# Architecture Review 06 — Gateway Integrations (Galaxy Driver + Historian Gateway Driver)

- **Date:** 2026-07-08
- **Commit:** `9cad9ed0` (master)
- **Scope:**
  - `src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy` (+ `.Contracts`, `.Browser`)
  - `src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway`
  - Test coverage: `tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests`, `.Galaxy.Browser.Tests`, `.Historian.Gateway.Tests`
  - Peripheral (read for context, not reviewed in depth): `Runtime/Historian/*` (recorder, options), `AddressSpaceApplier` provisioning/subscription hooks, `OtOpcUaNodeManager` tie-cluster paging.
- **Dimensions:** Stability, Performance, Conventions, Underdeveloped Areas.

---

## Architecture Overview

### Galaxy driver data flow (mxaccessgw)

`GalaxyDriver` (`GalaxyDriver.cs`) is a standard Tier-A in-process Equipment-kind driver registered under type name `GalaxyMxGateway`. All Galaxy access flows over gRPC to the external **mxaccessgw** gateway (sibling repo), consumed via the Gitea-feed packages `ZB.MOM.WW.MxGateway.Client` / `.Contracts` (`MxCommand` / `MxEvent` protos). The driver holds **three logical gRPC clients**:

1. **Worker session** — `GalaxyMxSession` wraps `MxGatewayClient.OpenSessionAsync` + MXAccess `Register`. All data-plane traffic rides it:
   - **Subscribe** — `GatewayGalaxySubscriber.SubscribeBulkAsync` (session-level `SetBufferedUpdateInterval` applied first, cached last-applied value), events consumed by the shared `EventPump` off the bidirectional `StreamEvents` RPC, fanned out through `SubscriptionRegistry`'s handle→subscription reverse map onto `OnDataChange`.
   - **Read** — MxAccess has no one-shot read; `ReadViaSubscribeOnceAsync` synthesises Read as SubscribeBulk → first-event wait per handle → UnsubscribeBulk.
   - **Write** — `GatewayGalaxyDataWriter`: lazy `AddItem` (or borrow a live handle from the subscription registry), `AdviseSupervisory` once per handle (required for commit under WriteUserId=0), then raw `Write` or `WriteSecured` routed on the discovery-captured per-tag `SecurityClassification`.
2. **Session-less client** (`_ownedMxClient`) — the always-on central alarm monitor: `GatewayGalaxyAlarmFeed` (StreamAlarms: active-alarm snapshot → `snapshot_complete` → live transitions, self-reconnecting) and `GatewayGalaxyAlarmAcknowledger` (unary `AcknowledgeAlarm`).
3. **Repository client** (`GalaxyRepositoryClient`) — hierarchy browse for `DiscoverAsync` (via `IGalaxyHierarchySource` → `GalaxyDiscoverer`) and the `DeployWatcher` deploy-event stream that raises `IRediscoverable.OnRediscoveryNeeded`.

Recovery is owned by `ReconnectSupervisor` (Healthy → TransportLost → Reopening → Replaying → Healthy, capped exponential backoff, never gives up): the `EventPump` stream fault feeds `ReportTransportFailure`; reopen routes through `GalaxyMxSession.RecreateAsync` (dispose stale session + client, rebuild) and invalidates the writer's handle/advise caches; replay recreates the EventPump then re-issues SubscribeBulk per tracked subscription and `Rebind`s the registry with the fresh handles. Host connectivity is surfaced through `HostStatusAggregator` (transport state from the supervisor + per-platform `ScanState` probes via `PerPlatformProbeWatcher`).

