R2-01 / STAB-14 shape, shared by the two pieces of I/O Initialize performs. It exists
+    ///     because a token is not a deadline: some ADO.NET providers implement the async path synchronously,
+    ///     and a wedged socket can hang <em>inside</em> the provider's own cancellation handshake. Without an
+    ///     independent wall clock, <c>DriverInstanceActor</c>'s init task would never complete and the driver
+    ///     would sit in Connecting forever with no retry — the exact frozen-peer wedge the S7 driver shipped.</para>
+    ///     <para>Both the linked CTS deadline and an outer <see cref="TaskExtensions"/> wait are used, because
+    ///     each covers a case the other does not: the CTS handles a provider that <em>does</em> honour
+    ///     cancellation, and the outer wait handles one that does not. An abandoned attempt keeps ownership of
+    ///     its own connection and disposes it; <see cref="Detach"/> observes its eventual fault.</para>
+    /// </remarks>
+    /// <typeparam name="T">The work's result type.</typeparam>
+    /// <param name="work">The operation to bound. Receives the deadline-linked token.</param>
+    /// <param name="budget">The wall-clock allowance.</param>
+    /// <param name="what">Sentence fragment naming the operation, e.g. "the catalog queries did not return".</param>
+    /// <param name="cancellationToken">The caller's token.</param>
+    /// <returns>The work's result.</returns>
+    /// <exception cref="TimeoutException">The budget elapsed first.</exception>
+    private static async Task<T> RunBoundedAsync<T>(
+        Func<CancellationToken, Task<T>> work,
+        TimeSpan budget,
+        string what,
+        CancellationToken cancellationToken)
+    {
+        var deadline = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
+        Task<T> running;
+        try
+        {
+            deadline.CancelAfter(budget);
+            running = Task.Run(
+                async () =>
+                {
+                    try { return await work(deadline.Token).ConfigureAwait(false); }
+                    finally { deadline.Dispose(); }
+                },
+                CancellationToken.None);
+        }
+        catch
+        {
+            // Ownership of the CTS transfers to the work task; release it only if that task never started.
+            deadline.Dispose();
+            throw;
+        }
+
+        try
+        {
+            return await running.WaitAsync(budget, cancellationToken).ConfigureAwait(false);
+        }
+        catch (TimeoutException)
+        {
+            Detach(running);
+            throw new TimeoutException($"{what} within {(int)budget.TotalMilliseconds} ms.");
+        }
+        catch (OperationCanceledException) when (!cancellationToken.IsCancellationRequested)
+        {
+            // Our deadline fired and the provider DID honour the linked token.
+            Detach(running);
+            throw new TimeoutException($"{what} within {(int)budget.TotalMilliseconds} ms.");
+        }
+    }
+
+    /// <summary>Opens a connection and executes the dialect's cheapest proof-of-life statement.</summary>
+    private async Task PingAsync(CancellationToken cancellationToken)
+    {
+        var connection = _factory.CreateConnection()
+                         ?? throw new InvalidOperationException(
+                             $"the {_dialect.Provider} provider factory returned no connection.");
+
+        await using (connection.ConfigureAwait(false))
+        {
+            connection.ConnectionString = _connectionString;
+            await connection.OpenAsync(cancellationToken).ConfigureAwait(false);
+
+            var command = connection.CreateCommand();
+            await using (command.ConfigureAwait(false))
+            {
+                command.CommandText = _dialect.LivenessSql;
+                // ADO.NET reads CommandTimeout = 0 as "wait forever" — the one value it must never become.
+                command.CommandTimeout = Math.Max(1, (int)Math.Ceiling(_options.CommandTimeout.TotalSeconds));
+                await command.ExecuteScalarAsync(cancellationToken).ConfigureAwait(false);
+            }
+        }
+    }
+
+    /// <summary>
+    ///     Observes an abandoned liveness attempt's eventual fault so it never surfaces as an unobserved
+    ///     task exception. The task still owns — and disposes — its own connection.
+    ///     <para>TODO(M2): a verbatim duplicate of <c>SqlPollReader.Detach</c>; both live in Driver.Sql and
+    ///     could hoist to one internal helper. Left in place here to keep this change off the reader.</para>
+    /// </summary>
+    private static void Detach(Task work)
+        => _ = work.ContinueWith(
+            static t => _ = t.Exception,
+            CancellationToken.None,
+            TaskContinuationOptions.OnlyOnFaulted | TaskContinuationOptions.ExecuteSynchronously,
+            TaskScheduler.Default);
+
+    // ---- endpoint description ----
+
+    /// <summary>
+    ///     Renders a connection string as <c>server/database</c>, reading only those two keys.
+    ///     <para>This is the <b>only</b> function permitted to look at the connection string outside the
+    ///     provider call, and it exists so that no other code is ever tempted to log the string itself:
+    ///     credentials live in <c>User ID</c> / <c>Password</c> / <c>Authentication</c>, which are never
+    ///     read here. A string that cannot be parsed yields <see cref="UnknownEndpoint"/> — an unusable
+    ///     description must not become a crash at construction.</para>
+    /// </summary>
+    /// <param name="connectionString">The resolved connection string.</param>
+    /// <returns>A credential-free description safe to log and display.</returns>
+    private static string DescribeEndpoint(string connectionString)
+    {
+        try
+        {
+            var builder = new DbConnectionStringBuilder { ConnectionString = connectionString };
+            var server = FirstValue(builder, ServerKeys);
+            if (string.IsNullOrWhiteSpace(server)) return UnknownEndpoint;
+            var database = FirstValue(builder, DatabaseKeys);
+            return string.IsNullOrWhiteSpace(database) ? server : $"{server}/{database}";
+        }
+        catch (ArgumentException)
+        {
+            return UnknownEndpoint;
+        }
+    }
+
+    /// <summary>Reads the first of <paramref name="keys"/> the builder carries; null when it carries none.</summary>
+    private static string? FirstValue(DbConnectionStringBuilder builder, string[] keys)
+    {
+        foreach (var key in keys)
+        {
+            // DbConnectionStringBuilder's key comparison is case-insensitive.
+            if (builder.TryGetValue(key, out var value) && value is not null)
+            {
+                var text = value.ToString();
+                if (!string.IsNullOrWhiteSpace(text)) return text;
+            }
+        }
+
+        return null;
+    }
+
+    // ---- teardown ----
+
+    /// <summary>
+    ///     Performs the same teardown as <see cref="ShutdownAsync"/>, so a caller that only uses
+    ///     <c>await using</c> does not leak the poll loops.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    public async ValueTask DisposeAsync() => await TeardownAsync().ConfigureAwait(false);
+
+    /// <summary>
+    ///     Shared teardown: stops every polled subscription and drops the authored table. Idempotent — safe
+    ///     to call any number of times, in any order, which is what makes
+    ///     <c>ShutdownAsync</c>-then-<c>DisposeAsync</c> (and <see cref="ReinitializeAsync"/>) safe.
+    ///     <para>There is no connection to close: the reader opens and disposes one per poll.</para>
+    /// </summary>
+    private async Task TeardownAsync()
+    {
+        await _poll.DisposeAsync().ConfigureAwait(false);
+        Volatile.Write(ref _tagsByRawPath, new Dictionary<string, SqlTagDefinition>(StringComparer.Ordinal));
+        Volatile.Write(ref _polledByRawPath, new Dictionary<string, SqlTagDefinition>(StringComparer.Ordinal));
+        _resolver.Clear();   // no-op in v3 (the resolver reads the live table by closure); kept for symmetry
+    }
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql/SqlDriverFactoryExtensions.cs

@@ -0,0 +1,252 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Core.Hosting;
+using ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql;
+
+/// <summary>
+///     Static factory registration helper for <see cref="SqlDriver"/> — the seam between a deployed
+///     <c>DriverConfig</c> blob and a live driver instance. The Server's composition root calls
+///     <see cref="Register"/> once at startup; the bootstrapper then materialises <c>Sql</c> DriverInstance
+///     rows into driver instances. Mirrors <c>ModbusDriverFactoryExtensions</c>.
+///     <para><b>This type owns the config validation the layers below deliberately skip.</b>
+///     <see cref="SqlPollReader"/> and <see cref="SqlDriver"/> stay usable with an inverted
+///     <c>operationTimeout</c>/<c>commandTimeout</c> pair on purpose (the frozen-database tests need that
+///     shape), so the factory is the only place a deployment can be stopped before it silently loses one of
+///     its two independent deadlines. Every knob is checked here, once, at construction.</para>
+///     <para><b>Enum fields are read leniently and written as names.</b> <see cref="JsonOptions"/> carries a
+///     <see cref="JsonStringEnumConverter"/>, so a <c>provider</c> authored as an ordinal still parses and a
+///     round-trip emits <c>"SqlServer"</c> — the systemic AdminUI defect where a page serialised an enum
+///     numerically while the consuming DTO was string-typed, faulting the driver at deploy time.</para>
+///     <para><b>The resolved connection string is a secret and never leaves this method except into the
+///     driver.</b> Every log line and every exception message here names the <c>connectionStringRef</c>, the
+///     environment variable, or <see cref="SqlDriver.Endpoint"/>'s credential-free <c>server/database</c>
+///     rendering — never the string itself.</para>
+/// </summary>
+public static class SqlDriverFactoryExtensions
+{
+    /// <summary>
+    ///     The driver-type string this factory registers under — chained off
+    ///     <see cref="SqlDriver.DriverTypeName"/>, which is
+    ///     <see cref="ZB.MOM.WW.OtOpcUa.Core.Abstractions.DriverTypeNames.Sql"/>.
+    /// </summary>
+    public const string DriverTypeName = SqlDriver.DriverTypeName;
+
+    /// <summary>
+    ///     How a <c>Sql</c> config blob is read.
+    ///     <list type="bullet">
+    ///         <item><see cref="JsonStringEnumConverter"/> — accepts an enum written as a name OR as an
+    ///         ordinal, and always writes the name (the enum-serialization guard).</item>
+    ///         <item><see cref="JsonUnmappedMemberHandling.Skip"/> — a blob authored against a different
+    ///         schema version must not brick the driver.</item>
+    ///         <item><see cref="JsonNamingPolicy.CamelCase"/> — the authored spelling
+    ///         (<c>connectionStringRef</c>, <c>rawTags</c>). Reads are case-insensitive anyway; the policy is
+    ///         what makes a <em>write</em> round-trip to the authored shape.</item>
+    ///     </list>
+    /// </summary>
+    internal static readonly JsonSerializerOptions JsonOptions = new()
+    {
+        PropertyNameCaseInsensitive = true,
+        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+        ReadCommentHandling = JsonCommentHandling.Skip,
+        AllowTrailingCommas = true,
+        UnmappedMemberHandling = JsonUnmappedMemberHandling.Skip,
+        Converters = { new JsonStringEnumConverter() },
+    };
+
+    /// <summary>The serializer options, exposed so tests can assert the enum guard on a real round-trip.</summary>
+    internal static JsonSerializerOptions JsonOptionsForTest => JsonOptions;
+
+    /// <summary>
+    ///     Registers the <c>Sql</c> factory with the driver registry. The optional
+    ///     <paramref name="loggerFactory"/> is captured at registration time and used to build a logger per
+    ///     driver instance; without it the driver runs with the null logger.
+    /// </summary>
+    /// <param name="registry">The driver factory registry to register with.</param>
+    /// <param name="loggerFactory">Optional logger factory for creating loggers per driver instance.</param>
+    /// <exception cref="ArgumentNullException"><paramref name="registry"/> is null.</exception>
+    public static void Register(DriverFactoryRegistry registry, ILoggerFactory? loggerFactory = null)
+    {
+        ArgumentNullException.ThrowIfNull(registry);
+        registry.Register(DriverTypeName, (id, json) => CreateInstance(id, json, loggerFactory));
+    }
+
+    /// <summary>Builds one driver instance from its config blob. For the Server bootstrapper and tests.</summary>
+    /// <param name="driverInstanceId">The central config DB's identity for this driver instance.</param>
+    /// <param name="driverConfigJson">The instance's <c>DriverConfig</c> JSON blob.</param>
+    /// <returns>The constructed <see cref="SqlDriver"/>.</returns>
+    public static SqlDriver CreateInstance(string driverInstanceId, string driverConfigJson)
+        => CreateInstance(driverInstanceId, driverConfigJson, loggerFactory: null);
+
+    /// <summary>
+    ///     Logger-aware overload — used by <see cref="Register"/>'s closure when wired through DI.
+    ///     <para>Constructs the driver only: the driver builds its own <see cref="SqlPollReader"/>, because
+    ///     the reader's <c>resolve</c> delegate must read the driver's live authored-tag table, which does not
+    ///     exist until the driver does.</para>
+    ///     <para>No I/O happens here. The database is first contacted by
+    ///     <see cref="SqlDriver.InitializeAsync"/>, so a database that is merely down yields a driver in
+    ///     Reconnecting rather than a deployment that cannot be constructed.</para>
+    /// </summary>
+    /// <param name="driverInstanceId">The central config DB's identity for this driver instance.</param>
+    /// <param name="driverConfigJson">The instance's <c>DriverConfig</c> JSON blob.</param>
+    /// <param name="loggerFactory">Optional logger factory for creating loggers per driver instance.</param>
+    /// <returns>The constructed <see cref="SqlDriver"/>.</returns>
+    /// <exception cref="ArgumentException">An argument is null, empty or whitespace.</exception>
+    /// <exception cref="InvalidOperationException">
+    ///     The blob is not valid JSON, omits <c>connectionStringRef</c>, names a provider this build cannot
+    ///     construct, carries an invalid knob, or the referenced connection string is not provisioned.
+    /// </exception>
+    public static SqlDriver CreateInstance(
+        string driverInstanceId, string driverConfigJson, ILoggerFactory? loggerFactory)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(driverInstanceId);
+        ArgumentException.ThrowIfNullOrWhiteSpace(driverConfigJson);
+
+        var dto = Deserialize(driverInstanceId, driverConfigJson);
+
+        if (string.IsNullOrWhiteSpace(dto.ConnectionStringRef))
+        {
+            throw new InvalidOperationException(
+                $"Sql driver config for '{driverInstanceId}' is missing the required connectionStringRef. " +
+                $"Author the NAME of a connection string (the value itself is supplied out-of-band through " +
+                $"the '{SqlConnectionStringResolver.EnvironmentVariablePrefix}<ref>' environment variable).");
+        }
+
+        var dialect = CreateDialect(dto.Provider, driverInstanceId);
+
+        // Resolved BEFORE the knob validation below, so that every subsequent throw is a path that HAS the
+        // secret in hand — which is exactly where a careless interpolation would leak it.
+        var connectionString = SqlConnectionStringResolver.Resolve(dto.ConnectionStringRef!);
+        var options = BuildOptions(dto, driverInstanceId);
+
+        var logger = (ILogger?)loggerFactory?.CreateLogger(typeof(SqlDriverFactoryExtensions).FullName!)
+                     ?? NullLogger.Instance;
+
+        if (dto.AllowWrites is true)
+        {
+            // Inert by construction (SqlDriver does not implement IWritable), so failing the driver over it
+            // would brick a deployment for a flag that cannot do harm. The operator who believes writes are
+            // on, however, can — so this is loud.
+            logger.LogWarning(
+                "Sql driver {DriverInstanceId} authored allowWrites=true, which this build ignores: the Sql " +
+                "driver is read-only (it implements no write capability), so no configuration can enable a " +
+                "write. Remove the flag, or expect reads only.",
+                driverInstanceId);
+        }
+
+        var driver = new SqlDriver(
+            options,
+            driverInstanceId,
+            dialect,
+            connectionString,
+            factory: null,
+            logger: loggerFactory?.CreateLogger<SqlDriver>());
+
+        // Endpoint is the credential-free server/database rendering — the ONLY form of the connection string
+        // permitted outside the provider call.
+        logger.LogInformation(
+            "Sql driver {DriverInstanceId} configured for {Provider} at {Endpoint} with {TagCount} " +
+            "authored tag(s), poll {PollInterval}, operation timeout {OperationTimeout}.",
+            driverInstanceId, dto.Provider, driver.Endpoint, options.RawTags.Count,
+            options.DefaultPollInterval, options.OperationTimeout);
+
+        return driver;
+    }
+
+    /// <summary>Deserialises the blob, turning a malformed one into an actionable, instance-named failure.</summary>
+    private static SqlDriverConfigDto Deserialize(string driverInstanceId, string driverConfigJson)
+    {
+        try
+        {
+            return JsonSerializer.Deserialize<SqlDriverConfigDto>(driverConfigJson, JsonOptions)
+                   ?? throw new InvalidOperationException(
+                       $"Sql driver config for '{driverInstanceId}' deserialised to null");
+        }
+        catch (JsonException ex)
+        {
+            throw new InvalidOperationException(
+                $"Sql driver config for '{driverInstanceId}' is not valid JSON: {ex.Message}", ex);
+        }
+    }
+
+    /// <summary>
+    ///     Selects the provider seam.
+    ///     <para>v1 constructs <see cref="SqlProvider.SqlServer"/> only. The other members exist on the shipped
+    ///     enum as reserved names; authoring one is a config mistake that must fail at construction with a
+    ///     message that says so, rather than silently degrading to T-SQL against a non-SQL-Server database.</para>
+    /// </summary>
+    private static ISqlDialect CreateDialect(SqlProvider provider, string driverInstanceId)
+        => provider switch
+        {
+            SqlProvider.SqlServer => new SqlServerDialect(),
+            _ => throw new InvalidOperationException(
+                $"Sql driver config for '{driverInstanceId}' names provider '{provider}', which is not " +
+                $"available in this build. Only '{nameof(SqlProvider.SqlServer)}' is supported."),
+        };
+
+    /// <summary>
+    ///     Applies the documented defaults and validates every knob (design §5.1 / §8.3).
+    ///     <para>Internal so the defaults and the rejections can be asserted directly, without a database or a
+    ///     provisioned connection string standing between the test and the rule.</para>
+    /// </summary>
+    /// <param name="dto">The deserialised config blob.</param>
+    /// <param name="driverInstanceId">Named in every rejection message, so a fleet-wide log identifies the row.</param>
+    /// <returns>The typed options the driver is constructed with.</returns>
+    /// <exception cref="InvalidOperationException">A knob is out of range, or the two deadlines are inverted.</exception>
+    internal static SqlDriverOptions BuildOptions(SqlDriverConfigDto dto, string driverInstanceId)
+    {
+        ArgumentNullException.ThrowIfNull(dto);
+
+        var defaultPollInterval = dto.DefaultPollInterval ?? TimeSpan.FromSeconds(5);
+        var operationTimeout = dto.OperationTimeout ?? TimeSpan.FromSeconds(15);
+        var commandTimeout = dto.CommandTimeout ?? TimeSpan.FromSeconds(10);
+        var maxConcurrentGroups = dto.MaxConcurrentGroups ?? 4;
+
+        RequirePositive(defaultPollInterval, "defaultPollInterval", driverInstanceId);
+        RequirePositive(operationTimeout, "operationTimeout", driverInstanceId);
+        RequirePositive(commandTimeout, "commandTimeout", driverInstanceId);
+        if (maxConcurrentGroups < 1)
+        {
+            throw new InvalidOperationException(
+                $"Sql driver config for '{driverInstanceId}' has maxConcurrentGroups {maxConcurrentGroups}; " +
+                $"it must be at least 1.");
+        }
+
+        // Design §8.3. The two deadlines are independent and BOTH are required: commandTimeout is the
+        // server-side backstop, operationTimeout the client-side wall-clock bound that alone survives a
+        // wedged socket (the R2-01/STAB-14 lesson). Inverted — or equal — the client-side abort always fires
+        // first and the backstop can never be reached, so a deployment quietly runs on one bound instead of
+        // two. Nothing downstream enforces this: the reader stays deliberately usable with it inverted.
+        if (operationTimeout <= commandTimeout)
+        {
+            throw new InvalidOperationException(
+                $"Sql driver config for '{driverInstanceId}' has operationTimeout {operationTimeout} which " +
+                $"is not greater than commandTimeout {commandTimeout}. The client-side operationTimeout must " +
+                $"be strictly greater than the server-side commandTimeout backstop, or the backstop can " +
+                $"never fire.");
+        }
+
+        return new SqlDriverOptions
+        {
+            RawTags = dto.RawTags is { Count: > 0 } rawTags ? [.. rawTags] : [],
+            DefaultPollInterval = defaultPollInterval,
+            OperationTimeout = operationTimeout,
+            CommandTimeout = commandTimeout,
+            MaxConcurrentGroups = maxConcurrentGroups,
+            NullIsBad = dto.NullIsBad ?? false,
+        };
+    }
+
+    /// <summary>Rejects a non-positive duration, naming the authored field.</summary>
+    private static void RequirePositive(TimeSpan value, string field, string driverInstanceId)
+    {
+        if (value <= TimeSpan.Zero)
+        {
+            throw new InvalidOperationException(
+                $"Sql driver config for '{driverInstanceId}' has {field} {value}; it must be greater than zero.");
+        }
+    }
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql/SqlDriverOptions.cs

@@ -0,0 +1,56 @@
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql;
+
+/// <summary>
+///     The typed form of a <c>Sql</c> driver instance's configuration — what
+///     <see cref="SqlDriverConfigDto"/> becomes once the factory has applied its defaults (design §5.1).
+///     Mirrors <c>ModbusDriverOptions</c>: the driver instance is constructed with these, and its
+///     <see cref="SqlDriver.InitializeAsync"/> serves them rather than re-parsing the config JSON.
+///     <para><b>No connection string here.</b> The resolved connection string is a separate constructor
+///     argument, because it is a secret and these options are safe to log, diff and hold in a snapshot.</para>
+/// </summary>
+public sealed class SqlDriverOptions
+{
+    /// <summary>
+    ///     The authored raw tags this driver serves. The deploy artifact hands each authored raw <c>Tag</c>
+    ///     as a <see cref="RawTagEntry"/> (RawPath identity + driver <c>TagConfig</c> blob); the driver maps
+    ///     each through <see cref="SqlEquipmentTagParser.TryParse"/> into its RawPath → definition table.
+    ///     A SQL source has no tag-discovery protocol — the driver serves exactly these.
+    /// </summary>
+    public IReadOnlyList<RawTagEntry> RawTags { get; init; } = [];
+
+    /// <summary>
+    ///     Poll interval used when a subscriber does not ask for one (design §4: <c>defaultPollInterval</c>,
+    ///     default 5 s). A subscriber that names an interval gets that interval, floored by
+    ///     <see cref="PollGroupEngine.DefaultMinInterval"/>.
+    /// </summary>
+    public TimeSpan DefaultPollInterval { get; init; } = TimeSpan.FromSeconds(5);
+
+    /// <summary>
+    ///     The client-side wall-clock ceiling on one group query (design §8.3, default 15 s). A breach
+    ///     publishes <see cref="SqlStatusCodes.BadTimeout"/> for that group's tags.
+    /// </summary>
+    public TimeSpan OperationTimeout { get; init; } = TimeSpan.FromSeconds(15);
+
+    /// <summary>
+    ///     The ADO.NET <c>CommandTimeout</c> server-side backstop (default 10 s), also the bound on the
+    ///     Initialize-time liveness check.
+    ///     <para>Authoring must keep <see cref="OperationTimeout"/> strictly greater than this (design §8.3);
+    ///     inverted, the client-side abort always fires first and masks the backstop. <b>That rule is
+    ///     enforced by config validation in the factory, not here</b> — the reader deliberately stays usable
+    ///     with the order inverted so the frozen-database tests can prove the client-side bound fires.</para>
+    /// </summary>
+    public TimeSpan CommandTimeout { get; init; } = TimeSpan.FromSeconds(10);
+
+    /// <summary>Cap on concurrently executing group queries — and therefore on concurrently open connections.</summary>
+    public int MaxConcurrentGroups { get; init; } = 4;
+
+    /// <summary>
+    ///     When <see langword="true"/>, a present row whose value cell is NULL publishes
+    ///     <see cref="SqlStatusCodes.Bad"/> instead of the default <see cref="SqlStatusCodes.Uncertain"/>.
+    ///     It never governs an absent row, which is always <see cref="SqlStatusCodes.BadNoData"/>.
+    /// </summary>
+    public bool NullIsBad { get; init; }
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql/SqlDriverProbe.cs

@@ -0,0 +1,171 @@
+using System.Data.Common;
+using System.Diagnostics;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql;
+
+/// <summary>
+///     The AdminUI "Test Connect" liveness check for the <c>Sql</c> driver: open a connection, run the
+///     dialect's <c>SELECT 1</c> (<see cref="ISqlDialect.LivenessSql"/>) under a bounded deadline, and report
+///     green with latency or red with a reason. Mirrors <c>ModbusDriverProbe</c>.
+///     <para><b>Parses the SAME factory DTO with the SAME converter as
+///     <see cref="SqlDriverFactoryExtensions"/></b> (R2-11, 05/CONV-2 — the OpcUaClient parity rule), so a
+///     config the operator Test-Connects is byte-for-byte the config that Deploys: a numerically serialised
+///     <c>provider</c> parses here exactly as it does at the factory, and the same
+///     <c>connectionStringRef</c> resolves the same way.</para>
+///     <para><b>Never throws</b> (the <see cref="IDriverProbe"/> contract). Every failure — malformed JSON, a
+///     missing <c>connectionStringRef</c>, an unprovisioned connection string, a provider open failure, a
+///     timeout, a cancellation — becomes a red <see cref="DriverProbeResult"/>, so the AdminUI has nothing to
+///     catch.</para>
+///     <para><b>The resolved connection string never reaches the result message.</b> A red result names the
+///     failure class, never the string — the same credential discipline the factory and the driver keep.</para>
+/// </summary>
+public sealed class SqlDriverProbe : IDriverProbe
+{
+    /// <summary>
+    ///     Selects the provider seam by <see cref="SqlProvider"/>. In production this constructs the real
+    ///     <see cref="SqlServerDialect"/>; <see cref="ForTest"/> injects a test dialect (and factory) so the
+    ///     probe can run against the SQLite fixture with no SQL Server and no network.
+    /// </summary>
+    private readonly Func<SqlProvider, ISqlDialect> _dialectFor;
+
+    /// <summary>
+    ///     Overrides the dialect's own <see cref="ISqlDialect.Factory"/> when non-null — the injection point
+    ///     the SQLite tests use to hand in <c>SqliteFactory</c> while keeping the test dialect's
+    ///     catalog SQL. Null in production: the dialect's own factory is used.
+    /// </summary>
+    private readonly DbProviderFactory? _factoryOverride;
+
+    /// <summary>Initializes a new <see cref="SqlDriverProbe"/> that constructs the real SQL Server dialect.</summary>
+    public SqlDriverProbe()
+        : this(DefaultDialectFor, factoryOverride: null)
+    {
+    }
+
+    private SqlDriverProbe(Func<SqlProvider, ISqlDialect> dialectFor, DbProviderFactory? factoryOverride)
+    {
+        _dialectFor = dialectFor;
+        _factoryOverride = factoryOverride;
+    }
+
+    /// <summary>
+    ///     Test seam: a probe that always uses <paramref name="dialect"/> and opens connections from
+    ///     <paramref name="factory"/>, so the SQLite fixture's create → open → <c>SELECT 1</c> → close cycle
+    ///     runs unmodified.
+    /// </summary>
+    /// <param name="factory">The provider factory the probe opens connections from.</param>
+    /// <param name="dialect">The dialect whose <see cref="ISqlDialect.LivenessSql"/> the probe runs.</param>
+    /// <returns>A probe wired to the supplied factory + dialect.</returns>
+    /// <exception cref="ArgumentNullException">A required argument is null.</exception>
+    internal static SqlDriverProbe ForTest(DbProviderFactory factory, ISqlDialect dialect)
+    {
+        ArgumentNullException.ThrowIfNull(factory);
+        ArgumentNullException.ThrowIfNull(dialect);
+        return new SqlDriverProbe(_ => dialect, factory);
+    }
+
+    /// <inheritdoc />
+    public string DriverType => SqlDriver.DriverTypeName;
+
+    /// <inheritdoc />
+    public async Task<DriverProbeResult> ProbeAsync(string configJson, TimeSpan timeout, CancellationToken ct)
+    {
+        // Parse + resolve first: a config that cannot even be read is a red result, not a connection attempt.
+        SqlDriverConfigDto? dto;
+        try
+        {
+            dto = System.Text.Json.JsonSerializer.Deserialize<SqlDriverConfigDto>(
+                configJson, SqlDriverFactoryExtensions.JsonOptions);
+        }
+        catch (Exception ex) when (ex is System.Text.Json.JsonException or ArgumentNullException)
+        {
+            return new DriverProbeResult(false, $"Config JSON is invalid: {ex.Message}", null);
+        }
+
+        if (dto is null)
+            return new DriverProbeResult(false, "Config JSON deserialized to null.", null);
+        if (string.IsNullOrWhiteSpace(dto.ConnectionStringRef))
+            return new DriverProbeResult(false, "Config has no connectionStringRef to resolve.", null);
+
+        ISqlDialect dialect;
+        string connectionString;
+        try
+        {
+            dialect = _dialectFor(dto.Provider);
+            connectionString = SqlConnectionStringResolver.Resolve(dto.ConnectionStringRef!);
+        }
+        catch (InvalidOperationException ex)
+        {
+            // Resolve throws with only the ref + env-var name — no secret in the message, so surfacing it is
+            // safe and actionable (it names the environment variable the operator must set).
+            return new DriverProbeResult(
+                false, $"Could not run the SQL liveness check ({ex.GetType().Name}).", null);
+        }
+
+        var factory = _factoryOverride ?? dialect.Factory;
+        return await RunLivenessAsync(factory, dialect, connectionString, timeout, ct).ConfigureAwait(false);
+    }
+
+    /// <summary>
+    ///     Opens one connection under a linked CTS bounded by <paramref name="timeout"/>, runs the dialect's
+    ///     liveness statement, and returns green with latency. Any failure becomes a red result whose message
+    ///     names the failure class — <b>never the connection string</b> (a provider exception can embed the
+    ///     data source, so its <c>.Message</c> is deliberately not surfaced).
+    /// </summary>
+    private static async Task<DriverProbeResult> RunLivenessAsync(
+        DbProviderFactory factory, ISqlDialect dialect, string connectionString, TimeSpan timeout,
+        CancellationToken ct)
+    {
+        var stopwatch = Stopwatch.StartNew();
+        using var cts = CancellationTokenSource.CreateLinkedTokenSource(ct);
+        if (timeout > TimeSpan.Zero) cts.CancelAfter(timeout);
+
+        try
+        {
+            var connection = factory.CreateConnection()
+                             ?? throw new InvalidOperationException(
+                                 $"the {dialect.Provider} provider factory returned no connection.");
+            await using (connection.ConfigureAwait(false))
+            {
+                connection.ConnectionString = connectionString;
+                await connection.OpenAsync(cts.Token).ConfigureAwait(false);
+
+                var command = connection.CreateCommand();
+                await using (command.ConfigureAwait(false))
+                {
+                    command.CommandText = dialect.LivenessSql;
+                    await command.ExecuteScalarAsync(cts.Token).ConfigureAwait(false);
+                }
+            }
+
+            stopwatch.Stop();
+            return new DriverProbeResult(true, "SQL SELECT 1 OK", stopwatch.Elapsed);
+        }
+        catch (OperationCanceledException) when (ct.IsCancellationRequested)
+        {
+            return new DriverProbeResult(false, "Probe cancelled.", null);
+        }
+        catch (OperationCanceledException)
+        {
+            return new DriverProbeResult(
+                false, $"Probe timed out after {timeout.TotalSeconds:F0}s.", null);
+        }
+        catch (Exception ex)
+        {
+            // The provider's own message can carry the data source (host/database), which is not a secret but
+            // is more than the operator needs — and keeping the message to a fixed class is what guarantees no
+            // credential-bearing connection string can ever slip through. Name the exception TYPE only.
+            return new DriverProbeResult(
+                false, $"Could not run the SQL liveness check ({ex.GetType().Name}).", null);
+        }
+    }
+
+    /// <summary>Constructs the production dialect for a provider; v1 supports SQL Server only.</summary>
+    private static ISqlDialect DefaultDialectFor(SqlProvider provider) => provider switch
+    {
+        SqlProvider.SqlServer => new SqlServerDialect(),
+        _ => throw new InvalidOperationException(
+            $"provider '{provider}' is not available in this build (only SqlServer is supported)."),
+    };
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql/SqlGroupPlanner.cs

