# Code Review — Contracts

| Field | Value |
|---|---|
| Module | `src/MxGateway.Contracts` |
| Reviewer | Claude Code |
| Review date | 2026-05-18 |
| Commit reviewed | `6c64030` |
| Status | Reviewed |
| Open findings | 8 |

## Checklist coverage

| # | Category | Result |
|---|---|---|
| 1 | Correctness & logic bugs | No functional bugs; one missing reply-payload case for the by-name ack command and an `int32`-typed `success` flag that reads like a bool (Contracts-002, Contracts-006). |
| 2 | mxaccessgw conventions | Additive-only evolution honored (no renumbered/removed tags), MXAccess-aligned naming consistent, generated code untouched; no `reserved` statements declared as a guardrail (Contracts-005). |
| 3 | Concurrency & thread safety | N/A — pure contract definitions plus a static const class with no shared mutable state. |
| 4 | Error handling & resilience | HRESULT / `MxStatusProxy` / `ProtocolStatus` carriers are complete; the worker-side by-name alarm ack has no dedicated reply payload (Contracts-002). |
| 5 | Security | Credential-sensitive fields are clearly commented; no secrets forced into loggable shapes. No issues found. |
| 6 | Performance & resource management | `DiscoverHierarchy` is paged; alarm-snapshot streams are server-streamed; no bloat issues. No issues found. |
| 7 | Design-document adherence | `.proto` files match design intent but `docs/Grpc.md` is stale (Contracts-001); worker vs public alarm-status shapes unreconciled in docs (Contracts-008). |
| 8 | Code organization & conventions | Package/file layout correct; `mxaccess_worker.proto` Protobuf item missing `ProtoRoot` (Contracts-003); stale class summary (Contracts-004). |
| 9 | Testing coverage | Gateway/worker/alarm round-trips covered; Galaxy Repository protos and raw `MxArray` paths untested (Contracts-007). |
| 10 | Documentation & comments | Proto comments accurate and domain-rich; one stale class summary (Contracts-004). |

## Findings

### Contracts-001

| Field | Value |
|---|---|
| Severity | Low |
| Category | Design-document adherence |
| Location | `docs/Grpc.md:13` (and `:3`, `:32`, `:39`) |
| Status | Open |

**Description:** `mxaccess_gateway.proto` now declares six RPCs on `MxAccessGateway` (`OpenSession`, `CloseSession`, `Invoke`, `StreamEvents`, `AcknowledgeAlarm`, `QueryActiveAlarms`). `docs/Grpc.md` still describes "the four `MxAccessGateway` RPCs" in its type table and omits `AcknowledgeAlarm`/`QueryActiveAlarms` from the Validation Rules table. CLAUDE.md requires docs to change in the same commit as the contract; the alarm RPC commits left this doc stale and misleading about the public surface.

**Recommendation:** Update `docs/Grpc.md` to enumerate all six RPCs and add `AcknowledgeAlarm`/`QueryActiveAlarms` to the type/handler and validation tables, or explicitly cross-reference `AlarmClientDiscovery.md`.

**Resolution:** _(open)_

### Contracts-002

| Field | Value |
|---|---|
| Severity | Medium |
| Category | Error handling & resilience |
| Location | `src/MxGateway.Contracts/Protos/mxaccess_gateway.proto:384-385`, `:95` |
| Status | Open |

**Description:** `MxCommandKind` includes `MX_COMMAND_KIND_ACKNOWLEDGE_ALARM_BY_NAME = 29` and `MxCommand.payload` carries `AcknowledgeAlarmByNameCommand acknowledge_alarm_by_name_command = 38`, but `MxCommandReply.payload` has only `acknowledge_alarm = 34` and `query_active_alarms = 35` — there is no by-name reply case. The by-name ack must reuse `AcknowledgeAlarmReplyPayload` or rely on the top-level `hresult`. The command/reply payload asymmetry is undocumented and easy to dispatch incorrectly.

**Recommendation:** Either add an explicit comment to `MxCommandReply` stating that by-name ack reuses the `acknowledge_alarm` payload case, or add a dedicated payload case for symmetry, and document the chosen contract in `docs/Contracts.md` / `AlarmClientDiscovery.md`.

**Resolution:** _(open)_

### Contracts-003

| Field | Value |
|---|---|
| Severity | Low |
| Category | Code organization & conventions |
| Location | `src/MxGateway.Contracts/MxGateway.Contracts.csproj:10` |
| Status | Open |

**Description:** The `<Protobuf>` item for `mxaccess_worker.proto` omits `ProtoRoot="Protos"`, while the items for `mxaccess_gateway.proto` (line 9) and `galaxy_repository.proto` (line 11) both set it. `mxaccess_worker.proto` does `import "mxaccess_gateway.proto"`, which resolves only because Grpc.Tools adds the importing file's own directory to the proto path. The inconsistency is fragile — tooling changes to ProtoRoot handling could break import resolution.