### Historian gateway data flow (HistorianGateway sidecar)

`Driver.Historian.Gateway` is the **sole historian backend**, consuming the `ZB.MOM.WW.HistorianGateway.Client` package (`historian_gateway.v1`) behind the proto-typed `IHistorianGatewayClient` seam (`HistorianGatewayClientAdapter` is a pure pass-through; channels are lazy — no I/O at construction). Four independent paths, each with **its own gRPC channel** to the same sidecar (documented deliberate trade-off, `GatewayHistorianServiceCollectionExtensions.cs:57-64`):

1. **Read** — `GatewayHistorianDataSource` (`IHistorianDataSource`): OPC UA HistoryRead Raw/Processed/AtTime/Events → `ReadRaw` / `ReadAggregate` / `ReadAtTime` / `ReadEvents`; at-time replies re-aligned one-snapshot-per-requested-timestamp; health counters under a single lock. Tie-cluster paging (`MaxTieClusterOverfetch`) lives server-side in `OtOpcUaNodeManager` (~line 2200), bound from `ServerHistorianOptions`.
2. **Alarm history write** — `GatewayAlarmHistorianWriter` (`SendEvent` per event) behind the durable `SqliteStoreAndForwardSink`; maps every outcome (ack, typed client exceptions, raw `RpcException`) to exactly one `Ack` / `RetryPlease` / `PermanentFail` per event and never throws.
3. **Continuous historization** — `ContinuousHistorizationRecorder` (Runtime actor) taps the dependency-mux value fan-out, appends to the crash-safe `FasterLogHistorizationOutbox` (PerEntry fsync or Periodic commit; bounded drop-oldest capacity; startup recovery scan), drains through `GatewayHistorianValueWriter` (`WriteLiveValues`, non-throwing bool).
4. **Tag provisioning** — `GatewayTagProvisioner` (`EnsureTags`), dispatched fire-and-forget from `AddressSpaceApplier.Apply` with a tally log; non-historizable data types skipped; can never block or fail a deploy.

---

## Findings

### 1. Stability

#### S-1 (High) — Galaxy write success is optimistic; a committed-write failure can never surface

`GatewayGalaxyDataWriter.TranslateReply` (`GatewayGalaxyDataWriter.cs:281-302`) honours the protocol status and the first MXAccess status row, **defaulting to `Good` when the statuses array is empty** — and the gateway's write execution is effectively fire-and-forget past dispatch (the reply reflects command acceptance, not the eventual COM-side commit). Two concrete consequences:

- The supervisory-advise failure path (`GatewayGalaxyDataWriter.cs:234-243`) logs a warning, forgets the handle, and **lets the write proceed anyway** — but the file's own comment (`:163-165`) states a raw Write without supervisory advise "doesn't throw (reply looks OK) but the value never reaches the galaxy". That is a silent write loss returning `Good` to the OPC UA client.
- The server's write-outcome self-correction (#5, reverts the node on a failed device write) can structurally never trigger for Galaxy, so a lost write leaves a phantom-Good node value indefinitely.

**Blast radius:** operator writes (WriteOperate-gated) to Galaxy attributes that silently don't commit, with no Bad status, no health degradation, no metric. Recommendation: (a) return `Uncertain` (not proceed-to-Good) when supervisory advise fails; (b) pursue a gateway-side `WriteComplete` correlation (the gw backlog's `OnWriteComplete` event family already exists in the proto — `EventPump.cs:200-206` filters it out) so the reply/statuses row carries the real commit outcome; (c) add a `galaxy.writes.unconfirmed` counter in the interim.

#### S-2 (Medium) — EventPump saturation drops the *newest* events (inverted staleness bias)

`EventPump.RunAsync` (`EventPump.cs:128-140`) uses `TryWrite` against a bounded channel: when the fan-out consumer stalls, the **just-arrived** event is dropped and 50 000 stale queued events are preserved. For last-value-wins OPC UA telemetry this is the wrong bias — after a stall clears, subscribers replay old values and the freshest one may be the dropped one. The drop is at least metered (`galaxy.events.dropped`). Recommendation: per-item-handle conflation (keep newest per handle) or drop-oldest ring semantics; either preserves the no-backpressure requirement while keeping recent data.