@@ -0,0 +1,250 @@
+using System.Globalization;
+using System.Text;
+using ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql;
+
+/// <summary>
+///     Folds a set of <see cref="SqlTagDefinition"/>s into the minimum number of parameterized queries
+///     (design §3.6) — the driver's batching core. Pure and side-effect free: no connection, no I/O, no clock.
+///     <para><b>The GroupKey is the correctness contract.</b> Two tags share a query <em>only</em> when every
+///     field that shapes the result set is identical. Too coarse and a tag silently reads a neighbour's cell;
+///     too fine and batching degenerates to one round-trip per tag. Both directions are pinned by
+///     <c>SqlGroupPlannerTests</c>.</para>
+///     <para><b>Injection boundary (design §8.1).</b> Identifiers reach the command text through
+///     <see cref="ISqlDialect.QuoteIdentifier"/> and nothing else; every authored value becomes a
+///     <c>@k0</c>/<c>@w</c> marker with the value carried in <see cref="SqlQueryPlan.Parameters"/>. There is no
+///     interpolation of tag content into SQL anywhere in this type.</para>
+/// </summary>
+public static class SqlGroupPlanner
+{
+    /// <summary>The parameter-marker prefix for a key-value model's <c>IN</c> list.</summary>
+    private const string KeyMarkerPrefix = "@k";
+
+    /// <summary>The single parameter marker for a wide-row model's row selector.</summary>
+    private const string RowSelectorMarker = "@w";
+
+    /// <summary>
+    ///     Groups <paramref name="tags"/> by source and emits one <see cref="SqlQueryPlan"/> per group.
+    ///     <para>Deterministic: groups appear in the input order of their first member, members keep their input
+    ///     order within a group, and parameters keep the first-appearance order of their distinct values — so a
+    ///     given tag list always yields byte-identical SQL.</para>
+    /// </summary>
+    /// <param name="tags">The tags to plan. An empty sequence yields no plans.</param>
+    /// <param name="dialect">Supplies identifier quoting and the provider's row-limit syntax.</param>
+    /// <returns>One plan per distinct group key.</returns>
+    /// <exception cref="ArgumentNullException"><paramref name="tags"/> or <paramref name="dialect"/> is null.</exception>
+    /// <exception cref="ArgumentException">
+    ///     A definition is missing a field its model requires (e.g. a wide-row tag with no row selector), or an
+    ///     identifier cannot be quoted (an empty table-name part, a control character — see
+    ///     <see cref="ISqlDialect.QuoteIdentifier"/>). <see cref="SqlEquipmentTagParser"/> rejects all of these
+    ///     up front, so reaching one here means a caller built a definition by hand with a broken invariant.
+    /// </exception>
+    /// <exception cref="NotSupportedException">
+    ///     A tag carries <see cref="SqlTagModel.Query"/> (design §5.4, deferred to P3).
+    ///     <b>Deliberately loud rather than skipped:</b> silently dropping a tag would leave an authored node
+    ///     permanently unfed with nothing in the log, and the parser makes this branch unreachable in practice.
+    /// </exception>
+    public static IReadOnlyList<SqlQueryPlan> Plan(IEnumerable<SqlTagDefinition> tags, ISqlDialect dialect)
+    {
+        ArgumentNullException.ThrowIfNull(tags);
+        ArgumentNullException.ThrowIfNull(dialect);
+
+        // Ordered grouping: the dictionary decides membership, the list decides emission order.
+        var order = new List<object>();
+        var groups = new Dictionary<object, List<SqlTagDefinition>>();
+
+        foreach (var tag in tags)
+        {
+            ArgumentNullException.ThrowIfNull(tag);
+            var key = BuildGroupKey(tag);
+            if (!groups.TryGetValue(key, out var members))
+            {
+                members = [];
+                groups.Add(key, members);
+                order.Add(key);
+            }
+
+            members.Add(tag);
+        }
+
+        var plans = new List<SqlQueryPlan>(order.Count);
+        foreach (var key in order)
+        {
+            var members = groups[key];
+            plans.Add(members[0].Model switch
+            {
+                SqlTagModel.KeyValue => BuildKeyValuePlan(key, members, dialect),
+                SqlTagModel.WideRow => BuildWideRowPlan(key, members, dialect),
+                _ => throw UnsupportedModel(members[0]),
+            });
+        }
+
+        return plans;
+    }
+
+    /// <summary>
+    ///     Composes the equality key that decides which tags share a query. Both models produce a 5-tuple whose
+    ///     first element is the model, so a key-value key can never compare equal to a wide-row key.
+    ///     <list type="bullet">
+    ///         <item>
+    ///             <see cref="SqlTagModel.KeyValue"/> → <c>(model, table, keyColumn, valueColumn, timestampColumn)</c>.
+    ///             Every one of those shapes the emitted SELECT: sharing a plan across two <c>valueColumn</c>s
+    ///             would make one tag publish the other's column.
+    ///         </item>
+    ///         <item>
+    ///             <see cref="SqlTagModel.WideRow"/> → <c>(model, table, whereColumn, whereValue, topByTimestamp)</c>
+    ///             — i.e. the table plus the whole row selector, exactly design §5.3's
+    ///             <c>(table, rowSelector)</c>. The members' own <c>columnName</c>/<c>timestampColumn</c> are
+    ///             deliberately <b>not</b> in the key: differing there is the point of the model (many columns,
+    ///             one row), and they are added to the SELECT list instead.
+    ///         </item>
+    ///     </list>
+    ///     <para>String comparison is <b>ordinal</b>. SQL Server object names are usually case-insensitive, so
+    ///     two tags authored <c>dbo.T</c> and <c>DBO.T</c> plan as two groups. That costs one extra round-trip
+    ///     and is never wrong; guessing the server's collation here could fold two genuinely different sources.</para>
+    /// </summary>
+    private static object BuildGroupKey(SqlTagDefinition tag) => tag.Model switch
+    {
+        SqlTagModel.KeyValue => (tag.Model, tag.Table, tag.KeyColumn, tag.ValueColumn, tag.TimestampColumn),
+        SqlTagModel.WideRow => (tag.Model, tag.Table, tag.RowSelectorColumn, tag.RowSelectorValue,
+            tag.RowSelectorTopByTimestamp),
+        _ => throw UnsupportedModel(tag),
+    };
+
+    /// <summary>
+    ///     Emits <c>SELECT &lt;key&gt;, &lt;value&gt;[, &lt;ts&gt;] FROM &lt;table&gt; WHERE &lt;key&gt; IN (@k0..@kN)</c>.
+    ///     The key column is selected because the reader indexes rows by it to slice values back per member.
+    ///     <para>Keys are de-duplicated (ordinal) before binding: two tags authored against the same
+    ///     <c>keyValue</c> bind one parameter but stay two members, so both nodes are fed from the one row.</para>
+    /// </summary>
+    private static SqlQueryPlan BuildKeyValuePlan(
+        object groupKey, List<SqlTagDefinition> members, ISqlDialect dialect)
+    {
+        var first = members[0];
+        var keyColumn = RequireIdentifier(first.KeyColumn, nameof(SqlTagDefinition.KeyColumn), first);
+        var valueColumn = RequireIdentifier(first.ValueColumn, nameof(SqlTagDefinition.ValueColumn), first);
+        var timestampColumn = Blank(first.TimestampColumn) ? null : first.TimestampColumn;
+
+        var selected = new List<string>(3);
+        AddDistinct(selected, keyColumn);
+        AddDistinct(selected, valueColumn);
+        if (timestampColumn is not null) AddDistinct(selected, timestampColumn);
+
+        // A keyValue may legitimately be the empty string, so only null is a broken invariant.
+        var names = new List<string>(members.Count);
+        var values = new List<object?>(members.Count);
+        var seen = new HashSet<string>(StringComparer.Ordinal);
+        foreach (var member in members)
+        {
+            var keyValue = member.KeyValue
+                           ?? throw MissingField(nameof(SqlTagDefinition.KeyValue), member);
+            if (!seen.Add(keyValue)) continue;
+            names.Add(KeyMarkerPrefix + values.Count.ToString(CultureInfo.InvariantCulture));
+            values.Add(keyValue);
+        }
+
+        var sql = new StringBuilder("SELECT ")
+            .Append(QuoteList(selected, dialect))
+            .Append(" FROM ").Append(QuoteQualifiedName(first.Table, dialect))
+            .Append(" WHERE ").Append(dialect.QuoteIdentifier(keyColumn))
+            .Append(" IN (").AppendJoin(", ", names).Append(')')
+            .ToString();
+
+        return new SqlQueryPlan(SqlTagModel.KeyValue, groupKey, sql, names, values, members, selected);
+    }
+
+    /// <summary>
+    ///     Emits <c>SELECT &lt;cols&gt; FROM &lt;table&gt; WHERE &lt;whereColumn&gt; = @w</c>, or — for a
+    ///     <c>topByTimestamp</c> selector — the single-row form
+    ///     <c>SELECT &lt;limit&gt; &lt;cols&gt; FROM &lt;table&gt; ORDER BY &lt;ts&gt; DESC &lt;limit&gt;</c>, whose
+    ///     row limit comes from <see cref="ISqlDialect.SingleRowLimitPrefix"/> /
+    ///     <see cref="ISqlDialect.SingleRowLimitSuffix"/> (T-SQL fills the prefix: <c>SELECT TOP 1 …</c>).
+    ///     <para>The SELECT list is each member's <c>columnName</c> (distinct, in first-appearance order),
+    ///     followed by each distinct member <c>timestampColumn</c> — so members of one row may carry different
+    ///     timestamp columns without splitting the group. The where-column itself is <b>not</b> selected: every
+    ///     row in the result already matches the bound value, so reading it back adds nothing.</para>
+    /// </summary>
+    private static SqlQueryPlan BuildWideRowPlan(
+        object groupKey, List<SqlTagDefinition> members, ISqlDialect dialect)
+    {
+        var first = members[0];
+
+        var selected = new List<string>(members.Count + 1);
+        foreach (var member in members)
+            AddDistinct(selected, RequireIdentifier(member.ColumnName, nameof(SqlTagDefinition.ColumnName), member));
+        foreach (var member in members)
+            if (!Blank(member.TimestampColumn))
+                AddDistinct(selected, member.TimestampColumn!);
+
+        var table = QuoteQualifiedName(first.Table, dialect);
+        var columns = QuoteList(selected, dialect);
+
+        // A where-pair wins over topByTimestamp; the parser already guarantees exactly one is populated.
+        if (!Blank(first.RowSelectorColumn) && first.RowSelectorValue is not null)
+        {
+            var sql = string.Concat(
+                "SELECT ", columns, " FROM ", table,
+                " WHERE ", dialect.QuoteIdentifier(first.RowSelectorColumn!), " = ", RowSelectorMarker);
+            return new SqlQueryPlan(
+                SqlTagModel.WideRow, groupKey, sql,
+                [RowSelectorMarker], [first.RowSelectorValue], members, selected);
+        }
+
+        if (!Blank(first.RowSelectorTopByTimestamp))
+        {
+            // The row limit is dialect syntax and sits at opposite ends of the statement per provider
+            // (T-SQL "SELECT TOP 1 …", SQLite/Postgres/MySQL "… LIMIT 1"), so both ends are emitted
+            // unconditionally and the dialect decides which one it fills. See ISqlDialect.SingleRowLimitPrefix.
+            var sql = string.Concat(
+                "SELECT ", dialect.SingleRowLimitPrefix, columns, " FROM ", table,
+                " ORDER BY ", dialect.QuoteIdentifier(first.RowSelectorTopByTimestamp!), " DESC",
+                dialect.SingleRowLimitSuffix);
+            return new SqlQueryPlan(SqlTagModel.WideRow, groupKey, sql, [], [], members, selected);
+        }
+
+        throw new ArgumentException(
+            $"Wide-row tag '{first.Name}' has no row selector: author either a rowSelector.whereColumn/" +
+            "whereValue pair or a rowSelector.topByTimestamp column.", nameof(members));
+    }
+
+    /// <summary>
+    ///     Quotes a possibly multi-part object name by splitting on <c>.</c> and quoting each part —
+    ///     <c>dbo.TagValues</c> becomes <c>[dbo].[TagValues]</c>.
+    ///     <para><see cref="ISqlDialect.QuoteIdentifier"/> quotes exactly <b>one</b> part; handing it the dotted
+    ///     form would yield <c>[dbo.TagValues]</c>, which is safe but names an object that does not exist. An
+    ///     empty part (<c>dbo..T</c>) is rejected by the dialect rather than emitted. As a consequence an object
+    ///     whose real name contains a literal <c>.</c> cannot be authored — an accepted v1 limitation.</para>
+    /// </summary>
+    private static string QuoteQualifiedName(string name, ISqlDialect dialect)
+    {
+        if (Blank(name))
+            throw new ArgumentException("A Sql tag's 'table' must be a non-empty object name.", nameof(name));
+
+        return string.Join('.', name.Split('.').Select(dialect.QuoteIdentifier));
+    }
+
+    /// <summary>Quotes each already-de-duplicated column name and joins them into a SELECT list.</summary>
+    private static string QuoteList(IReadOnlyList<string> columns, ISqlDialect dialect)
+        => string.Join(", ", columns.Select(dialect.QuoteIdentifier));
+
+    /// <summary>Appends <paramref name="value"/> unless an ordinal-equal entry is already present.</summary>
+    private static void AddDistinct(List<string> target, string value)
+    {
+        if (!target.Contains(value, StringComparer.Ordinal)) target.Add(value);
+    }
+
+    /// <summary>True when the string is null, empty, or all whitespace — i.e. cannot be an identifier.</summary>
+    private static bool Blank(string? value) => string.IsNullOrWhiteSpace(value);
+
+    /// <summary>Returns a required identifier field, or throws naming both the tag and the field.</summary>
+    private static string RequireIdentifier(string? value, string field, SqlTagDefinition tag)
+        => Blank(value) ? throw MissingField(field, tag) : value!;
+
+    private static ArgumentException MissingField(string field, SqlTagDefinition tag)
+        => new($"Sql tag '{tag.Name}' ({tag.Model}) is missing the required '{field}'.");
+
+    private static NotSupportedException UnsupportedModel(SqlTagDefinition tag)
+        => new($"Sql tag '{tag.Name}' uses the {tag.Model} model, which the poll planner does not support. " +
+               "v1 plans KeyValue and WideRow only; the named-query model is deferred (design §5.4).");
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql/SqlPollReader.cs

@@ -0,0 +1,839 @@
+using System.Data.Common;
+using System.Diagnostics;
+using System.Globalization;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql;
+
+/// <summary>
+///     Executes one poll pass: resolves each requested reference to a <see cref="SqlTagDefinition"/>, folds
+///     the definitions into the minimum number of queries via <see cref="SqlGroupPlanner"/>, runs one
+///     command per group under a bounded deadline, and slices each result set back to per-tag
+///     <see cref="DataValueSnapshot"/>s — <b>positionally aligned with the caller's reference list</b>
+///     (design §3.2). Structurally the SQL analogue of <c>ModbusDriver.ReadCoalescedAsync</c>: group → one
+///     round-trip → slice back.
+///     <para><b>N in, N out, in order.</b> The returned list always has exactly one entry per requested
+///     reference, at the same index, whatever happened. Per-tag failures are Bad-coded snapshots, never
+///     exceptions (the <see cref="IReadable"/> contract) — see <see cref="SqlStatusCodes"/> for which code
+///     means what. This matters more here than in a point-to-point driver: one result set feeds many tags,
+///     so a slicing defect does not fail loudly — it publishes <em>one tag's value onto another tag's
+///     node</em>.</para>
+///     <para><b>The whole call throws only when the database is unreachable</b> — that is, when opening a
+///     connection fails. That surfaces to <see cref="PollGroupEngine"/> as a poll failure and earns the
+///     capped-exponential backoff; the driver's <c>IHostConnectivityProbe</c> is what scopes Bad quality
+///     across the subtree during an outage, so nothing is lost by not manufacturing per-tag snapshots for
+///     an outage. A query that fails <em>after</em> the connection opened is the group's problem, not the
+///     server's, and Bad-codes that group only.</para>
+///     <para><b>Deadlines (design §8.3, the R2-01 frozen-peer lesson).</b> Two independent mechanisms, both
+///     required. <c>CommandTimeout</c> is the <em>server-side</em> backstop and bounds nothing on a wedged
+///     socket. The wall-clock bound is client-side and is what actually guarantees this method returns: see
+///     <see cref="RunGroupAsync"/>. A frozen database yields <see cref="SqlStatusCodes.BadTimeout"/>
+///     snapshots — it must never wedge the poll thread.</para>
+///     <para><b>Not a driver.</b> This type owns the read path only; it deliberately holds no health state,
+///     no subscription state and no connection between polls, so the driver shell can wrap it in
+///     <see cref="PollGroupEngine"/> and own those concerns.</para>
+/// </summary>
+public sealed class SqlPollReader
+{
+    /// <summary>Minimum spacing between "your source violates the query contract" warnings, per reader.</summary>
+    private static readonly TimeSpan ContractWarningInterval = TimeSpan.FromMinutes(1);
+
+    private readonly DbProviderFactory _factory;
+    private readonly string _connectionString;
+    private readonly ISqlDialect _dialect;
+    private readonly TimeSpan _operationTimeout;
+    private readonly int _commandTimeoutSeconds;
+    private readonly bool _nullIsBad;
+    private readonly Func<string, SqlTagDefinition?> _resolve;
+    private readonly ILogger _logger;
+
+    /// <summary>
+    ///     Caps concurrently executing group queries — and therefore concurrently held connections
+    ///     (design §8.4). Never disposed: a <see cref="SemaphoreSlim"/> only needs disposal once its
+    ///     <c>AvailableWaitHandle</c> has been touched, and not disposing it also removes the hazard of a
+    ///     timed-out-but-still-running group releasing into a disposed semaphore.
+    /// </summary>
+    private readonly SemaphoreSlim _gate;
+
+    private long _lastContractWarningTicks;
+
+    /// <summary>Initializes a new instance of the <see cref="SqlPollReader"/> class.</summary>
+    /// <param name="factory">
+    ///     Creates the provider's connections. Passed explicitly rather than taken from
+    ///     <paramref name="dialect"/> so the driver can hand in an instrumented or pre-configured factory.
+    /// </param>
+    /// <param name="connectionString">
+    ///     The resolved connection string (never the authored <c>connectionStringRef</c> — secrets are
+    ///     resolved by the driver at Initialize, design §8.2).
+    /// </param>
+    /// <param name="dialect">Supplies identifier quoting, row-limit syntax, and column-type mapping.</param>
+    /// <param name="commandTimeout">
+    ///     The ADO.NET <c>CommandTimeout</c> backstop. Rounded <b>up</b> to whole seconds and floored at 1,
+    ///     because ADO.NET reads <c>CommandTimeout = 0</c> as "wait forever" — the one value this option
+    ///     must never silently become.
+    /// </param>
+    /// <param name="operationTimeout">
+    ///     The wall-clock ceiling on one group's whole operation — waiting for a concurrency slot, opening
+    ///     the connection, and running the query. A breach Bad-codes that group with
+    ///     <see cref="SqlStatusCodes.BadTimeout"/>.
+    ///     <para>Authoring should keep this strictly greater than <paramref name="commandTimeout"/>
+    ///     (design §8.3): inverted, the client-side abort always fires first and masks the server-side
+    ///     backstop. That rule is <b>not</b> enforced here — it belongs to config validation, and this type
+    ///     stays usable for the tests that must deliberately invert it.</para>
+    /// </param>
+    /// <param name="maxConcurrentGroups">
+    ///     Maximum group queries — and connections — in flight at once. A timed-out group keeps its slot
+    ///     until it truly finishes, so this is a hard ceiling on connections even against a frozen database.
+    ///     See <see cref="RunGroupAsync"/> for why a high value is safe under
+    ///     <c>Microsoft.Data.SqlClient</c> but wants sizing against thread-pool headroom under a provider
+    ///     that blocks synchronously.
+    /// </param>
+    /// <param name="nullIsBad">
+    ///     <see langword="true"/> publishes <see cref="SqlStatusCodes.Bad"/> for a NULL value cell instead
+    ///     of the default <see cref="SqlStatusCodes.Uncertain"/>. It governs a <em>present</em> row with a
+    ///     NULL cell only — an absent row is always <see cref="SqlStatusCodes.BadNoData"/>.
+    /// </param>
+    /// <param name="resolve">
+    ///     RawPath → tag definition; <see langword="null"/> on a miss. Shaped to match
+    ///     <see cref="EquipmentTagRefResolver{TDef}"/>'s lookup so the driver can pass its authored table
+    ///     straight through.
+    /// </param>
+    /// <param name="logger">Optional; defaults to a no-op logger.</param>
+    /// <exception cref="ArgumentNullException">A required reference argument is null.</exception>
+    /// <exception cref="ArgumentException"><paramref name="connectionString"/> is blank.</exception>
+    /// <exception cref="ArgumentOutOfRangeException">A timeout is non-positive, or the cap is below 1.</exception>
+    public SqlPollReader(
+        DbProviderFactory factory,
+        string connectionString,
+        ISqlDialect dialect,
+        TimeSpan commandTimeout,
+        TimeSpan operationTimeout,
+        int maxConcurrentGroups,
+        bool nullIsBad,
+        Func<string, SqlTagDefinition?> resolve,
+        ILogger? logger = null)
+    {
+        ArgumentNullException.ThrowIfNull(factory);
+        ArgumentNullException.ThrowIfNull(dialect);
+        ArgumentNullException.ThrowIfNull(resolve);
+        if (string.IsNullOrWhiteSpace(connectionString))
+            throw new ArgumentException("A Sql poll reader needs a connection string.", nameof(connectionString));
+        ArgumentOutOfRangeException.ThrowIfLessThanOrEqual(commandTimeout, TimeSpan.Zero);
+        ArgumentOutOfRangeException.ThrowIfLessThanOrEqual(operationTimeout, TimeSpan.Zero);
+        ArgumentOutOfRangeException.ThrowIfLessThan(maxConcurrentGroups, 1);
+
+        _factory = factory;
+        _connectionString = connectionString;
+        _dialect = dialect;
+        _operationTimeout = operationTimeout;
+        _commandTimeoutSeconds = Math.Max(1, (int)Math.Ceiling(commandTimeout.TotalSeconds));
+        _nullIsBad = nullIsBad;
+        _resolve = resolve;
+        _logger = logger ?? NullLogger.Instance;
+        _gate = new SemaphoreSlim(maxConcurrentGroups, maxConcurrentGroups);
+    }
+
+    /// <summary>
+    ///     Reads every reference in one poll pass. Matches <see cref="IReadable.ReadAsync"/>'s shape so the
+    ///     driver shell can delegate to it directly.
+    /// </summary>
+    /// <param name="fullReferences">The RawPaths to read. Empty yields an empty result and touches no connection.</param>
+    /// <param name="cancellationToken">
+    ///     The caller's token. Its cancellation <b>propagates</b> as an
+    ///     <see cref="OperationCanceledException"/> — the engine asked the poll to stop, and nobody is
+    ///     waiting for the snapshots. This is deliberately asymmetric with an <c>operationTimeout</c>
+    ///     breach, which is a data-quality fact clients must see and so becomes
+    ///     <see cref="SqlStatusCodes.BadTimeout"/> snapshots.
+    /// </param>
+    /// <returns>One snapshot per reference, at the same index.</returns>
+    /// <exception cref="ArgumentNullException"><paramref name="fullReferences"/> is null.</exception>
+    /// <exception cref="OperationCanceledException"><paramref name="cancellationToken"/> was cancelled.</exception>
+    /// <exception cref="DbException">The database could not be reached (opening a connection failed).</exception>
+    public async Task<IReadOnlyList<DataValueSnapshot>> ReadAsync(
+        IReadOnlyList<string> fullReferences, CancellationToken cancellationToken)
+    {
+        ArgumentNullException.ThrowIfNull(fullReferences);
+
+        var results = new DataValueSnapshot[fullReferences.Count];
+        if (results.Length == 0) return results;
+
+        var readAt = DateTime.UtcNow;
+
+        // Resolve first. A miss is this tag's own problem (BadNodeIdUnknown) and must not reach the planner,
+        // whose members are the sole thing the slice-back walks.
+        var definitions = new List<SqlTagDefinition>(fullReferences.Count);
+        var slots = new Dictionary<SqlTagDefinition, List<int>>();
+        for (var i = 0; i < fullReferences.Count; i++)
+        {
+            var definition = fullReferences[i] is { } reference ? _resolve(reference) : null;
+            if (definition is null)
+            {
+                results[i] = new DataValueSnapshot(null, SqlStatusCodes.BadNodeIdUnknown, null, readAt);
+                continue;
+            }
+
+            definitions.Add(definition);
+            if (!slots.TryGetValue(definition, out var positions))
+                slots[definition] = positions = [];
+            positions.Add(i);
+        }
+
+        if (definitions.Count > 0)
+            await ReadGroupsAsync(definitions, slots, results, readAt, cancellationToken).ConfigureAwait(false);
+
+        // Fail-safe. Nothing above should leave a hole, but "N in, N out" is a contract the caller indexes
+        // blind — a null here would be a NullReferenceException in the publish fan-out, far from its cause.
+        for (var i = 0; i < results.Length; i++)
+            results[i] ??= new DataValueSnapshot(null, SqlStatusCodes.BadInternalError, null, readAt);
+
+        return results;
+    }
+
+    /// <summary>Plans the resolved definitions, runs every group concurrently, and slices the results back.</summary>
+    private async Task ReadGroupsAsync(
+        List<SqlTagDefinition> definitions,
+        Dictionary<SqlTagDefinition, List<int>> slots,
+        DataValueSnapshot[] results,
+        DateTime readAt,
+        CancellationToken cancellationToken)
+    {
+        IReadOnlyList<SqlQueryPlan> plans;
+        try
+        {
+            plans = SqlGroupPlanner.Plan(definitions, _dialect);
+        }
+        catch (Exception ex) when (ex is ArgumentException or NotSupportedException)
+        {
+            // A definition with a broken invariant — SqlEquipmentTagParser rejects all of these up front, so
+            // reaching here means a definition was built past the parser. It is an authoring fault, not a
+            // database fault: Bad-code the planned tags rather than throwing and triggering connection backoff.
+            _logger.LogError(ex, "Sql poll planning failed for {Count} tag(s); publishing BadConfigurationError.",
+                definitions.Count);
+            foreach (var definition in definitions)
+            {
+                if (!slots.TryGetValue(definition, out var positions)) continue;
+                var snapshot = new DataValueSnapshot(null, SqlStatusCodes.BadConfigurationError, null, readAt);
+                foreach (var position in positions) results[position] = snapshot;
+            }
+
+            return;
+        }
+
+        // Groups run concurrently; _gate — not the task count — is what bounds open connections. Each group
+        // carries its own deadline, so the whole call is bounded by ~operationTimeout rather than by
+        // plans.Count × operationTimeout.
+        var groups = new Task<GroupResult>[plans.Count];
+        for (var g = 0; g < plans.Count; g++)
+            groups[g] = RunGroupAsync(plans[g], cancellationToken);
+
+        // WhenAll waits for every group before surfacing a fault, so a thrown "database unreachable" never
+        // leaves a sibling group running against a connection nobody is watching.
+        var outcomes = await Task.WhenAll(groups).ConfigureAwait(false);
+
+        for (var g = 0; g < plans.Count; g++)
+            Slice(plans[g], outcomes[g], slots, results, readAt);
+    }
+
+    /// <summary>
+    ///     Runs one group's query under a hard wall-clock ceiling.
+    ///     <para><b>Why the ceiling is <c>Task.WaitAsync</c> and not just a linked
+    ///     <c>CancelAfter</c>.</b> A linked token only bounds a
+    ///     provider that <em>honours</em> it. The S7 R2-01 finding was exactly a provider whose async path
+    ///     ignored its deadline, and ADO.NET has the same shape: some providers implement
+    ///     <c>ExecuteReaderAsync</c> synchronously, and even a genuinely async one can hang inside its own
+    ///     cancellation handshake against a frozen socket. Both are used here: the linked token so a
+    ///     well-behaved provider unwinds cleanly and releases its connection, and <c>WaitAsync</c> so
+    ///     control returns at the deadline regardless.</para>
+    ///     <para>The work is started on the thread pool so a provider that blocks synchronously blocks a
+    ///     pool thread rather than the caller — without that, a synchronous provider never yields the task
+    ///     there would be to bound.</para>
+    ///     <para><b>Thread-pool scheduling and what a BadTimeout therefore means.</b> The group's clock
+    ///     starts before <c>Task.Run</c>, so in principle a group could burn budget queueing for a pool
+    ///     thread rather than waiting on the database. <c>TaskCreationOptions.LongRunning</c> (a dedicated
+    ///     OS thread) was considered and <b>rejected</b>: it would create and tear down one thread per group
+    ///     per poll, forever, on a driver whose whole job is to poll on a short cadence — a permanent cost
+    ///     paid against a hazard that cannot arise with the provider this driver actually ships.
+    ///     <c>Microsoft.Data.SqlClient</c>'s async path is genuinely asynchronous: the delegate reaches its
+    ///     first real await within microseconds and returns the pool thread, so a frozen SQL Server parks
+    ///     <em>zero</em> pool threads however long it stays frozen, and the driver cannot starve itself no
+    ///     matter how high <c>maxConcurrentGroups</c> goes. The queueing scenario needs a provider that
+    ///     degrades to synchronous blocking — which is exactly what the SQLite test rig exploits on purpose,
+    ///     and is not a shipped configuration. <b>Consequence for outage diagnosis (e.g. blackhole-testing a
+    ///     paused SQL Server):</b> under <c>Microsoft.Data.SqlClient</c> a
+    ///     <see cref="SqlStatusCodes.BadTimeout"/> means the database did not answer inside
+    ///     <c>operationTimeout</c> — it cannot be an artefact of this driver's own pool pressure. Under a
+    ///     synchronously-blocking provider it may also include queueing delay, so size
+    ///     <c>maxConcurrentGroups</c> below the process's readily-available worker count there.</para>
+    ///     <para><b>The concurrency slot is released by the work, not by the waiter.</b> A timed-out group
+    ///     keeps its slot until it truly finishes, so a frozen database can never accumulate more than
+    ///     <c>maxConcurrentGroups</c> connections however long it stays frozen. The slot wait is itself
+    ///     inside the deadline, so a poll behind a wedged group still returns on time — as BadTimeout.</para>
+    /// </summary>
+    private async Task<GroupResult> RunGroupAsync(SqlQueryPlan plan, CancellationToken cancellationToken)
+    {
+        var clock = Stopwatch.StartNew();
+
+        if (!await _gate.WaitAsync(Remaining(clock), cancellationToken).ConfigureAwait(false))
+            return GroupResult.TimedOut;
+
+        var handedOff = false;
+        var deadline = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
+        Task<GroupResult> work;
+        try
+        {
+            var budget = Remaining(clock);
+            if (budget <= TimeSpan.Zero) return GroupResult.TimedOut;
+            deadline.CancelAfter(budget);
+
+            work = Task.Run(
+                async () =>
+                {
+                    try
+                    {
+                        return await QueryAsync(plan, deadline.Token).ConfigureAwait(false);
+                    }
+                    finally
+                    {
+                        _gate.Release();
+                        deadline.Dispose();
+                    }
+                },
+                CancellationToken.None);
+            handedOff = true;
+        }
+        finally
+        {
+            // Ownership of both the slot and the CTS transfers to the work task; release them here only on
+            // the paths where that task was never created.
+            if (!handedOff)
+            {
+                _gate.Release();
+                deadline.Dispose();
+            }
+        }
+
+        try
+        {
+            return await work.WaitAsync(Remaining(clock), cancellationToken).ConfigureAwait(false);
+        }
+        catch (TimeoutException)
+        {
+            // Our wall-clock bound fired while the provider was still inside the call.
+            return TimedOut(plan, work);
+        }
+        catch (OperationCanceledException)
+        {
+            // Either the caller pulled the plug, or our deadline fired and the provider DID honour the
+            // linked token. Both leave the work running with nobody to observe its fault.
+            if (!cancellationToken.IsCancellationRequested) return TimedOut(plan, work);
+            Detach(work);
+            throw;
+        }
+    }
+
+    /// <summary>How much of this group's <c>operationTimeout</c> budget is left; never negative.</summary>
+    private TimeSpan Remaining(Stopwatch clock)
+    {
+        var remaining = _operationTimeout - clock.Elapsed;
+        return remaining > TimeSpan.Zero ? remaining : TimeSpan.Zero;
+    }
+
+    /// <summary>Records the deadline breach and detaches the abandoned work.</summary>
+    private GroupResult TimedOut(SqlQueryPlan plan, Task work)
+    {
+        // The table is named for the same reason the contract warnings name it: under a partial outage this
+        // line repeats every poll, and "which source is frozen" is the only question the operator has.
+        _logger.LogWarning(
+            "Sql poll group ({Model}, '{Table}', {Members} tag(s)) exceeded the {Timeout} ms operation " +
+            "timeout; publishing BadTimeout.",
+            plan.Model, plan.Members[0].Table, plan.Members.Count,
+            (int)_operationTimeout.TotalMilliseconds);
+
+        Detach(work);
+        return GroupResult.TimedOut;
+    }
+
+    /// <summary>
+    ///     Observes an abandoned group's eventual fault so it never surfaces as an unobserved task
+    ///     exception. The task still owns its connection and still releases the concurrency slot when it
+    ///     finally completes — that is what keeps a frozen database from accumulating connections.
+    /// </summary>
+    private static void Detach(Task work)
+        => _ = work.ContinueWith(
+            static t => _ = t.Exception,
+            CancellationToken.None,
+            TaskContinuationOptions.OnlyOnFaulted | TaskContinuationOptions.ExecuteSynchronously,
+            TaskScheduler.Default);
+
+    /// <summary>
+    ///     Opens a connection, executes the plan's single command, and materialises the result set.
+    ///     <para>The rows are read into memory <b>before</b> the reader is disposed — the slice-back needs
+    ///     random access across members, and holding a reader (and therefore a connection) open across that
+    ///     work is exactly how a poll loop exhausts a pool.</para>
+    /// </summary>
+    private async Task<GroupResult> QueryAsync(SqlQueryPlan plan, CancellationToken cancellationToken)
+    {
+        var connection = _factory.CreateConnection()
+                         ?? throw new InvalidOperationException(
+                             $"The {_dialect.Provider} provider factory returned no connection.");
+
+        await using (connection.ConfigureAwait(false))
+        {
+            connection.ConnectionString = _connectionString;
+
+            // Deliberately OUTSIDE the catch below: a failed open means the database is unreachable, which
+            // is the one condition IReadable says the whole call may throw on (→ PollGroupEngine backoff).
+            await connection.OpenAsync(cancellationToken).ConfigureAwait(false);
+
+            try
+            {
+                var command = connection.CreateCommand();
+                await using (command.ConfigureAwait(false))
+                {
+                    command.CommandText = plan.SqlText;
+                    command.CommandTimeout = _commandTimeoutSeconds;
+                    for (var i = 0; i < plan.ParameterNames.Count; i++)
+                    {
+                        var parameter = command.CreateParameter();
+                        // Bound by the plan's own index pairing — never by re-deriving the marker convention.
+                        parameter.ParameterName = plan.ParameterNames[i];
+                        parameter.Value = plan.Parameters[i] ?? DBNull.Value;
+                        command.Parameters.Add(parameter);
+                    }
+
+                    var reader = await command.ExecuteReaderAsync(cancellationToken).ConfigureAwait(false);
+                    await using (reader.ConfigureAwait(false))
+                    {
+                        return await MaterialiseAsync(plan, reader, cancellationToken).ConfigureAwait(false);
+                    }
+                }
+            }
+            catch (OperationCanceledException)
+            {
+                throw;
+            }
+            catch (Exception ex)
+            {
+                // The connection opened, so the server is up — this query is what failed (an identifier that
+                // is not in the catalog, a lock, a permission). That is this group's problem alone.
+                _logger.LogWarning(
+                    ex, "Sql poll group ({Model}, {Members} tag(s)) failed: {Sql}",
+                    plan.Model, plan.Members.Count, plan.SqlText);
+                return GroupResult.Failed;
+            }
+        }
+    }
+
+    /// <summary>
+    ///     Reads every row into memory, projected onto <see cref="SqlQueryPlan.SelectedColumns"/>. Row
+    ///     fetching stays on the async path so a result set that streams slowly still honours the deadline
+    ///     token mid-read, rather than only at the ExecuteReader boundary.
+    /// </summary>
+    private async Task<GroupResult> MaterialiseAsync(
+        SqlQueryPlan plan, DbDataReader reader, CancellationToken cancellationToken)
+    {
+        var selected = plan.SelectedColumns;
+        var ordinals = new int[selected.Count];
+        var typeNames = new string[selected.Count];
+        var columnIndex = new Dictionary<string, int>(selected.Count, StringComparer.Ordinal);
+        for (var c = 0; c < selected.Count; c++)
+        {
+            // GetOrdinal rather than the position in SelectedColumns: the list is documented to be in
+            // ordinal order, but resolving it against the live result set is what makes a wrong slice
+            // impossible rather than merely unlikely.
+            ordinals[c] = reader.GetOrdinal(selected[c]);
+            typeNames[c] = SafeTypeName(reader, ordinals[c]);
+            columnIndex[selected[c]] = c;
+        }
+
+        var rows = new List<object?[]>();
+        while (await reader.ReadAsync(cancellationToken).ConfigureAwait(false))
+        {
+            var row = new object?[selected.Count];
+            for (var c = 0; c < selected.Count; c++)
+                row[c] = reader.IsDBNull(ordinals[c]) ? null : reader.GetValue(ordinals[c]);
+            rows.Add(row);
+        }
+
+        return GroupResult.Ok(rows, columnIndex, typeNames);
+    }
+
+    /// <summary>Reads a column's provider type name, falling back to the dialect's unknown-type default.</summary>
+    private static string SafeTypeName(DbDataReader reader, int ordinal)
+    {
+        try
+        {
+            return reader.GetDataTypeName(ordinal) ?? string.Empty;
+        }
+        catch (Exception ex) when (ex is NotSupportedException or InvalidOperationException
+                                       or IndexOutOfRangeException)
+        {
+            // A provider that declines to report a type name must not fail the poll — the tag's declared
+            // type (or the dialect's String fallback) covers it.
+            return string.Empty;
+        }
+    }
+
+    /// <summary>Maps one group's outcome onto every slot its members occupy in the caller's list.</summary>
+    private void Slice(
+        SqlQueryPlan plan,
+        GroupResult outcome,
+        Dictionary<SqlTagDefinition, List<int>> slots,
+        DataValueSnapshot[] results,
+        DateTime readAt)
+    {
+        // KeyValue indexes rows by the key column; WideRow's members all read the one selected row, so the
+        // where-column is not even in the result set (design §5.3). Both selections happen ONCE per group —
+        // they are group-wide facts, and doing them per member would report a contract violation N times.
+        var byKey = outcome.Succeeded && plan.Model == SqlTagModel.KeyValue
+            ? IndexByKey(plan, outcome)
+            : null;
+        var wideRow = outcome.Succeeded && plan.Model == SqlTagModel.WideRow
+            ? SelectWideRow(plan, outcome)
+            : null;
+
+        foreach (var member in plan.Members)
+        {
+            // Members may repeat (two tags on one keyValue, or the same ref twice) — every occurrence is fed.
+            if (!slots.TryGetValue(member, out var positions)) continue;
+
+            var snapshot = outcome.Succeeded
+                ? MapMember(plan, member, outcome, byKey, wideRow, readAt)
+                : new DataValueSnapshot(null, outcome.FailureStatus, null, readAt);
+
+            foreach (var position in positions) results[position] = snapshot;
+        }
+    }
+
+    /// <summary>
+    ///     Builds the key → row index a key-value plan slices through. Later rows win, so a source that
+    ///     breaks the one-row-per-key contract (design §3.6) still yields a deterministic value; the
+    ///     violation is reported through a rate-limited warning rather than silently.
+    /// </summary>
+    private Dictionary<string, object?[]> IndexByKey(SqlQueryPlan plan, GroupResult outcome)
+    {
+        var index = new Dictionary<string, object?[]>(StringComparer.Ordinal);
+        if (plan.KeyColumn is null || !outcome.ColumnIndex.TryGetValue(plan.KeyColumn, out var keyAt))
+            return index;
+
+        var duplicated = 0;
+        foreach (var row in outcome.Rows)
+        {
+            // A NULL key cell indexes nothing: Convert.ToString would fold it to "", which would then be
+            // matched by a tag whose keyValue is legitimately the empty string.
+            if (row[keyAt] is not { } keyCell) continue;
+
+            // Stringified because the bound keyValue is authored text while the column may be any type
+            // (an INTEGER station id, say) — the provider coerces on the way in, so match on the way out.
+            var key = Convert.ToString(keyCell, CultureInfo.InvariantCulture);
+            if (key is null) continue;
+            if (!index.TryAdd(key, row))
+            {
+                index[key] = row;
+                duplicated++;
+            }
+        }
+
+        if (duplicated > 0 && ShouldWarnAboutContract())
+        {
+            _logger.LogWarning(
+                "Sql poll source '{Table}' returned more than one row for {Count} key(s) in one poll; the " +
+                "last row wins. The key-value model requires one row per key — point the tag at a " +
+                "current-values table or an operator-authored latest-per-key view.",
+                plan.Members[0].Table, duplicated);
+        }
+
+        return index;
+    }
+
+    /// <summary>
+    ///     Picks the single row every member of a wide-row plan reads, and reports an ambiguous selector.
+    ///     <para><b>Last row wins</b> — the same tie-break <see cref="IndexByKey"/> applies, so both models
+    ///     degrade the same way. It is deterministic only <em>within one result set</em>: the where-pair form
+    ///     emits no <c>ORDER BY</c>, so across polls the "last" row is whatever the server returned last,
+    ///     i.e. storage order. That is why more than one row is a reported contract violation and not merely
+    ///     a tie to break — the model's premise (design §5.3) is that the selector identifies one row.</para>
+    ///     <para><b>Why the where-pair form is deliberately NOT given the dialect's single-row limit.</b> A
+    ///     <c>TOP 1</c> with no <c>ORDER BY</c> is not deterministic either — it returns whichever row the
+    ///     plan happens to produce first, so it would trade one arbitrary row for a differently arbitrary
+    ///     one. Worse, it would destroy the only evidence this method has that the selector is ambiguous
+    ///     (<c>Rows.Count &gt; 1</c>), converting a loud misconfiguration into a permanently silent one —
+    ///     precisely the failure mode this class's summary calls its top risk. The <c>topByTimestamp</c>
+    ///     form keeps its row limit because there the <c>ORDER BY</c> makes "the first row" a defined
+    ///     answer. The accepted cost is that an ambiguous selector materialises every matching row for one
+    ///     poll; the warning is what gets it fixed.</para>
+    /// </summary>
+    private object?[]? SelectWideRow(SqlQueryPlan plan, GroupResult outcome)
+    {
+        if (outcome.Rows.Count == 0) return null;
+        if (outcome.Rows.Count > 1 && ShouldWarnAboutContract())
+        {
+            var first = plan.Members[0];
+            var selector = string.IsNullOrWhiteSpace(first.RowSelectorColumn)
+                ? string.Concat("topByTimestamp ", first.RowSelectorTopByTimestamp)
+                : string.Concat(first.RowSelectorColumn, " = ", first.RowSelectorValue);
+            _logger.LogWarning(
+                "Sql poll source '{Table}' returned {Rows} rows for the wide-row selector '{Selector}' in " +
+                "one poll; the last row read wins, and the query carries no ORDER BY, so which row that is " +
+                "depends on storage order. The wide-row model requires a selector matching exactly one row " +
+                "— narrow the whereColumn/whereValue pair, or point the tag at a latest-row view.",
+                first.Table, outcome.Rows.Count, selector);
+        }
+
+        return outcome.Rows[^1];
+    }
+
+    /// <summary>Maps one member's cell to a snapshot: value, quality, and source timestamp.</summary>
+    private DataValueSnapshot MapMember(
+        SqlQueryPlan plan,
+        SqlTagDefinition member,
+        GroupResult outcome,
+        Dictionary<string, object?[]>? byKey,
+        object?[]? wideRow,
+        DateTime readAt)
+    {
+        object?[]? row;
+        string? valueColumn;
+        string? timestampColumn;
+        if (plan.Model == SqlTagModel.KeyValue)
+        {
+            valueColumn = plan.ValueColumn;
+            timestampColumn = plan.TimestampColumn;
+            row = member.KeyValue is { } key && byKey is not null ? byKey.GetValueOrDefault(key) : null;
+        }
+        else
+        {
+            valueColumn = member.ColumnName;
+            // A wide-row plan's members may legitimately carry DIFFERENT timestamp columns (all of them are
+            // selected), which is why the plan-level TimestampColumn is null for this model by design.
+            timestampColumn = member.TimestampColumn;
+            row = wideRow;
+        }
+
+        // No row: the key was deleted, or the row selector matched nothing. Distinct from a NULL cell.
+        if (row is null) return new DataValueSnapshot(null, SqlStatusCodes.BadNoData, null, readAt);
+
+        // A timestamp that will not parse falls back to the poll clock rather than poisoning a good value.
+        var sourceTimestamp = ReadTimestamp(outcome, row, timestampColumn) ?? readAt;
+
+        if (valueColumn is null || !outcome.ColumnIndex.TryGetValue(valueColumn, out var valueAt))
+        {
+            // The planner selects every member's value column, so this is unreachable short of plan/result
+            // drift — loud rather than silently publishing someone else's cell.
+            _logger.LogError(
+                "Sql tag '{Tag}' reads column '{Column}', which the executed plan did not select.",
+                member.Name, valueColumn);
+            return new DataValueSnapshot(null, SqlStatusCodes.BadInternalError, sourceTimestamp, readAt);
+        }
+
+        var cell = row[valueAt];
+        if (cell is null)
+        {
+            return new DataValueSnapshot(
+                null, _nullIsBad ? SqlStatusCodes.Bad : SqlStatusCodes.Uncertain, sourceTimestamp, readAt);
+        }
+
+        var target = member.DeclaredType ?? _dialect.MapColumnType(outcome.TypeNames[valueAt]);
+        if (!TryCoerce(cell, target, out var value))
+        {
+            _logger.LogWarning(
+                "Sql tag '{Tag}' could not coerce a {Actual} cell to its {Declared} type.",
+                member.Name, cell.GetType().Name, target);
+            return new DataValueSnapshot(null, SqlStatusCodes.BadTypeMismatch, sourceTimestamp, readAt);
+        }
+
+        return new DataValueSnapshot(value, SqlStatusCodes.Good, sourceTimestamp, readAt);
+    }
+
+    /// <summary>Reads a row's source timestamp, or null when there is no column, no value, or no parse.</summary>
+    private static DateTime? ReadTimestamp(GroupResult outcome, object?[] row, string? timestampColumn)
+    {
+        if (string.IsNullOrWhiteSpace(timestampColumn)) return null;
+        if (!outcome.ColumnIndex.TryGetValue(timestampColumn, out var at)) return null;
+        if (row[at] is not { } cell) return null;
+        return TryCoerce(cell, DriverDataType.DateTime, out var value) ? (DateTime?)value : null;
+    }
+
+    /// <summary>
+    ///     Coerces a provider cell to the tag's effective <see cref="DriverDataType"/>, so the published CLR
+    ///     type matches the type the address space declared for the node. Never throws.
+    /// </summary>
+    private static bool TryCoerce(object cell, DriverDataType target, out object? value)
+    {
+        try
+        {
+            value = target switch
+            {
+                DriverDataType.Boolean => Convert.ToBoolean(cell, CultureInfo.InvariantCulture),
+                DriverDataType.Int16 => Convert.ToInt16(cell, CultureInfo.InvariantCulture),
+                DriverDataType.Int32 => Convert.ToInt32(cell, CultureInfo.InvariantCulture),
+                DriverDataType.Int64 => Convert.ToInt64(cell, CultureInfo.InvariantCulture),
+                DriverDataType.UInt16 => Convert.ToUInt16(cell, CultureInfo.InvariantCulture),
+                DriverDataType.UInt32 => Convert.ToUInt32(cell, CultureInfo.InvariantCulture),
+                DriverDataType.UInt64 => Convert.ToUInt64(cell, CultureInfo.InvariantCulture),
+                DriverDataType.Float32 => Convert.ToSingle(cell, CultureInfo.InvariantCulture),
+                // decimal/numeric collapse here, with the documented precision caveat (design §8.6).
+                DriverDataType.Float64 => Convert.ToDouble(cell, CultureInfo.InvariantCulture),
+                DriverDataType.DateTime => ToUtc(cell),
+                _ => Convert.ToString(cell, CultureInfo.InvariantCulture) ?? string.Empty,
+            };
+            return true;
+        }
+        catch (Exception ex) when (ex is InvalidCastException or FormatException
+                                       or OverflowException or ArgumentException)
+        {
+            value = null;
+            return false;
+        }
+    }
+
+    /// <summary>
+    ///     Normalises a timestamp cell to UTC. A naive <c>datetime</c> (no offset — the common SQL Server
+    ///     shape) is <b>assumed</b> to already be UTC rather than reinterpreted through the server's local
+    ///     zone, which would silently shift every source timestamp by the host's offset.
+    /// </summary>
+    private static DateTime ToUtc(object cell) => cell switch
+    {
+        DateTime { Kind: DateTimeKind.Utc } utc => utc,
+        DateTime { Kind: DateTimeKind.Local } local => local.ToUniversalTime(),
+        DateTime unspecified => DateTime.SpecifyKind(unspecified, DateTimeKind.Utc),
+        DateTimeOffset offset => offset.UtcDateTime,
+        string text => DateTime.Parse(
+            text, CultureInfo.InvariantCulture,
+            DateTimeStyles.AssumeUniversal | DateTimeStyles.AdjustToUniversal),
+        _ => DateTime.SpecifyKind(
+            Convert.ToDateTime(cell, CultureInfo.InvariantCulture), DateTimeKind.Utc),
+    };
+
+    /// <summary>Rate-limits the source-contract warning so a misconfigured table cannot flood the log.</summary>
+    private bool ShouldWarnAboutContract()
+    {
+        var now = Stopwatch.GetTimestamp();
+        var last = Interlocked.Read(ref _lastContractWarningTicks);
+        if (last != 0 && Stopwatch.GetElapsedTime(last, now) < ContractWarningInterval) return false;
+        return Interlocked.CompareExchange(ref _lastContractWarningTicks, now, last) == last;
+    }
+
+    /// <summary>One group's outcome: either a materialised result set, or the status its members inherit.</summary>
+    private sealed class GroupResult
+    {
+        private static readonly IReadOnlyList<object?[]> NoRows = [];
+        private static readonly IReadOnlyDictionary<string, int> NoColumns =
+            new Dictionary<string, int>(StringComparer.Ordinal);
+
+        private GroupResult(
+            uint failureStatus,
+            IReadOnlyList<object?[]> rows,
+            IReadOnlyDictionary<string, int> columnIndex,
+            IReadOnlyList<string> typeNames)
+        {
+            FailureStatus = failureStatus;
+            Rows = rows;
+            ColumnIndex = columnIndex;
+            TypeNames = typeNames;
+        }
+
+        /// <summary>The group exceeded its wall-clock deadline (design §8.3).</summary>
+        public static GroupResult TimedOut { get; } =
+            new(SqlStatusCodes.BadTimeout, NoRows, NoColumns, []);
+
+        /// <summary>The connection was fine but the query was not.</summary>
+        public static GroupResult Failed { get; } =
+            new(SqlStatusCodes.BadCommunicationError, NoRows, NoColumns, []);
+
+        /// <summary>The status every member inherits when <see cref="Succeeded"/> is false.</summary>
+        public uint FailureStatus { get; }
+
+        /// <summary>The materialised rows, projected onto the plan's selected columns.</summary>
+        public IReadOnlyList<object?[]> Rows { get; }
+
+        /// <summary>Selected column name → its position within each row array.</summary>
+        public IReadOnlyDictionary<string, int> ColumnIndex { get; }
+
+        /// <summary>Each selected column's provider type name, for dialect type inference.</summary>
+        public IReadOnlyList<string> TypeNames { get; }
+
+        /// <summary>True when the query ran; a zero-row result set is still a success.</summary>
+        public bool Succeeded => FailureStatus == SqlStatusCodes.Good;
+
+        /// <summary>A completed result set.</summary>
+        /// <param name="rows">The materialised rows.</param>
+        /// <param name="columnIndex">Selected column name → row-array position.</param>
+        /// <param name="typeNames">Each selected column's provider type name.</param>
+        /// <returns>A successful outcome.</returns>
+        public static GroupResult Ok(
+            IReadOnlyList<object?[]> rows,
+            IReadOnlyDictionary<string, int> columnIndex,
+            IReadOnlyList<string> typeNames)
+            => new(SqlStatusCodes.Good, rows, columnIndex, typeNames);
+    }
+}
+
+/// <summary>
+///     The OPC UA status codes the Sql driver publishes, and the quality-class predicates its tests read
+///     them back with.
+///     <para><b>Why a driver-local table rather than a shared one.</b> Every driver in this tree carries its
+///     own (<c>TwinCATStatusMapper</c>, <c>AbCipStatusMapper</c>, <c>FocasStatusMapper</c>,
+///     <c>AbLegacyStatusMapper</c>, Galaxy's <c>StatusCodeMap</c>) — there is no shared helper in
+///     <c>Core.Abstractions</c>, because drivers deliberately do not reference the OPC UA SDK and
+///     <see cref="DataValueSnapshot.StatusCode"/> is a bare <see cref="uint"/>. The values below were read
+///     off <c>Opc.Ua.StatusCodes</c> rather than copied from a sibling driver, since two of those tables
+///     carry transcription errors.</para>
+/// </summary>
+public static class SqlStatusCodes
+{
+    /// <summary>The value is good. (<c>Good</c>)</summary>
+    public const uint Good = 0x00000000u;
+
+    /// <summary>Quality is uncertain with no more specific reason — a NULL cell under <c>nullIsBad=false</c>.</summary>
+    public const uint Uncertain = 0x40000000u;
+
+    /// <summary>Quality is bad with no more specific reason — a NULL cell under <c>nullIsBad=true</c>.</summary>
+    public const uint Bad = 0x80000000u;
+
+    /// <summary>
+    ///     No row was returned for this tag — the key is absent from the result set, or the wide-row
+    ///     selector matched nothing. <b>Deliberately distinct from a NULL cell:</b> the row is gone, versus
+    ///     the row is there and the value is not.
+    /// </summary>
+    public const uint BadNoData = 0x809B0000u;
+
+    /// <summary>The group exceeded its client-side wall-clock deadline (design §8.3).</summary>
+    public const uint BadTimeout = 0x800A0000u;
+
+    /// <summary>The reference resolves to no authored tag.</summary>
+    public const uint BadNodeIdUnknown = 0x80340000u;
+
+    /// <summary>The query failed after the connection opened.</summary>
+    public const uint BadCommunicationError = 0x80050000u;
+
+    /// <summary>The cell could not be coerced to the tag's effective data type.</summary>
+    public const uint BadTypeMismatch = 0x80740000u;
+
+    /// <summary>A tag definition the planner rejected — an authoring fault, not a database fault.</summary>
+    public const uint BadConfigurationError = 0x80890000u;
+
+    /// <summary>A defect in the reader itself; never expected in the field.</summary>
+    public const uint BadInternalError = 0x80020000u;
+
+    /// <summary>The quality-class mask — the top two bits of an OPC UA status code.</summary>
+    private const uint SeverityMask = 0xC0000000u;
+
+    /// <summary>True when <paramref name="statusCode"/> is in the Good quality class.</summary>
+    /// <param name="statusCode">The status code to classify.</param>
+    /// <returns>True when the code's severity bits are Good.</returns>
+    public static bool IsGood(uint statusCode) => (statusCode & SeverityMask) == 0u;
+
+    /// <summary>True when <paramref name="statusCode"/> is in the Uncertain quality class.</summary>
+    /// <param name="statusCode">The status code to classify.</param>
+    /// <returns>True when the code's severity bits are Uncertain.</returns>
+    public static bool IsUncertain(uint statusCode) => (statusCode & SeverityMask) == Uncertain;
+
+    /// <summary>True when <paramref name="statusCode"/> is in the Bad quality class.</summary>
+    /// <param name="statusCode">The status code to classify.</param>
+    /// <returns>True when the code's severity bits are Bad.</returns>
+    public static bool IsBad(uint statusCode) => (statusCode & SeverityMask) >= Bad;
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql/SqlQueryPlan.cs

