# Code Review — Driver.AbCip

| Field | Value |
|---|---|
| Module | `src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbCip` |
| Reviewer | Claude Code |
| Review date | 2026-06-19 |
| Commit reviewed | `7286d320` |
| Status | Reviewed |
| Open findings | 0 |

## Checklist coverage

| # | Category | Result |
|---|---|---|
| 1 | Correctness & logic bugs | Driver.AbCip-001, Driver.AbCip-002, Driver.AbCip-003, Driver.AbCip-004, Driver.AbCip-005 |
| 2 | OtOpcUa conventions | Driver.AbCip-006, Driver.AbCip-007 |
| 3 | Concurrency & thread safety | Driver.AbCip-008, Driver.AbCip-009 |
| 4 | Error handling & resilience | Driver.AbCip-010, Driver.AbCip-011 |
| 5 | Security | No issues found |
| 6 | Performance & resource management | Driver.AbCip-012 |
| 7 | Design-document adherence | Driver.AbCip-013 |
| 8 | Code organization & conventions | No issues found |
| 9 | Testing coverage | Driver.AbCip-014 |
| 10 | Documentation & comments | Driver.AbCip-015 |

## Findings

### Driver.AbCip-001

| Field | Value |
|---|---|
| Severity | High |
| Category | Correctness & logic bugs |
| Location | `AbCipDriver.cs:111`, `AbCipDriver.cs:163-167` |
| Status | Resolved |

**Description:** `InitializeAsync(string driverConfigJson, ...)` never reads `driverConfigJson`. It builds all device/tag state from `_options`, captured at construction time. `ReinitializeAsync` calls `ShutdownAsync` then `InitializeAsync(driverConfigJson, ...)` and the JSON it is handed is silently discarded. `ReinitializeAsync` is documented (class remarks, lines 18-21) as the Tier-B escape hatch and is the IDriver entry point for picking up changed config. As written, a reinitialize with an updated config JSON (new device, new tag, changed timeout) applies none of the changes; the driver keeps running stale construction-time options. There is no validation that the passed JSON even matches the live options.

**Recommendation:** Either parse `driverConfigJson` inside `InitializeAsync` (re-deriving `AbCipDriverOptions` the way `AbCipDriverFactoryExtensions.CreateInstance` does, so config changes take effect on reinit), or, if config is intentionally immutable for the instance lifetime, document explicitly that AbCip ignores the parameter and assert the JSON is structurally identical to the construction options. Silently discarding it is the worst of both.

**Resolution:** Resolved 2026-05-22 — extracted `AbCipDriverFactoryExtensions.ParseOptions` and `InitializeAsync` now re-parses a content-bearing `driverConfigJson`, replacing `_options` (and recreating the alarm projection) so `ReinitializeAsync` applies config changes; a blank/empty-object JSON keeps construction-time options for the test seam.

### Driver.AbCip-002

| Field | Value |
|---|---|
| Severity | High |
| Category | Correctness & logic bugs |
| Location | `AbCipStatusMapper.cs:65-78` |
| Status | Resolved |

**Description:** `MapLibplctagStatus` maps negative libplctag codes that do not match the libplctag.NET `Status` enum / native `libplctag.h` constants. `LibplctagTagRuntime.GetStatus()` returns `(int)_tag.GetStatus()`, the underlying value of the `Status` enum, whose members carry the native `PLCTAG_ERR_*` integer values. The real constants are `PLCTAG_ERR_BAD_CONNECTION = -7` (the only one the code gets right), `PLCTAG_ERR_NOT_FOUND = -18` (code expects -14), `PLCTAG_ERR_NOT_ALLOWED = -19` (code expects -16), `PLCTAG_ERR_OUT_OF_BOUNDS = -22` (code expects -17), `PLCTAG_ERR_TIMEOUT = -32` (code expects -5). Consequently a real timeout, not-found, not-allowed, or out-of-bounds error all fall through the switch to the `_ => BadCommunicationError` default. The driver reports `BadCommunicationError` for a non-existent tag instead of `BadNodeIdUnknown`, for a read-only tag instead of `BadNotWritable`, and for a timeout instead of `BadTimeout`. This defeats the transient-vs-permanent error classification the resilience pipeline relies on.

**Recommendation:** Replace the hand-typed integer literals with the libplctag.NET `Status` enum members (Status.ErrorTimeout, Status.ErrorNotFound, Status.ErrorNotAllowed, Status.ErrorOutOfBounds, Status.ErrorBadConnection, etc.), or at minimum correct the integer values to -32 / -18 / -19 / -22. Map Status.Pending explicitly rather than treating "any positive value" as GoodMoreData.

**Resolution:** Resolved 2026-05-22 — `MapLibplctagStatus` now switches on the libplctag.NET `Status` enum members (Ok/Pending/ErrorTimeout/ErrorNotFound/ErrorNotAllowed/ErrorOutOfBounds/…) instead of hand-typed integers; the `int` overload casts to `Status` so the `GetStatus()` seam stays correct against the wrapper's contiguous renumbering. Note: the live libplctag.NET 1.5.2 `Status` enum is renumbered contiguously, so the correct underlying integers are -32/-19/-18/-27, not the native -32/-18/-19/-22 the finding suggested; switching on the enum members sidesteps the hazard entirely.