#### S-3 (Medium) — `ReadViaSubscribeOnceAsync` can wait forever on a non-cancellable token

The read synthesis (`GalaxyDriver.cs:738-755`) fills pending snapshots with `BadTimeout` **only via `cancellationToken.Register`**. If a caller passes `CancellationToken.None` (or a token that never fires) and a successfully subscribed tag never publishes an initial event (gateway hiccup between SubscribeBulk and first push), the awaits at `:753` never complete and the read hangs, holding the subscription open. Recommendation: race each pending TCS against an internal deadline derived from `DefaultCallTimeoutSeconds` / `PublishingIntervalMs` regardless of the caller's token.

#### S-4 (Medium) — Transport-failure detection is EventPump-only; a subscription-less driver never degrades

`ReconnectSupervisor.ReportTransportFailure` has exactly one production caller: the EventPump stream-fault callback (`GalaxyDriver.cs:929-949`). The pump only starts on the first subscribe/read. A driver doing only writes (or idle after discovery) whose gateway restarts will keep `GetHealth() == Healthy`; each write then fails per-request with `BadCommunicationError`, but no reopen/replay/`Degraded` transition ever runs, and the stale session persists until something subscribes. Failed unary RPCs (SubscribeBulk, Write, AcknowledgeAlarm) do not feed the supervisor either. Recommendation: report classified transport exceptions from the write/subscribe paths into the supervisor (idempotent by design, so this is cheap).

#### S-5 (Medium) — FasterLog outbox `RemoveAsync` truncates the FIFO prefix; out-of-order acks silently drop unacked entries

`FasterLogHistorizationOutbox.RemoveAsync` (`FasterLogHistorizationOutbox.cs:158-182`) removes the target **plus every older live entry** and truncates the log to the target's successor. The contract "recorder acks in FIFO order" is enforced only by comment. If the drain ever acks a mid-batch id first (e.g. per-tag partial write success in a future recorder change), all older unacked values are durably discarded without incrementing `DroppedCount`. Recommendation: count and warn when the prefix removal drops non-target entries, or make the API batch-oriented (`RemoveThroughAsync`) so the semantics are explicit at the call site.

#### S-6 (Medium) — Historian health snapshot's connection flags are dormant in production

`GatewayHistorianDataSource.RefreshConnectionStateAsync` (`GatewayHistorianDataSource.cs:219-244`) is documented as "intended to be driven by a periodic health hosted-service", but **no production caller exists** — only `GatewayHealthSnapshotTests` invokes it. `ProcessConnectionOpen` / `EventConnectionOpen` in `GetHealthSnapshot` are therefore permanently `false` in a deployed host, which any dashboard consuming the snapshot will read as "historian down" (or, if ignored, the flags are dead weight). Same shape as the memory's "register-AND-pass-into-consumer" trap that bit `GatewayTagProvisioner` in PR #423. Recommendation: add the periodic refresh hosted-service (or fold a refresh into the existing health probe cadence), or remove the flags from the snapshot.

#### S-7 (Low) — Alarm feed reconnect has no backoff

`GatewayGalaxyAlarmFeed.RunAsync` (`GatewayGalaxyAlarmFeed.cs:102-148`) re-opens on a fixed 5 s delay forever. `DeployWatcher` (capped exponential + jitter, `DeployWatcher.cs:212-233`) and `ReconnectSupervisor` both do this properly. A dead gateway gets hammered every 5 s per driver instance. Cosmetic at this scale, but inconsistent; align on capped exponential.

#### S-8 (Low) — `GalaxyMxSession` state is unsynchronized across reopen

`_session` / `_connected` (`GalaxyMxSession.cs:28-32`) are plain fields; `RecreateAsync` tears down while concurrent writers/subscribers may hold or fetch `Session`. In practice the supervisor's single-flight recovery plus the per-call try/catch (mapped to `BadCommunicationError`) contain it, and the caches are invalidated post-reopen — but the safety is emergent, not designed. Acceptable; document the invariant on `Session`.