@@ -0,0 +1,90 @@
+using System.Data.Common;
+using ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql;
+
+/// <summary>
+///     One compiled poll query and the tags it feeds (design §3.6, "group execution shape"). Every tag that
+///     shares a <see cref="GroupKey"/> reads from the <b>same</b> result set, so a poll pass executes one plan
+///     per group rather than one query per tag.
+///     <para><b>Injection boundary.</b> <see cref="SqlText"/> is built from dialect-quoted identifiers only;
+///     every authored <em>value</em> lives in <see cref="Parameters"/> and is bound as a
+///     <see cref="DbParameter"/> named by the positionally-aligned <see cref="ParameterNames"/>. There is no
+///     path by which a tag's <c>keyValue</c> or <c>whereValue</c> reaches the command text.</para>
+///     <para>Produced only by <see cref="SqlGroupPlanner.Plan"/>; consumed by the poll reader, which executes
+///     <see cref="SqlText"/> once and slices the rows back to per-member snapshots.</para>
+/// </summary>
+/// <param name="Model">
+///     The tag→value mapping model every member shares. Determines how the reader slices the result set:
+///     <see cref="SqlTagModel.KeyValue"/> indexes rows by <see cref="KeyColumn"/> and matches each member's
+///     <see cref="SqlTagDefinition.KeyValue"/>; <see cref="SqlTagModel.WideRow"/> takes the single row and
+///     reads each member's <see cref="SqlTagDefinition.ColumnName"/>.
+/// </param>
+/// <param name="GroupKey">
+///     The opaque equality key that decided this grouping — a value tuple, so two plans compare equal exactly
+///     when they would have folded together. Exposed for diagnostics and plan caching, never for parsing.
+/// </param>
+/// <param name="SqlText">The single parameterized statement to execute for this group.</param>
+/// <param name="ParameterNames">
+///     The parameter markers appearing in <see cref="SqlText"/>, in the order they appear, aligned index-for-index
+///     with <see cref="Parameters"/>. Carried explicitly so the reader never has to re-derive the naming
+///     convention.
+/// </param>
+/// <param name="Parameters">
+///     The values to bind, aligned with <see cref="ParameterNames"/>. Captured verbatim from the authored tags
+///     — a hostile value is inert here because it is data, not text.
+/// </param>
+/// <param name="Members">
+///     The tags this plan feeds, in the planner's input order. Never empty. Duplicates are preserved: two tags
+///     may legitimately read the same cell, and both must receive a value.
+/// </param>
+/// <param name="SelectedColumns">
+///     The bare (unquoted) column names in <see cref="SqlText"/>'s SELECT list, in order and distinct — the
+///     reader's map from result-set ordinal to source column.
+/// </param>
+public sealed record SqlQueryPlan(
+    SqlTagModel Model,
+    object GroupKey,
+    string SqlText,
+    IReadOnlyList<string> ParameterNames,
+    IReadOnlyList<object?> Parameters,
+    IReadOnlyList<SqlTagDefinition> Members,
+    IReadOnlyList<string> SelectedColumns)
+{
+    // A plan is documented as safe to cache and reuse across polls, so it must not stay aliased to the
+    // planner's mutable working lists — an IReadOnlyList<T> holding a List<T> is downcastable, and a
+    // mutation would silently corrupt every later poll that reuses the plan. Snapshot at the boundary.
+    /// <summary>The parameter markers in <see cref="SqlText"/>, aligned with <see cref="Parameters"/>.</summary>
+    public IReadOnlyList<string> ParameterNames { get; } = [.. ParameterNames];
+
+    /// <summary>The values to bind, aligned with <see cref="ParameterNames"/>.</summary>
+    public IReadOnlyList<object?> Parameters { get; } = [.. Parameters];
+
+    /// <summary>The tags this plan feeds, in input order; duplicates preserved.</summary>
+    public IReadOnlyList<SqlTagDefinition> Members { get; } = [.. Members];
+
+    /// <summary>The bare SELECT-list column names, in result-set ordinal order.</summary>
+    public IReadOnlyList<string> SelectedColumns { get; } = [.. SelectedColumns];
+
+    /// <summary>
+    ///     The key column all members are matched on — <see langword="null"/> for any model but
+    ///     <see cref="SqlTagModel.KeyValue"/>. Uniform across <see cref="Members"/> by the group-key invariant,
+    ///     so <c>Members[0]</c> is authoritative.
+    /// </summary>
+    public string? KeyColumn => Model == SqlTagModel.KeyValue ? Members[0].KeyColumn : null;
+
+    /// <summary>
+    ///     The column every member's value is read from — <see langword="null"/> for any model but
+    ///     <see cref="SqlTagModel.KeyValue"/>. Uniform across <see cref="Members"/> by the group-key invariant.
+    /// </summary>
+    public string? ValueColumn => Model == SqlTagModel.KeyValue ? Members[0].ValueColumn : null;
+
+    /// <summary>
+    ///     The shared source-timestamp column, or <see langword="null"/> when the group has none (the reader
+    ///     then stamps the poll time). <see cref="SqlTagModel.KeyValue"/> only — it is part of that model's
+    ///     group key, so it is uniform. A <see cref="SqlTagModel.WideRow"/> plan deliberately allows members to
+    ///     carry <em>different</em> timestamp columns (all of them are selected), so the reader must read
+    ///     <see cref="SqlTagDefinition.TimestampColumn"/> per member there.
+    /// </summary>
+    public string? TimestampColumn => Model == SqlTagModel.KeyValue ? Members[0].TimestampColumn : null;
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql/SqlServerDialect.cs

@@ -0,0 +1,159 @@
+using System.Data.Common;
+using System.Globalization;
+using Microsoft.Data.SqlClient;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Sql;
+
+/// <summary>
+///     Microsoft SQL Server dialect (design §2.2) — the only provider v1 constructs. Bracket quoting,
+///     <c>INFORMATION_SCHEMA</c> catalog SQL, and the design §3.7 type-family map.
+///     <para>Stateless and immutable, so a single instance is safely shared by the driver's poll reader and
+///     the AdminUI browse session.</para>
+/// </summary>
+public sealed class SqlServerDialect : ISqlDialect
+{
+    /// <summary>
+    ///     T-SQL's regular-identifier ceiling (<c>sysname</c> = <c>nvarchar(128)</c>). Enforced because a
+    ///     longer string cannot name a real catalog object — it is either a config mistake or padding, and
+    ///     rejecting it keeps the quoted output bounded.
+    /// </summary>
+    internal const int MaxIdentifierLength = 128;
+
+    /// <inheritdoc/>
+    public SqlProvider Provider => SqlProvider.SqlServer;
+
+    /// <inheritdoc/>
+    public DbProviderFactory Factory => SqlClientFactory.Instance;
+
+    /// <inheritdoc/>
+    public string LivenessSql => "SELECT 1";
+
+    /// <summary>
+    ///     T-SQL limits after the <c>SELECT</c> keyword, so the whole limit lives in the prefix —
+    ///     <c>"TOP 1 "</c>, trailing space included so <c>SELECT TOP 1 [col]</c> composes with no extra
+    ///     separator at the call site.
+    /// </summary>
+    public string SingleRowLimitPrefix => "TOP 1 ";
+
+    /// <summary>Empty — T-SQL has no trailing row-limit clause (<c>OFFSET/FETCH</c> is a paging construct, not this).</summary>
+    public string SingleRowLimitSuffix => string.Empty;
+
+    /// <inheritdoc/>
+    public string ListSchemasSql =>
+        "SELECT DISTINCT TABLE_SCHEMA FROM INFORMATION_SCHEMA.TABLES ORDER BY TABLE_SCHEMA";
+
+    /// <summary>
+    ///     <c>SCHEMA_NAME()</c> with no argument returns the calling principal's default schema — the one an
+    ///     unqualified object name resolves in, which is precisely the question the catalog gate asks.
+    /// </summary>
+    public string DefaultSchemaSql => "SELECT SCHEMA_NAME()";
+
+    /// <inheritdoc/>
+    public string ListTablesSql =>
+        "SELECT TABLE_NAME, TABLE_TYPE FROM INFORMATION_SCHEMA.TABLES " +
+        "WHERE TABLE_SCHEMA = @schema ORDER BY TABLE_NAME";
+
+    /// <inheritdoc/>
+    public string ListColumnsSql =>
+        "SELECT COLUMN_NAME, DATA_TYPE, IS_NULLABLE FROM INFORMATION_SCHEMA.COLUMNS " +
+        "WHERE TABLE_SCHEMA = @schema AND TABLE_NAME = @table ORDER BY ORDINAL_POSITION";
+
+    /// <summary>
+    ///     Brackets one identifier part, doubling any embedded <c>]</c> — the T-SQL escape rule, and the only
+    ///     metacharacter that could terminate a bracketed identifier early. <c>[</c>, quotes, semicolons and
+    ///     comment markers are inert inside brackets and are therefore passed through unchanged.
+    /// </summary>
+    /// <remarks>
+    ///     <para><b>Rejects</b> (all as <see cref="ArgumentException"/>): null / empty / all-whitespace; longer
+    ///     than <see cref="MaxIdentifierLength"/>; any control character (which covers embedded NUL, and the
+    ///     C0/C1 ranges that can truncate or corrupt a logged/audited statement); and any Unicode
+    ///     <see cref="System.Globalization.UnicodeCategory.Format"/> character — bidi overrides, zero-width
+    ///     spaces, soft hyphen, BOM. Those last cannot escape the brackets, but they spoof the <em>rendered</em>
+    ///     text of a log line or an AdminUI label while comparing byte-different from the real catalog name
+    ///     (the Trojan-Source class, CVE-2021-42574) — the same log/audit-integrity concern that motivates the
+    ///     control-character rule.</para>
+    ///     <para>The rejection messages deliberately do <b>not</b> echo the offending value — it is untrusted
+    ///     input and this exception's text reaches the driver log.</para>
+    ///     <para><b>This is a backstop, not the only defence.</b> Design §8.1's catalog gate
+    ///     (<see cref="SqlCatalogGate"/>) resolves an authored table/column against the live catalog at
+    ///     Initialize and substitutes the catalog's own spelling, so on the poll path the value arriving here
+    ///     is a string read back out of the catalog. The rules below still run — the gate uses them as its own
+    ///     charset filter, and they must hold for any future caller that has no catalog to check against.</para>
+    /// </remarks>
+    /// <param name="ident">The bare, unquoted identifier part.</param>
+    /// <returns>The bracket-quoted identifier.</returns>
+    /// <exception cref="ArgumentException">The value cannot be a valid SQL Server identifier.</exception>
+    public string QuoteIdentifier(string ident)
+    {
+        if (string.IsNullOrWhiteSpace(ident))
+            throw new ArgumentException(
+                "A SQL identifier must be a non-empty, non-whitespace name.", nameof(ident));
+
+        if (ident.Length > MaxIdentifierLength)
+            throw new ArgumentException(
+                $"A SQL Server identifier may not exceed {MaxIdentifierLength} characters (got {ident.Length}).",
+                nameof(ident));
+
+        foreach (var ch in ident)
+        {
+            if (char.IsControl(ch))
+                throw new ArgumentException(
+                    "A SQL identifier may not contain control characters (including NUL).", nameof(ident));
+
+            // Cf is a *separate* category from Cc, so char.IsControl misses every bidi override and
+            // zero-width character. They are inert inside brackets but spoof rendered log/UI text.
+            if (CharUnicodeInfo.GetUnicodeCategory(ch) == UnicodeCategory.Format)
+                throw new ArgumentException(
+                    "A SQL identifier may not contain Unicode format characters "
+                    + "(bidi overrides, zero-width spaces, soft hyphen, BOM).", nameof(ident));
+        }
+
+        return string.Concat("[", ident.Replace("]", "]]", StringComparison.Ordinal), "]");
+    }
+
+    /// <summary>
+    ///     Folds an <c>INFORMATION_SCHEMA.COLUMNS.DATA_TYPE</c> family name onto a
+    ///     <see cref="DriverDataType"/> per design §3.7.
+    /// </summary>
+    /// <remarks>
+    ///     <para><b>Precision caveat:</b> <c>decimal</c> / <c>numeric</c> / <c>money</c> / <c>smallmoney</c>
+    ///     collapse to <see cref="DriverDataType.Float64"/> in v1. A .NET <c>decimal</c> carries more
+    ///     significant digits than a <c>double</c>, so a high-precision column (e.g. <c>decimal(38,10)</c>)
+    ///     loses low-order digits. Authoring an explicit <c>"type": "String"</c> on the tag preserves the exact
+    ///     textual value when that matters.</para>
+    ///     <para><b>Fallback:</b> an unrecognised family maps to <see cref="DriverDataType.String"/> and never
+    ///     throws — a schema browse must render a table containing an exotic column (<c>xml</c>,
+    ///     <c>geography</c>, <c>hierarchyid</c>, <c>sql_variant</c>, a CLR UDT, <c>varbinary</c>) rather than
+    ///     crash on it. Null/blank input takes the same fallback.</para>
+    ///     <para><b>Deliberate non-mappings:</b> SQL Server's <c>timestamp</c>/<c>rowversion</c> is an opaque
+    ///     8-byte row version, <em>not</em> a date — it falls back to <see cref="DriverDataType.String"/>
+    ///     rather than being mistaken for a <see cref="DriverDataType.DateTime"/>. <c>time</c> is a
+    ///     time-of-day span, likewise not a point in time, and takes the same fallback.</para>
+    ///     <para><c>tinyint</c> widens to <see cref="DriverDataType.Int16"/> (it is unsigned 0–255 in T-SQL, so
+    ///     a signed 8-bit type would not hold it, and the driver type set has no <c>Byte</c>).</para>
+    /// </remarks>
+    /// <param name="sqlDataType">The bare SQL type family name; matched case-insensitively.</param>
+    /// <returns>The mapped driver data type, or <see cref="DriverDataType.String"/> when unrecognised.</returns>
+    public DriverDataType MapColumnType(string sqlDataType)
+    {
+        if (string.IsNullOrWhiteSpace(sqlDataType)) return DriverDataType.String;
+
+        return sqlDataType.Trim().ToLowerInvariant() switch
+        {
+            "bit" or "boolean" => DriverDataType.Boolean,
+            "tinyint" or "smallint" => DriverDataType.Int16,
+            "int" or "integer" => DriverDataType.Int32,
+            "bigint" => DriverDataType.Int64,
+            "real" => DriverDataType.Float32,
+            "float" or "double" or "double precision"
+                or "decimal" or "numeric" or "money" or "smallmoney" => DriverDataType.Float64,
+            "char" or "nchar" or "varchar" or "nvarchar" or "text" or "ntext"
+                or "uniqueidentifier" => DriverDataType.String,
+            "date" or "datetime" or "datetime2" or "smalldatetime"
+                or "datetimeoffset" => DriverDataType.DateTime,
+            _ => DriverDataType.String,
+        };
+    }
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql/ZB.MOM.WW.OtOpcUa.Driver.Sql.csproj

@@ -0,0 +1,24 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <LangVersion>latest</LangVersion>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+    <GenerateDocumentationFile>true</GenerateDocumentationFile>
+    <NoWarn>$(NoWarn);CS1591</NoWarn>
+    <RootNamespace>ZB.MOM.WW.OtOpcUa.Driver.Sql</RootNamespace>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\..\Core\ZB.MOM.WW.OtOpcUa.Core.Abstractions\ZB.MOM.WW.OtOpcUa.Core.Abstractions.csproj"/>
+    <ProjectReference Include="..\..\Core\ZB.MOM.WW.OtOpcUa.Core\ZB.MOM.WW.OtOpcUa.Core.csproj"/>
+    <ProjectReference Include="..\ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts\ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts.csproj"/>
+  </ItemGroup>
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Data.SqlClient" />
+    <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" />
+  </ItemGroup>
+  <ItemGroup>
+    <InternalsVisibleTo Include="ZB.MOM.WW.OtOpcUa.Driver.Sql.Tests"/>
+  </ItemGroup>
+</Project>

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT/TwinCATStatusMapper.cs

@@ -19,9 +19,9 @@ public static class TwinCATStatusMapper
     public const uint BadDeviceFailure      = 0x808B0000u;
     public const uint BadCommunicationError = 0x80050000u;
     public const uint BadTimeout            = 0x800A0000u;
-    public const uint BadTypeMismatch       = 0x80730000u;
-    public const uint BadOutOfService       = 0x80BE0000u;
-    public const uint BadInvalidState       = 0x80350000u;
+    public const uint BadTypeMismatch       = 0x80740000u;
+    public const uint BadOutOfService       = 0x808D0000u;
+    public const uint BadInvalidState       = 0x80AF0000u;
 
     // ---- AdsErrorCode numeric values (confirmed from Beckhoff.TwinCAT.Ads 7.0.172) ----
 

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Pages/Certificates.razor

@@ -81,7 +81,7 @@ else
                                 <tr>
                                     <td><span class="mono small">@c.Subject</span></td>
                                     <td><span class="mono small">@c.Issuer</span></td>
-                                    <td><span class="mono small">@c.Thumbprint[..16]…</span></td>
+                                    <td><span class="mono small">@DisplayText.Abbreviate(c.Thumbprint, 16)</span></td>
                                     <td>@c.NotBefore.ToString("u")</td>
                                     <td>@c.NotAfter.ToString("u")</td>
                                     @if (store.Kind is StoreKind.Trusted or StoreKind.Rejected)

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Pages/Clusters/ClusterOverview.razor