### Driver.AbCip-003

| Field | Value |
|---|---|
| Severity | High |
| Category | Correctness & logic bugs |
| Location | `AbCipUdtMemberLayout.cs:32-54`, `AbCipDriver.cs:426-430`, `AbCipUdtReadPlanner.cs:48` |
| Status | Resolved |

**Description:** The whole-UDT read path (`ReadGroupAsync`) decodes each grouped member at the byte offset produced by `AbCipUdtMemberLayout.TryBuild`, which computes offsets purely from declaration order of the configured `AbCipStructureMember` list under natural-alignment rules. Logix does not guarantee that the controller lays UDT members out in declaration order: the Studio 5000 compiler reorders members (largest-first packing, BOOL host bytes, nested-struct padding) and the on-wire offsets only come from the CIP Template Object. The class remarks on `AbCipUdtMemberLayout` and `driver-specs.md` both acknowledge this. The decoder for the real shape (`CipTemplateObjectDecoder` / `AbCipTemplateCache`) exists and is populated by `FetchUdtShapeAsync`, but `ReadGroupAsync` never consults it: it always uses the declaration-only layout. For any UDT whose member declaration order in config differs from the controller compiled layout, whole-UDT reads return values decoded from the wrong offsets, silently plausible wrong numbers.

**Recommendation:** In the read planner / `ReadGroupAsync`, prefer the cached `AbCipUdtShape` offsets (from `AbCipTemplateCache` / `FetchUdtShapeAsync`) when available, and only fall back to `AbCipUdtMemberLayout` declaration-order offsets when no template shape can be read. Even then, consider gating the declaration-only fast path behind an explicit opt-in flag, since it is correct only when the operator has hand-verified declaration order matches the controller.

**Resolution:** Resolved 2026-05-22 — the declaration-only whole-UDT grouping fast path is now gated behind the new opt-in `AbCipDriverOptions.EnableDeclarationOnlyUdtGrouping` flag (default `false`); `AbCipUdtReadPlanner.Build` forms no groups when it is off, so by default every UDT member reads per-tag instead of decoding at possibly-wrong declaration-order offsets. The richer CIP Template Object path remains the long-term fix.

### Driver.AbCip-004

| Field | Value |
|---|---|
| Severity | Medium |
| Category | Correctness & logic bugs |
| Location | `AbCipDataType.cs:51-58`, `LibplctagTagRuntime.cs:47-49,53` |
| Status | Resolved |

**Description:** `ToDriverDataType` maps `LInt`/`ULInt` to `DriverDataType.Int32` (a TODO comment notes the gap) and `Dt` to `Int32`. But `LibplctagTagRuntime.DecodeValueAt` returns an actual `long` for `LInt`/`ULInt` (`_tag.GetInt64`, `(long)_tag.GetUInt64`). The address space is built declaring an Int32 node while the driver hands the server a boxed `long` `DataValueSnapshot.Value` at runtime: a mismatch between the declared OPC UA data type and the runtime value type. For `LInt` values exceeding Int32.MaxValue there is data loss if any consumer narrows it. `UDInt` is declared Int32 but decoded as `(int)_tag.GetUInt32`, so values above int.MaxValue wrap to negative.

**Recommendation:** Either add Int64/UInt32/UInt64 to `DriverDataType` and map correctly, or, until that lands, decode `LInt`/`ULInt` consistently with the declared `Int32` type (and document the truncation), and decode `UDInt` as a value that fits Int32 semantics. The declared type and the runtime value type must agree.

**Resolution:** Resolved 2026-05-22 — `ToDriverDataType` now maps `LInt`→`Int64`, `ULInt`→`UInt64`, `UDInt`→`UInt32` (all already present in `DriverDataType`); `DecodeValueAt` updated to return `uint`/`ulong` for UDInt/ULInt respectively so the declared type and runtime value agree. The `(int)` and `(long)` casts that caused truncation/wrap are removed.

### Driver.AbCip-005

| Field | Value |
|---|---|
| Severity | Medium |
| Category | Correctness & logic bugs |
| Location | `AbCipDriver.cs:124-141` |
| Status | Resolved |

**Description:** In `InitializeAsync`, when a `Structure` tag declares `Members`, the loop registers each fanned-out member into `_tagsByName` but the parent Structure tag itself is also left in `_tagsByName` (added at line 125 before the member check). A subsequent `ReadAsync` of the parent name routes through `ReadSingleAsync` then `DecodeValue(AbCipDataType.Structure, ...)` which returns `null` with `Good` status. A client reading the parent UDT node thus gets a Good/null snapshot rather than a fault or a structured value. Also, member registration does not check for name collisions: if two configured tags produce the same parent-dot-member key (or a member name collides with an independently-declared tag), the later silently overwrites the earlier with no diagnostic.

**Recommendation:** Decide the parent-Structure read contract explicitly: either do not register the bare parent name as a readable tag, or have the Structure read return a proper status. Add a duplicate-key check during `_tagsByName` population that throws an `InvalidOperationException` naming both colliding tags, consistent with the fail-fast validation `AbCipHostAddress` parsing already does.

