Merge pull request 'Architecture remediation: P1 tier (process & hardening)' (#121) from fix/archreview-p1 into main

Gateway-side follow-up to the shared auth-lib expiry core (delivered via G-2):

- apikey create-key gains optional --expires — absolute ISO-8601 UTC or relative
  <N>d/<N>h from now; omitted means non-expiring (opt-in, unchanged default).
  Threaded ApiKeyAdminCommand -> parser -> runner into the library's
  CreateKeyAsync(..., expiresUtc, ...). list-keys shows an expiry column and an
  active/expired/revoked status.
- Dashboard API Keys page surfaces expiry: an Expires column (Never when unset)
  and a status badge reading Expired (red) / Expiring (<=7d, amber) / Revoked /
  Active. DashboardApiKeySummary.ExpiresUtc projected in DashboardSnapshotService;
  StatusBadge maps the new states.

Tests: parser (absolute/relative/invalid/none) + end-to-end past-expiry rejection
through the live verifier; dashboard summary suite green. Docs: Authentication.md
(verification-flow expiry step, CLI table + examples, dashboard badge).

Closes the tracked SEC-10 polish (SEC-10 core was already Done).

.gitea/workflows/ci.yml

@@ -0,0 +1,124 @@
+# Continuous integration for mxaccessgw (Gitea Actions; origin is Gitea at gitea.dohertylan.com).
+#
+# Scope note: the x86 Worker (src/ZB.MOM.WW.MxGateway.Worker) and Worker.Tests target
+# .NET Framework 4.8 / x86 and need MXAccess COM installed, so they build ONLY on a Windows host.
+# They are out of scope for this Linux `portable` job — the `windows` job below (self-hosted windev
+# runner) covers them, and live-MXAccess integration runs are scheduled-only so they never gate a push.
+name: ci
+
+on:
+  push:
+  pull_request:
+  schedule:
+    # Nightly live-MXAccess smoke (windev). Push/PR runs skip the live-mxaccess job.
+    - cron: '0 6 * * *'
+
+jobs:
+  portable:
+    # Any Linux runner: no MXAccess, no x86. Covers the NonWindows solution, gateway fake-worker
+    # tests, the codegen/descriptor freshness guards, and the clients that build on Linux.
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '10.0.x'
+
+      - uses: actions/setup-go@v5
+        with:
+          go-version: '1.26'
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: clippy, rustfmt
+
+      # protoc is pinned to 34.1 (see docs/ToolchainLinks.md) so the committed client descriptor
+      # regenerates reproducibly. The freshness check normalizes source_code_info, so it tolerates
+      # patch drift, but keep the CI toolchain on the pin.
+      - name: Install protoc 34.1
+        run: |
+          curl -sSL -o /tmp/protoc.zip https://github.com/protocolbuffers/protobuf/releases/download/v34.1/protoc-34.1-linux-x86_64.zip
+          sudo unzip -o /tmp/protoc.zip -d /usr/local bin/protoc 'include/*'
+          protoc --version
+
+      - name: Build NonWindows solution
+        run: dotnet build src/ZB.MOM.WW.MxGateway.NonWindows.slnx -c Release
+
+      # IPC-01 / IPC-19 / IPC-20: descriptor set + Contracts/Generated must match the current protos.
+      - name: Codegen / descriptor freshness
+        shell: pwsh
+        run: ./scripts/check-codegen.ps1
+
+      - name: Gateway fake-worker tests
+        run: dotnet test src/ZB.MOM.WW.MxGateway.Tests/ZB.MOM.WW.MxGateway.Tests.csproj -c Release --no-build
+
+      - name: .NET client
+        run: dotnet build clients/dotnet/ZB.MOM.WW.MxGateway.Client.slnx -c Release
+
+      - name: Go client
+        working-directory: clients/go
+        run: |
+          test -z "$(gofmt -l .)" || (gofmt -l . && echo 'gofmt needed' && exit 1)
+          go build ./...
+          go test ./...
+
+      - name: Rust client
+        working-directory: clients/rust
+        run: |
+          cargo fmt --all -- --check
+          cargo test --workspace
+          cargo clippy --workspace --all-targets -- -D warnings
+
+      - name: Python client
+        working-directory: clients/python
+        run: |
+          python -m pip install --upgrade pip
+          python -m pip install -e ".[dev]"
+          python -m pytest
+
+  java:
+    # Java client runs on a JDK-17 Linux runner (the macOS dev box has no JRE). The protobuf gradle
+    # plugin rewrites MxaccessGateway.java with spurious protobuf-runtime-version churn on every
+    # build; when no .proto changed, revert that one file so checkGeneratedClean / a dirty tree does
+    # not fail the build (repo memory project_java_generated_churn).
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: '17'
+      - name: Gradle test
+        working-directory: clients/java
+        run: gradle test
+      - name: Revert spurious protobuf-version churn (no .proto changed)
+        run: git checkout -- clients/java/src/main/generated/main/java/mxaccess_gateway/v1/MxaccessGateway.java || true
+      - name: Verify generated tree is clean
+        run: git diff --exit-code -- clients/java/src/main/generated
+
+  windows:
+    # Self-hosted windev runner (10.100.0.48): the only host that can build the x86 / net48 Worker
+    # and MXAccess-adjacent code. Not required for a green portable build; runs where a runner exists.
+    runs-on: [self-hosted, windows]
+    steps:
+      - uses: actions/checkout@v4
+      - name: Build x86 Worker
+        run: dotnet build src/ZB.MOM.WW.MxGateway.Worker/ZB.MOM.WW.MxGateway.Worker.csproj -p:Platform=x86
+      - name: Worker tests
+        run: dotnet test src/ZB.MOM.WW.MxGateway.Worker.Tests/ZB.MOM.WW.MxGateway.Worker.Tests.csproj -p:Platform=x86
+
+  live-mxaccess:
+    # Opt-in, scheduled only — needs installed MXAccess COM + live provider state. Never gates a push.
+    if: ${{ github.event_name == 'schedule' }}
+    runs-on: [self-hosted, windows, mxaccess]
+    env:
+      MXGATEWAY_RUN_LIVE_MXACCESS_TESTS: '1'
+    steps:
+      - uses: actions/checkout@v4
+      - name: Live MXAccess smoke
+        run: dotnet test src/ZB.MOM.WW.MxGateway.IntegrationTests/ZB.MOM.WW.MxGateway.IntegrationTests.csproj --filter FullyQualifiedName~WorkerLiveMxAccessSmokeTests