@@ -58,7 +58,7 @@ else
             }
             else
             {
-                <div class="kv"><span class="k">Revision</span><span class="v mono">@_lastDeployment.RevisionHash[..16]…</span></div>
+                <div class="kv"><span class="k">Revision</span><span class="v mono">@DisplayText.Abbreviate(_lastDeployment.RevisionHash, 16)</span></div>
                 <div class="kv"><span class="k">Status</span><span class="v">@_lastDeployment.Status</span></div>
                 <div class="kv"><span class="k">Created</span><span class="v">@_lastDeployment.CreatedAtUtc.ToString("u")</span></div>
                 @if (_lastDeployment.SealedAtUtc is not null)

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Pages/Clusters/NodeEdit.razor

@@ -9,6 +9,8 @@
 @using System.ComponentModel.DataAnnotations
 @using ZB.MOM.WW.OtOpcUa.Configuration
 @using ZB.MOM.WW.OtOpcUa.Configuration.Entities
+@using ZB.MOM.WW.OtOpcUa.Configuration.Validation
+@using ZB.MOM.WW.OtOpcUa.Core.Abstractions
 @inject IDbContextFactory<OtOpcUaConfigDbContext> DbFactory
 @inject NavigationManager Nav
 @inject AuthenticationStateProvider AuthState
@@ -34,6 +36,10 @@ else
 {
     <EditForm Model="_form" OnValidSubmit="SubmitAsync" FormName="nodeEdit">
         <DataAnnotationsValidator />
+        @* Without this, a validation failure suppresses OnValidSubmit with NO feedback whatsoever —
+           the Save button simply does nothing and the operator has no way to tell why. That is how the
+           NodeId-regex defect above stayed invisible. *@
+        <ValidationSummary class="alert alert-danger py-2 px-3" />
         <section class="panel rise" style="animation-delay:.02s">
             <div class="panel-head">Identity</div>
             <div style="padding:1rem">
@@ -178,6 +184,33 @@ else
             }
 
             await using var db = await DbFactory.CreateDbContextAsync();
+
+            // #499 — the third Sql-credential surface. DriverConfigOverridesJson is merged onto the
+            // cluster-level DriverConfig, so a literal connectionString pasted here leaks exactly as one
+            // pasted into the driver itself. The deploy gate cannot see it (DraftSnapshot carries no
+            // ClusterNode rows) and would be the wrong place anyway: node overrides never enter the
+            // artifact, so by the time a deploy ran the credential would already be stored. Refuse the
+            // save instead. The message names the driver instance but NEVER the value.
+            if (!string.IsNullOrWhiteSpace(_form.DriverConfigOverridesJson))
+            {
+                var sqlDriverIds = await db.DriverInstances
+                    .Where(d => d.ClusterId == ClusterId && d.DriverType == DriverTypeNames.Sql)
+                    .Select(d => d.DriverInstanceId)
+                    .ToListAsync();
+
+                var offenders = SqlCredentialGuard.FindNodeOverrideViolations(
+                    _form.DriverConfigOverridesJson, sqlDriverIds);
+                if (offenders.Count > 0)
+                {
+                    _error =
+                        $"Driver config overrides carry a '{SqlCredentialGuard.ForbiddenKey}' for Sql driver " +
+                        $"instance(s) {string.Join(", ", offenders)}. A Sql driver must name its credentials " +
+                        "indirectly via 'connectionStringRef', which resolves from the environment / secret " +
+                        "store at Initialize; a literal connection string here would be stored in the config " +
+                        "database, and the runtime ignores it anyway. Remove the key.";
+                    return;
+                }
+            }
             if (IsNew)
             {
                 if (await db.ClusterNodes.AnyAsync(n => n.NodeId == _form.NodeId))
@@ -194,7 +227,7 @@ else
                     OpcUaPort = _form.OpcUaPort,
                     DashboardPort = _form.DashboardPort,
                     ApplicationUri = _form.ApplicationUri,
-                    ServiceLevelBase = _form.ServiceLevelBase,
+                    ServiceLevelBase = (byte)_form.ServiceLevelBase,
                     Enabled = _form.Enabled,
                     DriverConfigOverridesJson = string.IsNullOrWhiteSpace(_form.DriverConfigOverridesJson) ? null : _form.DriverConfigOverridesJson,
                     CreatedAt = DateTime.UtcNow,
@@ -210,7 +243,7 @@ else
                 entity.OpcUaPort = _form.OpcUaPort;
                 entity.DashboardPort = _form.DashboardPort;
                 entity.ApplicationUri = _form.ApplicationUri;
-                entity.ServiceLevelBase = _form.ServiceLevelBase;
+                entity.ServiceLevelBase = (byte)_form.ServiceLevelBase;
                 entity.Enabled = _form.Enabled;
                 entity.DriverConfigOverridesJson = string.IsNullOrWhiteSpace(_form.DriverConfigOverridesJson) ? null : _form.DriverConfigOverridesJson;
             }
@@ -254,14 +287,26 @@ else
 
     private sealed class FormModel
     {
-        [Required, RegularExpression("^[A-Za-z0-9_-]+$")]
+        // The ':' and '.' are REQUIRED, not permissive. Every NodeId in this system is "host:port" —
+        // ClusterRoleInfo and ConfigPublishCoordinator derive it as member.Address.Host:Port, the seed
+        // writes "central-1:4053", and NodeDeploymentState.NodeId is FK-bound to it. The previous
+        // pattern forbade the colon, so EVERY existing node failed validation and OnValidSubmit never
+        // ran: the Save button did nothing at all, silently. Hostnames may also be dotted
+        // (line3-opc-a.plant.local:4053).
+        [Required, RegularExpression("^[A-Za-z0-9_.:-]+$")]
         public string NodeId { get; set; } = "";
         [Required] public string Host { get; set; } = "";
         [Range(1, 65535)] public int OpcUaPort { get; set; } = 4840;
         [Range(1, 65535)] public int DashboardPort { get; set; } = 8081;
         [Required, RegularExpression("^urn:[A-Za-z0-9_:./-]+$")]
         public string ApplicationUri { get; set; } = "";
-        [Range(0, 255)] public byte ServiceLevelBase { get; set; } = 200;
+        // int, NOT byte. Blazor's InputNumber<T> rejects System.Byte outright — its static
+        // constructor throws "The type 'System.Byte' is not a supported numeric type", which escapes
+        // BuildRenderTree unhandled and takes the WHOLE page to an HTTP 500. Binding this field to
+        // the entity's own byte type meant /clusters/{id}/nodes/{nodeId} and .../nodes/new never
+        // rendered at all. The Range attribute still holds it to a byte's domain, and SubmitAsync
+        // casts on the way to the entity, so the stored type is unchanged.
+        [Range(0, 255)] public int ServiceLevelBase { get; set; } = 200;
         public bool Enabled { get; set; } = true;
         public string? DriverConfigOverridesJson { get; set; }
     }

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Pages/Deployments.razor

@@ -55,7 +55,7 @@
         {
             <tr>
                 <td><code>@Short(d.DeploymentId)</code></td>
-                <td><code>@d.RevisionHash[..12]…</code></td>
+                <td><code>@DisplayText.Abbreviate(d.RevisionHash, 12)</code></td>
                 <td>@d.Status</td>
                 <td>@d.CreatedBy</td>
                 <td>@d.CreatedAtUtc.ToString("u")</td>
@@ -113,7 +113,7 @@
             _lastSuccess = result.Outcome == StartDeploymentOutcome.Accepted;
             _lastMessage = result.Outcome switch
             {
-                StartDeploymentOutcome.Accepted => $"Deployment {Short(result.DeploymentId!.Value.Value)} dispatched (rev {result.RevisionHash!.Value.Value[..12]}…).",
+                StartDeploymentOutcome.Accepted => $"Deployment {Short(result.DeploymentId!.Value.Value)} dispatched (rev {DisplayText.Abbreviate(result.RevisionHash!.Value.Value, 12)}).",
                 StartDeploymentOutcome.AnotherDeploymentInFlight => result.Message ?? "Another deployment is already in flight.",
                 StartDeploymentOutcome.NoChanges => "No changes detected since the last sealed deployment.",
                 _ => result.Message ?? "Deployment rejected.",

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Pages/Scripts.razor

@@ -38,7 +38,7 @@ else
                         <span class="mono">@s.ScriptId</span>
                         &middot; <span>@s.Name</span>
                         &middot; <span class="chip chip-idle ms-1">@s.Language</span>
-                        <span class="text-muted small ms-2 mono">hash=@s.SourceHash[..12]…</span>
+                        <span class="text-muted small ms-2 mono">hash=@DisplayText.Abbreviate(s.SourceHash, 12)</span>
                     </summary>
                     <div style="padding:0 1rem 1rem">
                         <div class="d-flex mb-2">

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/DisplayText.cs

@@ -0,0 +1,45 @@
+namespace ZB.MOM.WW.OtOpcUa.AdminUI.Components.Shared;
+
+/// <summary>
+///     Rendering helpers for operator-facing text that comes out of the database.
+/// </summary>
+/// <remarks>
+///     <para>
+///         <b>Why this exists (#504).</b> Several pages abbreviated a hash / thumbprint with the range
+///         operator — <c>@s.SourceHash[..12]…</c> — which throws
+///         <see cref="ArgumentOutOfRangeException"/> the moment the value is shorter than the slice.
+///         In Blazor that escapes <c>BuildRenderTree</c> unhandled and takes the <b>whole page</b> to an
+///         HTTP 500, not just the offending row. Nothing enforces a minimum length at the schema, the
+///         entity, or the render layer, so any hand-written / seeded / migrated row is a live page-kill.
+///         The docker-dev seed proved it: its placeholder <c>SourceHash</c> values (<c>h1</c>,
+///         <c>h-abs-hr200</c>) made <c>/scripts</c> a hard 500 on every stock bring-up.
+///     </para>
+///     <para>
+///         Use <see cref="Abbreviate"/> for <b>every</b> such prefix. It never throws, and it appends the
+///         ellipsis only when it actually truncated — a 2-character hash renders as <c>h1</c>, not
+///         <c>h1…</c>, so the display never implies more text than exists.
+///     </para>
+/// </remarks>
+public static class DisplayText
+{
+    /// <summary>Placeholder rendered for a null / blank value. Matches the em-dash convention the
+    /// Admin UI already uses for "nothing to show" cells.</summary>
+    public const string Empty = "—";
+
+    /// <summary>
+    ///     The first <paramref name="maxLength"/> characters of <paramref name="value"/>, followed by an
+    ///     ellipsis when (and only when) characters were dropped.
+    /// </summary>
+    /// <param name="value">The value to abbreviate. May be null, blank, or shorter than
+    /// <paramref name="maxLength"/> — none of which throw.</param>
+    /// <param name="maxLength">Maximum number of characters to keep. Values below 1 are treated as 1,
+    /// so a caller cannot turn a display bug into a crash.</param>
+    /// <returns><see cref="Empty"/> for a null/blank value; the value verbatim when it already fits;
+    /// otherwise the truncated prefix plus an ellipsis.</returns>
+    public static string Abbreviate(string? value, int maxLength)
+    {
+        if (string.IsNullOrWhiteSpace(value)) return Empty;
+        if (maxLength < 1) maxLength = 1;
+        return value.Length <= maxLength ? value : string.Concat(value.AsSpan(0, maxLength), "…");
+    }
+}

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Drivers/DriverConfigModal.razor

@@ -57,6 +57,9 @@
                             case DriverTypeNames.Galaxy:
                                 <GalaxyDriverForm @bind-DriverConfigJson="_driverConfigJson" @bind-ResilienceConfig="_resilienceConfig" />
                                 break;
+                            case DriverTypeNames.Sql:
+                                <SqlDriverForm @bind-DriverConfigJson="_driverConfigJson" @bind-ResilienceConfig="_resilienceConfig" />
+                                break;
                             default:
                                 <div class="alert alert-warning">No typed config form for driver type <span class="mono">@_driverType</span>.</div>
                                 break;

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Drivers/DriverIdentitySection.razor

@@ -36,6 +36,7 @@
                         <option value="Focas">Focas</option>
                         <option value="OpcUaClient">OpcUaClient</option>
                         <option value="GalaxyMxGateway">Galaxy</option>
+                        <option value="Sql">Sql</option>
                     </InputSelect>
                     <div class="form-text">Cannot be changed after creation — drives the actor type that owns this instance.</div>
                 </div>

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Drivers/Forms/ModbusDriverForm.razor

@@ -27,16 +27,6 @@
                     }
                 </InputSelect>
             </div>
-            <div class="col-md-3">
-                <label class="form-label">Transport</label>
-                <InputSelect @bind-Value="_form.Transport" @bind-Value:after="EmitAsync" class="form-select form-select-sm">
-                    @foreach (var e in Enum.GetValues<ModbusTransportMode>())
-                    {
-                        <option value="@e">@e</option>
-                    }
-                </InputSelect>
-                <div class="form-text">RtuOverTcp = talk raw RTU frames to a serial→Ethernet gateway; must match the gateway's mode.</div>
-            </div>
             <div class="col-md-3">
                 <label class="form-label">MELSEC sub-family</label>
                 <InputSelect @bind-Value="_form.MelsecSubFamily" @bind-Value:after="EmitAsync" class="form-select form-select-sm">
@@ -300,9 +290,6 @@
         public ModbusFamily Family { get; set; } = ModbusFamily.Generic;
         public MelsecFamily MelsecSubFamily { get; set; } = MelsecFamily.Q_L_iQR;
 
-        // Wire transport (Tcp = Modbus/TCP MBAP; RtuOverTcp = RTU framing over a serial→Ethernet gateway)
-        public ModbusTransportMode Transport { get; set; } = ModbusTransportMode.Tcp;
-
         // Transport flags
         public bool AutoReconnect { get; set; } = true;
         public int IdleDisconnectTimeoutSeconds { get; set; } = 0;
@@ -350,7 +337,6 @@
             TimeoutSeconds = (int)o.Timeout.TotalSeconds,
             Family = o.Family,
             MelsecSubFamily = o.MelsecSubFamily,
-            Transport = o.Transport,
             AutoReconnect = o.AutoReconnect,
             IdleDisconnectTimeoutSeconds = o.IdleDisconnectTimeout.HasValue ? (int)o.IdleDisconnectTimeout.Value.TotalSeconds : 0,
             MaxRegistersPerRead = o.MaxRegistersPerRead,
@@ -401,7 +387,6 @@
             MaxReadGap = (ushort)Math.Clamp(MaxReadGap, 0, 65535),
             Family = Family,
             MelsecSubFamily = MelsecSubFamily,
-            Transport = Transport,
             WriteOnChangeOnly = WriteOnChangeOnly,
             AutoReconnect = AutoReconnect,
             KeepAlive = new ModbusKeepAliveOptions

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Drivers/Forms/SqlDriverForm.razor

@@ -0,0 +1,198 @@
+@* Embeddable read-only Sql driver (connection/dialect) config form body. There is NO per-device
+   endpoint — the whole database connection is named indirectly by ConnectionStringRef (an env-var name,
+   resolved at Initialize), so no connection string is ever authored into the config. Hosted by
+   DriverConfigModal. Exposes GetConfigJson() for the parent to pull at save time and fires
+   DriverConfigJsonChanged for @bind support. Enums serialize by NAME (JsonStringEnumConverter) so the
+   factory's string-typed deserialize accepts them. *@
+@using System.Text.Json
+@using System.Text.Json.Nodes
+@using System.Text.Json.Serialization
+@using ZB.MOM.WW.OtOpcUa.AdminUI.Components.Shared.Drivers
+@using ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts
+
+@* Connection *@
+<section class="panel rise mt-3" style="animation-delay:.06s">
+    <div class="panel-head">Database connection</div>
+    <div style="padding:1rem">
+        <div class="row g-3">
+            <div class="col-md-4">
+                <label class="form-label">Provider</label>
+                <InputSelect @bind-Value="_form.Provider" @bind-Value:after="EmitAsync" class="form-select form-select-sm">
+                    @* v1 constructs only SqlServer; the other SqlProvider members are reserved (P2). *@
+                    <option value="@SqlProvider.SqlServer">@SqlProvider.SqlServer</option>
+                </InputSelect>
+                <div class="form-text">Only Microsoft SQL Server is supported in v1.</div>
+            </div>
+            <div class="col-md-8">
+                <label class="form-label">Connection string ref <span class="text-danger">*</span></label>
+                <InputText @bind-Value="_form.ConnectionStringRef" @bind-Value:after="EmitAsync" class="form-control form-control-sm mono"
+                           placeholder="MesStaging" />
+                <div class="form-text">
+                    Name of the <code>Sql__ConnectionStrings__&lt;ref&gt;</code> env var set on the driver + AdminUI hosts —
+                    <strong>not</strong> a connection string. The credential is resolved at startup and never stored in the config.
+                </div>
+                @if (string.IsNullOrWhiteSpace(_form.ConnectionStringRef))
+                {
+                    <div class="text-danger small mt-1">Connection string ref is required.</div>
+                }
+            </div>
+        </div>
+    </div>
+</section>
+
+@* Polling / timeouts *@
+<section class="panel rise mt-3" style="animation-delay:.08s">
+    <div class="panel-head">Polling &amp; timeouts</div>
+    <div style="padding:1rem">
+        <div class="row g-3">
+            <div class="col-md-3">
+                <label class="form-label">Default poll interval (s)</label>
+                <InputNumber @bind-Value="_form.DefaultPollIntervalSeconds" @bind-Value:after="EmitAsync" class="form-control form-control-sm" />
+                <div class="form-text">Blank = factory default. Applied to groups without their own interval.</div>
+            </div>
+            <div class="col-md-3">
+                <label class="form-label">Operation timeout (s)</label>
+                <InputNumber @bind-Value="_form.OperationTimeoutSeconds" @bind-Value:after="EmitAsync" class="form-control form-control-sm" />
+                <div class="form-text">Client-side per-query deadline. Should exceed the command timeout.</div>
+            </div>
+            <div class="col-md-3">
+                <label class="form-label">Command timeout (s)</label>
+                <InputNumber @bind-Value="_form.CommandTimeoutSeconds" @bind-Value:after="EmitAsync" class="form-control form-control-sm" />
+                <div class="form-text">ADO.NET server-side CommandTimeout backstop.</div>
+            </div>
+            <div class="col-md-3">
+                <label class="form-label">Max concurrent groups</label>
+                <InputNumber @bind-Value="_form.MaxConcurrentGroups" @bind-Value:after="EmitAsync" class="form-control form-control-sm" />
+                <div class="form-text">Blank = factory default. Caps concurrent group queries (pool guard).</div>
+            </div>
+        </div>
+    </div>
+</section>
+
+@* Value handling *@
+<section class="panel rise mt-3" style="animation-delay:.10s">
+    <div class="panel-head">Value handling</div>
+    <div style="padding:1rem">
+        <div class="row g-3">
+            <div class="col-md-4">
+                <div class="form-check form-switch mt-2">
+                    <InputCheckbox @bind-Value="_form.NullIsBad" @bind-Value:after="EmitAsync" class="form-check-input" id="sqlNullIsBad" />
+                    <label class="form-check-label" for="sqlNullIsBad">NULL cell publishes Bad</label>
+                </div>
+                <div class="form-text mt-0">Unchecked = factory default (a NULL cell publishes Uncertain).</div>
+            </div>
+            <div class="col-md-4">
+                <div class="form-check form-switch mt-2">
+                    <input type="checkbox" class="form-check-input" id="sqlAllowWrites" disabled checked="false" />
+                    <label class="form-check-label" for="sqlAllowWrites">Allow writes</label>
+                </div>
+                <div class="form-text mt-0">
+                    <span class="badge bg-secondary">Read-only</span> v1 does not implement writes — this flag is inert and is not authored.
+                </div>
+            </div>
+        </div>
+    </div>
+</section>
+
+<DriverResilienceSection ResilienceConfig="@ResilienceConfig" ResilienceConfigChanged="OnResilienceChanged" />
+
+@code {
+    /// <summary>The driver-level DriverConfig JSON (connection/dialect; there is no device endpoint).</summary>
+    [Parameter] public string DriverConfigJson { get; set; } = "{}";
+    /// <summary>Fired (camelCase-serialized) whenever a field changes — enables @bind-DriverConfigJson.</summary>
+    [Parameter] public EventCallback<string> DriverConfigJsonChanged { get; set; }
+    /// <summary>The per-instance resilience-pipeline overrides JSON, or null.</summary>
+    [Parameter] public string? ResilienceConfig { get; set; }
+    /// <summary>Fired when the resilience overrides change.</summary>
+    [Parameter] public EventCallback<string?> ResilienceConfigChanged { get; set; }
+
+    // camelCase + string enums + omit-nulls, matching the factory's JsonStringEnumConverter deserialize.
+    // WhenWritingNull keeps absent optionals out of the blob (absent ⇒ the factory applies its default) and
+    // drops the composer-owned rawTags (never authored here).
+    private static readonly JsonSerializerOptions _jsonOpts = new()
+    {
+        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+        UnmappedMemberHandling = JsonUnmappedMemberHandling.Skip,
+        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
+        WriteIndented = false,
+        Converters = { new JsonStringEnumConverter() },
+    };
+
+    private FormModel _form = new();
+    private string? _lastParsed;
+
+    protected override void OnParametersSet()
+    {
+        // Re-parse only when the inbound value actually changed (don't clobber in-progress edits).
+        if (!string.Equals(_lastParsed, DriverConfigJson, StringComparison.Ordinal))
+        {
+            var dto = TryDeserialize(DriverConfigJson) ?? new SqlDriverConfigDto();
+            _form = FormModel.FromDto(dto);
+            _lastParsed = DriverConfigJson;
+        }
+    }
+
+    /// <summary>Serializes the current connection/dialect config to camelCase JSON with enums as NAME strings.
+    /// rawTags is never emitted (the composer adds it at deploy); allowWrites is never emitted (v1 read-only).</summary>
+    public string GetConfigJson() => JsonSerializer.Serialize(_form.ToDto(), _jsonOpts);
+
+    private async Task EmitAsync()
+    {
+        var json = GetConfigJson();
+        _lastParsed = json;
+        await DriverConfigJsonChanged.InvokeAsync(json);
+    }
+
+    private async Task OnResilienceChanged(string? r)
+    {
+        ResilienceConfig = r;
+        await ResilienceConfigChanged.InvokeAsync(r);
+    }
+
+    private static SqlDriverConfigDto? TryDeserialize(string json)
+    {
+        try { return JsonSerializer.Deserialize<SqlDriverConfigDto>(json, _jsonOpts); }
+        catch { return null; }
+    }
+
+    /// <summary>Flat mutable mirror of the driver-level fields of <see cref="SqlDriverConfigDto"/>. TimeSpans are
+    /// edited as nullable whole-second ints (blank ⇒ null ⇒ the factory default). rawTags + allowWrites are not
+    /// mirrored — the composer owns rawTags and v1 is read-only.</summary>
+    public sealed class FormModel
+    {
+        public SqlProvider Provider { get; set; } = SqlProvider.SqlServer;
+        public string? ConnectionStringRef { get; set; }
+        public int? DefaultPollIntervalSeconds { get; set; }
+        public int? OperationTimeoutSeconds { get; set; }
+        public int? CommandTimeoutSeconds { get; set; }
+        public int? MaxConcurrentGroups { get; set; }
+        public bool NullIsBad { get; set; }
+
+        public static FormModel FromDto(SqlDriverConfigDto d) => new()
+        {
+            Provider = d.Provider,
+            ConnectionStringRef = d.ConnectionStringRef,
+            DefaultPollIntervalSeconds = ToSeconds(d.DefaultPollInterval),
+            OperationTimeoutSeconds = ToSeconds(d.OperationTimeout),
+            CommandTimeoutSeconds = ToSeconds(d.CommandTimeout),
+            MaxConcurrentGroups = d.MaxConcurrentGroups,
+            NullIsBad = d.NullIsBad ?? false,
+        };
+
+        public SqlDriverConfigDto ToDto() => new()
+        {
+            Provider = Provider,
+            ConnectionStringRef = string.IsNullOrWhiteSpace(ConnectionStringRef) ? null : ConnectionStringRef.Trim(),
+            DefaultPollInterval = ToTimeSpan(DefaultPollIntervalSeconds),
+            OperationTimeout = ToTimeSpan(OperationTimeoutSeconds),
+            CommandTimeout = ToTimeSpan(CommandTimeoutSeconds),
+            MaxConcurrentGroups = MaxConcurrentGroups,
+            // Emit nullIsBad only when true; unchecked ⇒ null ⇒ the factory default (Uncertain). allowWrites
+            // and rawTags are deliberately left null so they are omitted from the authored blob.
+            NullIsBad = NullIsBad ? true : null,
+        };
+
+        private static int? ToSeconds(TimeSpan? ts) => ts.HasValue ? (int)ts.Value.TotalSeconds : null;
+        private static TimeSpan? ToTimeSpan(int? secs) => secs.HasValue ? TimeSpan.FromSeconds(secs.Value) : null;
+    }
+}

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Drivers/Pickers/SqlAddressPickerBody.razor

@@ -0,0 +1,441 @@
+@* Sql address picker (read-only v1):
+     1. Manual entry (ALWAYS available): pick the model (KeyValue / WideRow), then fill the
+        table + key/row-selector fields by hand. An operator without DriverOperator, or browsing a
+        server the AdminUI can't reach, authors a tag entirely from these fields.
+     2. (DriverOperator-gated) Live schema browse: schema → table → column tree on the left, the
+        picked column's type in the attribute side-panel on the right. Clicking a column leaf prefills
+        `table`, the value/column field, and the inferred `type`.
+
+   The picker's OUTPUT (CurrentAddress) is the composed per-tag `TagConfig` JSON blob — exactly the
+   shape SqlEquipmentTagParser.TryParse reads (design §5.2 / §5.3). Field names + the string `model`/
+   `type` enums are matched to the parser precisely; a mismatch would author fine and never read.
+
+   Credential hygiene: the optional ad-hoc connection string is SESSION-ONLY. It is merged into the
+   JSON handed to BrowserService.OpenAsync for THIS browse only and is NEVER written into the composed
+   TagConfig blob nor back into the driver config — there is no code path here that persists it. *@
+@implements IAsyncDisposable
+@using System.Text.Json.Nodes
+@using ZB.MOM.WW.OtOpcUa.AdminUI.Browsing
+@using ZB.MOM.WW.OtOpcUa.Commons.Browsing
+@using ZB.MOM.WW.OtOpcUa.Core.Abstractions
+@using ZB.MOM.WW.OtOpcUa.Driver.Sql
+@using ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser
+@inject IBrowserSessionService BrowserService
+@inject AuthenticationStateProvider AuthState
+@inject IAuthorizationService AuthorizationService
+
+<div class="row g-3">
+    <div class="col-md-4">
+        <label class="form-label">Model</label>
+        <select class="form-select form-select-sm" @bind="_model" @bind:after="OnManualChangedAsync">
+            <option value="KeyValue">KeyValue</option>
+            <option value="WideRow">WideRow</option>
+        </select>
+        <div class="form-text">
+            KeyValue: one row per key. WideRow: many columns of one selected row.
+        </div>
+    </div>
+    <div class="col-md-5">
+        <label class="form-label">Table or view</label>
+        <input type="text" class="form-control form-control-sm mono" placeholder="dbo.TagValues"
+               @bind="_table" @bind:after="OnManualChangedAsync" />
+        <div class="form-text">Schema-qualified, e.g. <code>dbo.TagValues</code>.</div>
+    </div>
+    <div class="col-md-3">
+        <label class="form-label">Type</label>
+        <select class="form-select form-select-sm" @bind="_type" @bind:after="OnManualChangedAsync">
+            <option value="">(infer)</option>
+            @foreach (var t in Enum.GetValues<DriverDataType>())
+            {
+                <option value="@t">@t</option>
+            }
+        </select>
+        <div class="form-text">Blank ⇒ inferred from the column.</div>
+    </div>
+</div>
+
+@if (_model == "KeyValue")
+{
+    <div class="row g-3 mt-1">
+        <div class="col-md-4">
+            <label class="form-label">Key column</label>
+            <input type="text" class="form-control form-control-sm mono" placeholder="tag_name"
+                   @bind="_keyColumn" @bind:after="OnManualChangedAsync" />
+        </div>
+        <div class="col-md-4">
+            <label class="form-label">Key value</label>
+            <input type="text" class="form-control form-control-sm mono" placeholder="Line1.Speed"
+                   @bind="_keyValue" @bind:after="OnManualChangedAsync" />
+            <div class="form-text">Bound as a parameter — never interpolated.</div>
+        </div>
+        <div class="col-md-4">
+            <label class="form-label">Value column</label>
+            <input type="text" class="form-control form-control-sm mono" placeholder="num_value"
+                   @bind="_valueColumn" @bind:after="OnManualChangedAsync" />
+        </div>
+    </div>
+}
+else
+{
+    <div class="row g-3 mt-1">
+        <div class="col-md-4">
+            <label class="form-label">Value column</label>
+            <input type="text" class="form-control form-control-sm mono" placeholder="oven_temp"
+                   @bind="_columnName" @bind:after="OnManualChangedAsync" />
+            <div class="form-text">The column this tag reads from the selected row.</div>
+        </div>
+        <div class="col-md-4">
+            <label class="form-label">Row selector</label>
+            <select class="form-select form-select-sm" @bind="_selectorMode" @bind:after="OnManualChangedAsync">
+                <option value="Where">Where column = value</option>
+                <option value="Newest">Newest by timestamp</option>
+            </select>
+        </div>
+        @if (_selectorMode == "Where")
+        {
+            <div class="col-md-2">
+                <label class="form-label">Where column</label>
+                <input type="text" class="form-control form-control-sm mono" placeholder="station_id"
+                       @bind="_whereColumn" @bind:after="OnManualChangedAsync" />
+            </div>
+            <div class="col-md-2">
+                <label class="form-label">Where value</label>
+                <input type="text" class="form-control form-control-sm mono" placeholder="7"
+                       @bind="_whereValue" @bind:after="OnManualChangedAsync" />
+            </div>
+        }
+        else
+        {
+            <div class="col-md-4">
+                <label class="form-label">Order-by (timestamp) column</label>
+                <input type="text" class="form-control form-control-sm mono" placeholder="sample_ts"
+                       @bind="_topByTimestamp" @bind:after="OnManualChangedAsync" />
+            </div>
+        }
+    </div>
+}
+
+<div class="row g-3 mt-1">
+    <div class="col-md-6">
+        <label class="form-label">Timestamp column <span class="text-muted small">(optional)</span></label>
+        <input type="text" class="form-control form-control-sm mono" placeholder="sample_ts"
+               @bind="_timestampColumn" @bind:after="OnManualChangedAsync" />
+        <div class="form-text">Source-timestamp column; blank ⇒ the driver stamps the poll time.</div>
+    </div>
+</div>
+
+@if (_canOperate)
+{
+    <hr class="my-3" />
+    <div class="row g-3">
+        <div class="col-md-12">
+            <label class="form-label small">Ad-hoc connection string <span class="text-muted">(session-only, never saved)</span></label>
+            <input type="password" class="form-control form-control-sm mono" autocomplete="off"
+                   placeholder="Server=…;Database=…;User Id=…;Password=…"
+                   @bind="_adhocConnectionString" />
+            <div class="form-text">
+                Leave blank to browse via the driver's <code>connectionStringRef</code> (resolved from
+                the AdminUI host's <code>Sql__ConnectionStrings__&lt;ref&gt;</code> env var). Paste a
+                literal only for a one-off browse — it is used for this session and never persisted.
+            </div>
+        </div>
+    </div>
+
+    <div class="mt-2 d-flex align-items-center gap-2">
+        @if (_token == Guid.Empty)
+        {
+            <button type="button" class="btn btn-outline-primary btn-sm" disabled="@_opening"
+                    @onclick="OpenBrowseAsync">
+                @if (_opening) { <span class="spinner-border spinner-border-sm me-1"></span> }
+                Browse database
+            </button>
+        }
+        else
+        {
+            <span class="chip chip-ok">Browser open</span>
+            <button type="button" class="btn btn-outline-secondary btn-sm" @onclick="CloseBrowseAsync">Close</button>
+        }
+    </div>
+    @if (_openError is not null)
+    {
+        <div class="text-danger small mt-2">@_openError</div>
+    }
+
+    @if (_token != Guid.Empty)
+    {
+        <div class="row g-3 mt-1">
+            <div class="col-md-7">
+                <label class="form-label small">Schemas → tables → columns</label>
+                <DriverBrowseTree SessionToken="_token" OnNodeSelected="OnTreeSelectAsync"
+                                  SelectedNodeId="@_selectedColumnNodeId" />
+            </div>
+            <div class="col-md-5">
+                <label class="form-label small">Picked column</label>
+                <div class="border rounded p-2" style="max-height:420px; overflow:auto; min-height:240px">
+                    @if (_attrsLoading)
+                    {
+                        <span class="spinner-border spinner-border-sm me-1"></span>
+                    }
+                    else if (_attrsError is not null)
+                    {
+                        <span class="text-danger small">@_attrsError</span>
+                    }
+                    else if (_attrs is null)
+                    {
+                        <span class="text-muted small">Pick a column leaf.</span>
+                    }
+                    else if (_attrs.Count == 0)
+                    {
+                        <span class="text-muted small">Column no longer present.</span>
+                    }
+                    else
+                    {
+                        @foreach (var a in _attrs)
+                        {
+                            <div class="d-flex justify-content-between align-items-center py-1"
+                                 style="cursor:pointer" @onclick="@(() => ApplyAttributeAsync(a))">
+                                <span class="mono small">@a.Name</span>
+                                <span class="text-muted small">@a.DriverDataType · @a.SecurityClass</span>
+                            </div>
+                        }
+                    }
+                </div>
+            </div>
+        </div>
+    }
+}
+
+<div class="mt-3">
+    <span class="text-muted small">TagConfig:</span>
+    <code class="mono ms-2">@(_built.Length == 0 ? "—" : _built)</code>
+</div>
+
+@code {
+    [Parameter] public string CurrentAddress { get; set; } = "";
+    [Parameter] public EventCallback<string> CurrentAddressChanged { get; set; }
+
+    /// <summary>Live accessor for the selected driver's <c>DriverConfig</c> JSON (carries
+    /// <c>connectionStringRef</c> + <c>provider</c>). Fed to <c>BrowserService.OpenAsync("Sql", …)</c>.</summary>
+    [Parameter, EditorRequired] public Func<string> GetConfigJson { get; set; } = () => "{}";
+
+    /// <summary>Fires with the picker's suggested tag display name (<c>table.column</c>) whenever a
+    /// column is picked from the tree, so a host editor may default the raw tag's name. Optional —
+    /// the composed TagConfig blob itself carries no display name (it is not a parser field).</summary>
+    [Parameter] public EventCallback<string> SuggestedDisplayNameChanged { get; set; }
+
+    // Manual/composed tag fields (all editable by hand; browse only prefills a subset).
+    private string _model = "KeyValue";
+    private string _table = "";
+    private string _keyColumn = "";
+    private string _keyValue = "";
+    private string _valueColumn = "";
+    private string _columnName = "";
+    private string _selectorMode = "Where";
+    private string _whereColumn = "";
+    private string _whereValue = "";
+    private string _topByTimestamp = "";
+    private string _timestampColumn = "";
+    private string _type = "";
+
+    // Browse-only, session-scoped state.
+    private string _adhocConnectionString = "";
+    private string _built = "";
+    private string _selectedColumnNodeId = "";
+    private Guid _token = Guid.Empty;
+    private bool _opening;
+    private bool _canOperate;
+    private string? _openError;
+    private bool _attrsLoading;
+    private string? _attrsError;
+    private IReadOnlyList<AttributeInfo>? _attrs;
+
+    protected override async Task OnInitializedAsync()
+    {
+        var auth = await AuthState.GetAuthenticationStateAsync();
+        var authResult = await AuthorizationService.AuthorizeAsync(auth.User, null, AdminUiPolicies.DriverOperator);
+        _canOperate = authResult.Succeeded;
+        _built = Build();
+        await CurrentAddressChanged.InvokeAsync(_built);
+    }
+
+    private async Task OpenBrowseAsync()
+    {
+        _opening = true;
+        _openError = null;
+        StateHasChanged();
+        try
+        {
+            // Merge the ad-hoc literal into the OpenAsync config for THIS session only. The literal is
+            // never written to the composed TagConfig blob nor back to the driver config — this is the
+            // sole place it is read, and it dies with the local variable.
+            var json = BuildBrowseConfig();
+            var result = await BrowserService.OpenAsync(SqlDriver.DriverTypeName, json, default);
+            if (result.Ok) { _token = result.Token; }
+            else { _openError = result.Message; }
+        }
+        finally { _opening = false; StateHasChanged(); }
+    }
+
+    /// <summary>
+    ///     Builds the JSON handed to the browser: the driver config plus, when the operator pasted one,
+    ///     a top-level <c>connectionString</c> literal. The literal wins over any <c>connectionStringRef</c>
+    ///     server-side (SqlDriverBrowser precedence) and is session-only.
+    /// </summary>
+    private string BuildBrowseConfig()
+    {
+        var baseJson = GetConfigJson() ?? "{}";
+        if (string.IsNullOrWhiteSpace(_adhocConnectionString)) { return baseJson; }
+
+        JsonObject o;
+        try { o = JsonNode.Parse(baseJson) as JsonObject ?? new JsonObject(); }
+        catch (System.Text.Json.JsonException) { o = new JsonObject(); }
+        o["connectionString"] = _adhocConnectionString;
+        return o.ToJsonString();
+    }
+
+    private async Task CloseBrowseAsync()
+    {
+        var t = _token;
+        _token = Guid.Empty;
+        _attrs = null;
+        _selectedColumnNodeId = "";
+        StateHasChanged();
+        if (t != Guid.Empty) { await BrowserService.CloseAsync(t); }
+    }
+
+    /// <summary>
+    ///     Handles a tree click. Only a COLUMN leaf commits a prefill; schema/table folder clicks are
+    ///     navigation, not selection. The NodeId is decoded with <see cref="SqlBrowseNodeId.TryParse"/>
+    ///     — never split by hand, because SQL identifiers may contain '.' and '|'.
+    /// </summary>
+    private async Task OnTreeSelectAsync(BrowseNode node)
+    {
+        if (!SqlBrowseNodeId.TryParse(node.NodeId, out var reference)
+            || reference.Kind != SqlBrowseNodeKind.Column)
+        {
+            return;
+        }
+
+        _selectedColumnNodeId = node.NodeId;
+        _table = $"{reference.Schema}.{reference.Table}";
+        if (_model == "WideRow") { _columnName = reference.Column!; }
+        else { _valueColumn = reference.Column!; }
+
+        // Suggested display name uses the BARE table name (the blob's `table` stays schema-qualified).
+        await SuggestedDisplayNameChanged.InvokeAsync($"{reference.Table}.{reference.Column}");
+
+        _attrs = null;
+        _attrsLoading = true;
+        _attrsError = null;
+        StateHasChanged();
+        try
+        {
+            _attrs = await BrowserService.AttributesAsync(_token, node.NodeId, default);
+            var picked = _attrs.Count > 0 ? _attrs[0] : null;
+            if (picked is not null) { PrefillType(picked); }
+        }
+        catch (Exception ex) { _attrsError = ex.Message; }
+        finally
+        {
+            _attrsLoading = false;
+            await OnChangedAsync();
+        }
+    }
+
+    /// <summary>Re-applies the side-panel column's inferred type (and value-column) on click.</summary>
+    private async Task ApplyAttributeAsync(AttributeInfo a)
+    {
+        if (_model == "WideRow") { _columnName = a.Name; }
+        else { _valueColumn = a.Name; }
+        PrefillType(a);
+        await OnChangedAsync();
+    }
+
+    /// <summary>Prefills the type dropdown from the browsed column's mapped DriverDataType, if it maps.</summary>
+    private void PrefillType(AttributeInfo a)
+    {
+        if (Enum.TryParse<DriverDataType>(a.DriverDataType, out _)) { _type = a.DriverDataType; }
+    }
+
+    private async Task OnManualChangedAsync() => await OnChangedAsync();
+
+    private async Task OnChangedAsync()
+    {
+        _built = Build();
+        await CurrentAddressChanged.InvokeAsync(_built);
+    }
+
+    /// <summary>
+    ///     Composes the per-tag TagConfig blob (design §5.2 / §5.3), matched field-for-field to
+    ///     <c>SqlEquipmentTagParser</c>. Returns "" until the selected model's required fields are all
+    ///     present, so the "Use this address" button never commits a half-blob the parser would reject.
+    ///     <c>model</c> and <c>type</c> are written as NAME strings (the parser reads them strictly).
+    /// </summary>
+    private string Build()
+    {
+        var table = _table.Trim();
+        if (table.Length == 0) { return ""; }
+
+        var o = new JsonObject
+        {
+            ["driver"] = "Sql",
+            ["model"] = _model,
+            ["table"] = table,
+        };
+
+        if (_model == "KeyValue")
+        {
+            var keyColumn = _keyColumn.Trim();
+            var valueColumn = _valueColumn.Trim();
+            var keyValue = _keyValue.Trim();
+            if (keyColumn.Length == 0 || valueColumn.Length == 0 || keyValue.Length == 0) { return ""; }
+            o["keyColumn"] = keyColumn;
+            o["keyValue"] = keyValue;
+            o["valueColumn"] = valueColumn;
+        }
+        else // WideRow
+        {
+            var columnName = _columnName.Trim();
+            if (columnName.Length == 0) { return ""; }
+            o["columnName"] = columnName;
+
+            var rowSelector = new JsonObject();
+            if (_selectorMode == "Where")
+            {
+                var whereColumn = _whereColumn.Trim();
+                var whereValue = _whereValue.Trim();
+                if (whereColumn.Length == 0 || whereValue.Length == 0) { return ""; }
+                rowSelector["whereColumn"] = whereColumn;
+                rowSelector["whereValue"] = whereValue;
+            }
+            else // Newest
+            {
+                var topByTimestamp = _topByTimestamp.Trim();
+                if (topByTimestamp.Length == 0) { return ""; }
+                rowSelector["topByTimestamp"] = topByTimestamp;
+            }
+
+            o["rowSelector"] = rowSelector;
+        }
+
+        var timestampColumn = _timestampColumn.Trim();
+        if (timestampColumn.Length > 0) { o["timestampColumn"] = timestampColumn; }
+
+        if (_type.Length > 0) { o["type"] = _type; }
+
+        // v1 is read-only; every SQL tag is non-writable (SecurityClass = ViewOnly server-side).
+        o["writable"] = false;
+
+        return o.ToJsonString();
+    }
+
+    public ValueTask DisposeAsync()
+    {
+        if (_token != Guid.Empty)
+        {
+            // Fire-and-forget — don't block circuit teardown on a slow database.
+            _ = BrowserService.CloseAsync(_token);
+        }
+        return ValueTask.CompletedTask;
+    }
+}