**Resolution:** Resolved 2026-05-22 — The parent Structure tag remains in `_tagsByName` so the whole-UDT grouping planner (Driver.AbCip-003 fast path) and alarm projection can still find it. `ReadSingleAsync` now detects a direct read of a Structure-with-Members and returns `BadNotSupported` instead of Good/null, documenting that callers must address individual member paths. Both scalar and member fan-out registration perform a duplicate-key check that throws `InvalidOperationException` naming both colliding entries (fail-fast, consistent with `AbCipHostAddress` validation).

### Driver.AbCip-006

| Field | Value |
|---|---|
| Severity | Medium |
| Category | OtOpcUa conventions |
| Location | `PlcTagHandle.cs:28-59`, `AbCipDriver.cs:806-807,832-833`, `LibplctagTagRuntime.cs:117` |
| Status | Resolved |

**Description:** `driver-specs.md` makes the SafeHandle-wrapped native handle a non-negotiable Tier-B protection ("Wrap every libplctag handle in a SafeHandle with finalizer calling plc_tag_destroy"). The repo ships `PlcTagHandle : SafeHandle` for this, but it is dead code: `ReleaseHandle` is a permanent no-op (the comment says the `plc_tag_destroy` P/Invoke "is deferred to PR 3", well past the commit under review), and `DeviceState.TagHandles` is never populated anywhere in the driver. The real native lifetime is delegated to the libplctag.NET `Tag` object own `Dispose()`. The mandated finalizer-backed leak protection therefore does not exist: if a `LibplctagTagRuntime` is GC-collected without `Dispose` (owning thread crashes, exception bypasses the device dispose path), whether the native tag is freed depends entirely on whether libplctag.NET `Tag` has its own finalizer, which is not guaranteed by this driver code as the design requires.

**Recommendation:** Either delete `PlcTagHandle` and `DeviceState.TagHandles` as misleading dead scaffolding and document that native lifetime is owned by libplctag.NET `Tag` finalizer (verifying that `Tag` actually has one), or finish the intended design by making `LibplctagTagRuntime` hold a real `PlcTagHandle` with a working `ReleaseHandle` calling `plc_tag_destroy`.

**Resolution:** Resolved 2026-05-22 — `PlcTagHandle.cs` deleted; `DeviceState.TagHandles` removed from `DeviceState`; its `DisposeHandles` loop cleaned up. The class-level doc comment on `AbCipDriver` updated to document that native lifetime is owned by libplctag.NET `Tag.Dispose()` (called in `DisposeHandles`) with the library's own finalizer covering GC-collected instances. The two dead-code test methods for `PlcTagHandle` removed from `AbCipDriverTests`.

### Driver.AbCip-007

| Field | Value |
|---|---|
| Severity | Low |
| Category | OtOpcUa conventions |
| Location | `AbCipDriver.cs` (whole file), `AbCipAlarmProjection.cs`, `LibplctagTagRuntime.cs` |
| Status | Resolved |

**Description:** `CLAUDE.md` Library Preferences mandate Serilog with a rolling daily file sink. The driver has no logging at all: no `ILogger`/Serilog dependency is injected or used. Failure paths instead swallow exceptions into the `_health` string (`ReadSingleAsync`, `WriteAsync`, `FetchUdtShapeAsync` catch-all, `ProbeLoopAsync` empty catch, `AbCipAlarmProjection.RunPollLoopAsync` empty catch). An operator looking at server logs sees nothing for a probe loop failing every tick for hours, a template decode that silently returned null, or an alarm poll loop throwing every interval. The health surface carries only the last error message, so a transient error immediately overwrites a more important earlier one.

**Recommendation:** Inject an `ILogger` (Serilog) and log at least device init failures, per-call read/write transport errors (debounced), probe-loop failures, template-read failures, and alarm-poll-loop exceptions. The health surface is for state, not for the audit trail.

**Resolution:** Resolved 2026-05-23 — `AbCipDriver` and `AbCipAlarmProjection` now accept an optional `ILogger<AbCipDriver>` / `ILogger` (defaulting to `NullLogger` so the existing constructor surface stays compatible). Failure paths log through it: `InitializeAsync` (`LogError` on fault), `ReadSingleAsync` / `ReadGroupAsync` / `WriteAsync` (`LogWarning` on non-zero libplctag status + transport / type-conversion exceptions, with the affected tag + device on each entry), `ProbeLoopAsync` (`LogDebug` per swallowed tick), `FetchUdtShapeAsync` (`LogWarning` on template-read failure), and `AbCipAlarmProjection.RunPollLoopAsync` (`LogDebug` on swallowed tick). Six regression tests in `AbCipLoggingTests` exercise the new logger seam.

### Driver.AbCip-008

| Field | Value |
|---|---|
| Severity | High |
| Category | Concurrency & thread safety |
| Location | `AbCipDriver.cs:144-152`, `AbCipDriver.cs:169-183`, `AbCipDriver.cs:235-281` |
| Status | Resolved |

**Description:** Probe loops are started fire-and-forget (`_ = Task.Run(() => ProbeLoopAsync(state, ct), ct)`) and the resulting Task is never stored or awaited. `ShutdownAsync` cancels `state.ProbeCts`, then immediately disposes it, sets it null, and calls `state.DisposeHandles()` without waiting for `ProbeLoopAsync` to observe the cancellation and exit. Races: (1) the still-running probe loop may be mid-await against a `ProbeCts` that `ShutdownAsync` has already disposed, producing `ObjectDisposedException` on the loop thread; (2) `DisposeHandles` clears `Runtimes`/`ParentRuntimes` while a concurrent `ReadAsync`/`WriteAsync` from the alarm projection or a subscription poll could be iterating or adding to those plain `Dictionary` instances (not thread-safe), corrupting the dictionary or throwing; (3) the probe runtime created inside `ProbeLoopAsync` is never tracked by `DeviceState`, so `DisposeHandles` cannot dispose it; only the loop own finally does, which may run after `ShutdownAsync` returns.