#### S-9 (Positive) — Store-and-forward + outbox crash-safety discipline is strong

- `GatewayAlarmHistorianWriter` (`GatewayAlarmHistorianWriter.cs:66-118`) short-circuits remaining batch entries to `RetryPlease` on shutdown, classifies auth failures as retryable (an auth blip never dead-letters), and defaults unknowns to `PermanentFail` so poison events cannot loop.
- `FasterLogHistorizationOutbox` PerEntry mode fsyncs before append returns; recovery rebuilds the index from `BeginAddress`; the capacity-overflow-after-crash convergence case is analysed in-source (`FasterLogHistorizationOutbox.cs:200-204`).
- Partial-open recovery in `GalaxyMxSession.ConnectAsync` (`GalaxyMxSession.cs:95-101`) tears down half-open state so retry rebuilds cleanly.

#### S-10 (Positive) — TLS / API-key posture

Both integrations support TLS with CA pinning (`CaCertificatePath`), the historian's `AllowUntrustedServerCertificate` inversion is explicitly documented at the mapping site (`HistorianGatewayClientAdapter.cs:49-52`), and keys are never logged. See C-1 for the resolver.

### 2. Performance

#### P-1 (Medium) — Galaxy Read costs three gateway round-trips plus a publish wait per OPC UA Read

`ReadViaSubscribeOnceAsync` = SubscribeBulk + first-event wait (up to `PublishingIntervalMs`) + UnsubscribeBulk, with server-side AddItem/RemoveItem churn per read (`GalaxyDriver.cs:644-780`). This is forced by MxAccess (no one-shot read RPC) and is correctly batched per request, but a client polling via Read instead of subscribing multiplies gateway/COM load ~3×. Recommendation: document "subscribe, don't poll" as the supported pattern; consider a short-lived read-through cache keyed on full reference if polling clients appear.

#### P-2 (Medium) — Alarm-history drain is one unary `SendEvent` per event

`GatewayAlarmHistorianWriter.WriteBatchAsync` (`GatewayAlarmHistorianWriter.cs:66-80`) serializes the batch — deliberate poison-event isolation, but an alarm storm of N events costs N sequential RPC round-trips out of the SQLite drain worker. If the gateway ever grows a batched `SendEvents` with per-event status rows, adopt it; until then this is an accepted, well-documented ceiling.

#### P-3 (Low) — Four channels to the historian sidecar; two-plus to mxaccessgw

Each historian path owns its channel (read / alarm-write / provisioner / value-writer) and the Galaxy driver holds a session client, a session-less client, and a repository client. All are lazy, HTTP/2-multiplexed, and the trade-off (clean independent dispose ownership over channel sharing) is argued in-source (`GatewayHistorianServiceCollectionExtensions.cs:57-64`). No action; noted so nobody "optimizes" it into a shared-singleton dispose bug.

#### P-4 (Positive) — Fan-in/fan-out paths are indexed, bounded, and metered

- `SubscriptionRegistry` maintains a handle→subscriptions reverse map with a per-entry handle→fullRef index, so `ResolveSubscribers` is O(subscribers), not O(bindings) (`SubscriptionRegistry.cs:97-111`), and `TryResolveItemHandle` lets the writer skip AddItem for subscribed tags with a stale-entry cross-check (`:128-142`).
- Subscribe/replay correlation uses a one-pass result index (`GalaxyDriver.BuildResultIndex`, fixing a former O(n²) on the 50k-tag path).
- EventPump decouples network read from dispatch via a bounded channel (default 50 000, configurable) with received/dispatched/dropped counters.

#### P-5 (Low) — HistoryRead buffers whole replies; `maxEvents <= 0` is unbounded

`ReadRawAsync` / `ReadProcessedAsync` / `ReadEventsAsync` (`GatewayHistorianDataSource.cs:59-182`) drain the stream into a list before mapping. Raw reads are capped by `maxValuesPerNode`, but an events read with `maxEvents <= 0` collects without limit (the gateway's `RuntimeDb:EventReadMaxRows` is the only cap, and it's a remote deployment knob). The tie-cluster paging bound (`MaxTieClusterOverfetch`, validated > 0 in `ServerHistorianOptions.Validate`, enforced at `OtOpcUaNodeManager.cs:2200-2214`) is well-designed. Recommendation: clamp events reads to a server-side default cap when the caller passes 0.