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Raw/RawDriverTypeDialog.razor

@@ -68,6 +68,7 @@
         ("FOCAS", DriverTypeNames.FOCAS),
         ("OpcUaClient", DriverTypeNames.OpcUaClient),
         ("Galaxy", DriverTypeNames.Galaxy),
+        ("Sql", DriverTypeNames.Sql),
         ("Calculation", "Calculation"),
     ];
 

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Uns/TagEditors/SqlTagConfigEditor.razor

@@ -0,0 +1,211 @@
+@* Typed TagConfig editor for the read-only Sql driver. Thin shell over SqlTagConfigModel: every field edit
+   goes model → ToJson → ConfigJsonChanged (the model is the single source of the blob shape + enum-name
+   serialisation; never hand-composed here). The Model dropdown (KeyValue/WideRow) shows the matching field
+   group; the "Build address" picker is the ASSISTED path — every field is also hand-editable. Dispatched
+   from the TagModal via TagConfigEditorMap with the same (ConfigJson/ConfigJsonChanged/DriverType/
+   GetDriverConfigJson) parameter shape every typed editor takes; validation is surfaced centrally by
+   TagConfigValidator (save-gate), exactly as the sibling editors do — no inline validation here. *@
+@using ZB.MOM.WW.OtOpcUa.AdminUI.Uns.TagEditors
+@using ZB.MOM.WW.OtOpcUa.Core.Abstractions
+@using ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts
+@using ZB.MOM.WW.OtOpcUa.AdminUI.Components.Shared.Drivers
+@using ZB.MOM.WW.OtOpcUa.AdminUI.Components.Shared.Drivers.Pickers
+
+<div class="row g-2">
+    <div class="col-md-4"><label class="form-label">Model</label>
+        <select class="form-select form-select-sm" value="@_m.Model" @onchange="@(e => Update(() => _m.Model = ParseEnum(e.Value, SqlTagModel.KeyValue)))">
+            @* Query is deferred (P3) and rejected by the parser/validator — only offer the two v1 models. *@
+            <option value="@SqlTagModel.KeyValue">KeyValue</option>
+            <option value="@SqlTagModel.WideRow">WideRow</option>
+        </select></div>
+    <div class="col-md-5"><label class="form-label">Table or view</label>
+        <input class="form-control form-control-sm mono" value="@_m.Table" placeholder="dbo.TagValues" @onchange="@(e => Update(() => _m.Table = NullIfBlank(e.Value)))" /></div>
+    <div class="col-md-3"><label class="form-label">Type override</label>
+        <select class="form-select form-select-sm" value="@(_m.Type?.ToString() ?? "")" @onchange="@(e => Update(() => _m.Type = ParseNullableEnum<DriverDataType>(e.Value)))">
+            <option value="">(infer from column)</option>
+            @foreach (var v in Enum.GetValues<DriverDataType>()) { <option value="@v">@v</option> }
+        </select></div>
+</div>
+
+@if (_m.Model == SqlTagModel.KeyValue)
+{
+    <div class="row g-2 mt-1">
+        <div class="col-md-4"><label class="form-label">Key column</label>
+            <input class="form-control form-control-sm mono" value="@_m.KeyColumn" placeholder="tag_name" @onchange="@(e => Update(() => _m.KeyColumn = NullIfBlank(e.Value)))" /></div>
+        <div class="col-md-4"><label class="form-label">Key value</label>
+            <input class="form-control form-control-sm mono" value="@_m.KeyValue" placeholder="Line1.Speed" @onchange="@(e => Update(() => _m.KeyValue = e.Value?.ToString()))" />
+            <div class="form-text">Bound as a parameter — never interpolated.</div></div>
+        <div class="col-md-4"><label class="form-label">Value column</label>
+            <input class="form-control form-control-sm mono" value="@_m.ValueColumn" placeholder="num_value" @onchange="@(e => Update(() => _m.ValueColumn = NullIfBlank(e.Value)))" /></div>
+    </div>
+}
+else
+{
+    <div class="row g-2 mt-1">
+        <div class="col-md-4"><label class="form-label">Value column</label>
+            <input class="form-control form-control-sm mono" value="@_m.ColumnName" placeholder="oven_temp" @onchange="@(e => Update(() => _m.ColumnName = NullIfBlank(e.Value)))" />
+            <div class="form-text">The column this tag reads from the selected row.</div></div>
+        <div class="col-md-4"><label class="form-label">Row selector</label>
+            <select class="form-select form-select-sm" value="@_selectorMode" @onchange="@(e => OnSelectorModeChanged(e.Value?.ToString()))">
+                <option value="Where">Where column = value</option>
+                <option value="Newest">Newest by timestamp</option>
+            </select></div>
+        @if (_selectorMode == "Where")
+        {
+            <div class="col-md-2"><label class="form-label">Where column</label>
+                <input class="form-control form-control-sm mono" value="@_m.RowSelector.WhereColumn" placeholder="station_id" @onchange="@(e => Update(() => _m.RowSelector.WhereColumn = NullIfBlank(e.Value)))" /></div>
+            <div class="col-md-2"><label class="form-label">Where value</label>
+                <input class="form-control form-control-sm mono" value="@_m.RowSelector.WhereValue" placeholder="7" @onchange="@(e => Update(() => _m.RowSelector.WhereValue = e.Value?.ToString()))" /></div>
+        }
+        else
+        {
+            <div class="col-md-4"><label class="form-label">Order-by (timestamp) column</label>
+                <input class="form-control form-control-sm mono" value="@_m.RowSelector.TopByTimestamp" placeholder="sample_ts" @onchange="@(e => Update(() => _m.RowSelector.TopByTimestamp = NullIfBlank(e.Value)))" /></div>
+        }
+    </div>
+}
+
+<div class="row g-2 mt-1">
+    <div class="col-md-6"><label class="form-label">Timestamp column <span class="text-muted small">(optional)</span></label>
+        <input class="form-control form-control-sm mono" value="@_m.TimestampColumn" placeholder="sample_ts" @onchange="@(e => Update(() => _m.TimestampColumn = NullIfBlank(e.Value)))" />
+        <div class="form-text">Source-timestamp column; blank ⇒ the driver stamps the poll time.</div></div>
+    <div class="col-12 mt-1">
+        <button type="button" class="btn btn-sm btn-outline-secondary" @onclick="@(() => _showPicker = true)">Build address</button>
+    </div>
+</div>
+
+@if (_showPicker)
+{
+    <DriverTagPicker @bind-Visible="_showPicker"
+                     Title="Sql tag builder"
+                     CurrentAddress="@_pickerAddress"
+                     OnPickAddress="@OnAddressPicked">
+        <SqlAddressPickerBody CurrentAddress="@_pickerAddress"
+                              CurrentAddressChanged="@((s) => _pickerAddress = s)"
+                              GetConfigJson="@GetDriverConfigJson" />
+    </DriverTagPicker>
+}
+
+@code {
+    /// <summary>The tag's current TagConfig JSON.</summary>
+    [Parameter] public string? ConfigJson { get; set; }
+
+    /// <summary>Raised with the updated TagConfig JSON when the model changes.</summary>
+    [Parameter] public EventCallback<string> ConfigJsonChanged { get; set; }
+
+    /// <summary>DriverType of the selected driver — accepted for dispatch uniformity.</summary>
+    [Parameter] public string DriverType { get; set; } = "";
+
+    /// <summary>Live accessor for the selected driver's DriverConfig JSON (browse connect config).</summary>
+    [Parameter] public Func<string> GetDriverConfigJson { get; set; } = () => "{}";
+
+    private SqlTagConfigModel _m = new();
+    private string? _lastConfigJson;
+    private bool _showPicker;
+    private string _pickerAddress = "";
+
+    // Local UI discriminator for the WideRow row selector (where-pair vs newest-by-timestamp). The model
+    // carries no explicit selector "mode" — it is inferred from which selector fields are populated. Kept in
+    // the editor (not the model) because an operator mid-edit may have BOTH selector fields blank, a state
+    // the mode can't be re-derived from; DeriveSelectorMode only overrides it when the model unambiguously
+    // says otherwise, so switching to "Newest" then round-tripping doesn't snap back to "Where".
+    private string _selectorMode = "Where";
+
+    // Re-parse only when the incoming JSON actually changes, so an unrelated parent re-render (Blazor Server
+    // live-status pushes do this) can't reset the user's in-progress edits (mirrors the other typed editors).
+    protected override void OnParametersSet()
+    {
+        if (ConfigJson == _lastConfigJson) { return; }
+        _lastConfigJson = ConfigJson;
+        _m = SqlTagConfigModel.FromJson(ConfigJson);
+        DeriveSelectorMode();
+    }
+
+    // Sets the row-selector mode from the model ONLY when the populated fields make it unambiguous; leaves
+    // the operator's current choice untouched when both selector fields are blank (an in-progress edit).
+    private void DeriveSelectorMode()
+    {
+        if (!string.IsNullOrWhiteSpace(_m.RowSelector.TopByTimestamp) && string.IsNullOrWhiteSpace(_m.RowSelector.WhereColumn))
+        {
+            _selectorMode = "Newest";
+        }
+        else if (!string.IsNullOrWhiteSpace(_m.RowSelector.WhereColumn))
+        {
+            _selectorMode = "Where";
+        }
+    }
+
+    // TryParse so a bad/empty change value can never throw into the Blazor circuit — it falls back. Reads by
+    // NAME (never an ordinal cast), matching the model's strict name-string serialisation.
+    private static TEnum ParseEnum<TEnum>(object? v, TEnum fallback) where TEnum : struct, Enum
+        => Enum.TryParse<TEnum>(v?.ToString(), out var r) ? r : fallback;
+
+    // "" (the "(infer)" option) ⇒ null; a parseable NAME ⇒ that type; anything else ⇒ null. Enum round-trip
+    // is by name — never an ordinal cast — so the model re-serialises `type` as its strict name string.
+    private static TEnum? ParseNullableEnum<TEnum>(object? v) where TEnum : struct, Enum
+    {
+        var s = v?.ToString();
+        if (string.IsNullOrEmpty(s)) { return null; }
+        return Enum.TryParse<TEnum>(s, out var r) ? r : null;
+    }
+
+    // Identifier fields (table/column names): a blank input means "absent" — store null so ToJson omits the
+    // key. (KeyValue/WhereValue are deliberately NOT run through this: the model treats an empty-string value
+    // as present-and-empty, distinct from absent, so those keep e.Value verbatim.)
+    private static string? NullIfBlank(object? v)
+    {
+        var s = v?.ToString();
+        return string.IsNullOrWhiteSpace(s) ? null : s;
+    }
+
+    private async Task Update(Action apply)
+    {
+        apply();
+        await ConfigJsonChanged.InvokeAsync(_m.ToJson());
+    }
+
+    // The WideRow selector is either a where-pair OR newest-by-timestamp — never both. Clear the fields of
+    // the mode being left so the composed blob carries exactly one selector (a stale where-pair would win
+    // over topByTimestamp at read time, silently overriding the operator's choice).
+    private async Task OnSelectorModeChanged(string? mode)
+    {
+        _selectorMode = mode == "Newest" ? "Newest" : "Where";
+        await Update(() =>
+        {
+            if (_selectorMode == "Newest")
+            {
+                _m.RowSelector.WhereColumn = null;
+                _m.RowSelector.WhereValue = null;
+            }
+            else
+            {
+                _m.RowSelector.TopByTimestamp = null;
+            }
+        });
+    }
+
+    // The Sql picker emits a COMPLETE parser-shaped TagConfig blob (not a single address token like the
+    // other drivers' pickers). Parse it through the model and adopt its mapping fields onto the working
+    // model — mutating _m in place preserves any platform keys already on the tag (e.g. isHistorized) that
+    // the picker never authors.
+    private async Task OnAddressPicked(string blob)
+    {
+        if (string.IsNullOrWhiteSpace(blob)) { return; }
+        var picked = SqlTagConfigModel.FromJson(blob);
+        await Update(() =>
+        {
+            _m.Model = picked.Model;
+            _m.Table = picked.Table;
+            _m.KeyColumn = picked.KeyColumn;
+            _m.KeyValue = picked.KeyValue;
+            _m.ValueColumn = picked.ValueColumn;
+            _m.ColumnName = picked.ColumnName;
+            _m.TimestampColumn = picked.TimestampColumn;
+            _m.Type = picked.Type;
+            _m.RowSelector.WhereColumn = picked.RowSelector.WhereColumn;
+            _m.RowSelector.WhereValue = picked.RowSelector.WhereValue;
+            _m.RowSelector.TopByTimestamp = picked.RowSelector.TopByTimestamp;
+        });
+        DeriveSelectorMode();
+    }
+}

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/EndpointRouteBuilderExtensions.cs

@@ -11,6 +11,7 @@ using ZB.MOM.WW.OtOpcUa.Commons.Browsing;
 using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
 using ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Browser;
 using ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser;
+using ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser;
 using ZB.MOM.WW.Secrets.Ui;
 
 namespace ZB.MOM.WW.OtOpcUa.AdminUI;
@@ -74,6 +75,11 @@ public static class EndpointRouteBuilderExtensions
         services.AddScoped<RawTagCsvExportReader>();
         services.AddSingleton<IDriverBrowser, OpcUaClientDriverBrowser>();
         services.AddSingleton<IDriverBrowser, GalaxyDriverBrowser>();
+        // Bespoke Sql schema browser (server → schema → table → column). Constructible bare — every
+        // ctor param has a production default. The universal-browser DI line is deliberately NOT added
+        // for Sql: SqlDriver.CanBrowse is false, and this bespoke IDriverBrowser wins by construction
+        // (BrowserSessionService indexes bespoke browsers by DriverType before falling back to universal).
+        services.AddSingleton<IDriverBrowser, SqlDriverBrowser>();
         // Universal Discover-backed fallback browser (Wave 0). IDriverFactory is bound by the
         // fused Host's DriverFactoryBootstrap; a standalone AdminUI has none → NullDriverFactory
         // → CanBrowse false → pickers gracefully stay manual-entry (design §6).

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Uns/TagEditors/SqlTagConfigModel.cs

@@ -0,0 +1,212 @@
+using System.Text.Json.Nodes;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
+
+namespace ZB.MOM.WW.OtOpcUa.AdminUI.Uns.TagEditors;
+
+/// <summary>
+/// Typed working model for a read-only Sql tag's TagConfig JSON (the driver-specific table/column
+/// mapping; name/writable live on the Tag entity). Mirrors — byte-for-byte on the fields it owns — the
+/// authoritative runtime reader <see cref="SqlEquipmentTagParser.TryParse"/>: the <c>model</c> and
+/// <c>type</c> enums are written as their NAME strings (never numbers), and <see cref="Validate"/>
+/// enforces the same required-field/selector shape the parser accepts. Preserves unrecognised JSON keys
+/// (top-level and inside <c>rowSelector</c>) across a load→save so a future field survives an edit.
+/// </summary>
+public sealed class SqlTagConfigModel
+{
+    /// <summary>Tag→value mapping model. v1 accepts <see cref="SqlTagModel.KeyValue"/> and
+    /// <see cref="SqlTagModel.WideRow"/>; <see cref="SqlTagModel.Query"/> is deferred and rejected.</summary>
+    public SqlTagModel Model { get; set; } = SqlTagModel.KeyValue;
+
+    /// <summary>The table or view to read (e.g. <c>dbo.TagValues</c>). Required for every model.</summary>
+    public string? Table { get; set; }
+
+    /// <summary><see cref="SqlTagModel.KeyValue"/>: the column matched against <see cref="KeyValue"/>.</summary>
+    public string? KeyColumn { get; set; }
+
+    /// <summary><see cref="SqlTagModel.KeyValue"/>: this tag's key value (bound as a parameter at read time).</summary>
+    public string? KeyValue { get; set; }
+
+    /// <summary><see cref="SqlTagModel.KeyValue"/>: the column the value is read from.</summary>
+    public string? ValueColumn { get; set; }
+
+    /// <summary>Optional source-timestamp column; absent ⇒ the driver stamps the poll time. Both models.</summary>
+    public string? TimestampColumn { get; set; }
+
+    /// <summary><see cref="SqlTagModel.WideRow"/>: the column this tag reads from the selected row.</summary>
+    public string? ColumnName { get; set; }
+
+    /// <summary><see cref="SqlTagModel.WideRow"/>: which row to read — a where-pair or newest-by-timestamp.</summary>
+    public SqlRowSelectorModel RowSelector { get; set; } = new();
+
+    /// <summary>Optional explicit OPC UA data type override (the blob's <c>type</c> field). <c>null</c> ⇒ the
+    /// driver infers the type from the result-set column metadata.</summary>
+    public DriverDataType? Type { get; set; }
+
+    private JsonObject _bag = new();
+
+    // The raw offending string when "model"/"type" is present-but-invalid (a typo). Mirrors the parser's
+    // strict-enum reject: absent OR present-non-string ⇒ null (nothing to validate).
+    private string? _invalidModelRaw;
+    private string? _invalidTypeRaw;
+
+    /// <summary>Loads a model from a TagConfig JSON string, defaulting any absent field and retaining every
+    /// original key (so fields this editor doesn't expose survive a load→save).</summary>
+    /// <param name="json">The raw TagConfig JSON string, or <c>null</c> for a new/empty config.</param>
+    /// <returns>The populated <see cref="SqlTagConfigModel"/>.</returns>
+    public static SqlTagConfigModel FromJson(string? json)
+    {
+        var o = TagConfigJson.ParseOrNew(json);
+        var (model, invalidModel) = ReadEnumStrict<SqlTagModel>(o, "model");
+        var (type, invalidType) = ReadEnumStrict<DriverDataType>(o, "type");
+
+        var selectorObj = o.TryGetPropertyValue("rowSelector", out var sn) && sn is JsonObject so ? so : null;
+
+        return new SqlTagConfigModel
+        {
+            Model = model ?? SqlTagModel.KeyValue,
+            Table = TagConfigJson.GetString(o, "table"),
+            KeyColumn = TagConfigJson.GetString(o, "keyColumn"),
+            KeyValue = TagConfigJson.GetString(o, "keyValue"),
+            ValueColumn = TagConfigJson.GetString(o, "valueColumn"),
+            TimestampColumn = TagConfigJson.GetString(o, "timestampColumn"),
+            ColumnName = TagConfigJson.GetString(o, "columnName"),
+            RowSelector = SqlRowSelectorModel.FromJson(selectorObj),
+            Type = type,
+            _bag = o,
+            _invalidModelRaw = invalidModel,
+            _invalidTypeRaw = invalidType,
+        };
+    }
+
+    /// <summary>Serialises this model back to a TagConfig JSON string, writing the exposed fields (enums as
+    /// their name strings) over the preserved key bag. The nested <c>rowSelector</c> object is rebuilt from
+    /// <see cref="RowSelector"/> (preserving its own unknown keys) and omitted entirely when empty.</summary>
+    /// <returns>The serialised TagConfig JSON string.</returns>
+    public string ToJson()
+    {
+        TagConfigJson.Set(_bag, "model", Model);
+        TagConfigJson.Set(_bag, "table", Table);
+        TagConfigJson.Set(_bag, "keyColumn", KeyColumn);
+        TagConfigJson.Set(_bag, "keyValue", KeyValue);
+        TagConfigJson.Set(_bag, "valueColumn", ValueColumn);
+        TagConfigJson.Set(_bag, "timestampColumn", TimestampColumn);
+        TagConfigJson.Set(_bag, "columnName", ColumnName);
+        TagConfigJson.Set(_bag, "type", Type);
+
+        var selector = RowSelector.ToJsonObject();
+        if (selector is null) { _bag.Remove("rowSelector"); }
+        else { _bag["rowSelector"] = selector; }
+
+        return TagConfigJson.Serialize(_bag);
+    }
+
+    /// <summary>Validates the model against the exact accept/reject boundary of
+    /// <see cref="SqlEquipmentTagParser.TryParse"/>. Returns an error message, or <c>null</c> when valid.</summary>
+    /// <returns>An error message describing the validation failure, or <c>null</c> when the model is valid.</returns>
+    public string? Validate()
+    {
+        // Strict enums (mirrors the parser's TryReadEnumStrict): a present-but-invalid string rejects the tag.
+        if (_invalidModelRaw is not null) { return $"model: '{_invalidModelRaw}' is not a valid Sql tag model."; }
+        if (_invalidTypeRaw is not null) { return $"type: '{_invalidTypeRaw}' is not a valid data type."; }
+
+        // Query is design §5.4 / P3 — the parser rejects it; the editor must too.
+        if (Model == SqlTagModel.Query) { return "model 'Query' is deferred (P3) and not supported."; }
+
+        if (string.IsNullOrWhiteSpace(Table)) { return "table is required."; }
+
+        switch (Model)
+        {
+            case SqlTagModel.KeyValue:
+                if (string.IsNullOrWhiteSpace(KeyColumn)) { return "keyColumn is required for a KeyValue tag."; }
+                if (string.IsNullOrWhiteSpace(ValueColumn)) { return "valueColumn is required for a KeyValue tag."; }
+                if (KeyValue is null) { return "keyValue is required for a KeyValue tag."; }
+                return null;
+
+            case SqlTagModel.WideRow:
+                if (string.IsNullOrWhiteSpace(ColumnName)) { return "columnName is required for a WideRow tag."; }
+                // A where-pair needs BOTH whereColumn and whereValue (whereValue may be an empty string, but
+                // must be present) — mirrors the parser's `!blank(whereColumn) && whereValue is not null`.
+                var hasWherePair = !string.IsNullOrWhiteSpace(RowSelector.WhereColumn) && RowSelector.WhereValue is not null;
+                if (!hasWherePair && string.IsNullOrWhiteSpace(RowSelector.TopByTimestamp))
+                {
+                    return "a WideRow tag needs a row selector: a whereColumn/whereValue pair, or topByTimestamp.";
+                }
+                return null;
+
+            default:
+                return "model is not a supported Sql tag model.";
+        }
+    }
+
+    // Reads an enum-valued string field the way the parser's TryReadEnumStrict does: absent OR present-but-
+    // non-string ⇒ (null, null) — nothing to validate; a present string that parses ⇒ (value, null); a
+    // present string that does NOT parse ⇒ (null, offendingString) so Validate can reject it.
+    private static (TEnum? value, string? invalidRaw) ReadEnumStrict<TEnum>(JsonObject o, string name)
+        where TEnum : struct, Enum
+    {
+        if (!o.TryGetPropertyValue(name, out var n) || n is not JsonValue v || !v.TryGetValue<string>(out var s))
+        {
+            return (null, null);
+        }
+        return Enum.TryParse<TEnum>(s, ignoreCase: true, out var parsed) ? (parsed, null) : (null, s);
+    }
+}
+
+/// <summary>
+/// Typed working model for a <see cref="SqlTagModel.WideRow"/> tag's nested <c>rowSelector</c> object.
+/// Holds a where-pair (<see cref="WhereColumn"/>/<see cref="WhereValue"/>) or a newest-by-timestamp
+/// selector (<see cref="TopByTimestamp"/>). Preserves unknown keys inside the selector across load→save.
+/// </summary>
+public sealed class SqlRowSelectorModel
+{
+    /// <summary>The column that picks the row (matched against <see cref="WhereValue"/>).</summary>
+    public string? WhereColumn { get; set; }
+
+    /// <summary>The value <see cref="WhereColumn"/> is matched against (bound as a parameter at read time).
+    /// Captured as text whether the blob authored it as a JSON string or a JSON number/boolean, mirroring
+    /// the parser's scalar read.</summary>
+    public string? WhereValue { get; set; }
+
+    /// <summary>Newest-row selector: the timestamp column to order by (used when no where-pair is authored).</summary>
+    public string? TopByTimestamp { get; set; }
+
+    private JsonObject _bag = new();
+
+    /// <summary>Loads a selector model from the nested <c>rowSelector</c> JSON object (or a fresh empty model
+    /// when the object is absent), retaining any unknown keys.</summary>
+    /// <param name="o">The nested <c>rowSelector</c> object, or <c>null</c> when absent.</param>
+    /// <returns>The populated <see cref="SqlRowSelectorModel"/>.</returns>
+    public static SqlRowSelectorModel FromJson(JsonObject? o)
+    {
+        // Deep-clone so the selector owns an independent node tree (safe to re-attach on ToJson).
+        var bag = o?.DeepClone().AsObject() ?? new JsonObject();
+        return new SqlRowSelectorModel
+        {
+            WhereColumn = TagConfigJson.GetString(bag, "whereColumn"),
+            WhereValue = ReadScalarText(bag, "whereValue"),
+            TopByTimestamp = TagConfigJson.GetString(bag, "topByTimestamp"),
+            _bag = bag,
+        };
+    }
+
+    /// <summary>Rebuilds the nested <c>rowSelector</c> JSON object from the exposed fields over the preserved
+    /// key bag, or returns <c>null</c> when the selector carries nothing (so the parent omits the key).</summary>
+    /// <returns>The <c>rowSelector</c> <see cref="JsonObject"/>, or <c>null</c> when empty.</returns>
+    public JsonObject? ToJsonObject()
+    {
+        var o = _bag.DeepClone().AsObject();
+        TagConfigJson.Set(o, "whereColumn", WhereColumn);
+        TagConfigJson.Set(o, "whereValue", WhereValue);
+        TagConfigJson.Set(o, "topByTimestamp", TopByTimestamp);
+        return o.Count == 0 ? null : o;
+    }
+
+    // Reads a scalar as its textual form: a JSON string yields its contents, a number/boolean yields its raw
+    // token — so an authored whereValue of either shape is captured verbatim (mirrors the parser's ReadScalar).
+    private static string? ReadScalarText(JsonObject o, string name)
+    {
+        if (!o.TryGetPropertyValue(name, out var n) || n is not JsonValue v) { return null; }
+        return v.TryGetValue<string>(out var s) ? s : v.ToJsonString();
+    }
+}

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Uns/TagEditors/TagConfigEditorMap.cs

@@ -1,4 +1,5 @@
 using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.Sql;
 
 namespace ZB.MOM.WW.OtOpcUa.AdminUI.Uns.TagEditors;
 
@@ -21,6 +22,10 @@ public static class TagConfigEditorMap
             [DriverTypeNames.FOCAS]       = typeof(Components.Shared.Uns.TagEditors.FocasTagConfigEditor),
             [DriverTypeNames.OpcUaClient] = typeof(Components.Shared.Uns.TagEditors.OpcUaClientTagConfigEditor),
             [DriverTypeNames.Calculation] = typeof(Components.Shared.Uns.TagEditors.CalculationTagConfigEditor),
+            // Keyed off SqlDriver.DriverTypeName (= "Sql") rather than DriverTypeNames.Sql: that shared
+            // constant is deliberately absent until Task 11 wires the factory (DriverTypeNamesGuardTests
+            // asserts bidirectional parity). Task 11 repoints all Sql keys onto DriverTypeNames.Sql.
+            [SqlDriver.DriverTypeName]     = typeof(Components.Shared.Uns.TagEditors.SqlTagConfigEditor),
         };
 
     /// <summary>Returns the editor component type for a driver type, or null if none is registered.</summary>

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Uns/TagEditors/TagConfigValidator.cs

@@ -1,4 +1,5 @@
 using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.Sql;
 
 namespace ZB.MOM.WW.OtOpcUa.AdminUI.Uns.TagEditors;
 
@@ -23,6 +24,8 @@ public static class TagConfigValidator
             [DriverTypeNames.FOCAS]       = j => FocasTagConfigModel.FromJson(j).Validate(),
             [DriverTypeNames.OpcUaClient] = j => OpcUaClientTagConfigModel.FromJson(j).Validate(),
             [DriverTypeNames.Calculation] = j => CalculationTagConfigModel.FromJson(j).Validate(),
+            // Keyed off SqlDriver.DriverTypeName (= "Sql") — see the note in TagConfigEditorMap.
+            [SqlDriver.DriverTypeName]     = j => SqlTagConfigModel.FromJson(j).Validate(),
         };
 
     /// <summary>

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/ZB.MOM.WW.OtOpcUa.AdminUI.csproj