**Recommendation:** Store each probe Task on `DeviceState`; in `ShutdownAsync` cancel the CTS, then await Task.WhenAll (with a timeout) before disposing the CTS or the handles. Guard `Runtimes`/`ParentRuntimes` with a lock or switch to `ConcurrentDictionary`. Make `ShutdownAsync` idempotent and safe against in-flight `ReadAsync`/`WriteAsync`.

**Resolution:** Resolved 2026-05-22 — each probe loop's `Task` is stored on `DeviceState.ProbeTask`; `ShutdownAsync` now runs three phases (cancel every CTS, then await each probe Task with a 10s timeout, then dispose the CTS + handles) so the loop never touches a disposed CTS or cleared dictionary. `DeviceState.Runtimes` / `ParentRuntimes` are now `ConcurrentDictionary`, and `EnsureTagRuntimeAsync` / `EnsureParentRuntimeAsync` use `TryAdd` and dispose the losing concurrent creator instead of leaking it. `ShutdownAsync` stays idempotent (a second call sees the cleared `_devices`).

### Driver.AbCip-009

| Field | Value |
|---|---|
| Severity | Medium |
| Category | Concurrency & thread safety |
| Location | `AbCipDriver.cs:621-648`, `AbCipDriver.cs:591-614` |
| Status | Resolved |

**Description:** `EnsureTagRuntimeAsync` and `EnsureParentRuntimeAsync` are check-then-act on a non-thread-safe `Dictionary` (`device.Runtimes` / `device.ParentRuntimes`). `ReadAsync` is `IReadable` and may be invoked concurrently: the server read path, each polled subscription loop, and the alarm projection poll loop all call `ReadAsync` independently. Two concurrent `ReadAsync` calls that both miss the cache for the same tag both create a `LibplctagTagRuntime`, both initialize it, and both write into the dictionary; the loser leaks an initialized native tag (never disposed, since only the dictionary value is disposed at shutdown), and concurrent `Dictionary` mutation can throw or corrupt the bucket structure. `WriteBitInDIntAsync` serializes the parent via a per-parent `SemaphoreSlim`, but `EnsureParentRuntimeAsync` still runs the same unguarded check-then-act on the shared `ParentRuntimes` dict.

**Recommendation:** Use `ConcurrentDictionary` for `Runtimes` and `ParentRuntimes`, creating the runtime via `GetOrAdd` with a lazily-initialized factory, or guard the ensure path with a per-device lock / `SemaphoreSlim`. Ensure the losing creator runtime is disposed rather than leaked.

**Resolution:** Resolved 2026-05-22 — already addressed as part of the Driver.AbCip-008 fix: `DeviceState.Runtimes` and `ParentRuntimes` were switched to `ConcurrentDictionary`; both `EnsureTagRuntimeAsync` and `EnsureParentRuntimeAsync` use the `TryGetValue` → create → `TryAdd` → dispose-loser pattern so concurrent callers that both miss the cache produce exactly one live runtime and the losing creator is disposed rather than leaked.

### Driver.AbCip-010

| Field | Value |
|---|---|
| Severity | Medium |
| Category | Error handling & resilience |
| Location | `AbCipDriver.cs:621-648`, `AbCipDriver.cs:346-391` |
| Status | Resolved |

**Description:** Once `EnsureTagRuntimeAsync` successfully creates and initializes a `LibplctagTagRuntime`, that runtime is cached for the lifetime of the device and never re-created on failure. If the underlying native tag enters a permanently-bad state (connection dropped, controller rebooted, tag handle invalidated by a PLC program download), every subsequent `ReadAsync`/`WriteAsync` reuses the same dead handle and returns errors forever. The probe loop does tear down and recreate its runtime after a failure, but the read/write path has no equivalent recovery; only a full `ReinitializeAsync` (itself broken, see Driver.AbCip-001) clears the cache. The normal data path should self-heal from a transient handle fault without operator-driven reinitialize.

**Recommendation:** On a non-zero libplctag status or transport exception in `ReadSingleAsync`/`ReadGroupAsync`/`WriteAsync`, evict the offending runtime from `device.Runtimes` (and dispose it) so the next call re-creates and re-initializes it. Mirror the probe loop recreate-on-failure behavior.

**Resolution:** Resolved 2026-05-22 — added `EvictRuntime(device, tagName)` helper that calls `ConcurrentDictionary.TryRemove` + disposes the evicted instance; called from `ReadSingleAsync`, `ReadGroupAsync`, and `WriteAsync` on both non-zero libplctag status and transport exceptions (type/value-conversion exceptions are not transport faults and do not evict). The next read/write for the affected tag re-runs `EnsureTagRuntimeAsync`, which creates and initializes a fresh handle, mirroring the probe loop's recreate-on-failure behaviour.