#### P-6 (Low) — Outbox peek holds the state lock across disk I/O

`PeekBatchAsync` scans FasterLog from the logical head under `_state` (`FasterLogHistorizationOutbox.cs:140-155`), blocking a concurrent `AppendAsync`'s index update for the duration of a (mostly page-cached) disk scan. At the recorder's 64-entry default batch this is negligible; revisit only if drain batches grow.

### 3. Conventions

#### C-1 (Positive) — Secret handling is a model for the other drivers

`GalaxySecretRef` (`Galaxy.Contracts/GalaxySecretRef.cs`) resolves `env:` / `file:` / `dev:` / literal with fail-fast on unset env vars and a startup warning on unprefixed cleartext; it lives in Contracts so the runtime driver and the AdminUI browser share one implementation (`GalaxyDriverBrowser.cs:125`). The historian side takes `ServerHistorian__ApiKey` via env with a "never commit" doc contract and an empty-key `Validate()` warning. No key value is ever logged on either path.

#### C-2 (Positive) — Seam quality and driver-family consistency

- `IHistorianGatewayClient` is a clean single seam: every consumer (`GatewayHistorianDataSource`, `GatewayAlarmHistorianWriter`, `GatewayTagProvisioner`, `GatewayHistorianValueWriter`) depends only on it; `FakeHistorianGatewayClient` backs the offline suite; the adapter is a zero-translation pass-through.
- The Galaxy capability seams (`IGalaxyHierarchySource`, `IGalaxyDataReader/Writer`, `IGalaxySubscriber`, `IGalaxyAlarmFeed/Acknowledger`) plus the internal test ctor mirror the protocol-driver pattern; tracing decorators (`Traced*`) wrap the production seams without an OpenTelemetry dependency.
- `GalaxyDriverFactoryExtensions.CreateInstance` throws precise, instance-named errors on missing required fields (`GalaxyDriverFactoryExtensions.cs:56-75`), and `GalaxyDriverProbe` uses `JsonStringEnumConverter` (the FB-9/FB-10 enum-serialization lesson applied).

#### C-3 (Medium) — The historian seam leaks wire types by design; keep it contained

`IHistorianGatewayClient` signatures use `HistorianGateway.Contracts.Grpc` types (`HistorianSample`, `RetrievalMode`, `WriteAck`, ...) — documented as deliberate (`IHistorianGatewayClient.cs:5-11`). This is fine while the driver is the only consumer, but the pure `Mapping/` layer is the real anti-corruption boundary: any future consumer must sit **above** `GatewayHistorianDataSource`, never on the seam. Worth a one-line guard note in the interface doc.

#### C-4 (Low) — Options-validation styles diverge

Galaxy: throw-on-construct for required fields; DataAnnotations attributes on the records are decorative (nothing runs `Validator`). Historian: `Validate()` returns operator warnings and never throws (registration logs them). Both are defensible, but the repo now has two idioms for "driver-adjacent options validation". Pick one for new sections (the warnings-list style is the friendlier operational contract).

#### C-5 (Low) — Retired Wonderware project directories still on disk

`src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware{,.Client,.Client.Contracts}` (and their test dirs) remain in the tree but are absent from `ZB.MOM.WW.OtOpcUa.slnx` (0 references). Dead directories invite grep noise and accidental resurrection; delete them (git history preserves the code).

#### C-6 (Low) — EventPump silently drops unknown event families with no metric

`Dispatch` (`EventPump.cs:192-207`) returns without counting on any non-`OnDataChange` family. The rationale comment is good, but a gateway version emitting `OnBufferedDataChange` (or a new family) would silently discard data with zero observability — the alarm feed counts its decode drops (`AlarmTransitionsDecodingFailures`); the pump should count filtered/unknown families the same way.