@@ -39,6 +39,10 @@
         <ProjectReference Include="..\..\Drivers\ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Contracts\ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Contracts.csproj"/>
         <ProjectReference Include="..\..\Drivers\ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser\ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser.csproj"/>
         <ProjectReference Include="..\..\Drivers\ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Browser\ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Browser.csproj"/>
+        <!-- Sql schema-browse (IDriverBrowser, SqlBrowseNodeId codec, SqlEquipmentTagParser). Pulls
+             Driver.Sql + .Contracts + Microsoft.Data.SqlClient transitively — reviewed/accepted, see
+             the Browser project's own csproj comment (AdminUI already carries SqlClient for ConfigDb). -->
+        <ProjectReference Include="..\..\Drivers\ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser\ZB.MOM.WW.OtOpcUa.Driver.Sql.Browser.csproj"/>
     </ItemGroup>
 
 </Project>

src/Server/ZB.MOM.WW.OtOpcUa.Host/Drivers/DriverFactoryBootstrap.cs

@@ -18,6 +18,7 @@ using FocasProbe     = Driver.FOCAS.FocasDriverProbe;
 using OpcUaProbe     = Driver.OpcUaClient.OpcUaClientDriverProbe;
 using GalaxyProbe    = Driver.Galaxy.GalaxyDriverProbe;
 using CalculationProbe = Driver.Calculation.CalculationDriverProbe;
+using SqlProbe       = Driver.Sql.SqlDriverProbe;
 
 /// <summary>
 ///     Wires every cross-platform driver assembly's <c>Register(registry, loggerFactory)</c>
@@ -122,6 +123,7 @@ public static class DriverFactoryBootstrap
         services.TryAddEnumerable(ServiceDescriptor.Singleton<IDriverProbe, OpcUaProbe>());
         services.TryAddEnumerable(ServiceDescriptor.Singleton<IDriverProbe, GalaxyProbe>());
         services.TryAddEnumerable(ServiceDescriptor.Singleton<IDriverProbe, CalculationProbe>());
+        services.TryAddEnumerable(ServiceDescriptor.Singleton<IDriverProbe, SqlProbe>());
 
         return services;
     }
@@ -146,6 +148,7 @@ public static class DriverFactoryBootstrap
         Driver.Modbus.ModbusDriverFactoryExtensions.Register(registry, loggerFactory);
         Driver.OpcUaClient.OpcUaClientDriverFactoryExtensions.Register(registry, loggerFactory, secretResolver);
         Driver.S7.S7DriverFactoryExtensions.Register(registry);
+        Driver.Sql.SqlDriverFactoryExtensions.Register(registry, loggerFactory);
         Driver.TwinCAT.TwinCATDriverFactoryExtensions.Register(registry);
     }
 }

src/Server/ZB.MOM.WW.OtOpcUa.Host/ZB.MOM.WW.OtOpcUa.Host.csproj

@@ -76,6 +76,7 @@
         <ProjectReference Include="..\..\Drivers\ZB.MOM.WW.OtOpcUa.Driver.Modbus\ZB.MOM.WW.OtOpcUa.Driver.Modbus.csproj"/>
         <ProjectReference Include="..\..\Drivers\ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient\ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.csproj"/>
         <ProjectReference Include="..\..\Drivers\ZB.MOM.WW.OtOpcUa.Driver.S7\ZB.MOM.WW.OtOpcUa.Driver.S7.csproj"/>
+        <ProjectReference Include="..\..\Drivers\ZB.MOM.WW.OtOpcUa.Driver.Sql\ZB.MOM.WW.OtOpcUa.Driver.Sql.csproj"/>
         <ProjectReference Include="..\..\Drivers\ZB.MOM.WW.OtOpcUa.Driver.TwinCAT\ZB.MOM.WW.OtOpcUa.Driver.TwinCAT.csproj"/>
     </ItemGroup>
 

src/Server/ZB.MOM.WW.OtOpcUa.Runtime/Drivers/DriverInstanceActor.cs

@@ -170,6 +170,7 @@ public sealed class DriverInstanceActor : ReceiveActor, IWithTimers
     /// <summary>Interval between bounded post-connect re-discovery passes. Production default 2s; tests
     /// inject a tiny value so the loop runs without real-time waits.</summary>
     private readonly TimeSpan _rediscoverInterval;
+    private readonly TimeSpan _healthPollInterval;
 
     /// <summary>Cap on the number of post-connect re-discovery passes — a backstop so a never-stabilising
     /// (or perpetually-empty) discovered set cannot spin the loop forever. Production default 15.</summary>
@@ -239,6 +240,9 @@ public sealed class DriverInstanceActor : ReceiveActor, IWithTimers
     /// <param name="rediscoverDiscoverTimeout">Optional per-pass timeout for <see cref="ITagDiscovery.DiscoverAsync"/>; defaults to 30 seconds.</param>
     /// <param name="invoker">Optional Phase 6.1 resilience invoker wrapping this driver's capability
     /// calls; defaults to <see cref="NullDriverCapabilityInvoker"/> (pass-through) when not supplied.</param>
+    /// <param name="healthPollInterval">Optional period of the health-poll heartbeat, which also drives the
+    /// subscription reconcile (<see cref="ReconcileSubscription"/>); defaults to
+    /// <see cref="HealthPollInterval"/>. Exists so a test can drive the reconcile without waiting 30 s.</param>
     /// <returns>A <see cref="Akka.Actor.Props"/> instance configured to create the wrapped <see cref="DriverInstanceActor"/>.</returns>
     public static Props Props(
         IDriver driver,
@@ -249,7 +253,8 @@ public sealed class DriverInstanceActor : ReceiveActor, IWithTimers
         TimeSpan? rediscoverInterval = null,
         int rediscoverMaxAttempts = DefaultRediscoverMaxAttempts,
         TimeSpan? rediscoverDiscoverTimeout = null,
-        IDriverCapabilityInvoker? invoker = null) =>
+        IDriverCapabilityInvoker? invoker = null,
+        TimeSpan? healthPollInterval = null) =>
         Akka.Actor.Props.Create(() => new DriverInstanceActor(
             driver,
             reconnectInterval ?? DefaultReconnectInterval,
@@ -259,7 +264,8 @@ public sealed class DriverInstanceActor : ReceiveActor, IWithTimers
             rediscoverInterval,
             rediscoverMaxAttempts,
             rediscoverDiscoverTimeout,
-            invoker));
+            invoker,
+            healthPollInterval));
 
     /// <summary>
     /// Returns true when the driver should boot in DEV-STUB mode based on host platform and
@@ -293,6 +299,8 @@ public sealed class DriverInstanceActor : ReceiveActor, IWithTimers
     /// <param name="rediscoverDiscoverTimeout">Per-pass timeout for <see cref="ITagDiscovery.DiscoverAsync"/>; defaults to 30 seconds.</param>
     /// <param name="invoker">Phase 6.1 resilience invoker wrapping this driver's capability calls;
     /// defaults to <see cref="NullDriverCapabilityInvoker"/> (pass-through) when null.</param>
+    /// <param name="healthPollInterval">Period of the health-poll heartbeat, which also drives the
+    /// subscription reconcile; defaults to <see cref="HealthPollInterval"/> when null.</param>
     public DriverInstanceActor(
         IDriver driver,
         TimeSpan reconnectInterval,
@@ -302,7 +310,8 @@ public sealed class DriverInstanceActor : ReceiveActor, IWithTimers
         TimeSpan? rediscoverInterval = null,
         int rediscoverMaxAttempts = DefaultRediscoverMaxAttempts,
         TimeSpan? rediscoverDiscoverTimeout = null,
-        IDriverCapabilityInvoker? invoker = null)
+        IDriverCapabilityInvoker? invoker = null,
+        TimeSpan? healthPollInterval = null)
     {
         _driver = driver;
         _invoker = invoker ?? NullDriverCapabilityInvoker.Instance;
@@ -313,6 +322,7 @@ public sealed class DriverInstanceActor : ReceiveActor, IWithTimers
         _rediscoverInterval = rediscoverInterval ?? DefaultRediscoverInterval;
         _rediscoverMaxAttempts = rediscoverMaxAttempts;
         _rediscoverDiscoverTimeout = rediscoverDiscoverTimeout ?? DefaultRediscoverDiscoverTimeout;
+        _healthPollInterval = healthPollInterval ?? HealthPollInterval;
         OtOpcUaTelemetry.DriverInstanceLifecycle.Add(1,
             new KeyValuePair<string, object?>("event", startStubbed ? "spawn_stub" : "spawn"),
             new KeyValuePair<string, object?>("driver_type", driver.DriverType));
@@ -335,7 +345,7 @@ public sealed class DriverInstanceActor : ReceiveActor, IWithTimers
         // actor starts, before any state transition fires. Also start the periodic heartbeat so
         // long-lived Healthy drivers keep their snapshot fresh for newly-joined SignalR clients.
         PublishHealthSnapshot();
-        Timers.StartPeriodicTimer("health-poll", HealthPollTick.Instance, HealthPollInterval);
+        Timers.StartPeriodicTimer("health-poll", HealthPollTick.Instance, _healthPollInterval);
     }
 
     private void Stubbed()
@@ -489,7 +499,58 @@ public sealed class DriverInstanceActor : ReceiveActor, IWithTimers
         // to Self (HandleSubscribeAsync already logged the underlying cause). Swallow it so it doesn't dead-letter.
         Receive<SubscriptionFailed>(msg =>
             _log.Debug("DriverInstance {Id}: resubscribe reported failure: {Reason}", _driverInstanceId, msg.Reason));
-        Receive<HealthPollTick>(_ => PublishHealthSnapshot());
+        Receive<HealthPollTick>(_ =>
+        {
+            PublishHealthSnapshot();
+            ReconcileSubscription();
+        });
+    }
+
+    /// <summary>
+    ///     Periodic desired-vs-actual subscription reconcile (#488), riding the existing <c>health-poll</c>
+    ///     tick. While Connected, a driver that has a desired subscription set but no live handle is
+    ///     re-subscribed.
+    /// </summary>
+    /// <remarks>
+    ///     <para>
+    ///         The desired set is otherwise only (re)applied on a <b>Connected transition</b>
+    ///         (<see cref="ResubscribeDesired"/>) or on a deploy's <see cref="SetDesiredSubscriptions"/>.
+    ///         Nothing re-asserted it for a subscription that was lost while the driver <i>stayed</i>
+    ///         Connected — a failed subscribe whose retry never came, or a handle dropped down an error
+    ///         path. That is the hole this closes.
+    ///     </para>
+    ///     <para>
+    ///         <b>This is a state-machine consistency check, not a probe.</b> It can only see that this
+    ///         actor holds no handle; it cannot detect a handle that is present but dead server-side,
+    ///         because <c>ISubscriptionHandle</c> is opaque (a <c>DiagnosticId</c> string and nothing
+    ///         else). Detecting that needs a liveness member on <c>ISubscribable</c> implemented across
+    ///         all eight drivers, each with different subscription mechanics — deliberately deferred
+    ///         until a real occurrence shows the handle outliving the subscription.
+    ///     </para>
+    ///     <para>
+    ///         Gated on <see cref="ISubscribable"/>: a driver that cannot subscribe at all may still have
+    ///         been handed a desired set, and re-telling <c>Subscribe</c> to it every tick would fail
+    ///         every tick, forever.
+    ///     </para>
+    ///     <para>
+    ///         A redundant <c>Subscribe</c> is possible but harmless: a tick sitting in the mailbox ahead
+    ///         of an already-queued <c>Subscribe</c> observes the same "no handle" state and tells a
+    ///         second one. <see cref="HandleSubscribeAsync"/> is a <c>ReceiveAsync</c> (so no tick can be
+    ///         processed mid-subscribe) and drops any prior subscription before establishing the new one,
+    ///         so the duplicate costs one extra round-trip and converges. Suppressing it would need a
+    ///         pending-subscribe flag threaded through every self-tell site — more state than the race
+    ///         is worth.
+    ///     </para>
+    /// </remarks>
+    private void ReconcileSubscription()
+    {
+        if (_driver is not ISubscribable) return;
+        if (_desiredRefs.Count == 0 || _subscriptionHandle is not null) return;
+
+        _log.Info(
+            "DriverInstance {Id}: connected with {Count} desired subscription ref(s) but no live subscription handle — re-subscribing (periodic reconcile)",
+            _driverInstanceId, _desiredRefs.Count);
+        Self.Tell(new Subscribe(_desiredRefs, _desiredInterval));
     }
 
     private void Reconnecting()

src/Server/ZB.MOM.WW.OtOpcUa.Runtime/ScriptedAlarms/ScriptedAlarmHostActor.cs

@@ -288,8 +288,101 @@ public sealed class ScriptedAlarmHostActor : ReceiveActor
         // so a re-Apply with a fresh union simply supersedes the old one — no explicit unregister needed.
         _mux?.Tell(new DependencyMuxActor.RegisterInterest(msg.DepRefs, Self));
         _log.Debug("ScriptedAlarmHost: loaded; registered mux interest for {Count} dep refs", msg.DepRefs.Count);
+
+        ReassertConditionNodes();
     }
 
+    /// <summary>
+    ///     #487 — re-project every loaded alarm that is NOT in the Part 9 "no-event" position back onto
+    ///     its condition node, right after a (re)load.
+    ///
+    ///     <para>
+    ///         <b>The bug this closes.</b> A deploy that triggers a FULL address-space rebuild clears
+    ///         <c>_alarmConditions</c> and re-materialises every condition node fresh — inactive, acked,
+    ///         confirmed, unshelved. The engine, meanwhile, restores each alarm's persisted state and
+    ///         re-derives Active from the predicate, so a still-active alarm ends the reload
+    ///         <i>correctly Active in the engine</i> but produces <see cref="EmissionKind.None"/> (there
+    ///         is no transition to report) — and <see cref="OnEngineEmission"/> drops None. Nothing then
+    ///         writes the node, so an active alarm with static dependencies reads NORMAL to every OPC UA
+    ///         client until its next real transition, which may never come. Same shape as the VirtualTag
+    ///         redeploy-reset the <c>ReassertValue</c> fix closed.
+    ///     </para>
+    ///
+    ///     <para>
+    ///         <b>Node-only, by construction.</b> This sends <see cref="OpcUaPublishActor.AlarmStateUpdate"/>
+    ///         and nothing else — it never publishes to the <c>alerts</c> topic and never touches the
+    ///         telemetry hub. That is the whole reason it reads <see cref="ScriptedAlarmEngine.GetProjections"/>
+    ///         (a plain read returning <see cref="ScriptedAlarmProjection"/>) rather than re-emitting: an
+    ///         <c>alerts</c> row per alarm per deploy would append a duplicate historian / AVEVA record
+    ///         every time anyone deploys — the alarm analogue of the VirtualTag M1 historian issue.
+    ///     </para>
+    ///
+    ///     <para>
+    ///         <b>Ordering.</b> <c>DriverHostActor</c> Tells <c>RebuildAddressSpace</c> to the publish
+    ///         actor BEFORE it Tells <see cref="ApplyScriptedAlarms"/> here, and this runs later still —
+    ///         after an <c>await</c>ed <see cref="ScriptedAlarmEngine.LoadAsync"/> pipes back. Both Tells
+    ///         enqueue synchronously into the publish actor's local mailbox, so the re-materialise is
+    ///         already queued ahead of these writes: the node exists by the time they are handled.
+    ///     </para>
+    ///
+    ///     <para>
+    ///         <b>Why only non-normal alarms.</b> An alarm sitting in the no-event position already
+    ///         matches what the materialise just built, so writing it would be a pure no-op on state —
+    ///         but it would still overwrite the node's Message (the materialise seeds it with the alarm's
+    ///         display name; a projection carries the resolved template). Skipping them keeps a
+    ///         never-fired alarm byte-identical to a deploy without this pass, and keeps the write count
+    ///         at zero on the overwhelmingly common all-normal deploy.
+    ///     </para>
+    ///
+    ///     <para>
+    ///         <b>Duplicate events.</b> None. <c>WriteAlarmCondition</c>'s delta-gate compares the
+    ///         incoming snapshot against the node's CURRENT state, so a re-assert onto a freshly
+    ///         materialised (normal) node is a genuine delta and fires one Part 9 event — correct, since
+    ///         the rebuild reset what clients see — while a re-assert onto a surgically-preserved node
+    ///         that already holds the same state is suppressed. This write is ungated by redundancy role,
+    ///         like every other node write here: the Secondary keeps its address space warm for failover.
+    ///     </para>
+    /// </summary>
+    private void ReassertConditionNodes()
+    {
+        var reasserted = 0;
+        foreach (var projection in _engine.GetProjections())
+        {
+            if (IsInNoEventPosition(projection.Condition))
+            {
+                continue;
+            }
+
+            _publishActor.Tell(new OpcUaPublishActor.AlarmStateUpdate(
+                AlarmNodeId: projection.AlarmId,
+                State: ToSnapshot(projection),
+                // The instant the state we are re-asserting actually came about — NOT the deploy time.
+                // A client reading Time/ReceiveTime after a rebuild should still see when the alarm went
+                // active, not when the address space happened to be rebuilt.
+                TimestampUtc: projection.Condition.LastTransitionUtc,
+                Realm: AddressSpaceRealm.Uns));
+            reasserted++;
+        }
+
+        if (reasserted > 0)
+        {
+            _log.Info("ScriptedAlarmHost: re-asserted {Count} non-normal condition node(s) after (re)load", reasserted);
+        }
+    }
+
+    /// <summary>Whether <paramref name="condition"/> sits in the Part 9 "no-event" position — exactly the
+    /// state <see cref="AlarmConditionState.Fresh"/> produces and a freshly materialised condition node
+    /// already carries. Anything else (active, unacknowledged, unconfirmed, disabled, or shelved) is state
+    /// a rebuild would silently lose, so it is what <see cref="ReassertConditionNodes"/> re-projects.</summary>
+    /// <param name="condition">The engine's current condition state.</param>
+    /// <returns><c>true</c> when the condition carries nothing a rebuild could lose.</returns>
+    private static bool IsInNoEventPosition(AlarmConditionState condition)
+        => condition.Enabled == AlarmEnabledState.Enabled
+           && condition.Active == AlarmActiveState.Inactive
+           && condition.Acked == AlarmAckedState.Acknowledged
+           && condition.Confirmed == AlarmConfirmedState.Confirmed
+           && condition.Shelving.Kind == ShelvingKind.Unshelved;
+
     private void OnDependencyChanged(VirtualTagActor.DependencyValueChanged msg)
     {
         // Feed the live value into the upstream the engine subscribes from. #478 — carry the source
@@ -594,18 +687,38 @@ public sealed class ScriptedAlarmHostActor : ReceiveActor
     /// Severity is the OPC UA 1..1000 value <see cref="SeverityToInt"/> derives from the coarse engine
     /// bucket, cast to the <c>ushort</c> the SDK <c>SetSeverity</c> expects. Shelving's 3-way Core kind
     /// maps 1:1 onto the Commons <see cref="AlarmShelvingKind"/>.</summary>
-    private static AlarmConditionSnapshot ToSnapshot(ScriptedAlarmEvent e) => new(
-        Active: e.Condition.Active == AlarmActiveState.Active,
-        Acknowledged: e.Condition.Acked == AlarmAckedState.Acknowledged,
-        Confirmed: e.Condition.Confirmed == AlarmConfirmedState.Confirmed,
-        Enabled: e.Condition.Enabled == AlarmEnabledState.Enabled,
-        Shelving: MapShelving(e.Condition.Shelving.Kind),
-        Severity: (ushort)SeverityToInt(e.Severity),
-        Message: e.Message,
+    private static AlarmConditionSnapshot ToSnapshot(ScriptedAlarmEvent e)
+        => ToSnapshot(e.Condition, e.Severity, e.Message, e.WorstInputStatusCode);
+
+    /// <summary>#487 — the same projection for a <see cref="ScriptedAlarmProjection"/>: a state READ used
+    /// to restore a condition node after a rebuild, never an emission. Shares
+    /// <see cref="ToSnapshot(AlarmConditionState, AlarmSeverity, string, uint)"/> with the transition path
+    /// so a re-asserted node is byte-identical to what the alarm's own transition would have written.</summary>
+    /// <param name="p">The engine projection to map.</param>
+    /// <returns>The Commons snapshot the SDK sink projects onto the condition node.</returns>
+    private static AlarmConditionSnapshot ToSnapshot(ScriptedAlarmProjection p)
+        => ToSnapshot(p.Condition, p.Severity, p.Message, p.WorstInputStatusCode);
+
+    /// <summary>The single Core → Commons condition projection, shared by the emission and re-assert
+    /// paths.</summary>
+    /// <param name="condition">The Part 9 condition state.</param>
+    /// <param name="severity">The engine's coarse severity bucket.</param>
+    /// <param name="message">The resolved condition message.</param>
+    /// <param name="worstInputStatusCode">The worst OPC UA StatusCode across the script's input tags.</param>
+    /// <returns>The Commons snapshot the SDK sink projects onto the condition node.</returns>
+    private static AlarmConditionSnapshot ToSnapshot(
+        AlarmConditionState condition, AlarmSeverity severity, string message, uint worstInputStatusCode) => new(
+        Active: condition.Active == AlarmActiveState.Active,
+        Acknowledged: condition.Acked == AlarmAckedState.Acknowledged,
+        Confirmed: condition.Confirmed == AlarmConfirmedState.Confirmed,
+        Enabled: condition.Enabled == AlarmEnabledState.Enabled,
+        Shelving: MapShelving(condition.Shelving.Kind),
+        Severity: (ushort)SeverityToInt(severity),
+        Message: message,
         // #478 — the condition's Quality is the worst quality across the script's input tags at evaluation
         // time (carried on the event by the engine). A transition fired while an input is Uncertain projects
         // Uncertain here so the full-snapshot write doesn't clobber quality back to Good.
-        Quality: QualityFromStatus(e.WorstInputStatusCode));
+        Quality: QualityFromStatus(worstInputStatusCode));
 
     /// <summary>Maps the Core <see cref="ShelvingKind"/> onto the Commons <see cref="AlarmShelvingKind"/>
     /// mirror (the Commons assembly can't see the Core enum).</summary>

tests/Core/ZB.MOM.WW.OtOpcUa.Configuration.Tests/DraftValidatorSqlSecretTests.cs

@@ -0,0 +1,173 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Configuration.Entities;
+using ZB.MOM.WW.OtOpcUa.Configuration.Validation;
+
+namespace ZB.MOM.WW.OtOpcUa.Configuration.Tests;
+
+/// <summary>
+///     The Gitea #498 deploy gate: a <c>Sql</c> driver's persisted config may never carry a literal
+///     <c>connectionString</c>. The typed DTO already drops the key on <em>read</em>; these pin the
+///     <em>write</em> side, which is where a credential would actually land in the config database.
+/// </summary>
+[Trait("Category", "Unit")]
+public sealed class DraftValidatorSqlSecretTests
+{
+    private const string Code = "SqlConnectionStringPersisted";
+
+    /// <summary>A realistic leak: the literal an operator would paste into a raw-JSON config textarea.</summary>
+    private const string LeakedConfig =
+        """{"provider":"SqlServer","connectionString":"Server=sql,1433;Database=Mes;User ID=sa;Password=hunter2"}""";
+
+    private static DriverInstance SqlDriver(string config) => new()
+    {
+        DriverInstanceId = "di-sql", ClusterId = "c", Name = "line3-sql",
+        DriverType = "Sql", DriverConfig = config,
+    };
+
+    private static Device Device(string driverInstanceId, string config) => new()
+    {
+        DeviceId = "dev-1", DriverInstanceId = driverInstanceId, Name = "Device1", DeviceConfig = config,
+    };
+
+    private static DraftSnapshot Draft(DriverInstance driver, Device? device = null) => new()
+    {
+        GenerationId = 1,
+        ClusterId = "c",
+        DriverInstances = [driver],
+        Devices = device is null ? [] : [device],
+    };
+
+    [Fact]
+    public void Literal_connectionString_in_DriverConfig_is_a_deploy_error()
+    {
+        var errors = DraftValidator.Validate(Draft(SqlDriver(LeakedConfig)));
+
+        errors.ShouldContain(e => e.Code == Code && e.Context == "di-sql");
+    }
+
+    /// <summary>
+    ///     The error text reaches the AdminUI, the deploy log and the audit trail, so it must describe the
+    ///     problem without repeating the credential it is refusing to store.
+    /// </summary>
+    [Fact]
+    public void Error_message_does_not_echo_the_credential()
+    {
+        var error = DraftValidator.Validate(Draft(SqlDriver(LeakedConfig))).First(e => e.Code == Code);
+
+        error.Message.ShouldNotContain("hunter2");
+        error.Message.ShouldNotContain("Server=sql,1433");
+        error.Message.ShouldContain("connectionStringRef");
+    }
+
+    /// <summary>
+    ///     System.Text.Json binds <c>ConnectionString</c> to a <c>connectionString</c> property by default, so
+    ///     a case variant is the same key — matching it ordinally would leave the obvious bypass wide open.
+    /// </summary>
+    [Theory]
+    [InlineData("ConnectionString")]
+    [InlineData("CONNECTIONSTRING")]
+    [InlineData("connectionstring")]
+    public void Key_match_is_case_insensitive(string key)
+    {
+        var config = $$"""{"provider":"SqlServer","{{key}}":"Server=s;Password=p"}""";
+
+        DraftValidator.Validate(Draft(SqlDriver(config)))
+            .ShouldContain(e => e.Code == Code && e.Context == "di-sql");
+    }
+
+    /// <summary>
+    ///     DeviceConfig is merged onto DriverConfig before the driver's DTO sees it, so a credential pasted
+    ///     there is the identical leak and must fail the same way.
+    /// </summary>
+    [Fact]
+    public void Literal_connectionString_in_a_Sql_devices_DeviceConfig_is_a_deploy_error()
+    {
+        var draft = Draft(SqlDriver("""{"connectionStringRef":"DevSql"}"""), Device("di-sql", LeakedConfig));
+
+        DraftValidator.Validate(draft).ShouldContain(e => e.Code == Code && e.Context == "dev-1");
+    }
+
+    [Fact]
+    public void A_properly_authored_connectionStringRef_passes()
+    {
+        var draft = Draft(
+            SqlDriver("""{"provider":"SqlServer","connectionStringRef":"DevSql","nullIsBad":true}"""),
+            Device("di-sql", """{"pollIntervalMs":1000}"""));
+
+        DraftValidator.Validate(draft).ShouldNotContain(e => e.Code == Code);
+    }
+
+    /// <summary>
+    ///     The rule is scoped to the Sql driver type. A non-Sql driver is not in its remit — widening the gate
+    ///     to every driver is a separate decision, and silently failing an unrelated driver's deploy here would
+    ///     be a regression, not defence in depth.
+    /// </summary>
+    [Fact]
+    public void A_non_Sql_driver_carrying_the_key_is_not_flagged_by_this_rule()
+    {
+        var modbus = new DriverInstance
+        {
+            DriverInstanceId = "di-mb", ClusterId = "c", Name = "mb",
+            DriverType = "Modbus", DriverConfig = LeakedConfig,
+        };
+
+        DraftValidator.Validate(Draft(modbus)).ShouldNotContain(e => e.Code == Code);
+    }
+
+    /// <summary>
+    ///     A device under a <em>different</em> driver must not be attributed to the Sql instance — the device
+    ///     scan keys off DriverInstanceId, and getting that wrong would flag innocent devices.
+    /// </summary>
+    [Fact]
+    public void A_device_under_a_non_Sql_driver_is_not_flagged()
+    {
+        var draft = new DraftSnapshot
+        {
+            GenerationId = 1,
+            ClusterId = "c",
+            DriverInstances =
+            [
+                SqlDriver("""{"connectionStringRef":"DevSql"}"""),
+                new DriverInstance
+                {
+                    DriverInstanceId = "di-mb", ClusterId = "c", Name = "mb",
+                    DriverType = "Modbus", DriverConfig = "{}",
+                },
+            ],
+            Devices = [Device("di-mb", LeakedConfig)],
+        };
+
+        DraftValidator.Validate(draft).ShouldNotContain(e => e.Code == Code);
+    }
+
+    /// <summary>
+    ///     Malformed or non-object config must not throw out of the validator: shaping the JSON is another
+    ///     rule's job, and a parse failure here would take down every other check in the same pass.
+    /// </summary>
+    [Theory]
+    [InlineData("")]
+    [InlineData("   ")]
+    [InlineData("not json at all")]
+    [InlineData("[1,2,3]")]
+    [InlineData("\"connectionString\"")]
+    [InlineData("{\"provider\":\"SqlServer\"")]
+    public void Malformed_config_neither_throws_nor_flags(string config)
+    {
+        Should.NotThrow(() => DraftValidator.Validate(Draft(SqlDriver(config))))
+            .ShouldNotContain(e => e.Code == Code);
+    }
+
+    /// <summary>
+    ///     Only the top level is scanned. The DTO is flat, so a nested occurrence cannot bind to anything and
+    ///     is not the credential-shaped mistake this rule exists to catch; flagging it would be a false
+    ///     positive on, say, a tag blob that happens to describe a connection string.
+    /// </summary>
+    [Fact]
+    public void A_nested_connectionString_is_not_flagged()
+    {
+        var config = """{"connectionStringRef":"DevSql","notes":{"connectionString":"documented elsewhere"}}""";
+
+        DraftValidator.Validate(Draft(SqlDriver(config))).ShouldNotContain(e => e.Code == Code);
+    }
+}

tests/Core/ZB.MOM.WW.OtOpcUa.Configuration.Tests/SqlCredentialGuardTests.cs

@@ -0,0 +1,132 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Configuration.Validation;
+
+namespace ZB.MOM.WW.OtOpcUa.Configuration.Tests;
+
+/// <summary>
+///     <see cref="SqlCredentialGuard"/> — the shared "a Sql driver never persists a literal connection
+///     string" check behind both the #498 deploy gate and the #499 node-override save gate.
+/// </summary>
+/// <remarks>
+///     The node-override half is the one #499 is about: <c>ClusterNode.DriverConfigOverridesJson</c> is a
+///     map keyed by <c>DriverInstanceId</c> that is merged onto the cluster-level <c>DriverConfig</c>, and
+///     it is invisible to <c>DraftSnapshot</c> — so nothing gated it at all before.
+/// </remarks>
+[Trait("Category", "Unit")]
+public sealed class SqlCredentialGuardTests
+{
+    /// <summary>The literal an operator would paste into a raw-JSON textarea.</summary>
+    private const string Leaked =
+        """{"provider":"SqlServer","connectionString":"Server=sql,1433;Database=Mes;User ID=sa;Password=hunter2"}""";
+
+    private const string Clean = """{"provider":"SqlServer","connectionStringRef":"Sql:Line3"}""";
+
+    // ---- CarriesLiteralConnectionString --------------------------------------------------------
+
+    /// <summary>The key is caught at the top level of a config blob.</summary>
+    [Fact]
+    public void A_literal_connectionString_is_detected()
+        => SqlCredentialGuard.CarriesLiteralConnectionString(Leaked).ShouldBeTrue();
+
+    /// <summary>The supported indirect form is not a violation — otherwise the rule would block the fix
+    /// it tells operators to apply.</summary>
+    [Fact]
+    public void The_indirect_connectionStringRef_form_is_clean()
+        => SqlCredentialGuard.CarriesLiteralConnectionString(Clean).ShouldBeFalse();
+
+    /// <summary>System.Text.Json binds <c>ConnectionString</c> to a <c>connectionString</c> property by
+    /// default, so a case variant is the same key — not a bypass.</summary>
+    [Theory]
+    [InlineData("""{"ConnectionString":"Server=x;Password=p"}""")]
+    [InlineData("""{"CONNECTIONSTRING":"Server=x;Password=p"}""")]
+    [InlineData("""{"connectionstring":"Server=x;Password=p"}""")]
+    public void Case_variants_are_the_same_key(string json)
+        => SqlCredentialGuard.CarriesLiteralConnectionString(json).ShouldBeTrue();
+
+    /// <summary>Blank, malformed and non-object blobs simply have no keys. Shaping the config JSON is
+    /// another rule's job, and throwing here would turn a formatting mistake into a credential failure.
+    /// </summary>
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("   ")]
+    [InlineData("{ not json")]
+    [InlineData("[1,2,3]")]
+    [InlineData("\"a string\"")]
+    public void Blank_malformed_and_non_object_blobs_are_not_violations(string? json)
+        => SqlCredentialGuard.CarriesLiteralConnectionString(json).ShouldBeFalse();
+
+    /// <summary>Only the top level is scanned. The DTO is flat, so a nested occurrence cannot bind and is
+    /// not the credential-shaped mistake this rule exists to catch.</summary>
+    [Fact]
+    public void A_nested_occurrence_is_not_flagged()
+        => SqlCredentialGuard
+            .CarriesLiteralConnectionString("""{"nested":{"connectionString":"Server=x"}}""")
+            .ShouldBeFalse();
+
+    // ---- FindNodeOverrideViolations (#499) -----------------------------------------------------
+
+    /// <summary>The #499 leak: a credential pasted into a node's per-driver override map.</summary>
+    [Fact]
+    public void A_credential_in_a_node_override_for_a_Sql_driver_is_a_violation()
+    {
+        var overrides = $$"""{"di-sql": {{Leaked}} }""";
+
+        SqlCredentialGuard.FindNodeOverrideViolations(overrides, ["di-sql"])
+            .ShouldBe(["di-sql"]);
+    }
+
+    /// <summary>Every offending instance is reported, not just the first — an operator fixing one at a
+    /// time would otherwise need as many save attempts as there are leaks.</summary>
+    [Fact]
+    public void Every_offending_instance_is_reported()
+    {
+        var overrides = $$"""{"di-a": {{Leaked}}, "di-clean": {{Clean}}, "di-b": {{Leaked}} }""";
+
+        SqlCredentialGuard.FindNodeOverrideViolations(overrides, ["di-a", "di-b", "di-clean"])
+            .ShouldBe(["di-a", "di-b"]);
+    }
+
+    /// <summary>Keys outside the Sql set are ignored. A non-Sql driver never made the
+    /// indirect-credential guarantee, so flagging it would break a config that is legitimate today —
+    /// a regression, not defence in depth.</summary>
+    [Fact]
+    public void An_override_for_a_non_Sql_driver_is_ignored()
+    {
+        var overrides = $$"""{"di-modbus": {{Leaked}} }""";
+
+        SqlCredentialGuard.FindNodeOverrideViolations(overrides, ["di-sql"]).ShouldBeEmpty();
+    }
+
+    /// <summary>The realistic override — a node-specific endpoint — must keep saving.</summary>
+    [Fact]
+    public void A_normal_override_is_clean()
+    {
+        var overrides = """{"di-sql": {"commandTimeoutSeconds": 45}}""";
+
+        SqlCredentialGuard.FindNodeOverrideViolations(overrides, ["di-sql"]).ShouldBeEmpty();
+    }
+
+    /// <summary>Nothing to check when the cluster has no Sql drivers, or the node has no overrides.</summary>
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("   ")]
+    [InlineData("{ not json")]
+    [InlineData("[1,2,3]")]
+    public void Blank_and_malformed_override_maps_yield_no_violations(string? overrides)
+        => SqlCredentialGuard.FindNodeOverrideViolations(overrides, ["di-sql"]).ShouldBeEmpty();
+
+    /// <summary>An empty Sql-driver set short-circuits — there is no instance the key could belong to.</summary>
+    [Fact]
+    public void No_Sql_drivers_means_no_violations()
+        => SqlCredentialGuard.FindNodeOverrideViolations($$"""{"di-sql": {{Leaked}} }""", [])
+            .ShouldBeEmpty();
+
+    /// <summary>A non-object override entry cannot carry config keys, and must not throw.</summary>
+    [Fact]
+    public void A_non_object_override_entry_is_skipped()
+        => SqlCredentialGuard.FindNodeOverrideViolations("""{"di-sql": "connectionString"}""", ["di-sql"])
+            .ShouldBeEmpty();
+}