### Driver.AbCip-011

| Field | Value |
|---|---|
| Severity | Low |
| Category | Error handling & resilience |
| Location | `AbCipDriver.cs:144-152`, `AbCipDriverOptions.cs:131-143` |
| Status | Resolved |

**Description:** `InitializeAsync` only starts probe loops when `_options.Probe.Enabled` is true AND `Probe.ProbeTagPath` is non-blank. When `Probe.Enabled` is true (the default) but `ProbeTagPath` is null (also the default; the doc comment says "PR 8 wires this up"), no probe runs at all and the device `HostState` stays `HostState.Unknown` forever. `GetHostStatuses()` then reports every device as Unknown indefinitely with no warning. An operator who enables the probe but does not set a probe tag gets a silently inert health surface rather than an error or a log line.

**Recommendation:** When `Probe.Enabled` is true but no `ProbeTagPath` is configured, either fail initialization with a clear message, fall back to a family-default probe tag (the doc comment stated intent), or at minimum log a warning that the probe is enabled-but-inert.

**Resolution:** Resolved 2026-05-23 — `InitializeAsync` now emits a `LogWarning` when `Probe.Enabled` is `true`, devices are configured, but `Probe.ProbeTagPath` is null/blank. The warning names the driver instance and explicitly states that no probe loops were started and `GetHostStatuses()` will report every device as `Unknown` until either a `ProbeTagPath` is set or `Probe.Enabled` is set to `false`. Initialization still succeeds (the probe is optional telemetry, not a hard requirement). Two `AbCipLoggingTests` cases cover the warn-on-enabled-but-blank and no-warn-on-disabled paths. The `AbCipProbeOptions.ProbeTagPath` doc-comment was also updated so the misconfiguration is documented in-place.

### Driver.AbCip-012

| Field | Value |
|---|---|
| Severity | Low |
| Category | Performance & resource management |
| Location | `LibplctagTemplateReader.cs:15-35`, `AbCipDriver.cs:88-92` |
| Status | Resolved |

**Description:** `LibplctagTemplateReader` is created per `FetchUdtShapeAsync` call, and each call constructs a fresh libplctag `Tag` for the @udt pseudo-tag, initializes it (a CIP connection handshake), reads, and disposes it. There is no reuse of the `Tag` across template reads for the same device: every UDT shape fetch pays a full connect/init cost. `AbCipTemplateCache` caches the decoded shape so this only bites on the first fetch of each type, but discovery of a UDT-heavy controller still does one connect per type. The same per-call `Tag` construction applies to `LibplctagTagEnumerator`.

**Recommendation:** Acceptable for a low-frequency discovery path, but consider pooling/reusing a single @udt-capable `Tag` per device for the duration of a discovery run, or document that the per-type connect cost is accepted.

**Resolution:** Resolved 2026-05-23 — accepted per the recommendation's "document the per-type connect cost is accepted" branch; `AbCipTemplateCache` caches the decoded shape so only the first fetch per `(device, templateInstanceId)` pays the connect cost, and libplctag itself pools the underlying CIP connections per gateway+path so the TCP/EIP session is reused even when individual `Tag` instances are torn down. The class-level remarks on `LibplctagTemplateReader` now spell that out and call out when to revisit (telemetry showing discovery latency dominated by template-read connects).

### Driver.AbCip-013

| Field | Value |
|---|---|
| Severity | Low |
| Category | Design-document adherence |
| Location | `AbCipDriverOptions.cs:70-73`, `PlcFamilies/AbCipPlcFamilyProfile.cs:13-19`, `LibplctagTagRuntime.cs:16-27` |
| Status | Resolved |

**Description:** `driver-specs.md` specifies the AB CIP per-device connection settings as discrete fields: Host, Path, PlcType, TimeoutMs, AllowPacking, ConnectionSize. The implementation instead collapses host + path into a single opaque ab:// URL string and exposes `PlcFamily` (which adds GuardLogix, not in the spec table). AllowPacking and ConnectionSize from the spec are not configurable per device: `AbCipPlcFamilyProfile` hard-codes `SupportsRequestPacking` and `DefaultConnectionSize` per family, and `LibplctagTagRuntime` never passes a connection-size or packing attribute to the `Tag` (it is constructed with only Gateway/Path/PlcType/Protocol/Name/Timeout). The family profile `DefaultConnectionSize`/`SupportsRequestPacking`/`MaxFragmentBytes` fields are computed but never applied to the wire layer: dead configuration.

**Recommendation:** Either update `driver-specs.md` to describe the actual ab:// host-address model and the family-profile approach, and wire the profile ConnectionSize/packing values through to the libplctag `Tag` attributes; or expose AllowPacking/ConnectionSize as per-device options per the spec.