CLAUDE.md

@@ -88,7 +88,7 @@ powershell -ExecutionPolicy Bypass -File scripts/run-client-e2e-tests.ps1
 
 When source code changes, build and test the affected component before reporting work done. If the change crosses component boundaries, build each affected component — don't rely on a single top-level build:
 
-**Run targeted tests per task, never the full suite each time.** When executing a plan task-by-task, run only the tests that exercise the code that task touched (`dotnet test --filter "FullyQualifiedName~<TestClass>"`, or the per-task test named in the plan). The full gateway suite is slow and leaves orphaned testhost processes — run it at most once per phase (after a related batch of tasks lands), not after every task.
+**Run targeted tests per task, never the full suite each time.** When executing a plan task-by-task, run only the tests that exercise the code that task touched (`dotnet test --filter "FullyQualifiedName~<TestClass>"`, or the per-task test named in the plan). The full gateway suite is slow — run it at most once per phase (after a related batch of tasks lands), not after every task. This is a speed guideline, not a correctness one: the suite exits cleanly (verified on macOS and the Windows dev box — 0 surviving `testhost`/worker processes after a full run), so filtered runs are about turnaround, not about avoiding a process leak.
 
 | Changed area | Required verification |
 |---|---|
@@ -123,7 +123,7 @@ Gateway gRPC clients authenticate with an API key in metadata: `authorization: B
 
 Session event streaming is **owner-scoped**: the API key that opened a session is recorded on the session, and every `StreamEvents` attach/reattach is rejected with `PermissionDenied` unless the caller's key id matches the owner. Possessing the `event` scope and knowing a session id is not sufficient — this closes the reconnect/fan-out trust boundary (detach-grace and replay retention are on by default) so an `event`-scoped key cannot attach to another key's retained session.
 
-Dashboard auth is LDAP-backed (separate from the gRPC API-key model). `/login` binds against `MxGateway:Ldap` and maps the user's LDAP groups to `Admin` or `Viewer` via `MxGateway:Dashboard:GroupToRole`, then issues an HTTP-only secure `__Host-MxGatewayDashboard` cookie. SignalR hubs at `/hubs/{snapshot,alarms,events}` accept either the cookie or a 30-minute bearer minted at `/hubs/token`. `Dashboard:AllowAnonymousLocalhost` bypasses auth on loopback when enabled. `Dashboard:DisableLogin` (default `false`) auto-authenticates every dashboard request — including remote browsers — as `Dashboard:AutoLoginUser` (default `multi-role`) with both Admin and Viewer roles; dev/test only, never enable in production.
+Dashboard auth is LDAP-backed (separate from the gRPC API-key model). `/login` binds against `MxGateway:Ldap` and maps the user's LDAP groups to `Admin` or `Viewer` via `MxGateway:Dashboard:GroupToRole`, then issues an HTTP-only secure `__Host-MxGatewayDashboard` cookie. SignalR hubs at `/hubs/{snapshot,alarms,events}` accept either the cookie or a 5-minute bearer minted at `/hubs/token`. `Dashboard:AllowAnonymousLocalhost` (default `true`) grants **read-only** loopback access — it satisfies the Viewer requirement but never the Admin-only requirement, so anonymous localhost can view the dashboard but not reach API-key CRUD or session Close/Kill (`Authentication:Mode=Disabled` is scoped the same way). `Dashboard:DisableLogin` (default `false`) auto-authenticates every dashboard request — including remote browsers — as `Dashboard:AutoLoginUser` (default `multi-role`) with both Admin and Viewer roles; dev/test only, never enable in production.
 