tests/Core/ZB.MOM.WW.OtOpcUa.Core.Abstractions.Tests/StatusCodeParityTests.cs

@@ -0,0 +1,160 @@
+using System.Reflection;
+using Shouldly;
+using Xunit;
+
+namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions.Tests;
+
+/// <summary>
+///     Guards every driver's hard-coded OPC UA status-code constant against
+///     <see cref="Opc.Ua.StatusCodes"/> — the pinned SDK is the oracle, and a constant whose
+///     <em>name</em> disagrees with its <em>value</em> fails here.
+///     <para><b>Why the drivers hard-code these at all.</b> The driver layer is deliberately SDK-free: a
+///     driver assembly must not drag in the OPC UA stack just to spell a status code, so each one declares
+///     the handful it needs as bare <c>uint</c> literals. That is a sound layering decision with one
+///     failure mode — nothing checks the literal against the name — and it is exactly the failure mode
+///     Gitea #497 found in six places across four drivers.</para>
+///     <para><b>Discovery is reflection-driven, not a hand-copied list</b> (the same convention
+///     <see cref="DriverTypeNamesGuardTests"/> uses): the test scans every
+///     <c>ZB.MOM.WW.OtOpcUa.Driver.*.dll</c> deployed to its output directory for <c>const uint</c> fields
+///     whose name reads as a status code, so a brand-new driver assembly referenced by this project is
+///     covered automatically, with no edit here.</para>
+///     <para><b>An inline literal is invisible to this guard.</b> Reflection can only see a <em>named</em>
+///     constant, so <c>StatusCode: 0x800B0000u, // BadTimeout</c> written at a call site is unguarded —
+///     which is how <c>GalaxyDriver</c> shipped <c>BadServiceUnsupported</c> under a <c>BadTimeout</c>
+///     comment. Hoist a status literal into a named constant rather than writing it at the call site.</para>
+/// </summary>
+public sealed class StatusCodeParityTests
+{
+    /// <summary>
+    ///     Name prefixes that mark a <c>uint</c> constant as an OPC UA status code. These are the three
+    ///     Part 4 severity categories, so they cover the whole space by construction — a status constant
+    ///     that does not start with one of them is not a status constant.
+    /// </summary>
+    private static readonly string[] StatusPrefixes = ["Good", "Uncertain", "Bad"];
+
+    /// <summary>
+    ///     Field-name prefixes stripped before the name is looked up on <see cref="Opc.Ua.StatusCodes"/>.
+    ///     Drivers vary the spelling (<c>SampleMapper.StatusBadNoData</c> vs
+    ///     <c>SqlStatusCodes.BadTimeout</c>); the SDK member is <c>BadNoData</c> either way.
+    /// </summary>
+    private static readonly string[] NamePrefixesToStrip = ["Status"];
+
+    /// <summary>Every <c>Opc.Ua.StatusCodes</c> member, by name — the oracle this test checks against.</summary>
+    private static readonly IReadOnlyDictionary<string, uint> SdkStatusCodes =
+        typeof(Opc.Ua.StatusCodes)
+            .GetFields(BindingFlags.Public | BindingFlags.Static)
+            .Where(f => f.IsLiteral && f.FieldType == typeof(uint))
+            .ToDictionary(f => f.Name, f => (uint)f.GetRawConstantValue()!, StringComparer.Ordinal);
+
+    /// <summary>
+    ///     Every status-shaped <c>const uint</c> declared anywhere in the deployed driver assemblies, as
+    ///     <c>(assembly, declaring type, field name, SDK member name, declared value)</c>.
+    /// </summary>
+    /// <remarks>
+    ///     Non-public types and fields are included on purpose — <c>SampleMapper.StatusBadNoData</c> is a
+    ///     <c>private const</c> on an <c>internal</c> class, and it carried one of the #497 defects. Access
+    ///     modifiers say nothing about whether a value reaches an OPC UA client.
+    /// </remarks>
+    public static TheoryData<string, string, string, string, uint> DeclaredStatusConstants()
+    {
+        var data = new TheoryData<string, string, string, string, uint>();
+
+        var binDir = Path.GetDirectoryName(typeof(StatusCodeParityTests).Assembly.Location)!;
+        foreach (var dll in Directory.GetFiles(binDir, "ZB.MOM.WW.OtOpcUa.Driver.*.dll").OrderBy(p => p, StringComparer.Ordinal))
+        {
+            Assembly asm;
+            try { asm = Assembly.LoadFrom(dll); }
+            catch { continue; }
+
+            Type?[] types;
+            try { types = asm.GetTypes(); }
+            catch (ReflectionTypeLoadException ex) { types = ex.Types; }
+
+            foreach (var type in types)
+            {
+                if (type is null) continue;
+
+                var fields = type.GetFields(
+                    BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.DeclaredOnly);
+
+                foreach (var field in fields)
+                {
+                    if (!field.IsLiteral || field.IsInitOnly || field.FieldType != typeof(uint)) continue;
+
+                    var sdkName = StripKnownPrefix(field.Name);
+                    if (!StatusPrefixes.Any(p => sdkName.StartsWith(p, StringComparison.Ordinal))) continue;
+
+                    data.Add(
+                        asm.GetName().Name!,
+                        type.FullName ?? type.Name,
+                        field.Name,
+                        sdkName,
+                        (uint)field.GetRawConstantValue()!);
+                }
+            }
+        }
+
+        return data;
+    }
+
+    /// <summary>Removes a leading <c>Status</c>-style prefix so the remainder can be looked up on the SDK type.</summary>
+    private static string StripKnownPrefix(string fieldName)
+    {
+        foreach (var prefix in NamePrefixesToStrip)
+        {
+            if (fieldName.Length > prefix.Length && fieldName.StartsWith(prefix, StringComparison.Ordinal))
+                return fieldName[prefix.Length..];
+        }
+
+        return fieldName;
+    }
+
+    /// <summary>
+    ///     A driver's status constant must carry the value the SDK gives the code it is named after.
+    /// </summary>
+    /// <param name="assembly">The declaring driver assembly (failure-message context).</param>
+    /// <param name="type">The declaring type's full name (failure-message context).</param>
+    /// <param name="field">The constant's name as declared.</param>
+    /// <param name="sdkName">The <see cref="Opc.Ua.StatusCodes"/> member the name resolves to.</param>
+    /// <param name="declared">The value the driver declares.</param>
+    [Theory]
+    [MemberData(nameof(DeclaredStatusConstants))]
+    public void Driver_status_constant_matches_the_pinned_SDK(
+        string assembly, string type, string field, string sdkName, uint declared)
+    {
+        SdkStatusCodes.ShouldContainKey(sdkName,
+            $"{type}.{field} (in {assembly}) reads as an OPC UA status code, but '{sdkName}' is not a member " +
+            "of Opc.Ua.StatusCodes. Either the constant is misnamed, or it is not a status code and should " +
+            "not start with Good/Uncertain/Bad.");
+
+        var expected = SdkStatusCodes[sdkName];
+        declared.ShouldBe(expected,
+            $"{type}.{field} (in {assembly}) is declared 0x{declared:X8}, but Opc.Ua.StatusCodes.{sdkName} " +
+            $"is 0x{expected:X8}" +
+            (SdkStatusCodes.FirstOrDefault(kv => kv.Value == declared) is { Key: { } actual } && actual.Length > 0
+                ? $" — 0x{declared:X8} is actually {actual}, which is what OPC UA clients would branch on."
+                : ". The declared value is not any OPC UA status code."));
+    }
+
+    /// <summary>
+    ///     Discovery must find constants in more than one driver assembly. A zero (or near-zero) here means
+    ///     the bin scan broke or the drivers stopped declaring these by convention — either way the theory
+    ///     above would pass vacuously, which is the one outcome a guard test must never do quietly.
+    /// </summary>
+    [Fact]
+    public void Discovery_finds_status_constants_across_multiple_driver_assemblies()
+    {
+        var found = DeclaredStatusConstants();
+        found.Count.ShouldBeGreaterThan(20,
+            "the driver bin scan found almost no status constants — the assemblies did not deploy to bin, " +
+            "or the naming convention changed");
+
+        var assemblies = found
+            .Select(row => row.Data.Item1)
+            .Distinct(StringComparer.Ordinal)
+            .ToArray();
+
+        assemblies.Length.ShouldBeGreaterThan(3,
+            "status constants were found in fewer than four driver assemblies: " + string.Join(", ", assemblies));
+    }
+}

tests/Core/ZB.MOM.WW.OtOpcUa.Core.Abstractions.Tests/ZB.MOM.WW.OtOpcUa.Core.Abstractions.Tests.csproj

@@ -12,6 +12,8 @@
     <ItemGroup>
         <PackageReference Include="xunit.v3"/>
         <PackageReference Include="Shouldly"/>
+        <!-- StatusCodeParityTests only; supplies Opc.Ua.StatusCodes as the oracle. -->
+        <PackageReference Include="OPCFoundation.NetStandard.Opc.Ua.Core"/>
         <PackageReference Include="Microsoft.NET.Test.Sdk"/>
         <PackageReference Include="xunit.runner.visualstudio">
             <PrivateAssets>all</PrivateAssets>
@@ -34,6 +36,11 @@
         <ProjectReference Include="..\..\..\src\Drivers\ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient\ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.csproj"/>
         <ProjectReference Include="..\..\..\src\Drivers\ZB.MOM.WW.OtOpcUa.Driver.Galaxy\ZB.MOM.WW.OtOpcUa.Driver.Galaxy.csproj"/>
         <ProjectReference Include="..\..\..\src\Drivers\ZB.MOM.WW.OtOpcUa.Driver.Calculation\ZB.MOM.WW.OtOpcUa.Driver.Calculation.csproj"/>
+        <ProjectReference Include="..\..\..\src\Drivers\ZB.MOM.WW.OtOpcUa.Driver.Sql\ZB.MOM.WW.OtOpcUa.Driver.Sql.csproj"/>
+        <!-- Ships no driver factory (it is a historian backend, not an Equipment driver), so the
+             DriverTypeNames guard skips it — but it does hard-code OPC UA status constants, which
+             puts it in StatusCodeParityTests' scope. -->
+        <ProjectReference Include="..\..\..\src\Drivers\ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway\ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.csproj"/>
     </ItemGroup>
 
 </Project>

tests/Core/ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms.Tests/ScriptedAlarmProjectionTests.cs

@@ -0,0 +1,180 @@
+using Serilog;
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms;
+using ZB.MOM.WW.OtOpcUa.Core.Scripting;
+
+namespace ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms.Tests;
+
+/// <summary>
+///     #487 — <see cref="ScriptedAlarmEngine.GetProjections"/>: the read that lets a caller restore an
+///     alarm's condition node after a full address-space rebuild, without waiting for the alarm's next
+///     transition (which for a still-active alarm with static dependencies may never come).
+/// </summary>
+/// <remarks>
+///     The load that motivates this is deliberately the one that emits NOTHING: an alarm whose persisted
+///     state is already Active and whose predicate is still true produces <see cref="EmissionKind.None"/>,
+///     so the transition stream cannot carry its state. These tests pin both halves — the projection does
+///     report the state, and reading it does not fire an emission.
+/// </remarks>
+[Trait("Category", "Unit")]
+public sealed class ScriptedAlarmProjectionTests
+{
+    private static ScriptedAlarmDefinition Alarm(
+        string id = "HighTemp",
+        string predicate = """return (int)ctx.GetTag("Temp").Value > 100;""",
+        string msg = "Temp is {Temp}",
+        AlarmSeverity sev = AlarmSeverity.High) =>
+        new(AlarmId: id,
+            EquipmentPath: "Plant/Line1/Reactor",
+            AlarmName: id,
+            Kind: AlarmKind.AlarmCondition,
+            Severity: sev,
+            MessageTemplate: msg,
+            PredicateScriptSource: predicate);
+
+    /// <summary>An already-Active persisted state, as a store would hold it across a restart/redeploy.</summary>
+    private static AlarmConditionState PersistedActive(
+        string alarmId = "HighTemp",
+        AlarmAckedState acked = AlarmAckedState.Unacknowledged,
+        DateTime? lastTransitionUtc = null) =>
+        new(alarmId,
+            AlarmEnabledState.Enabled,
+            AlarmActiveState.Active,
+            acked,
+            AlarmConfirmedState.Confirmed,
+            ShelvingState.Unshelved,
+            lastTransitionUtc ?? DateTime.UtcNow,
+            LastActiveUtc: lastTransitionUtc ?? DateTime.UtcNow,
+            LastClearedUtc: null,
+            LastAckUtc: null, LastAckUser: null, LastAckComment: null,
+            LastConfirmUtc: null, LastConfirmUser: null, LastConfirmComment: null,
+            Comments: []);
+
+    private static ScriptedAlarmEngine Build(FakeUpstream up, IAlarmStateStore store)
+    {
+        var logger = new LoggerConfiguration().CreateLogger();
+        return new ScriptedAlarmEngine(up, store, new ScriptLoggerFactory(logger), logger);
+    }
+
+    /// <summary>The core of #487: a reload of a still-active alarm emits NOTHING, yet the projection
+    /// reports it Active — so a caller has a way to restore the node the rebuild reset.</summary>
+    [Fact]
+    public async Task A_still_active_alarm_emits_nothing_on_reload_but_projects_Active()
+    {
+        var up = new FakeUpstream();
+        up.Set("Temp", 150); // predicate still true — no transition to report
+        var store = new InMemoryAlarmStateStore();
+        await store.SaveAsync(PersistedActive(), TestContext.Current.CancellationToken);
+
+        using var eng = Build(up, store);
+        var emissions = new List<ScriptedAlarmEvent>();
+        eng.OnEvent += (_, e) => { lock (emissions) emissions.Add(e); }; // subscribe BEFORE the load
+
+        await eng.LoadAsync([Alarm()], TestContext.Current.CancellationToken);
+
+        // The premise. If this ever starts emitting, the bug's shape has changed and the re-assert
+        // in ScriptedAlarmHostActor may have become a duplicate rather than the only source of truth.
+        lock (emissions)
+        {
+            emissions.ShouldBeEmpty("a still-active alarm has no transition to report on reload");
+        }
+
+        var projection = eng.GetProjections().ShouldHaveSingleItem();
+        projection.AlarmId.ShouldBe("HighTemp");
+        projection.Condition.Active.ShouldBe(AlarmActiveState.Active);
+        projection.Condition.Acked.ShouldBe(AlarmAckedState.Unacknowledged);
+    }
+
+    /// <summary>The projection carries the definition's severity and the message template resolved against
+    /// the live value cache — so a re-asserted node is indistinguishable from one a real transition wrote.</summary>
+    [Fact]
+    public async Task Projection_carries_definition_severity_and_a_resolved_message()
+    {
+        var up = new FakeUpstream();
+        up.Set("Temp", 150);
+        var store = new InMemoryAlarmStateStore();
+        await store.SaveAsync(PersistedActive(), TestContext.Current.CancellationToken);
+
+        using var eng = Build(up, store);
+        await eng.LoadAsync([Alarm(sev: AlarmSeverity.Critical)], TestContext.Current.CancellationToken);
+
+        var projection = eng.GetProjections().ShouldHaveSingleItem();
+        projection.Severity.ShouldBe(AlarmSeverity.Critical);
+        projection.Message.ShouldBe("Temp is 150", "the template resolves against the current value cache");
+    }
+
+    /// <summary>Reading projections is a pure read — it must never raise <see cref="ScriptedAlarmEngine.OnEvent"/>,
+    /// or every deploy would append a duplicate historian / alerts row.</summary>
+    [Fact]
+    public async Task Reading_projections_never_fires_an_emission()
+    {
+        var up = new FakeUpstream();
+        up.Set("Temp", 150);
+        var store = new InMemoryAlarmStateStore();
+        await store.SaveAsync(PersistedActive(), TestContext.Current.CancellationToken);
+
+        using var eng = Build(up, store);
+        await eng.LoadAsync([Alarm()], TestContext.Current.CancellationToken);
+
+        var emissions = 0;
+        eng.OnEvent += (_, _) => Interlocked.Increment(ref emissions);
+
+        for (var i = 0; i < 5; i++) eng.GetProjections().ShouldNotBeEmpty();
+
+        Volatile.Read(ref emissions).ShouldBe(0);
+    }
+
+    /// <summary>An alarm that is genuinely normal projects the no-event position, so a caller can tell
+    /// "nothing to restore" from "restore this".</summary>
+    [Fact]
+    public async Task A_normal_alarm_projects_the_no_event_position()
+    {
+        var up = new FakeUpstream();
+        up.Set("Temp", 50); // predicate false
+        using var eng = Build(up, new InMemoryAlarmStateStore());
+
+        await eng.LoadAsync([Alarm()], TestContext.Current.CancellationToken);
+
+        var projection = eng.GetProjections().ShouldHaveSingleItem();
+        projection.Condition.Active.ShouldBe(AlarmActiveState.Inactive);
+        projection.Condition.Acked.ShouldBe(AlarmAckedState.Acknowledged);
+        projection.Condition.Enabled.ShouldBe(AlarmEnabledState.Enabled);
+        projection.Condition.Shelving.Kind.ShouldBe(ShelvingKind.Unshelved);
+    }
+
+    /// <summary>The worst-input quality rides the projection, so restoring a node whose script inputs are
+    /// Bad does not clobber its Quality back to Good (#478's invariant, on the re-assert path).</summary>
+    [Fact]
+    public async Task Projection_carries_the_last_observed_worst_input_quality()
+    {
+        var up = new FakeUpstream();
+        up.Set("Temp", 150);
+        var store = new InMemoryAlarmStateStore();
+        await store.SaveAsync(PersistedActive(), TestContext.Current.CancellationToken);
+
+        using var eng = Build(up, store);
+        await eng.LoadAsync([Alarm()], TestContext.Current.CancellationToken);
+        eng.GetProjections().ShouldHaveSingleItem().WorstInputStatusCode.ShouldBe(0u, "inputs start Good");
+
+        up.Push("Temp", 150, 0x80000000u); // input goes Bad — condition freezes, quality is annotated
+
+        // The push re-evaluates on a background worker; poll for the tracked bucket to move.
+        var deadline = DateTime.UtcNow.AddSeconds(10);
+        while (eng.GetProjections()[0].WorstInputStatusCode == 0u && DateTime.UtcNow < deadline)
+        {
+            await Task.Delay(20, TestContext.Current.CancellationToken);
+        }
+
+        (eng.GetProjections()[0].WorstInputStatusCode >> 30).ShouldBe(2u, "a Bad input projects Bad quality");
+    }
+
+    /// <summary>Before the first load there is nothing to project — the read is safe, not a throw.</summary>
+    [Fact]
+    public void Projections_are_empty_before_the_first_load()
+    {
+        using var eng = Build(new FakeUpstream(), new InMemoryAlarmStateStore());
+        eng.GetProjections().ShouldBeEmpty();
+    }
+}

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests/Runtime/EventPumpBoundedChannelTests.cs

@@ -10,59 +10,109 @@ using ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Runtime;
 namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests.Runtime;
 
 /// <summary>
-///     PR 6.2 — pins the EventPump's bounded-channel + drop-newest behavior. We
-///     hold the dispatch loop with a slow handler so the channel fills, then verify
-///     the producer keeps reading from the gw stream and increments the
-///     <c>galaxy.events.dropped</c> counter rather than blocking.
+///     PR 6.2 — pins the EventPump's bounded-channel + drop-newest behavior. We hold the dispatch loop
+///     with a blocking handler so the channel fills, then verify the producer keeps reading from the gw
+///     stream and increments the <c>galaxy.events.dropped</c> counter rather than blocking.
 /// </summary>
+/// <remarks>
+///     These tests observe two background loops (<c>RunAsync</c> / <c>DispatchLoopAsync</c>) through a
+///     process-wide <see cref="Meter"/>, so every wait here is a <b>presence</b> assertion polled up to
+///     <see cref="Budget"/> — never a fixed sleep. A fixed sleep is a bet that both loops get scheduled
+///     within it, and #503 is what losing that bet looks like when the box is busy running other test
+///     assemblies.
+/// </remarks>
 public sealed class EventPumpBoundedChannelTests
 {
-    /// <summary>Verifies that the event pump drops newest events when the bounded channel fills and records metrics for dropped events.</summary>
+    /// <summary>Upper bound on how long a poll waits for a background loop to reach its terminal state.
+    /// Generous on purpose: it is spent only when something is genuinely broken, and it cannot turn a
+    /// failing assertion into a passing one.</summary>
+    private static readonly TimeSpan Budget = TimeSpan.FromSeconds(15);
+
+    /// <summary>
+    ///     With the dispatch loop genuinely held and the channel therefore full, the producer keeps
+    ///     draining the gw stream and counts every rejected write on <c>galaxy.events.dropped</c> —
+    ///     newest-dropped, not back-pressure.
+    /// </summary>
+    /// <remarks>
+    ///     <para>
+    ///         The arrangement is staged so the arithmetic is exact rather than scheduler-dependent
+    ///         (#503): emit ONE event, wait until the dispatcher has actually entered the handler (so it
+    ///         holds that event and the channel is empty), and only then emit the remaining nine. The
+    ///         channel accepts <c>capacity</c> of them and the rest must be dropped —
+    ///         <c>10 − 1 held − 2 buffered = 7</c>, every run.
+    ///     </para>
+    /// </remarks>
     [Fact]
     public async Task Drops_newest_when_channel_fills_and_records_metric()
     {
-        var counters = StartMeterCapture();
+        const int totalEvents = 10;
+        const int channelCapacity = 2;
+        // One event is held inside the handler; `channelCapacity` more fit in the channel; the rest are dropped.
+        const int expectedDropped = totalEvents - 1 - channelCapacity;
+
+        // Unique per run: the counters are filtered to this exact galaxy.client tag, which is what keeps a
+        // parallel sibling test's pump out of them (#503). A literal name would work today and break the
+        // day someone reuses it.
+        var clientName = $"PumpTest-{Guid.NewGuid():N}";
+        var counters = StartMeterCapture(clientName);
+
+        // A SYNCHRONOUS gate, deliberately. OnDataChange is EventHandler<T> — void-returning — so an
+        // `async (_, _) => await gate` lambda is async void: it returns to the dispatch loop at the first
+        // await and holds nothing. That is exactly what #503 was: the loop drained freely, drops happened
+        // only when the producer happened to outrun the consumer, and the assertions rode on scheduling
+        // luck. Blocking the loop's own thread is what makes "the dispatcher is held" true.
+        var dispatchGate = new ManualResetEventSlim(false);
+        var handlerEntered = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
+        EventPump? pump = null;
         try
         {
             var subscriber = new ManualSubscriber();
             var registry = new SubscriptionRegistry();
             registry.Register(1, [new TagBinding("Tag.A", ItemHandle: 7)]);
 
-            // Tiny channel + slow handler ⇒ producer hits FullMode.Wait → TryWrite false
-            // for every overflow event.
-            var dispatchGate = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
-            await using var pump = new EventPump(
-                subscriber, registry, channelCapacity: 2, clientName: "PumpTest");
-            pump.OnDataChange += async (_, _) =>
+            pump = new EventPump(
+                subscriber, registry, channelCapacity: channelCapacity, clientName: clientName);
+            pump.OnDataChange += (_, _) =>
             {
-                // Block the dispatch loop until we've shoved enough events through to
-                // overflow the bounded channel. Consume the gate exactly once.
-                await dispatchGate.Task.ConfigureAwait(false);
+                handlerEntered.TrySetResult();
+                dispatchGate.Wait();
             };
             pump.Start();
 
-            const int totalEvents = 10;
-            for (var i = 0; i < totalEvents; i++)
+            // Stage 1 — one event, then wait for the dispatcher to take it and block. After this the
+            // channel is provably empty and exactly one event is in flight inside the handler.
+            await subscriber.EmitAsync(itemHandle: 7, value: 0);
+            await handlerEntered.Task.WaitAsync(Budget);
+
+            // Stage 2 — the rest. `channelCapacity` are accepted; the remainder must be dropped.
+            for (var i = 1; i < totalEvents; i++)
             {
                 await subscriber.EmitAsync(itemHandle: 7, value: i);
             }
-            // Give the producer a beat to run TryWrite for every event.
-            await Task.Delay(150);
 
-            // Capacity 2 + 1 in-flight in the dispatcher = 3 may have been accepted; the
-            // remainder should have hit the dropped counter. Don't pin exact counts —
-            // the scheduler can interleave; pin the invariants instead.
-            counters.Received.ShouldBeGreaterThanOrEqualTo(totalEvents);
-            counters.Dropped.ShouldBeGreaterThan(0,
-                "with capacity=2 and a held dispatcher we must drop at least one of 10 events");
-            (counters.Received).ShouldBe(counters.Dispatched + counters.Dropped + counters.InFlight,
-                "received = dispatched + dropped + (events still queued)");
+            // PRESENCE assertion on the discriminator (#500's rule): poll until the drop count reaches its
+            // terminal value rather than sleeping a fixed 150 ms and hoping the producer got scheduled.
+            // The budget is an upper bound before giving up — spending it costs nothing on the happy path,
+            // and no amount of it can make a genuinely broken pump pass. Dropped starts at 0, so this
+            // cannot be satisfied by the initial state.
+            await WaitUntilAsync(() => counters.Dropped == expectedDropped,
+                $"expected {expectedDropped} dropped events");
 
-            // Release the dispatcher so DisposeAsync can drain cleanly.
-            dispatchGate.TrySetResult();
+            counters.Received.ShouldBe(totalEvents,
+                "the producer must keep reading the gw stream through the overflow, not back-pressure");
+            counters.Dropped.ShouldBe(expectedDropped);
+            counters.Dispatched.ShouldBe(0,
+                "the dispatch loop is still blocked in the handler, so nothing has completed dispatch — " +
+                "if this is non-zero the handler is not actually holding the loop and the test proves nothing");
         }
         finally
         {
+            // Release BEFORE disposing: DisposeAsync awaits the dispatch loop, and that loop is parked on
+            // this gate. Releasing it here (not at the end of the try) is what keeps a failed assertion a
+            // failure instead of a hang.
+            dispatchGate.Set();
+            if (pump is not null) await pump.DisposeAsync();
+            dispatchGate.Dispose();
             counters.Dispose();
         }
     }
@@ -110,23 +160,21 @@ public sealed class EventPumpBoundedChannelTests
             // Poll until at least one galaxy.events.received measurement tagged
             // galaxy.client=Driver-X lands in the listener, rather than using a
             // fixed delay that races under parallel test load on a busy box.
-            var deadline = DateTime.UtcNow.AddSeconds(5);
-            bool found = false;
-            while (DateTime.UtcNow < deadline)
-            {
-                listener.RecordObservableInstruments();
-                bool hasMatch;
-                lock (captured)
+            // Budget, not 5 s: the same contention that produced #503 stretches how long the
+            // producer loop takes to be scheduled, and a presence poll costs nothing to over-budget.
+            await WaitUntilAsync(
+                () =>
                 {
-                    hasMatch = captured.Any(c =>
-                        c.Instrument == "galaxy.events.received" &&
-                        c.Tags.Any(t => t.Key == "galaxy.client" &&
-                            string.Equals((string?)t.Value, "Driver-X", StringComparison.Ordinal)));
-                }
-                if (hasMatch) { found = true; break; }
-                await Task.Delay(25);
-            }
-            _ = found; // assertion happens below after dispose
+                    listener.RecordObservableInstruments();
+                    lock (captured)
+                    {
+                        return captured.Any(c =>
+                            c.Instrument == "galaxy.events.received" &&
+                            c.Tags.Any(t => t.Key == "galaxy.client" &&
+                                string.Equals((string?)t.Value, "Driver-X", StringComparison.Ordinal)));
+                    }
+                },
+                "a galaxy.events.received measurement tagged galaxy.client=Driver-X");
         }
 
         // The static Meter is shared across all EventPump instances in the test
@@ -146,7 +194,46 @@ public sealed class EventPumpBoundedChannelTests
         ours.ShouldContain(c => c.Instrument == "galaxy.events.received");
     }
 
-    private static CounterCapture StartMeterCapture()
+    /// <summary>Polls <paramref name="condition"/> until it holds or <see cref="Budget"/> elapses, failing
+    /// with <paramref name="what"/> on timeout. The presence-assertion counterpart to a fixed delay.</summary>
+    private static async Task WaitUntilAsync(Func<bool> condition, string what)
+    {
+        var deadline = DateTime.UtcNow + Budget;
+        while (DateTime.UtcNow < deadline)
+        {
+            if (condition()) return;
+            await Task.Delay(10);
+        }
+        condition().ShouldBeTrue($"timed out after {Budget.TotalSeconds:0}s waiting: {what}");
+    }
+
+    /// <summary>
+    ///     Captures the three EventPump counters for <b>one specific pump</b>, identified by its
+    ///     <c>galaxy.client</c> tag.
+    /// </summary>
+    /// <remarks>
+    ///     <para>
+    ///         The <c>galaxy.client</c> filter is the fix for #503, and it is not optional. The pump's
+    ///         <see cref="Meter"/> is <b>static</b> — one instance for the whole process — and
+    ///         <c>InstrumentPublished</c> can only select by <i>meter</i>, so an unfiltered listener
+    ///         receives measurements from every <see cref="EventPump"/> alive anywhere in the assembly.
+    ///         xUnit runs test classes in parallel and several of them build pumps
+    ///         (<c>EventPumpStreamFaultTests</c>, the <c>Driver-X</c> test below), so a sibling's events
+    ///         landed in these counters — that is why the flake needed a busy box: it needed the two
+    ///         tests to overlap in time. The leak was measured directly, as <c>Received = 11</c> in a run
+    ///         that emitted 10.
+    ///     </para>
+    ///     <para>
+    ///         The old <c>Received == Dispatched + Dropped + InFlight</c> assertion is what turned the
+    ///         leak into a failure: a foreign increment landing between its four separate
+    ///         <see cref="Interlocked.Read(ref long)"/> calls made the two sides disagree. Hence the
+    ///         reported subject, <c>counters.Received</c>.
+    ///     </para>
+    /// </remarks>
+    /// <param name="clientName">The <c>galaxy.client</c> tag value to accept. Must be unique to the
+    /// calling test — pass a fresh GUID-suffixed name rather than a literal, so a future sibling test
+    /// cannot silently reintroduce the leak by reusing the same name.</param>
+    private static CounterCapture StartMeterCapture(string clientName)
     {
         var capture = new CounterCapture();
         var listener = new MeterListener();
@@ -154,8 +241,20 @@ public sealed class EventPumpBoundedChannelTests
         {
             if (instr.Meter.Name == EventPump.MeterName) l.EnableMeasurementEvents(instr);
         };
-        listener.SetMeasurementEventCallback<long>((instr, value, _, _) =>
+        listener.SetMeasurementEventCallback<long>((instr, value, tags, _) =>
         {
+            var mine = false;
+            foreach (var tag in tags)
+            {
+                if (tag.Key == "galaxy.client" &&
+                    string.Equals((string?)tag.Value, clientName, StringComparison.Ordinal))
+                {
+                    mine = true;
+                    break;
+                }
+            }
+            if (!mine) return;
+
             switch (instr.Name)
             {
                 case "galaxy.events.received": Interlocked.Add(ref capture._received, value); break;
@@ -178,8 +277,11 @@ public sealed class EventPumpBoundedChannelTests
         public long Dispatched => Interlocked.Read(ref _dispatched);
         /// <summary>Gets the count of dropped events.</summary>
         public long Dropped => Interlocked.Read(ref _dropped);
-        /// <summary>Gets the count of in-flight events.</summary>
-        public long InFlight => Math.Max(0, Received - Dispatched - Dropped);
+        // There is deliberately no InFlight member. It could only be DERIVED as
+        // Received - Dispatched - Dropped, which made the old
+        // `Received == Dispatched + Dropped + InFlight` assertion a tautology: it could not fail on a
+        // real defect, only on a torn read across the four separate Interlocked.Read calls. Assert the
+        // three measured counters directly instead (#503).
         /// <summary>Disposes the meter listener.</summary>
         public void Dispose() => Listener?.Dispose();
     }

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests/Runtime/StatusCodeMapTests.cs

@@ -19,12 +19,12 @@ public sealed class StatusCodeMapTests
     /// <param name="expected">The expected OPC UA status code.</param>
     [Theory]
     [InlineData((byte)192, 0x00000000u)]   // Good
-    [InlineData((byte)216, 0x00D80000u)]   // Good_LocalOverride
+    [InlineData((byte)216, 0x00960000u)]   // Good_LocalOverride
     [InlineData((byte)64,  0x40000000u)]   // Uncertain
-    [InlineData((byte)68,  0x40A40000u)]   // Uncertain_LastUsableValue
-    [InlineData((byte)80,  0x408D0000u)]   // Uncertain_SensorNotAccurate
-    [InlineData((byte)84,  0x408E0000u)]   // Uncertain_EngineeringUnitsExceeded
-    [InlineData((byte)88,  0x408F0000u)]   // Uncertain_SubNormal
+    [InlineData((byte)68,  0x40900000u)]   // Uncertain_LastUsableValue
+    [InlineData((byte)80,  0x40930000u)]   // Uncertain_SensorNotAccurate
+    [InlineData((byte)84,  0x40940000u)]   // Uncertain_EngineeringUnitsExceeded
+    [InlineData((byte)88,  0x40950000u)]   // Uncertain_SubNormal
     [InlineData((byte)0,   0x80000000u)]   // Bad
     [InlineData((byte)4,   0x80890000u)]   // Bad_ConfigurationError
     [InlineData((byte)8,   0x808A0000u)]   // Bad_NotConnected
@@ -132,9 +132,9 @@ public sealed class StatusCodeMapTests
     /// <param name="expected">The expected OPC DA category byte.</param>
     [Theory]
     [InlineData(0x00000000u, (byte)192)]  // Good
-    [InlineData(0x00D80000u, (byte)192)]  // GoodLocalOverride — still Good category
+    [InlineData(0x00960000u, (byte)192)]  // GoodLocalOverride — still Good category
     [InlineData(0x40000000u, (byte)64)]   // Uncertain
-    [InlineData(0x408F0000u, (byte)64)]   // UncertainSubNormal — still Uncertain category
+    [InlineData(0x40950000u, (byte)64)]   // UncertainSubNormal — still Uncertain category
     [InlineData(0x80000000u, (byte)0)]    // Bad
     [InlineData(0x808A0000u, (byte)0)]    // BadNotConnected — still Bad category
     [InlineData(0x80020000u, (byte)0)]    // BadInternalError — still Bad category

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/Mapping/GatewayQualityMapperTests.cs

@@ -7,7 +7,7 @@ public sealed class GatewayQualityMapperTests
 {
     [Theory]
     [InlineData(192, 0x00000000u)] // Good
-    [InlineData(216, 0x00D80000u)] // Good_LocalOverride
+    [InlineData(216, 0x00960000u)] // Good_LocalOverride
     [InlineData(64,  0x40000000u)] // Uncertain
     [InlineData(0,   0x80000000u)] // Bad
     [InlineData(8,   0x808A0000u)] // Bad_NotConnected

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/Mapping/SampleMapperTests.cs

@@ -37,7 +37,7 @@ public sealed class SampleMapperTests
     {
         var a = new HistorianAggregateSample { Tag = "T", /* Value unset, no Good quality */ EndTime = Ts(2026, 1, 1, 0, 0, 0) };
         var snap = SampleMapper.ToAggregateSnapshot(a);
-        Assert.Equal(0x800E0000u, snap.StatusCode); // BadNoData
+        Assert.Equal(0x809B0000u, snap.StatusCode); // BadNoData
         Assert.Null(snap.Value);
     }
 