**Resolution:** Resolved 2026-05-23 — took the "expose per-device options per the spec" branch. `AbCipDeviceOptions` now carries optional `AllowPacking` and `ConnectionSize` overrides (both default to `null` to inherit the family profile); `AbCipTagCreateParams` carries the resolved values; `DeviceState.BuildCreateParams` collapses every old per-call-site clone (read, write, probe, template, enumerator) into one helper that combines the per-device override with the family profile's `SupportsRequestPacking` / `DefaultConnectionSize` defaults. `LibplctagTagRuntime` now honours `AllowPacking` via the `Tag.AllowPacking` property — fixing the previously-dead family-profile setting. `ConnectionSize` is plumbed through `AbCipTagCreateParams` for forward-compat; libplctag.NET 1.5.2 has no direct `ConnectionSize` property, so an XML comment on `LibplctagTagRuntime` documents that current builds rely on the family-profile default at the wire layer until the wrapper exposes a direct property or we ship a custom tag-attribute path. `AbCipDriverFactoryExtensions` ParseOptions now reads `AllowPacking` + `ConnectionSize` from the driver-config JSON. Six regression tests in `AbCipPerDeviceConnectionOptionsTests` cover the new options.

### Driver.AbCip-014

| Field | Value |
|---|---|
| Severity | Medium |
| Category | Testing coverage |
| Location | `tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbCip.Tests/AbCipStatusMapperTests.cs:28-40` |
| Status | Resolved |

**Description:** `AbCipStatusMapperTests.MapLibplctagStatus_maps_known_codes` asserts the mapper against the same wrong integer constants (-5, -7, -14, -16, -17) the production code uses (see Driver.AbCip-002). The test locks in the bug rather than catching it, giving false confidence that libplctag error mapping is correct. There is no test that drives an actual libplctag `Status` enum value through `LibplctagTagRuntime.GetStatus()` plus `MapLibplctagStatus` end-to-end. Separately, the broken `ReinitializeAsync` config-discard behavior (Driver.AbCip-001) and the declaration-order whole-UDT decode risk (Driver.AbCip-003) have no test that would fail when those defects are present: `AbCipDriverWholeUdtReadTests` only exercises a UDT whose declaration order happens to match a simple alignment layout.

**Recommendation:** Rewrite the libplctag-status test to use the real `libplctag.Status` enum members and their documented integer values. Add a test that `ReinitializeAsync` with a changed config JSON actually applies the change (or asserts the documented immutability contract). Add a whole-UDT decode test where the controller compiled layout differs from declaration order.

**Resolution:** Resolved 2026-05-22 — status mapper test already uses real `Status` enum members (fixed with Driver.AbCip-002); `ReinitializeAsync` config-change coverage already added with Driver.AbCip-001. Added to `AbCipDriverCodeReviewRegressionTests`: three tests for 004 (LInt/ULInt/UDInt type-mapping theory + UDInt decoded-as-uint assertion), three tests for 005 (Structure parent read returns BadNotSupported, duplicate scalar key throws, member-collision-with-independent-tag throws), and one test for 010 (eviction on bad status means next read creates a fresh handle). `AbCipDriverTests.AbCipDataType_maps_atomics_to_driver_types` extended with LInt/ULInt/UDInt assertions.

### Driver.AbCip-015

| Field | Value |
|---|---|
| Severity | Low |
| Category | Documentation & comments |
| Location | `AbCipDriver.cs:9-11`, `PlcTagHandle.cs:23-27,53-58`, `AbCipTemplateCache.cs:12-15`, `IAbCipTagEnumerator.cs:6-11`, `AbCipDriverOptions.cs:21` |
| Status | Resolved |

**Description:** Numerous comments are stale relative to the commit under review. `AbCipDriver.cs:9-11` says the driver "Implements IDriver only for now" with capabilities shipping "in subsequent PRs (3-8)" while the class already implements all of them. `PlcTagHandle.cs` says the plc_tag_destroy P/Invoke "is deferred to PR 3 ... PR 2 ships the lifetime scaffold + tests only" and `ReleaseHandle` "is a no-op", which now reads as a permanent unfinished-work marker (see Driver.AbCip-006). `AbCipTemplateCache.cs:12-15` says "Template shape read ... lands with PR 6 ... no reader writes to it yet" while `CipTemplateObjectDecoder` and `LibplctagTemplateReader` both exist and `FetchUdtShapeAsync` writes to the cache. `IAbCipTagEnumerator.cs:6-11` says the enumerator "Defaults to EmptyAbCipTagEnumeratorFactory" while the production default is `LibplctagTagEnumeratorFactory`. `AbCipDriverOptions.cs:21` says "AB discovery lands in PR 5", already shipped. `StyleGuide.md` explicitly says not to leave stale coming-soon notes.

**Recommendation:** Sweep the module for PR-N forward references and "lands in PR X" notes that have been delivered; update them to describe present behavior. Where a comment marks genuinely unfinished work (e.g. `PlcTagHandle.ReleaseHandle`), convert it to a tracked TODO with an issue reference rather than a PR-number milestone.