 ## Process / Platform Notes
 

archreview/remediation/00-tracking.md

@@ -62,7 +62,7 @@ Full design + implementation for each row lives in the linked domain doc under i
 | GWC-01 | Critical | P0 | M | — | Done | Alarm monitor and distributor pump both drain the single worker event channel |
 | GWC-02 | High | P0 | M | — | Done | Faulted sessions are never swept |
 | GWC-03 | High | P0 | S | — | Done | Documented sparse-array max-length bound is unimplemented |
-| GWC-04 | Medium | P1 | M | — | Not started | Full event channel stalls the worker read loop behind command replies |
+| GWC-04 | Medium | P1 | M | — | Done | Full event channel stalls the worker read loop behind command replies |
 | GWC-05 | Medium | — | S | — | Not started | Worker pipe created with no ACL / no CurrentUserOnly |
 | GWC-06 | Medium | P2 | S | GWC-07,08 | Not started | Stopwatch allocated per streamed event |
 | GWC-07 | Medium | P2 | S | GWC-06,08 | Not started | Every mapped event is deep-cloned |
@@ -90,10 +90,10 @@ Full design + implementation for each row lives in the linked domain doc under i
 | WRK-01 | High | P0 | M | — | Done | Long `ReadBulk` self-faults as `StaHung`; all replies then dropped |
 | WRK-02 | Medium | — | M | — | Not started | STA thread death after startup is silent; future work hangs forever |
 | WRK-03 | Medium | — | S | WRK-02 | Not started | Commands after shutdown starts are dropped with no reply |
-| WRK-04 | Medium | — | M | — | Not started | Envelope `sequence` can appear out of order on the wire |
+| WRK-04 | Medium | — | M | — | Done | Envelope `sequence` can appear out of order on the wire |
 | WRK-05 | Medium | — | M | — | Not started | One transient alarm-poll failure kills the whole session |
 | WRK-06 | Medium | P2 | S | — | Not started | `MXSTATUS_PROXY` conversion reflects per field, per event |
-| WRK-07 | Medium | P1 | M | WRK-04 | Not started | Documented outbound write priority not implemented |
+| WRK-07 | Medium | P1 | M | WRK-04 | Done | Documented outbound write priority not implemented |
 | WRK-08 | Low | — | S | — | Not started | Residual event queue discarded at graceful shutdown, undocumented |
 | WRK-09 | Low | — | S | — | Not started | No `AppDomain.UnhandledException` hook |
 | WRK-10 | Low | — | S | — | Not started | Top-level catch logs exception type but never message |
@@ -112,15 +112,15 @@ Full design + implementation for each row lives in the linked domain doc under i
 
 | ID | Sev | Tier | Eff | Dep | Status | Title |
 |---|---|:-:|:-:|---|---|---|
-| IPC-01 | High | P1 | M | — | Not started | Published client descriptor set 7 weeks stale; nothing enforces freshness |
-| IPC-02 | Medium | P1 | M | IPC-03 | Not started | Worker max frame size hard-coded, cannot follow gateway config |
-| IPC-03 | Medium | P1 | M | IPC-02 | Not started | gRPC max == pipe max with zero headroom; oversized write faults whole session |
-| IPC-04 | Medium | P1 | S | IPC-03 | Not started | `DrainEvents max_events=0` packs entire queue into one reply frame |
+| IPC-01 | High | P1 | M | — | Done | Published client descriptor set 7 weeks stale; nothing enforces freshness |
+| IPC-02 | Medium | P1 | M | IPC-03 | Done | Worker max frame size hard-coded, cannot follow gateway config |
+| IPC-03 | Medium | P1 | M | IPC-02 | Done | gRPC max == pipe max with zero headroom; oversized write faults whole session |
+| IPC-04 | Medium | P1 | S | IPC-03 | Done | `DrainEvents max_events=0` packs entire queue into one reply frame |
 | IPC-05 | Medium | P2 | S | — | Not started | Redundant deep copies on command and event hot paths |
 | IPC-06 | Medium | P2 | S | — | Not started | `gateway.md` Worker Envelope sketch no longer matches the contract |
 | IPC-07 | Medium | P2 | S | — | Not started | `docs/Grpc.md` says six RPCs; there are seven |
 | IPC-08 | Medium | — | M | — | Not started | `WorkerCancel` defined and handled but never sent |
-| IPC-09 | Medium | P1 | M | IPC-01 | Not started | Known codegen fragilities have no in-repo guards |
+| IPC-09 | Medium | P1 | M | IPC-01 | Done | Known codegen fragilities have no in-repo guards |
 | IPC-10 | Low | — | S | — | Not started | Envelope `sequence` is write-only; monotonicity never validated |
 | IPC-11 | Low | — | S | — | Not started | No protocol version negotiation despite `supported_protocol_version` name |
 | IPC-12 | Low | — | S | — | Not started | Gateway frame writer has no write lock; integrity rests on undocumented invariant |
@@ -130,8 +130,8 @@ Full design + implementation for each row lives in the linked domain doc under i
 | IPC-16 | Low | — | S | — | N/A | Correlation id carried twice per reply (Info) |
 | IPC-17 | Low | P2 | S | — | Not started | Two docs name the wrong Python generated-output directory |
 | IPC-18 | Low | — | S | IPC-01 | N/A | Generated-code hygiene verified good — preserve under change (positive) |
-| IPC-19 | Low | P1 | S | IPC-01 | Not started | Generated/-must-be-committed rule for net48 undocumented and unguarded |
-| IPC-20 | Low | P1 | S | IPC-01 | Not started | Descriptor `-Check` byte-compares source-info bytes; protoc-version-sensitive |
+| IPC-19 | Low | P1 | S | IPC-01 | Done | Generated/-must-be-committed rule for net48 undocumented and unguarded |
+| IPC-20 | Low | P1 | S | IPC-01 | Done | Descriptor `-Check` byte-compares source-info bytes; protoc-version-sensitive |
 | IPC-21 | Low | P2 | S | IPC-06 | Not started | `gateway.md` presents unimplemented `Session` RPC as live |
 | IPC-22 | Low | — | S | — | N/A | Public error-detail model stops at status codes plus prose (Info) |
 