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/Docker/Dockerfile

@@ -21,10 +21,7 @@ COPY profiles/ /fixtures/
 # compose profile. See Docker/README.md §exception injection.
 COPY exception_injector.py /fixtures/
 
-# 5020 = the shared port for the standard/dl205/mitsubishi/s7_1500/exception_injection
-# profiles (only one binds it at a time); 5021 = the rtu_over_tcp profile, which co-runs
-# with standard. Image-metadata honesty only — compose's ports: mapping doesn't need EXPOSE.
-EXPOSE 5020 5021
+EXPOSE 5020
 
 # Default to the standard profile; docker-compose.yml overrides per service.
 # --http_port intentionally omitted; pymodbus 3.13's web UI binds on a

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/Docker/README.md

@@ -2,16 +2,15 @@
 
 The Modbus driver's integration tests talk to a
 [`pymodbus`](https://pymodbus.readthedocs.io/) simulator running as a
-pinned Docker container. One image, per-profile service in compose. Most
-profiles bind `:5020`, so only one of *those* runs at a time; the
-`rtu_over_tcp` profile binds `:5021` and is designed to co-run alongside
-`standard`. Docker is the only supported launch path — a fresh clone needs
-Docker Desktop and nothing else.
+pinned Docker container. One image, per-profile service in compose, same
+port binding (`5020`) regardless of which profile is live. Docker is the
+only supported launch path — a fresh clone needs Docker Desktop and
+nothing else.
 
 | File | Purpose |
 |---|---|
 | [`Dockerfile`](Dockerfile) | `python:3.12-slim-bookworm` + `pymodbus[simulator]==3.13.0` + every profile JSON + `exception_injector.py` |
-| [`docker-compose.yml`](docker-compose.yml) | One service per profile (`standard` / `dl205` / `mitsubishi` / `s7_1500` / `exception_injection` bind `:5020`, so only one of those runs at a time; `rtu_over_tcp` binds `:5021` and can run alongside `standard`) |
+| [`docker-compose.yml`](docker-compose.yml) | One service per profile (`standard` / `dl205` / `mitsubishi` / `s7_1500` / `exception_injection`); all bind `:5020` so only one runs at a time |
 | [`profiles/*.json`](profiles/) | Same seed-register definitions the native launcher uses — canonical source |
 | [`exception_injector.py`](exception_injector.py) | Pure-stdlib Modbus/TCP server that emits arbitrary exception codes per rule — used by the `exception_injection` profile |
 
@@ -44,11 +43,10 @@ docker compose -f tests\...\Docker\docker-compose.yml --profile dl205 up -d
 docker compose -f tests\...\Docker\docker-compose.yml --profile dl205 down
 ```
 
-Only one of the `:5020` profiles binds at a time; switch by stopping the
-current service + starting another. (`rtu_over_tcp` is the exception — it
-binds `:5021` and co-runs with `standard`.) The integration tests
-discriminate by a separate `MODBUS_SIM_PROFILE` env var so they skip
-correctly when the wrong profile is live.
+Only one profile binds `:5020` at a time; switch by stopping the current
+service + starting another. The integration tests discriminate by a
+separate `MODBUS_SIM_PROFILE` env var so they skip correctly when the
+wrong profile is live.
 
 > **⚠️ Profile-cycling gotcha (bit us in the 2026-07 sweep — see
 > `archreview/plans/INTEGRATION-SWEEP-STATUS.md`).** Each profile is a

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/Docker/docker-compose.yml

@@ -78,30 +78,6 @@ services:
       "--json_file",      "/fixtures/s7_1500.json"
     ]
 
-  # RTU-over-TCP profile. Same pymodbus simulator, but the server is framed
-  # RTU (framer=rtu) instead of socket/MBAP — this is what a serial→Ethernet
-  # gateway presents. Binds :5021 (NOT the shared :5020) so it co-runs with
-  # the `standard` profile: two families, two ports, no conflict. Serves
-  # rtu_over_tcp.json (byte-for-byte standard.json + framer/port swap).
-  rtu_over_tcp:
-    profiles: ["rtu_over_tcp"]
-    image: otopcua-pymodbus:3.13.0
-    build:
-      context: .
-      dockerfile: Dockerfile
-    container_name: otopcua-pymodbus-rtu_over_tcp
-    labels:
-      project: lmxopcua
-    restart: "no"
-    ports:
-      - "5021:5021"
-    command: [
-      "pymodbus.simulator",
-      "--modbus_server", "srv",
-      "--modbus_device",  "dev",
-      "--json_file",      "/fixtures/rtu_over_tcp.json"
-    ]
-
   # Exception-injection profile. Runs the standalone pure-stdlib Modbus/TCP
   # server shipped as exception_injector.py instead of the pymodbus
   # simulator — pymodbus naturally emits only exception codes 02 + 03, and

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/Docker/profiles/rtu_over_tcp.json

@@ -1,97 +0,0 @@
-{
-  "_comment": "rtu_over_tcp.json — RTU-over-TCP Modbus server for the integration suite (RTU framing tunnelled over a socket, as a serial→Ethernet gateway presents it). Byte-for-byte standard.json EXCEPT the server block: framer=\"rtu\" (not \"socket\") + port 5021 (not 5020), so it co-runs with the standard profile on :5020. pymodbus 3.13's simulator honors framer=rtu on a TCP server — confirmed on the wire (controller spike, 2026-07-24): raw RTU FC03 read of HR[5] returned `01 03 02 00 05 78 47`, a pure RTU frame with no MBAP header. Layout is identical to standard.json: HR[0..31]=address-as-value, HR[100]=auto-increment, HR[200..209]=scratch, coils 1024..1055=alternating, coils 1100..1109=scratch. NOTE: pymodbus rejects unknown keys at device-list / setup level; explanatory comments live in the README + git history.",
-
-  "server_list": {
-    "srv": {
-      "comm": "tcp",
-      "host": "0.0.0.0",
-      "port": 5021,
-      "framer": "rtu",
-      "device_id": 1
-    }
-  },
-
-  "device_list": {
-    "dev": {
-      "setup": {
-        "co size": 2048,
-        "di size": 2048,
-        "hr size": 2048,
-        "ir size": 2048,
-        "shared blocks": true,
-        "type exception": false,
-        "defaults": {
-          "value":  {"bits": 0, "uint16": 0, "uint32": 0, "float32": 0.0, "string": " "},
-          "action": {"bits": null, "uint16": null, "uint32": null, "float32": null, "string": null}
-        }
-      },
-      "invalid": [],
-      "write": [
-        [0, 31],
-        [100, 100],
-        [200, 209],
-        [1024, 1055],
-        [1100, 1109]
-      ],
-
-      "uint16": [
-        {"addr":  0, "value":  0}, {"addr":  1, "value":  1},
-        {"addr":  2, "value":  2}, {"addr":  3, "value":  3},
-        {"addr":  4, "value":  4}, {"addr":  5, "value":  5},
-        {"addr":  6, "value":  6}, {"addr":  7, "value":  7},
-        {"addr":  8, "value":  8}, {"addr":  9, "value":  9},
-        {"addr": 10, "value": 10}, {"addr": 11, "value": 11},
-        {"addr": 12, "value": 12}, {"addr": 13, "value": 13},
-        {"addr": 14, "value": 14}, {"addr": 15, "value": 15},
-        {"addr": 16, "value": 16}, {"addr": 17, "value": 17},
-        {"addr": 18, "value": 18}, {"addr": 19, "value": 19},
-        {"addr": 20, "value": 20}, {"addr": 21, "value": 21},
-        {"addr": 22, "value": 22}, {"addr": 23, "value": 23},
-        {"addr": 24, "value": 24}, {"addr": 25, "value": 25},
-        {"addr": 26, "value": 26}, {"addr": 27, "value": 27},
-        {"addr": 28, "value": 28}, {"addr": 29, "value": 29},
-        {"addr": 30, "value": 30}, {"addr": 31, "value": 31},
-
-        {"addr": 100, "value": 0,
-         "action": "increment",
-         "parameters": {"minval": 0, "maxval": 65535}},
-
-        {"addr": 200, "value": 0}, {"addr": 201, "value": 0},
-        {"addr": 202, "value": 0}, {"addr": 203, "value": 0},
-        {"addr": 204, "value": 0}, {"addr": 205, "value": 0},
-        {"addr": 206, "value": 0}, {"addr": 207, "value": 0},
-        {"addr": 208, "value": 0}, {"addr": 209, "value": 0}
-      ],
-
-      "bits": [
-        {"addr": 1024, "value": 1}, {"addr": 1025, "value": 0},
-        {"addr": 1026, "value": 1}, {"addr": 1027, "value": 0},
-        {"addr": 1028, "value": 1}, {"addr": 1029, "value": 0},
-        {"addr": 1030, "value": 1}, {"addr": 1031, "value": 0},
-        {"addr": 1032, "value": 1}, {"addr": 1033, "value": 0},
-        {"addr": 1034, "value": 1}, {"addr": 1035, "value": 0},
-        {"addr": 1036, "value": 1}, {"addr": 1037, "value": 0},
-        {"addr": 1038, "value": 1}, {"addr": 1039, "value": 0},
-        {"addr": 1040, "value": 1}, {"addr": 1041, "value": 0},
-        {"addr": 1042, "value": 1}, {"addr": 1043, "value": 0},
-        {"addr": 1044, "value": 1}, {"addr": 1045, "value": 0},
-        {"addr": 1046, "value": 1}, {"addr": 1047, "value": 0},
-        {"addr": 1048, "value": 1}, {"addr": 1049, "value": 0},
-        {"addr": 1050, "value": 1}, {"addr": 1051, "value": 0},
-        {"addr": 1052, "value": 1}, {"addr": 1053, "value": 0},
-        {"addr": 1054, "value": 1}, {"addr": 1055, "value": 0},
-
-        {"addr": 1100, "value": 0}, {"addr": 1101, "value": 0},
-        {"addr": 1102, "value": 0}, {"addr": 1103, "value": 0},
-        {"addr": 1104, "value": 0}, {"addr": 1105, "value": 0},
-        {"addr": 1106, "value": 0}, {"addr": 1107, "value": 0},
-        {"addr": 1108, "value": 0}, {"addr": 1109, "value": 0}
-      ],
-
-      "uint32":  [],
-      "float32": [],
-      "string":  [],
-      "repeat":  []
-    }
-  }
-}

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/ModbusRtuOverTcpFixture.cs

@@ -1,82 +0,0 @@
-using System.Net.Sockets;
-
-namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests;
-
-/// <summary>
-///     Reachability probe for the RTU-over-TCP Modbus simulator (pymodbus in Docker with
-///     <c>framer=rtu</c>, see <c>Docker/docker-compose.yml</c> profile <c>rtu_over_tcp</c>) or a
-///     real serial→Ethernet Modbus gateway. Mirrors <see cref="ModbusSimulatorFixture"/> but reads
-///     <c>MODBUS_RTU_SIM_ENDPOINT</c> (default <c>10.100.0.35:5021</c> — the shared Docker host, a
-///     distinct port from the standard profile's <c>:5020</c> so the two fixtures co-run). TCP-connects
-///     once at fixture construction; each test checks <see cref="SkipReason"/> and calls
-///     <c>Assert.Skip</c> when the endpoint was unreachable, so a dev box without a running simulator
-///     still passes `dotnet test` cleanly.
-/// </summary>
-/// <remarks>
-///     Same one-shot-probe discipline as <see cref="ModbusSimulatorFixture"/>: the probe socket is
-///     not held for the life of the fixture (tests open their own <see cref="ModbusRtuOverTcpTransport"/>
-///     against the same endpoint), and the fixture is a collection fixture so the probe runs once per
-///     session rather than per test.
-/// </remarks>
-public sealed class ModbusRtuOverTcpFixture : IAsyncDisposable
-{
-    // :5021 (not the standard profile's :5020) so the rtu_over_tcp container can co-run with the
-    // standard container on the shared Docker host. 10.100.0.35 = the shared Docker host (see
-    // CLAUDE.md "Docker Workflow"). Override with MODBUS_RTU_SIM_ENDPOINT to point at a real
-    // serial→Ethernet Modbus gateway, or a locally-running container.
-    private const string DefaultEndpoint = "10.100.0.35:5021";
-    private const string EndpointEnvVar = "MODBUS_RTU_SIM_ENDPOINT";
-
-    /// <summary>Gets the host address of the RTU-over-TCP Modbus simulator.</summary>
-    public string Host { get; }
-
-    /// <summary>Gets the port of the RTU-over-TCP Modbus simulator.</summary>
-    public int Port { get; }
-
-    /// <summary>Gets the skip reason if the simulator is unreachable; otherwise null.</summary>
-    public string? SkipReason { get; }
-
-    /// <summary>Initializes a new instance of the <see cref="ModbusRtuOverTcpFixture"/> class.</summary>
-    public ModbusRtuOverTcpFixture()
-    {
-        var raw = Environment.GetEnvironmentVariable(EndpointEnvVar) ?? DefaultEndpoint;
-        var parts = raw.Split(':', 2);
-        Host = parts[0];
-        Port = parts.Length == 2 && int.TryParse(parts[1], out var p) ? p : 502;
-
-        try
-        {
-            // Force IPv4 on the probe — pymodbus binds 0.0.0.0 (IPv4 only) while .NET default-resolves
-            // "localhost" → IPv6 ::1 first and only then tries IPv4, surfacing as a 2s timeout under
-            // .NET 10. Resolving + dialing explicit IPv4 sidesteps the dual-stack ordering. (Same
-            // rationale as ModbusSimulatorFixture.)
-            using var client = new TcpClient(System.Net.Sockets.AddressFamily.InterNetwork);
-            var task = client.ConnectAsync(
-                System.Net.Dns.GetHostAddresses(Host)
-                    .FirstOrDefault(a => a.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)
-                    ?? System.Net.IPAddress.Loopback,
-                Port);
-            if (!task.Wait(TimeSpan.FromSeconds(2)) || !client.Connected)
-            {
-                SkipReason = $"RTU-over-TCP Modbus simulator at {Host}:{Port} did not accept a TCP connection within 2s. " +
-                             $"Start the pymodbus Docker container (docker compose -f Docker/docker-compose.yml --profile rtu_over_tcp up -d --build) " +
-                             $"or override {EndpointEnvVar}, then re-run.";
-            }
-        }
-        catch (Exception ex)
-        {
-            SkipReason = $"RTU-over-TCP Modbus simulator at {Host}:{Port} unreachable: {ex.GetType().Name}: {ex.Message}. " +
-                         $"Start the pymodbus Docker container (docker compose -f Docker/docker-compose.yml --profile rtu_over_tcp up -d --build) " +
-                         $"or override {EndpointEnvVar}, then re-run.";
-        }
-    }
-
-    /// <inheritdoc />
-    public ValueTask DisposeAsync() => ValueTask.CompletedTask;
-}
-
-[Xunit.CollectionDefinition(Name)]
-public sealed class ModbusRtuOverTcpCollection : Xunit.ICollectionFixture<ModbusRtuOverTcpFixture>
-{
-    public const string Name = "ModbusRtuOverTcp";
-}

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/ModbusRtuOverTcpTests.cs

@@ -1,94 +0,0 @@
-using Shouldly;
-using Xunit;
-using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
-
-namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests;
-
-/// <summary>
-///     End-to-end round-trip against the <c>rtu_over_tcp.json</c> pymodbus profile (or a real
-///     serial→Ethernet Modbus gateway when <c>MODBUS_RTU_SIM_ENDPOINT</c> points at one), driving the
-///     full <see cref="ModbusDriver"/> + real <see cref="ModbusRtuOverTcpTransport"/> stack with
-///     <see cref="ModbusTransportMode.RtuOverTcp"/>. Proves the driver reads a seeded holding register
-///     and writes+reads-back a scratch register when the wire carries RTU framing
-///     (<c>[addr][PDU][CRC-16]</c>, no MBAP header) rather than Modbus/TCP.
-/// </summary>
-/// <remarks>
-///     pymodbus 3.13's simulator honors <c>framer=rtu</c> on a TCP server — confirmed on the wire
-///     (controller spike, 2026-07-24): a raw RTU FC03 read of HR[5] returned
-///     <c>01 03 02 00 05 78 47</c>, a pure RTU frame with no MBAP header (data 0x0005 = 5). So the
-///     fixture is the plain pymodbus simulator with framer/port swapped — no stdlib fallback server.
-/// </remarks>
-[Collection(ModbusRtuOverTcpCollection.Name)]
-[Trait("Category", "Integration")]
-[Trait("Device", "RtuOverTcp")]
-public sealed class ModbusRtuOverTcpTests(ModbusRtuOverTcpFixture sim)
-{
-    /// <summary>Reads a seeded holding register (HR[5]=5) over RTU-over-TCP framing.</summary>
-    [Fact]
-    public async Task Reads_a_seeded_holding_register_over_rtu_framing()
-    {
-        if (sim.SkipReason is not null) Assert.Skip(sim.SkipReason);
-        var opts = new ModbusDriverOptions
-        {
-            Host = sim.Host,
-            Port = sim.Port,
-            UnitId = 1,
-            Transport = ModbusTransportMode.RtuOverTcp,
-            Timeout = TimeSpan.FromSeconds(2),
-            Probe = new ModbusProbeOptions { Enabled = false },
-            RawTags = ModbusRawTags.Entries([
-                new ModbusTagDefinition(
-                    Name: "HR5",
-                    Region: ModbusRegion.HoldingRegisters,
-                    Address: 5,
-                    DataType: ModbusDataType.UInt16,
-                    Writable: false),
-            ]),
-        };
-        await using var driver = new ModbusDriver(opts, driverInstanceId: "modbus-rtu-int");
-        await driver.InitializeAsync(driverConfigJson: "{}", TestContext.Current.CancellationToken);
-
-        var results = await driver.ReadAsync(["HR5"], TestContext.Current.CancellationToken);
-
-        results.Count.ShouldBe(1);
-        results[0].StatusCode.ShouldBe(0u);       // Good
-        results[0].Value.ShouldBe((ushort)5);     // HR[5] seeded = address-as-value
-    }
-
-    /// <summary>Writes then reads back a scratch holding register (HR[200]) over RTU-over-TCP framing.</summary>
-    [Fact]
-    public async Task Writes_and_reads_back_a_holding_register_over_rtu_framing()
-    {
-        if (sim.SkipReason is not null) Assert.Skip(sim.SkipReason);
-        var opts = new ModbusDriverOptions
-        {
-            Host = sim.Host,
-            Port = sim.Port,
-            UnitId = 1,
-            Transport = ModbusTransportMode.RtuOverTcp,
-            Timeout = TimeSpan.FromSeconds(2),
-            Probe = new ModbusProbeOptions { Enabled = false },
-            RawTags = ModbusRawTags.Entries([
-                new ModbusTagDefinition(
-                    Name: "HR200",
-                    Region: ModbusRegion.HoldingRegisters,
-                    Address: 200,
-                    DataType: ModbusDataType.UInt16,
-                    Writable: true),
-            ]),
-        };
-        await using var driver = new ModbusDriver(opts, driverInstanceId: "modbus-rtu-int-w");
-        await driver.InitializeAsync(driverConfigJson: "{}", TestContext.Current.CancellationToken);
-
-        var writes = await driver.WriteAsync(
-            [new WriteRequest("HR200", (ushort)4242)],
-            TestContext.Current.CancellationToken);
-        writes.Count.ShouldBe(1);
-        writes[0].StatusCode.ShouldBe(0u);
-
-        var back = await driver.ReadAsync(["HR200"], TestContext.Current.CancellationToken);
-        back.Count.ShouldBe(1);
-        back[0].StatusCode.ShouldBe(0u);
-        back[0].Value.ShouldBe((ushort)4242);
-    }
-}

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Tests/ModbusCrcTests.cs

@@ -1,27 +0,0 @@
-using Shouldly;
-using Xunit;
-
-namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.Tests;
-
-public sealed class ModbusCrcTests
-{
-    // Known CRC-16/MODBUS vectors (init 0xFFFF, poly 0xA001). CRC returned as ushort;
-    // on the wire it is appended low-byte-first.
-    [Theory]
-    // FC03 read HR: unit 1, addr 0, qty 1  -> CRC 0x0A84  (bytes 84 0A on the wire)
-    [InlineData(new byte[] { 0x01, 0x03, 0x00, 0x00, 0x00, 0x01 }, (ushort)0x0A84)]
-    // "123456789" canonical check value for CRC-16/MODBUS = 0x4B37
-    [InlineData(new byte[] { 0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x38,0x39 }, (ushort)0x4B37)]
-    public void Compute_matches_known_vectors(byte[] frame, ushort expected)
-        => ModbusCrc.Compute(frame).ShouldBe(expected);
-
-    [Fact]
-    public void AppendLowByteFirst_writes_lo_then_hi()
-    {
-        var body = new byte[] { 0x01, 0x03, 0x00, 0x00, 0x00, 0x01 };
-        var withCrc = ModbusCrc.Append(body);
-        withCrc.Length.ShouldBe(body.Length + 2);
-        withCrc[^2].ShouldBe((byte)0x84); // CRC low byte
-        withCrc[^1].ShouldBe((byte)0x0A); // CRC high byte
-    }
-}

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Tests/ModbusEdgeCaseValidationTests.cs

@@ -14,7 +14,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.Tests;
 ///     (2) Sub-second <see cref="TimeSpan"/> values on <c>ModbusKeepAliveOptions.Time</c> /
 ///     <c>Interval</c> — the int-cast in <c>EnableKeepAlive</c> truncated <c>500&#160;ms</c> to
 ///     <c>0</c>, which most OSes interpret as "use the default", silently defeating the
-///     configured timing. <c>ModbusSocketLifecycle.ClampToWholeSeconds</c> rounds up to a minimum
+///     configured timing. <c>ModbusTcpTransport.ClampToWholeSeconds</c> rounds up to a minimum
 ///     of 1&#160;second.
 /// </summary>
 [Trait("Category", "Unit")]
@@ -70,7 +70,7 @@ public sealed class ModbusEdgeCaseValidationTests
     [InlineData(60_000, 60)]
     public void ClampToWholeSeconds_rounds_up_to_at_least_one_second(int ms, int expected)
     {
-        ModbusSocketLifecycle.ClampToWholeSeconds(TimeSpan.FromMilliseconds(ms)).ShouldBe(expected);
+        ModbusTcpTransport.ClampToWholeSeconds(TimeSpan.FromMilliseconds(ms)).ShouldBe(expected);
     }
 
     /// <summary>Verifies that negative time spans are treated as one second.</summary>
@@ -80,6 +80,6 @@ public sealed class ModbusEdgeCaseValidationTests
         // Defensive — operators occasionally configure a negative TimeSpan thinking it disables
         // the feature. The OS would reject the negative int — clamping to 1 keeps the socket
         // valid until the operator fixes the config.
-        ModbusSocketLifecycle.ClampToWholeSeconds(TimeSpan.FromSeconds(-5)).ShouldBe(1);
+        ModbusTcpTransport.ClampToWholeSeconds(TimeSpan.FromSeconds(-5)).ShouldBe(1);
     }
 }

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Tests/ModbusRtuFramingTests.cs

@@ -1,134 +0,0 @@
-using Shouldly;
-using Xunit;
-
-namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.Tests;
-
-public sealed class ModbusRtuFramingTests
-{
-    private static MemoryStream Canned(params byte[] frame) => new(frame);
-
-    [Fact]
-    public void BuildAdu_prefixes_unit_and_appends_crc()
-    {
-        var adu = ModbusRtuFraming.BuildAdu(0x01, new byte[] { 0x03, 0x00, 0x00, 0x00, 0x01 });
-        adu.ShouldBe(new byte[] { 0x01, 0x03, 0x00, 0x00, 0x00, 0x01, 0x84, 0x0A });
-    }
-
-    [Fact]
-    public async Task ReadResponse_FC03_returns_bare_pdu()
-    {
-        // addr=01 fc=03 byteCount=02 data=00 0A  + CRC(lo,hi)
-        var body = new byte[] { 0x01, 0x03, 0x02, 0x00, 0x0A };
-        var frame = ModbusCrc.Append(body);
-        await using var s = Canned(frame);
-        var pdu = await ModbusRtuFraming.ReadResponsePduAsync(s, 0x01, TestContext.Current.CancellationToken);
-        pdu.ShouldBe(new byte[] { 0x03, 0x02, 0x00, 0x0A }); // fc + byteCount + data, no addr/CRC
-    }
-
-    [Fact]
-    public async Task ReadResponse_exception_frame_throws_ModbusException()
-    {
-        // addr=01 fc=0x83 exc=0x02 + CRC
-        var frame = ModbusCrc.Append(new byte[] { 0x01, 0x83, 0x02 });
-        await using var s = Canned(frame);
-        var ex = await Should.ThrowAsync<ModbusException>(
-            ModbusRtuFraming.ReadResponsePduAsync(s, 0x01, TestContext.Current.CancellationToken));
-        ex.FunctionCode.ShouldBe((byte)0x03);
-        ex.ExceptionCode.ShouldBe((byte)0x02);
-    }
-
-    [Fact]
-    public async Task ReadResponse_bad_crc_throws_desync()
-    {
-        var frame = ModbusCrc.Append(new byte[] { 0x01, 0x03, 0x02, 0x00, 0x0A });
-        frame[^1] ^= 0xFF; // corrupt CRC high byte
-        await using var s = Canned(frame);
-        var ex = await Should.ThrowAsync<ModbusTransportDesyncException>(
-            ModbusRtuFraming.ReadResponsePduAsync(s, 0x01, TestContext.Current.CancellationToken));
-        ex.Reason.ShouldBe(ModbusTransportDesyncException.DesyncReason.CrcMismatch);
-    }
-
-    [Fact]
-    public async Task ReadResponse_FC06_write_echo_returns_four_byte_pdu()
-    {
-        // addr=01 fc=06 addr=00 07 value=00 2A + CRC  -> PDU = 06 00 07 00 2A
-        var frame = ModbusCrc.Append(new byte[] { 0x01, 0x06, 0x00, 0x07, 0x00, 0x2A });
-        await using var s = Canned(frame);
-        var pdu = await ModbusRtuFraming.ReadResponsePduAsync(s, 0x01, TestContext.Current.CancellationToken);
-        pdu.ShouldBe(new byte[] { 0x06, 0x00, 0x07, 0x00, 0x2A });
-    }
-
-    [Fact]
-    public async Task ReadResponse_wrong_unit_address_throws_desync()
-    {
-        // CRC-valid FC03 frame addressed to unit 0x02, but we asked for 0x01 -> unit-mismatch desync.
-        var frame = ModbusCrc.Append(new byte[] { 0x02, 0x03, 0x02, 0x00, 0x0A });
-        await using var s = Canned(frame);
-        var ex = await Should.ThrowAsync<ModbusTransportDesyncException>(
-            ModbusRtuFraming.ReadResponsePduAsync(s, 0x01, TestContext.Current.CancellationToken));
-        ex.Reason.ShouldBe(ModbusTransportDesyncException.DesyncReason.UnitMismatch);
-    }
-
-    [Fact]
-    public async Task ReadResponse_FC03_deframes_correctly_when_delivered_in_dribbles()
-    {
-        // Same valid FC03 frame, but the stream hands back only 1-2 bytes per ReadAsync — proves
-        // the ReadExactlyAsync accumulation loop reassembles a length-less frame across many reads.
-        var frame = ModbusCrc.Append(new byte[] { 0x01, 0x03, 0x02, 0x00, 0x0A });
-        await using var s = new DribbleStream(frame, chunk: 2);
-        var pdu = await ModbusRtuFraming.ReadResponsePduAsync(s, 0x01, TestContext.Current.CancellationToken);
-        pdu.ShouldBe(new byte[] { 0x03, 0x02, 0x00, 0x0A });
-    }
-
-    [Fact]
-    public async Task ReadResponse_stream_ends_early_throws_desync()
-    {
-        // Only the first 4 bytes of a 7-byte FC03 frame are available, then EOF (ReadAsync returns 0)
-        // -> the truncation path in ReadExactlyAsync must surface a desync, not hang or mis-parse.
-        var frame = ModbusCrc.Append(new byte[] { 0x01, 0x03, 0x02, 0x00, 0x0A });
-        var truncated = frame[..4];
-        await using var s = new DribbleStream(truncated, chunk: 2);
-        var ex = await Should.ThrowAsync<ModbusTransportDesyncException>(
-            ModbusRtuFraming.ReadResponsePduAsync(s, 0x01, TestContext.Current.CancellationToken));
-        ex.Reason.ShouldBe(ModbusTransportDesyncException.DesyncReason.TruncatedFrame);
-    }
-
-    /// <summary>
-    ///     A read-only test double that dribbles its backing bytes out at most <c>chunk</c> at a time
-    ///     per <see cref="ReadAsync(Memory{byte}, CancellationToken)"/> call, then returns 0 (EOF)
-    ///     once exhausted. Exercises the partial-read accumulation loop and the truncation → desync
-    ///     path that a single-shot <see cref="MemoryStream"/> never reaches.
-    /// </summary>
-    private sealed class DribbleStream(byte[] data, int chunk) : Stream
-    {
-        private int _pos;
-
-        public override int Read(byte[] buffer, int offset, int count)
-        {
-            var n = Math.Min(Math.Min(chunk, count), data.Length - _pos);
-            if (n <= 0) return 0;
-            Array.Copy(data, _pos, buffer, offset, n);
-            _pos += n;
-            return n;
-        }
-
-        public override ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default)
-        {
-            var n = Math.Min(Math.Min(chunk, buffer.Length), data.Length - _pos);
-            if (n <= 0) return ValueTask.FromResult(0);
-            data.AsSpan(_pos, n).CopyTo(buffer.Span);
-            _pos += n;
-            return ValueTask.FromResult(n);
-        }
-
-        public override bool CanRead => true;
-        public override bool CanSeek => false;
-        public override bool CanWrite => false;
-        public override long Length => data.Length;
-        public override long Position { get => _pos; set => throw new NotSupportedException(); }
-        public override void Flush() { }
-        public override long Seek(long offset, SeekOrigin origin) => throw new NotSupportedException();
-        public override void SetLength(long value) => throw new NotSupportedException();
-        public override void Write(byte[] buffer, int offset, int count) => throw new NotSupportedException();
-    }
-}

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Tests/ModbusRtuOverTcpTransportTests.cs

@@ -1,110 +0,0 @@
-using Shouldly;
-using Xunit;
-
-namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.Tests;
-
-/// <summary>
-///     Exercises <see cref="ModbusRtuOverTcpTransport"/>'s send/receive orchestration, single-flight,
-///     and per-op deadline against an in-memory duplex fake injected through the <c>ForTest</c> seam —
-///     no real socket. The fake records the request ADU the transport writes and replays a canned RTU
-///     response on read, or blocks forever (honouring cancellation) when <c>stall</c> is set.
-/// </summary>
-[Trait("Category", "Unit")]
-public sealed class ModbusRtuOverTcpTransportTests
-{
-    [Fact]
-    public async Task SendAsync_writes_rtu_adu_and_returns_deframed_pdu()
-    {
-        // Response the fake gateway will emit: FC03, 1 reg = 0x000A.
-        var response = ModbusCrc.Append(new byte[] { 0x01, 0x03, 0x02, 0x00, 0x0A });
-        var fake = new CapturingDuplexStream(response);
-
-        await using var transport = ModbusRtuOverTcpTransport.ForTest(fake, TimeSpan.FromSeconds(2));
-        var pdu = await transport.SendAsync(0x01, new byte[] { 0x03, 0x00, 0x00, 0x00, 0x01 },
-            TestContext.Current.CancellationToken);
-
-        pdu.ShouldBe(new byte[] { 0x03, 0x02, 0x00, 0x0A });
-        // The request went out as an RTU ADU: unit + pdu + CRC, NO MBAP header.
-        fake.Written.ShouldBe(new byte[] { 0x01, 0x03, 0x00, 0x00, 0x00, 0x01, 0x84, 0x0A });
-    }
-
-    [Fact]
-    public async Task SendAsync_exception_pdu_surfaces_ModbusException()
-    {
-        var response = ModbusCrc.Append(new byte[] { 0x01, 0x83, 0x02 });
-        var fake = new CapturingDuplexStream(response);
-        await using var transport = ModbusRtuOverTcpTransport.ForTest(fake, TimeSpan.FromSeconds(2));
-        await Should.ThrowAsync<ModbusException>(
-            transport.SendAsync(0x01, new byte[] { 0x03, 0x00, 0x00, 0x00, 0x01 },
-                TestContext.Current.CancellationToken));
-    }
-
-    [Fact]
-    public async Task SendAsync_stalled_gateway_hits_per_op_deadline()
-    {
-        var fake = new CapturingDuplexStream(respondBytes: Array.Empty<byte>(), stall: true);
-        await using var transport = ModbusRtuOverTcpTransport.ForTest(fake, TimeSpan.FromMilliseconds(200));
-        await Should.ThrowAsync<ModbusTransportDesyncException>(
-            transport.SendAsync(0x01, new byte[] { 0x03, 0x00, 0x00, 0x00, 0x01 },
-                TestContext.Current.CancellationToken));
-    }
-
-    /// <summary>
-    ///     In-memory duplex <see cref="Stream"/> test double: records everything written and replays
-    ///     <c>respondBytes</c> on read. When <c>stall</c> is set the read blocks until its cancellation
-    ///     token fires (simulating a frozen gateway) so the transport's per-op deadline is exercised.
-    /// </summary>
-    private sealed class CapturingDuplexStream : Stream
-    {
-        private readonly byte[] _response;
-        private readonly bool _stall;
-        private readonly MemoryStream _written = new();
-        private int _readPos;
-
-        public CapturingDuplexStream(byte[] respondBytes, bool stall = false)
-        {
-            _response = respondBytes;
-            _stall = stall;
-        }
-
-        /// <summary>Gets the bytes the transport wrote to this stream (the request ADU).</summary>
-        public byte[] Written => _written.ToArray();
-
-        public override bool CanRead => true;
-        public override bool CanSeek => false;
-        public override bool CanWrite => true;
-        public override long Length => throw new NotSupportedException();
-        public override long Position { get => throw new NotSupportedException(); set => throw new NotSupportedException(); }
-
-        public override async ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken ct = default)
-        {
-            if (_stall)
-            {
-                // Frozen gateway: never answer. Block until the per-op deadline (or caller) cancels.
-                var tcs = new TaskCompletionSource();
-                await using (ct.Register(() => tcs.TrySetCanceled(ct)))
-                    await tcs.Task.ConfigureAwait(false);
-                return 0; // unreachable — the await above always throws when cancelled
-            }
-
-            var remaining = _response.Length - _readPos;
-            if (remaining <= 0) return 0;
-            var n = Math.Min(remaining, buffer.Length);
-            _response.AsSpan(_readPos, n).CopyTo(buffer.Span);
-            _readPos += n;
-            return n;
-        }
-
-        public override async ValueTask WriteAsync(ReadOnlyMemory<byte> buffer, CancellationToken ct = default)
-        {
-            await _written.WriteAsync(buffer, ct).ConfigureAwait(false);
-        }
-
-        public override Task FlushAsync(CancellationToken ct) => Task.CompletedTask;
-        public override void Flush() { }
-        public override int Read(byte[] buffer, int offset, int count) => throw new NotSupportedException();
-        public override void Write(byte[] buffer, int offset, int count) => throw new NotSupportedException();
-        public override long Seek(long offset, SeekOrigin origin) => throw new NotSupportedException();
-        public override void SetLength(long value) => throw new NotSupportedException();
-    }
-}