**Resolution:** Resolved 2026-05-23 — swept the module for stale PR-N forward references and replaced each with a description of present behaviour: `AbCipDriver.TemplateCache` summary, `AbCipDataType.cs` (PR 5 / PR 6 → references `CipTemplateObjectDecoder` + `AbCipTemplateCache`), `AbCipTagPath.cs` (PR 6 → references `AbCipTemplateCache`), `AbCipTemplateCache.cs` (the "lands with PR 6" remarks and the `AbCipUdtShape` summary), `IAbCipTagEnumerator.cs` (the `EmptyAbCipTagEnumeratorFactory`-defaults claim and the PR-5 stub line; `EmptyAbCipTagEnumerator` summary), `LibplctagTagEnumerator.cs` ("Task #178 closed the stub gap from PR 5"), `LibplctagTagRuntime.cs` (`Whole-UDT writes land in PR 6`), `AbCipDriverOptions.cs` (`Tags` summary, `ProbeTagPath` summary), and `AbCipPlcFamilyProfile.cs` ("Family-specific wire tests ship in PRs 9–12"). `PlcTagHandle.cs` was already deleted as part of Driver.AbCip-006's resolution. The only remaining "lands in" reference is the `AbCipDataType.Dt` ⇒ `Date/Time` mapping, which is product-domain wording, not a PR reference.

## Re-review 2026-06-19 (commit 7286d320)

Re-review at `7286d320` (the module is byte-identical at the working-tree HEAD `ae3f0719`).
Since the prior review at `76d35d1` the module grew substantially: the option/contract
records (`AbCipDriverOptions`, `AbCipDeviceOptions`, `AbCipTagDefinition`,
`AbCipStructureMember`, the `AbCipDataType` enum) moved out into a sibling
`Driver.AbCip.Contracts` project (**out of scope** for this module's review); a new
two-phase `AbCipDriverProbe` (`IDriverProbe`) and `AbCipDataTypeExtensions` landed; the
driver gained the `EquipmentTagRefResolver`, 1-D array support, controller-discovered
nested-UDT fan-out (Template Object + Symbol Object decoders), and string-enum
serialization in the probe (correctly using `JsonStringEnumConverter`, addressing the
systemic AdminUI enum-serialization hazard). All 15 prior findings remain Resolved and
were spot-checked as still in force.

#### Checklist coverage (re-review)

| # | Category | Result |
|---|---|---|
| 1 | Correctness & logic bugs | Driver.AbCip-016, Driver.AbCip-018 |
| 2 | OtOpcUa conventions | No issues found |
| 3 | Concurrency & thread safety | No issues found |
| 4 | Error handling & resilience | No issues found |
| 5 | Security | No issues found |
| 6 | Performance & resource management | No issues found |
| 7 | Design-document adherence | No issues found |
| 8 | Code organization & conventions | No issues found |
| 9 | Testing coverage | No issues found (covered by Driver.AbCip-016 regression tests) |
| 10 | Documentation & comments | Driver.AbCip-017 |

### Driver.AbCip-016

| Field | Value |
|---|---|
| Severity | Medium |
| Category | Correctness & logic bugs |
| Location | `AbCipDriver.cs:276-282` (member fan-out), `AbCipUdtMemberLayout.cs:42-52` (declaration-only layout) |
| Status | Resolved |

**Description:** A declared UDT member that is a 1-D array read its value as a single scalar
rather than as a typed array — a declared-type-vs-runtime-value mismatch in the same family
as Driver.AbCip-004. Two cooperating defects:

1. **Member fan-out dropped the array shape.** `InitializeAsync` fans each
   `AbCipStructureMember` out into a member-level `AbCipTagDefinition`
   (`{tag}.{member}`) but constructed it without `ElementCount` / `IsArray`, so they
   defaulted to `1` / `false`. Discovery (`DiscoverAsync`, line ~1033) DOES emit an array
   node for an array member (`member.IsArray || member.ElementCount > 1` → `IsArray` +
   `ArrayDim`). At read time the fanned-out runtime def therefore went through
   `ReadSingleAsync` with `IsArrayTag(def) == false` and decoded a single scalar via
   `DecodeValue`, not the `DecodeArray` path. The address space advertised, e.g.,
   `Motor.Setpoints : REAL[4]` as an array node, but a read returned one element (or `null`).
   There was an existing discovery test (`Udt_array_member_discovers_as_IsArray_with_ArrayDim`)
   but no test that *read* a declared UDT array member, so the mismatch went uncaught.

2. **Declaration-only whole-UDT grouping mis-handled array members.**
   `AbCipUdtMemberLayout.TryBuild` ignored each member's `ElementCount`, advancing the
   layout cursor by the *scalar* element size only. A UDT with an array member would place
   every *subsequent* member at a wrong offset, and `ReadGroupAsync` decodes one scalar per
   member via `DecodeValueAt` (it cannot return an array). This only bites the opt-in
   `EnableDeclarationOnlyUdtGrouping` path (default off), but it compounds the Driver.AbCip-003
   declaration-order risk.

**Recommendation:** Thread `ElementCount` / `IsArray` from the `AbCipStructureMember` into the
fanned-out member `AbCipTagDefinition` so the read path takes the array branch (matching
discovery). Make `AbCipUdtMemberLayout.TryBuild` opt out of grouping (return `null`) when any
member is an array, sending array members to the per-tag read path that decodes them correctly
— mirroring the existing Bool/String/Structure opt-out.