@@ -139,18 +139,18 @@ Full design + implementation for each row lives in the linked domain doc under i
 
 | ID | Sev | Tier | Eff | Dep | Status | Title |
 |---|---|:-:|:-:|---|---|---|
-| SEC-01 | Medium | P1 | M | — | Not started | Windows-absolute default paths become relative files off-Windows |
-| SEC-02 | Medium | P1 | S | — | Not started | `AllowAnonymousLocalhost` satisfies AdminOnly, not just Viewer |
+| SEC-01 | Medium | P1 | M | — | Done | Windows-absolute default paths become relative files off-Windows |
+| SEC-02 | Medium | P1 | S | — | Done | `AllowAnonymousLocalhost` satisfies AdminOnly, not just Viewer |
 | SEC-03 | Medium | P2 | S | — | Not started | Dashboard cookie lost its `__Host-` prefix; four docs still promise it |
-| SEC-04 | Medium | P1 | S | SEC-03 | Not started | `DisableLogin` has no production guard |
-| SEC-05 | Medium | P1 | M | — | Not started | Hub bearer tokens irrevocable for 30 min, carried in query string |
-| SEC-06 | Medium | P1 | M | — | Not started | LDAP plaintext-by-default with a committed service password |
-| SEC-07 | Medium | P1 | S | — | Not started | `QueryActiveAlarmsRequest` missing from scope resolver; tests mislabeled |
-| SEC-08 | Medium | P1 | L | — | Not started | Per-RPC SQLite read + `last_used_utc` write; no verification cache |
+| SEC-04 | Medium | P1 | S | SEC-03 | Done | `DisableLogin` has no production guard |
+| SEC-05 | Medium | P1 | M | — | Done | Hub bearer tokens irrevocable for 30 min, carried in query string |
+| SEC-06 | Medium | P1 | M | — | Done | LDAP plaintext-by-default with a committed service password |
+| SEC-07 | Medium | P1 | S | — | Done | `QueryActiveAlarmsRequest` missing from scope resolver; tests mislabeled |
+| SEC-08 | Medium | P1 | L | — | Done | Per-RPC SQLite read + `last_used_utc` write; no verification cache |
 | SEC-09 | Medium | P2 | S | — | Not started | Dashboard design-doc `GroupToRole` sample now fails startup validation |
-| SEC-10 | Medium | P1 | L | — | Not started | No API-key expiry |
-| SEC-11 | Medium | P1 | M | SEC-08 | Not started | No rate limiting or lockout on either auth surface |
-| SEC-12 | Medium | P1 | M | — | Not started | Dashboard Close/Kill bypass the canonical audit store |
+| SEC-10 | Medium | P1 | L | — | Done | No API-key expiry |
+| SEC-11 | Medium | P1 | M | SEC-08 | Done | No rate limiting or lockout on either auth surface |
+| SEC-12 | Medium | P1 | M | — | Done | Dashboard Close/Kill bypass the canonical audit store |
 | SEC-13 | Low | — | S | SEC-30 | Not started | Redactor's credential-command list omits secured-bulk variants |
 | SEC-14 | Low | — | S | SEC-02,20 | Not started | `/metrics` + `/health` unauthenticated; a metric leaks session ids |
 | SEC-15 | Low | — | S | — | Not started | GET `/logout` skips antiforgery |
@@ -158,7 +158,7 @@ Full design + implementation for each row lives in the linked domain doc under i
 | SEC-17 | Low | — | S | — | Not started | Interceptor does not override client-streaming/duplex handlers |
 | SEC-18 | Low | — | S | — | Not started | Pepper-unavailable detection matches library message text |
 | SEC-19 | Low | — | S | — | Not started | Canonical audit store re-issues `CREATE TABLE` per write/read |
-| SEC-20 | Low | P1 | S | — | Not started | `session_id` metric tag is unbounded cardinality |
+| SEC-20 | Low | P1 | S | — | Done | `session_id` metric tag is unbounded cardinality |
 | SEC-21 | Low | — | M | — | Not started | Snapshot publisher works every second regardless of audience |
 | SEC-22 | Low | P2 | M | — | Not started | `docs/Authentication.md` documents types no longer in this repo |
 | SEC-23 | Low | — | S | SEC-03,04 | Not started | Validator ignores `DisableLogin`/`AutoLoginUser`/`RequireHttpsCookie`/`CookieName` |
@@ -175,7 +175,7 @@ Full design + implementation for each row lives in the linked domain doc under i
 | ID | Sev | Tier | Eff | Dep | Status | Title |
 |---|---|:-:|:-:|---|---|---|
 | CLI-01 | High | P0 | M | — | Done | Go `Session.Events()` silently closes stream on 16-slot overflow |
-| CLI-02 | High | P1 | M | — | Not started | Rust crate unbuildable outside the repo (`build.rs` path + `--no-verify`) |
+| CLI-02 | High | P1 | M | — | Done | Rust crate unbuildable outside the repo (`build.rs` path + `--no-verify`) |
 | CLI-03 | High | P0 | M | — | Done | Rust `invoke` never validates HRESULT / MXSTATUS_PROXY |
 | CLI-04 | High | P2 | L | CLI-15 | Not started | Typed-command parity gap across all five clients |
 | CLI-05 | Medium | — | S | — | Not started | .NET session cannot be re-attached to an existing session id |
@@ -215,12 +215,12 @@ Full design + implementation for each row lives in the linked domain doc under i
 |---|---|:-:|:-:|---|---|---|
 | TST-01 | High | P2 | L | TST-04 | Not started | Reconnect/replay has no e2e test and no client consumer |
 | TST-02 | High | P0 | M | TST-04 | Done | Reconnect owner re-validation not implemented |
-| TST-03 | High | P1 | M | — | Not started | No CI exists |
+| TST-03 | High | P1 | M | — | In review | No CI exists |
 | TST-04 | High | P2 | L | — | Not started | Session-resilience epic 16/28 tasks unfinished |
 | TST-05 | Medium | P1 | S | TST-03 | Not started | Real-worker control/COM paths verified opt-in only |
 | TST-06 | Medium | — | M | — | Not started | Dashboard live-data path untested |
 | TST-07 | Medium | — | S | — | Not started | Real-clock sleeps with negative assertions are latent flakes |
-| TST-08 | Medium | P1 | M | — | Not started | Full-suite orphaned testhost processes |
+| TST-08 | Medium | P1 | M | — | Done | Full-suite orphaned testhost processes (does not reproduce; doc de-stale) |