**Recommendation:** Add `ProtoRoot="Protos"` to the `mxaccess_worker.proto` `<Protobuf>` item so all three entries are consistent.

**Resolution:** _(open)_

### Contracts-004

| Field | Value |
|---|---|
| Severity | Low |
| Category | Documentation & comments |
| Location | `src/MxGateway.Contracts/GatewayContractInfo.cs:3-6` |
| Status | Open |

**Description:** The XML summary says the class exposes version metadata "before generated protobuf contracts are introduced." Generated protobuf contracts have long been introduced and are consumed across the solution. The comment is stale; the class now holds the authoritative `GatewayProtocolVersion`/`WorkerProtocolVersion` advertised in `OpenSessionReply` and used to validate `WorkerEnvelope` framing.

**Recommendation:** Reword the summary to describe the current purpose — version constants advertised in `OpenSessionReply` and used to validate `WorkerEnvelope` protocol framing.

**Resolution:** _(open)_

### Contracts-005

| Field | Value |
|---|---|
| Severity | Low |
| Category | mxaccessgw conventions |
| Location | `src/MxGateway.Contracts/Protos/mxaccess_gateway.proto`, `src/MxGateway.Contracts/Protos/mxaccess_worker.proto` |
| Status | Open |

**Description:** The ProtobufStyleGuide mandates reserving removed field numbers / enum values. Evolution to date has been purely additive, so this is not a current violation — but none of the `.proto` files contain any `reserved` declarations, leaving no in-file guardrail for the first removal. This is a latent maintainability gap.

**Recommendation:** When any field or enum value is eventually removed, add a `reserved` range/name in the same change. Consider a short comment block in each message documenting the policy so future editors apply `reserved` rather than reusing tags.

**Resolution:** _(open)_

### Contracts-006

| Field | Value |
|---|---|
| Severity | Low |
| Category | Correctness & logic bugs |
| Location | `src/MxGateway.Contracts/Protos/mxaccess_gateway.proto:647` |
| Status | Open |

**Description:** `MxStatusProxy.success` is declared `int32 success = 1` with no comment. The name reads like a boolean flag but the type is a 32-bit integer (mirroring MXAccess `MXSTATUS_PROXY`, which stores a numeric success/HResult-like value). Without a comment a client author can reasonably misinterpret the field (treat non-1 as failure, or expect only 0/1).

**Recommendation:** Add a comment clarifying the semantic — what range of values it carries and how 0 vs non-zero map to MXAccess status — per the style guide rule to comment fields carrying raw MXAccess status detail.

**Resolution:** _(open)_

### Contracts-007

| Field | Value |
|---|---|
| Severity | Low |
| Category | Testing coverage |
| Location | `src/MxGateway.Tests/Contracts/ProtobufContractRoundTripTests.cs` |
| Status | Open |

**Description:** `ProtobufContractRoundTripTests` covers gateway command/reply/event, alarm transition, alarm ack request/reply, active-alarm snapshot, and the worker envelope. It has no coverage for: (a) any `galaxy_repository.proto` message (`DiscoverHierarchy*`, `GalaxyObject`, `GalaxyAttribute`, `DeployEvent`, the `root` oneof, wrapper-typed fields); (b) `BulkSubscribeReply`/`SubscribeResult` and the bulk command kinds; (c) `MxValue`/`MxArray` `raw_value`/`RawArray` (`bytes`) paths and the `WorkerFault`/`WorkerHeartbeat` IPC bodies.

**Recommendation:** Add round-trip tests for the Galaxy Repository messages (including the `root` oneof and proto wrapper fields), the bulk-subscribe reply, and the remaining `WorkerEnvelope` body cases.

**Resolution:** _(open)_

### Contracts-008

| Field | Value |
|---|---|
| Severity | Low |
| Category | Design-document adherence |
| Location | `src/MxGateway.Contracts/Protos/mxaccess_gateway.proto:451-459`, `:627-636` |
| Status | Open |

**Description:** The worker-side `AcknowledgeAlarmReplyPayload` carries the alarm-ack outcome as `int32 native_status`, while the public `AcknowledgeAlarmReply` carries it as `MxStatusProxy status` plus `optional int32 hresult`. The comment explains the worker echoes `native_status` into `AcknowledgeAlarmReply.hresult`, but the two outcome shapes (raw `int32` vs structured `MxStatusProxy`) are not reconciled in `docs/Contracts.md` / `AlarmClientDiscovery.md`. A reader cannot tell whether `MxStatusProxy status` is always populated or only on COM-layer failure.

**Recommendation:** Document in `docs/Contracts.md` (or `AlarmClientDiscovery.md`) how the worker `native_status` maps onto the public reply's `status`/`hresult` pair so client authors know which field is authoritative.

**Resolution:** _(open)_