**Resolution:** Resolved 2026-06-19 — (1) the member fan-out in `AbCipDriver.InitializeAsync`
now passes `ElementCount: member.ElementCount` + `IsArray: member.IsArray` into the fanned-out
`AbCipTagDefinition`, so `IsArrayTag(def)` matches the discovery array-node decision exactly and
a declared UDT array member reads as a typed CLR array. (2) `AbCipUdtMemberLayout.TryBuild` now
returns `null` when any member has `IsArray` set or `ElementCount > 1`, opting the whole group
out of declaration-only grouping so array members always take the per-tag read path. Regression
tests: `AbCipArrayTests.Declared_udt_array_member_reads_as_typed_array` (a declared `REAL[4]`
member reads as `float[4]` + threads `elem_count`/`isArray` to libplctag) and
`AbCipUdtMemberLayoutTests.Returns_Null_When_A_Member_Is_An_Array` (both the explicit `IsArray`
flag and the legacy `ElementCount > 1` paths opt out). Full suite green (303 tests).

### Driver.AbCip-017

| Field | Value |
|---|---|
| Severity | Low |
| Category | Documentation & comments |
| Location | `AbCipAlarmProjection.cs:173-185` (`Tick`) |
| Status | Resolved |

**Description:** `AbCipAlarmProjection.Tick` gates each node on the `InFaulted` snapshot's
`StatusCode` (`if (inFaultedDv.StatusCode != Good) continue;`) but reads the `Severity`
snapshot's *value* without checking *its* `StatusCode`. When a severity read returns Bad
(value `null`), `ToInt(null)` yields `0`, which `MapSeverity` buckets as `Low` — so a raise
event during a partial-read tick can be emitted with an artificially-`Low` severity rather
than the alarm's real severity (or a deliberately-chosen "unknown" sentinel). In practice
`InFaulted` and `Severity` are members of the same ALMD UDT read in one batch, so a Good
`InFaulted` almost always implies a Good `Severity`, which is why the impact is Low and this is
recorded as a documentation/robustness note rather than a behavioural bug. The current
"default-to-Low-on-unknown-severity" behaviour is also undocumented.

**Recommendation:** Either check `severityDv.StatusCode` and carry a documented fallback (e.g.
retain the last-known severity, or map to `Medium`/an explicit "unknown" bucket) when the
severity read is Bad, or add an XML/inline comment on `Tick` stating that severity defaults to
`Low` when its read fails. Deferred (Open): the right fallback is a small alarm-semantics design
decision (what severity to surface when it is genuinely unknown) rather than a mechanical fix,
and the impact is negligible given the single-batch read shape.

**Resolution:** Resolved 2026-06-20 — added an inline comment on the `severity` read line in
`Tick` documenting that `severityDv.StatusCode` is not checked, that a Bad Severity read yields
`ToInt(null)=0` → `MapSeverity` buckets as Low, and that this is acceptable because InFaulted
and Severity are members of the same ALMD UDT read in one batch (a Good InFaulted almost always
implies a Good Severity). No behaviour change.

### Driver.AbCip-018

| Field | Value |
|---|---|
| Severity | Medium |
| Category | Correctness & logic bugs |
| Location | `AbCipDriverFactoryExtensions.cs:89-109` (`BuildTag`), `AbCipDriverFactoryExtensions.cs:205-246` (`AbCipTagDto`), `AbCipDriverFactoryExtensions.cs:248-269` (`AbCipMemberDto`) |
| Status | Resolved |

**Description:** The driver-config factory path dropped the array shape of a pre-declared tag.
`AbCipTagDto` and `AbCipMemberDto` had no `ElementCount` / `IsArray` fields, so a `tags[]` entry
in the driver-config JSON authored with an explicit `"isArray": true, "elementCount": 4`
deserialised into a **scalar** `AbCipTagDefinition` (both fields silently dropped → defaulting to
`IsArray=false` / `ElementCount=1`). At read time `IsArrayTag(def)` was therefore `false`, so the
tag decoded via `DecodeValue` (single scalar) instead of the `DecodeArray` path — a declared
`REAL[4]` array tag read as one element. This is the factory/driver-config path; the
equipment-tag path (`AbCipEquipmentTagParser` in Driver.AbCip.Contracts) already threads array
shape correctly, and the in-driver UDT member fan-out was fixed under Driver.AbCip-016 — but the
factory `tags[]` array still lost the signal.

#### Recommendation

Add `ElementCount` (int?) and `IsArray` (bool) to `AbCipTagDto` and `AbCipMemberDto` with the
correct camelCase `[JsonPropertyName]` (`elementCount` / `isArray`), and thread them into the
`AbCipTagDefinition` / `AbCipStructureMember` construction in `BuildTag`, applying the
positive-value guard (`elementCount is > 0` ⇒ value, else `1`). Additive/optional — a config
without the fields keeps the legacy scalar default.

**Resolution:** Resolved 2026-06-19 — `AbCipTagDto` + `AbCipMemberDto` gained `IsArray` (bool,
`[JsonPropertyName("isArray")]`) and `ElementCount` (int?, `[JsonPropertyName("elementCount")]`);
`BuildTag` threads them into the `AbCipTagDefinition` and each fanned-out `AbCipStructureMember`
with the `m.ElementCount is > 0 ? m.ElementCount.Value : 1` guard (mirroring the equipment-tag
parser), so a driver-config array tag now reads as a typed array. Additive — missing fields still
produce a scalar. Regression: `AbCipFactoryArrayTagTests` (4 cases — top-level tag, UDT member,
absent-fields-stay-scalar, non-positive-elementCount-clamps-to-1). Full suite green (307 tests).