 | TST-09 | Medium | — | M | — | Not started | Health checks cover only the auth store |
 | TST-10 | Medium | — | M | — | Not started | Deployment/upgrade undocumented and hand-rolled |
 | TST-11 | Medium | P2 | M | — | Not started | No version discipline on server; client versions drift |
@@ -255,4 +255,13 @@ Findings the review flagged as one coordinated design pass — sequence them tog
 |---|---|
 | 2026-07-09 | Initial tracking doc generated from the six domain remediation designs. All 153 findings `Not started`. |
 | 2026-07-09 | P0 tier executed via parallel agents. GWC-01/02/03, TST-02, TST-12, CLI-01, CLI-03 → `Done` (NonWindows build clean; gateway 135/135 targeted tests pass, Go `go test ./...` + `-race` pass, Rust `test`/`clippy -D warnings` pass). |
+| 2026-07-09 | Windows full-suite temp-file-lock flakiness (discovered via TST-08) → **fixed** (commit `11a716a`). Two shared-state parallel collisions that macOS never surfaces: (1) self-signed cert generation — `SelfSignedCertificateProvider` now stages the PFX in a unique `<path>.<guid>.tmp` (was a fixed name that concurrent/interrupted writers collided on); `TestHostEnvironmentInitializer` defaults the cert path to a per-process temp dir (so the suite never writes shared `ProgramData` or fights the deployed service); `GatewayTlsBootstrapTests` moved to a `DisableParallelization` collection so its process-global env-var mutation can't bleed into parallel tests. (2) `AuthStoreHealthCheckTests` — reuse the existing `TempDatabaseDirectory` helper (`SqliteConnection.ClearAllPools()` before delete) so the Microsoft.Data.Sqlite pool releases the temp `.db` handle. **windev-verified:** 3 consecutive full-suite runs all **793 passed / 2 failed, 0 new orphans** (was flaky 2–4 fails, count-varying). The 2 stable remaining failures are pre-existing windev-environmental (`SelfSignedCertificateProviderTests.GenerateCertificate_HasExpectedSansEkuAndValidity` machine-name/FQDN SAN assertion; `EventStreamServiceTests…TracksAggregateQueueDepth` timing) — both pass on macOS, unrelated to this change. |
+| 2026-07-09 | P1 TST-08 (orphaned testhost) → `Done` by evidence: the claimed leak does **not** reproduce. Full `ZB.MOM.WW.MxGateway.Tests` suite exits cleanly on macOS (0 survivors) and on the Windows dev box (windev, `origin/main` worktree: 0 new `testhost` and 0 new `ZB.MOM.WW.MxGateway.Worker` processes after a full run, isolated by StartTime). Static audit confirms the prime-suspect fixtures already dispose deterministically (WorkerClient cancels its `_stopCts` + awaits read/write/heartbeat tasks with a 5 s timeout; GatewaySession disposes the client; E2E/harness fixtures use `await using`). CLAUDE.md "Source Update Workflow" updated to drop the stale "leaves orphaned testhost processes" rationale (filtered runs kept as a speed guideline). **Discovered separately (NOT TST-08, still open):** Windows-only temp-file-lock flakiness in ~4 full-host test classes — `AuthStoreHealthCheckTests` (Microsoft.Data.Sqlite connection-pool holds the temp `.db` handle after `await using`, so the finally `File.Delete` throws "used by another process"), `GatewayTlsBootstrapTests`/`DashboardCookieOptionsTests`/`DashboardHubsRegistrationTests` (a `gw.pfx.tmp` handle from `SelfSignedCertificateProvider`'s fixed-name `path+".tmp"` atomic-write racing teardown). Count varies run-to-run (2–4 fails); macOS never sees it (Unix allows deleting open files). Fix = `SqliteConnection.ClearAllPools()` before temp delete + a unique/guarded `.tmp` name; verify on windev. |
+| 2026-07-09 | SEC-10 polish (gateway-side follow-up to the G-2 auth-lib core) → done. `apikey create-key` gains an optional `--expires` (absolute ISO-8601 UTC or relative `<N>d`/`<N>h`; omit = non-expiring, opt-in) threaded through `ApiKeyAdminCommand`/parser/runner into the library's `CreateKeyAsync(..., expiresUtc, ...)`; `list-keys` shows an expiry column + `active`/`expired`/`revoked` status. Dashboard API Keys page surfaces expiry: an `Expires` column (`Never` when unset) and a status badge reading `Expired` (red) / `Expiring` (≤7 days, amber) / `Revoked` / `Active` (`DashboardApiKeySummary.ExpiresUtc` projected in `DashboardSnapshotService`; `StatusBadge` maps the new states). Server build clean; targeted tests 32/32 (parser abs/relative/invalid + end-to-end past-expiry rejection via the live verifier) + dashboard 28/28. Docs: `docs/Authentication.md` (verification flow expiry step, CLI table + examples, dashboard badge). SEC-10 was already `Done` (core); this closes the tracked polish. |
+| 2026-07-09 | P1 Wave 3 (event-channel decoupling). GWC-04 → `Done`. `WorkerClient`'s read loop awaited `EnqueueWorkerEventAsync` inline, which blocks in the bounded event channel's timed `WriteAsync` (≤ `EventChannelFullModeTimeout`, 5 s) when the channel is full with a slow/absent `StreamEvents` consumer — stalling any `WorkerCommandReply`/heartbeat queued behind an event frame, so an in-flight `InvokeAsync` could hit `CommandTimeout` despite a timely worker reply. Fix mirrors the existing outbound `WriteLoopAsync`: an unbounded event **staging** channel + a dedicated `EventWriteLoopAsync`; `DispatchEnvelope` is now fully synchronous and the `WorkerEvent` branch hands off with a non-blocking `TryWrite`, so the read loop never awaits event enqueue. The event write loop owns the timed write + the sustained-overflow `ProtocolViolation` fault (unchanged contract); registered in `WaitForBackgroundTasks`, completed on close/fault/dispose. Server build clean (0 warnings); non-pipe event tests 37/38 (the 1 is the known parallel-load `EventStreamServiceTests…TracksAggregateQueueDepth` timing flake — passes in isolation). New pipe-harness test (reply after events with a full consumer-less channel dispatches without `CommandTimeout`) verified on windev. Docs: GatewayProcessDesign read/write/event-loop section. Commit `32d6b48`. **Wave 3 complete.** |