### 4. Underdeveloped Areas

#### U-1 (High, documentation-drift) — CLAUDE.md KNOWN LIMITATION 2 is stale: the historized-ref feed is now wired

CLAUDE.md states the recorder is "spawned with an EMPTY historized-ref set … registers interest in nothing and historizes nothing" pending a `SetHistorizedRefs`-style feed. The code has closed that gap: `WithOtOpcUaRuntimeActors` still spawns with `historizedRefs: Array.Empty<string>()` (`Runtime/ServiceCollectionExtensions.cs:272`) **but** wraps the recorder in `ActorHistorizedTagSubscriptionSink` and hands it to the applier (`:287-307`), `AddressSpaceApplier` pushes the per-deploy add/remove delta (`AddressSpaceApplier.cs:343`), and the recorder handles `UpdateHistorizedRefs` (`ContinuousHistorizationRecorder.cs:186`) — the in-source comment explicitly says this "clos[es] the T18 ref-feed gap". Actions: (1) update CLAUDE.md; (2) the end-to-end value-capture path (deploy → delta → mux tap → outbox → `WriteLiveValues`) has, as far as the tree shows, **never been live-verified** — given this repo's repeated "wired-but-inert in prod" history (F10b `DeferredAddressSpaceSink`, PR #423 provisioner), a live `/run` against a real gateway is the required close-out.

#### U-2 (Medium) — KNOWN LIMITATION 1: the live-validation gate is built but only partially run

The `Category=LiveIntegration` suite is complete and skip-clean: `GatewayLiveFixture` env-gates on `HISTGW_GATEWAY_ENDPOINT`/`APIKEY` (+ per-test `HISTGW_TEST_TAG`, `HISTGW_WRITE_SANDBOX_TAG`, `HISTGW_ALARM_SOURCE`) with a bounded 3 s TCP probe so a down VPN skips instead of hanging (`Live/GatewayLiveFixture.cs`). Four live tests cover read, EnsureTags+write, alarm SendEvent→ReadEvents round-trip, and a SendEvent contract check. Recent history (merge `245316d8`, "assert FU-1 alarm SendEvent→ReadEvents round-trip (gateway C4 fixed)") shows the alarm leg has been run live at least once, but CLAUDE.md still flags the whole cutover as unvalidated. A full documented run of the suite (and a CLAUDE.md status update) is the remaining work — the infrastructure is not the gap.

#### U-3 (Medium) — WriteSecured / VerifiedWrite user identity is stubbed at zero

`InvokeWriteSecuredAsync` hardcodes `CurrentUserId = 0, VerifierUserId = 0` (`GatewayGalaxyDataWriter.cs:263-264`). ArchestrA secured/verified writes exist precisely to attribute and dual-authorize the operation; user 0 will be rejected or unattributed by any galaxy that actually classifies tags SecuredWrite/VerifiedWrite. There is no mapping from the OPC UA session identity (the LDAP-authenticated principal is available server-side) to an ArchestrA user id. Until that lands, writes to secured-classification tags are effectively unsupported — document it, or fail fast with a clear status instead of sending user 0.

#### U-4 (Medium) — Dormant paths inventory

- `GatewayHistorianDataSource.RefreshConnectionStateAsync` — no production caller (see S-6).
- Replay still fans out per-subscription `SubscribeBulk`; the gateway's batched `ReplaySubscriptionsCommand` remains a "PR 6.x can swap this" note (`GalaxyDriver.cs:314-316`).
- `GalaxyDriver.FlushOptionalCachesAsync` is a no-op and `GetMemoryFootprint` is a constants-based estimate (`GalaxyDriver.cs:561-575`) — fine, but the server's cache-flush heuristic gets synthetic data from this driver.
- `HistorianGatewayClientAdapter.ReadEventsAsync` never forwards `maxEvents` on the wire (client-side cap only, documented at `IHistorianGatewayClient.cs:58-63`) and the source filter is re-applied client-side defensively (`GatewayHistorianDataSource.cs:152-157`) because the gateway-side filter "may not be present" — both are polite workarounds for gateway gaps that should be tracked against the sidecar repo.