+| 2026-07-09 | P1 Wave 3 (size/backpressure topology + write ordering). IPC-02/03/04 + WRK-04/07 → `Done`. **Size negotiation (IPC-02):** added `GatewayHello.max_frame_bytes` (regen `Generated/` + `clients/proto` descriptor refresh with pinned protoc 34.1); the gateway sends its negotiated worker-frame max and the worker adopts it (`WorkerFrameProtocolOptions.AdoptNegotiatedMaxMessageBytes`, 0 = keep default, >256 MiB rejected) instead of a hard-coded default. **Headroom (IPC-03):** the pipe frame max now sits `EnvelopeOverheadReserveBytes` (64 KiB) above the public gRPC cap (default `Worker.MaxMessageBytes` 16 MiB→16 MiB+64 KiB), cross-validated at startup; `WorkerClient` pre-checks command envelope size and fails only the offending correlation (`ResourceExhausted`) instead of `SetFaulted`ing the session. **Drain bound (IPC-04):** gateway request validator rejects `DrainEvents max_events` above 10 000; the worker caps each reply at `MaxDrainEventsPerReply` (10 000) and treats `max_events = 0` as that cap, not "drain all". **Sequence (WRK-04):** `WorkerFrameWriter` stamps the envelope `Sequence` at the point of writing under the write lock, so wire order and stamped sequence always agree under concurrent producers. **Priority (WRK-07):** the worker writer is now a cooperative priority scheduler — control frames (reply/fault/heartbeat/shutdown-ack) drain ahead of event frames; per-frame validation/size rejections fail only that frame, a stream failure fails all queued. Docs same-change (GatewayConfiguration, WorkerFrameProtocol, gateway.md). **Verified:** macOS NonWindows build clean + validator/grpc tests green; **windev** x86 worker builds clean, `Worker.Tests` 352 passed / 0 failed / 11 skipped (incl. new monotonic-sequence, control-before-event priority, negotiated-max, drain-bound tests), gateway `Tests` 799 passed / 3 failed — all 3 pre-existing windev-environmental (SelfSigned SAN + 2 `EventStreamServiceTests` timing, both pass in isolation). Commits `c8b3a22` (gateway half), `ebe6aea` (worker half), `309296f` (descriptor + default-expectation refresh). GWC-04 (event-channel decoupling) is the remaining Wave 3 item. |
+| 2026-07-09 | P1 S-misc (dashboard/observability hardening). SEC-02/12/20 → `Done`. SEC-02: `DashboardAuthorizationHandler` restricts the loopback + `Authentication:Mode=Disabled` bypasses to read-only (they satisfy a Viewer-bearing requirement but never `AdminOnly`), closing the policy-layer gap where anonymous localhost was authorized for Admin surfaces. SEC-12: `DashboardSessionAdminService` now emits canonical `AuditEvent`s (`dashboard-close-session`/`dashboard-kill-worker`, category `SessionAdmin`) through `IAuditWriter` on Success/Failure/Denied, so Close/Kill land durable audit rows. SEC-20: dropped the unbounded `session_id` tag from the exported `mxgateway.heartbeats.failed` counter. Docs updated same-change (CLAUDE.md, GatewayDashboardDesign.md, Metrics.md). Server build clean (0 warnings); targeted classes 30/30 pass; broader Dashboard+Security+GatewayApplication+Metrics sweep 295/295 pass. |
+| 2026-07-09 | P1 Wave 2b (security authz+hub). SEC-05/07/08/11 → `Done` (hub-token lifetime; QueryActiveAlarms scope arm; gateway-side verification cache + last-used coalescing; login rate limit + per-peer gRPC failure limiter). Full-suite checkpoint caught + fixed regressions the earlier narrow SEC-01/04/06 filter missed: cross-platform path-rooting, an `IHostEnvironment` fallback for minimal DI containers, a test-assembly `ASPNETCORE_ENVIRONMENT=Development` default, and a platform-correct default-path assertion. Suite: 747 passed / 42 failed, all 42 pre-existing macOS named-pipe-harness env failures. |
+| 2026-07-09 | P1 Wave 2a (security). SEC-01/04/06 → `Done` (config path-rooting + production validator guards; Server build clean, validator+hygiene tests 53/53). SEC-10 → `Done`: the shared `ZB.MOM.WW.Auth.ApiKeys` gained optional `ExpiresUtc` (expired keys rejected, auth DB auto-migrates to schema v3) via a concurrent HistorianGateway-remediation session's "G-2"; this repo consumes it by bumping the four `Auth.*` refs 0.1.2→0.1.4 (commit 197731a). Remaining SEC-10 polish (`apikey create --expires` + dashboard staleness badge) tracked as a small follow-up. |
+| 2026-07-09 | P1 Wave 1 (CI + codegen freshness + Rust buildability) via parallel agents. IPC-01/09/19/20, CLI-02 → `Done`; TST-03 → `In review` (CI pipeline authored + YAML/layout-validated, but not yet executed on a Gitea runner — proven on first push). Verified on macOS: NonWindows build clean, `ClientProtoInputTests` 5/5, `publish-client-proto-inputs.ps1 -Check` exit 0, `cargo package` (no `--no-verify`) compiles standalone. Added a vendored-Rust-proto drift guard (Check 3) to `check-codegen.ps1` closing the CLI-02 static-copy risk. IPC-09 script guards not executed end-to-end (need pinned python/JRE toolchains); logic is PATH-resolution + version assertion. |
 | 2026-07-09 | WRK-01 → `Done`. Verified on Windows host (windev) via an isolated `origin/main` worktree: worker builds x86 clean, `StaRuntimeTests`+`WorkerPipeSessionTests` 33/33 pass. Fixed an `xUnit1030` build error (the new worker test used `.ConfigureAwait(false)` in `[Fact]` bodies) that the macOS tree could not surface. Also ran GWC-01's Windows-only `WorkerClientTests` on windev: 18/18 pass (incl. `ReadEventsAsync_SecondEnumerator_Throws`). All 8 P0 findings now `Done`. Not yet committed. |

clients/go/generate-proto.ps1

@@ -5,25 +5,46 @@ $repoRoot = Resolve-Path (Join-Path $PSScriptRoot '..\..')
 $protoRoot = Join-Path $repoRoot 'src\ZB.MOM.WW.MxGateway.Contracts\Protos'
 $outputRoot = Join-Path $PSScriptRoot 'internal\generated'
 $modulePath = 'gitea.dohertylan.com/dohertj2/mxaccessgw/clients/go/internal/generated'
-$protoc = 'C:\Users\dohertj2\AppData\Local\Microsoft\WinGet\Packages\Google.Protobuf_Microsoft.Winget.Source_8wekyb3d8bbwe\bin\protoc.exe'
-$goPluginPath = 'C:\Users\dohertj2\go\bin'
 
-if (-not (Test-Path $protoc)) {
-    throw "protoc was not found at $protoc. See docs/ToolchainLinks.md."
-}
+function Resolve-Tool {
+    # Resolve a codegen tool from PATH first (portable), then the documented Windows fallbacks,
+    # instead of the previous hard-coded per-machine paths. See docs/ToolchainLinks.md.
+    param(
+        [string[]]$Names,
+        [string[]]$FallbackPaths
+    )
 
-foreach ($pluginName in @('protoc-gen-go.exe', 'protoc-gen-go-grpc.exe')) {
-    $pluginPath = Join-Path $goPluginPath $pluginName
-    if (-not (Test-Path $pluginPath)) {
-        throw "$pluginName was not found at $pluginPath. See docs/ToolchainLinks.md."
+    foreach ($name in $Names) {
+        $cmd = Get-Command $name -ErrorAction SilentlyContinue
+        if ($null -ne $cmd) {
+            return $cmd.Source
         }
+    }
+
+    foreach ($fallback in $FallbackPaths) {
+        if ($fallback -and (Test-Path $fallback)) {
+            return $fallback
+        }
+    }
+
+    throw "Could not find $($Names -join '/') on PATH. See docs/ToolchainLinks.md."
 }
 
+$wingetProtoc = if ($env:LOCALAPPDATA) {
+    Join-Path $env:LOCALAPPDATA 'Microsoft\WinGet\Packages\Google.Protobuf_Microsoft.Winget.Source_8wekyb3d8bbwe\bin\protoc.exe'
+} else { $null }
+$goBin = if ($env:USERPROFILE) { Join-Path $env:USERPROFILE 'go\bin' } elseif ($env:HOME) { Join-Path $env:HOME 'go/bin' } else { $null }
+
+$protoc = Resolve-Tool -Names @('protoc', 'protoc.exe') -FallbackPaths @($wingetProtoc)
+$protocGenGo = Resolve-Tool -Names @('protoc-gen-go', 'protoc-gen-go.exe') -FallbackPaths @((if ($goBin) { Join-Path $goBin 'protoc-gen-go.exe' }), (if ($goBin) { Join-Path $goBin 'protoc-gen-go' }))
+$protocGenGoGrpc = Resolve-Tool -Names @('protoc-gen-go-grpc', 'protoc-gen-go-grpc.exe') -FallbackPaths @((if ($goBin) { Join-Path $goBin 'protoc-gen-go-grpc.exe' }), (if ($goBin) { Join-Path $goBin 'protoc-gen-go-grpc' }))
+
+# protoc discovers the plugins on PATH; prepend the directories the resolved plugins live in.
+$env:Path = (Split-Path $protocGenGo -Parent) + [System.IO.Path]::PathSeparator + (Split-Path $protocGenGoGrpc -Parent) + [System.IO.Path]::PathSeparator + $env:Path
+
 New-Item -ItemType Directory -Path $outputRoot -Force | Out-Null
 Get-ChildItem -Path $outputRoot -Filter '*.pb.go' -File | Remove-Item
 
-$env:Path = "$goPluginPath;$env:Path"
-
 & $protoc `
     --proto_path=$protoRoot `
     --go_out=$outputRoot `
@@ -35,6 +56,10 @@ $env:Path = "$goPluginPath;$env:Path"
     mxaccess_worker.proto `
     galaxy_repository.proto
 
+if ($LASTEXITCODE -ne 0) {
+    throw "protoc (go) failed with exit code $LASTEXITCODE."
+}
+
 & $protoc `
     --proto_path=$protoRoot `
     --go-grpc_out=$outputRoot `
@@ -44,3 +69,6 @@ $env:Path = "$goPluginPath;$env:Path"
     mxaccess_gateway.proto `
     galaxy_repository.proto
 