#### U-5 (Low) — Outbox serializer has no version/format byte

`HistorizationOutboxEntrySerializer` writes a fixed positional layout with no version prefix (`HistorizationOutboxEntrySerializer.cs:14-16`). Any future field addition breaks recovery of pre-existing on-disk entries with an undiagnosable deserialization failure mid-`RecoverState`. One reserved byte now is free; a migration later is not.

#### U-6 — Test coverage assessment

- **Galaxy** (~250 test methods across 34 files): strong unit coverage of the hard parts — reconnect orchestration (`GalaxyMxSessionReconnectTests`, `ReconnectSupervisorTests`), pump fault/bounded-channel behaviour, registry rebind/handle-resolve, writer caches, alarm feed decode, value encode/decode, status mapping, probe, factory. Three skip-gated live smokes (`GatewayGalaxyLiveReopenAndWriteTests` — proven 2/2 against `10.100.0.48:5120` per project memory — and `GatewayGalaxyAlarmFeedLiveTests`) gated on `MXGW_ENDPOINT` + `GALAXY_MXGW_API_KEY`.
- **Historian.Gateway** (~15 files): mappers fully covered, writer/provisioner/data-source outcome classification covered via `FakeHistorianGatewayClient`, outbox recovery/capacity covered, plus the 4-test live suite.
- **Thin spots:** no test drives `GalaxyDriver` write-through the supervisory-advise *failure* branch asserting the returned status (S-1's blast radius is untested); no test exercises out-of-order `RemoveAsync` on the outbox (S-5); nothing covers the read-hang case in S-3; `EventPump` unknown-family filtering has no assertion (C-6).

---

## Maturity Ratings

| Dimension | Rating (1-5) | Justification |
|---|---|---|
| Stability | **4** | Layered recovery (supervisor, self-reconnecting feeds, backoff, partial-open teardown) and disciplined never-throw write sinks; docked for the Galaxy silent-write-loss blast radius (S-1), EventPump-only fault detection (S-4), and the dormant health refresh (S-6). |
| Performance | **4** | Bounded channels with drop metering, O(1) fan-out indexes, handle borrowing, and a bounded tie-cluster over-fetch; docked for the 3-round-trip read synthesis (P-1) and serial alarm sends (P-2), both documented and gateway-constrained. |
| Conventions | **4** | Exemplary seams, shared secret resolver, consistent driver-family shape and tracing decorators; docked for the dual options-validation idiom, on-disk retired Wonderware dirs, and the unmetered pump filter. |
| Underdeveloped areas | **3** | Live-validation infrastructure is complete but the gate is only partially run and CLAUDE.md's limitation 2 is stale against code that has closed the gap; WriteSecured identity is stubbed; several polite client-side workarounds paper over gateway gaps. |

---

## Cross-Cutting Themes

1. **"Wired but never invoked" is this codebase's recurring failure mode** — the provisioner (PR #423), the F10b sink forwarding, and now `RefreshConnectionStateAsync` (S-6). Any new capability interface or hook needs an explicit production-caller check plus a live `/run`, not just unit tests.
2. **Optimistic-Good on fire-and-forget writes** — Galaxy structurally cannot report a failed commit (S-1); reviewers of the node-write router / write-outcome self-correction should not assume driver parity here.
3. **CLAUDE.md drift** — KNOWN LIMITATION 2 is closed in code (U-1) and LIMITATION 1 is partially exercised (U-2); the doc should be reconciled before it misleads the next session.
4. **Gateway-gap workarounds accrue client-side** — defensive source filters, client-side event caps, missing batched replay/SendEvents; these belong on the sister repos' backlogs with links from the in-source comments.