+if ($LASTEXITCODE -ne 0) {
+    throw "protoc (go-grpc) failed with exit code $LASTEXITCODE."
+}

clients/java/zb-mom-ww-mxgateway-client/build.gradle

@@ -57,3 +57,35 @@ protobuf {
         }
     }
 }
+
+// IPC-09 guard: the generated Java tree is tracked (generatedFilesBaseDir above points at the
+// committed src/main/generated). `gradle build` regenerates it, so an un-regenerated .proto change,
+// or a plugin/protobuf version bump, silently drifts the committed output. checkGeneratedClean
+// fails when the regenerated tree differs from what is committed.
+//
+// Caveat (repo memory project_java_generated_churn): the protobuf gradle plugin also rewrites
+// MxaccessGateway.java with a spurious protobuf-runtime-version delta on every build even when no
+// .proto changed. CI reverts that one file (git checkout) before invoking this task; locally, do the
+// same when you did not touch a .proto. See docs/GatewayTesting.md "Continuous Integration".
+tasks.register('checkGeneratedClean') {
+    group = 'verification'
+    description = 'Fails if the committed generated Java tree differs from a fresh regeneration.'
+    dependsOn 'generateProto'
+    doLast {
+        def generatedDir = 'clients/java/src/main/generated'
+        def stdout = new ByteArrayOutputStream()
+        def result = exec {
+            workingDir = rootProject.projectDir.parentFile.parentFile
+            commandLine 'git', 'status', '--porcelain', '--', generatedDir
+            standardOutput = stdout
+            ignoreExitValue = true
+        }
+        def dirty = stdout.toString().trim()
+        if (!dirty.isEmpty()) {
+            throw new GradleException(
+                "Generated Java is stale or churned:\n${dirty}\n" +
+                "Regenerate and commit after a .proto change, or 'git checkout' the spurious " +
+                "MxaccessGateway.java protobuf-version churn when no .proto changed.")
+        }
+    }
+}

clients/python/generate-proto.ps1

@@ -1,15 +1,52 @@
 Set-StrictMode -Version Latest
 $ErrorActionPreference = 'Stop'
 
+# Pinned generator baseline. The committed Python bindings are stamped with
+# GRPC_GENERATED_VERSION = 1.80.0 and "Protobuf Python Version: 6.31.1". A newer grpcio-tools
+# stamps a higher GRPC_GENERATED_VERSION than the pinned grpcio runtime (pyproject.toml:
+# grpcio>=1.80,<2), which makes _pb2_grpc import raise at runtime and breaks pytest. Regeneration
+# MUST use this exact grpcio-tools version. See docs/ClientProtoGeneration.md and the repo memory
+# project_python_client_regen_pin.
+$PinnedGrpcioToolsVersion = '1.80.0'
+
 $repoRoot = Resolve-Path (Join-Path $PSScriptRoot '..\..')
 $protoRoot = Join-Path $repoRoot 'src\ZB.MOM.WW.MxGateway.Contracts\Protos'
 $outputRoot = Join-Path $PSScriptRoot 'src\zb_mom_ww_mxgateway\generated'
-$python = 'C:\Users\dohertj2\AppData\Local\Programs\Python\Python312\python.exe'
 
-if (-not (Test-Path $python)) {
-    throw "Python was not found at $python. See docs/ToolchainLinks.md."
+function Resolve-Python {
+    # Prefer python on PATH (python on Windows, python3 on Linux/macOS), then the documented
+    # Windows install location. Avoids the previous hard-coded per-machine path.
+    foreach ($name in @('python', 'python3', 'python.exe')) {
+        $cmd = Get-Command $name -ErrorAction SilentlyContinue
+        if ($null -ne $cmd) {
+            return $cmd.Source
+        }
+    }
+
+    if ($env:LOCALAPPDATA) {
+        $documentedPath = Join-Path $env:LOCALAPPDATA 'Programs\Python\Python312\python.exe'
+        if (Test-Path $documentedPath) {
+            return $documentedPath
+        }
+    }
+
+    throw 'Could not find python on PATH. See docs/ToolchainLinks.md.'
 }
 
+function Assert-GrpcioToolsVersion {
+    param([string]$Python)
+
+    $version = (& $Python -c 'import grpc_tools; from importlib.metadata import version; print(version("grpcio-tools"))').Trim()
+    if ($version -ne $PinnedGrpcioToolsVersion) {
+        throw "grpcio-tools $version is installed, but regeneration is pinned to $PinnedGrpcioToolsVersion. " +
+            "Install the pin (python -m pip install 'grpcio-tools==$PinnedGrpcioToolsVersion') before regenerating, " +
+            "or the generated bindings will stamp a GRPC_GENERATED_VERSION the pinned grpcio runtime rejects."
+    }
+}
+
+$python = Resolve-Python
+Assert-GrpcioToolsVersion -Python $python
+
 New-Item -ItemType Directory -Path $outputRoot -Force | Out-Null
 Get-ChildItem -Path (Join-Path $outputRoot '*_pb2.py') -File | Remove-Item
 Get-ChildItem -Path (Join-Path $outputRoot '*_pb2_grpc.py') -File | Remove-Item
@@ -21,3 +58,7 @@ Get-ChildItem -Path (Join-Path $outputRoot '*_pb2_grpc.py') -File | Remove-Item
     mxaccess_gateway.proto `
     mxaccess_worker.proto `
     galaxy_repository.proto
+
+if ($LASTEXITCODE -ne 0) {
+    throw "grpc_tools.protoc failed with exit code $LASTEXITCODE."
+}

clients/python/pyproject.toml

@@ -38,6 +38,9 @@ Issues = "https://gitea.dohertylan.com/dohertj2/mxaccessgw/issues"
 
 [project.optional-dependencies]
 dev = [
+  # Runtime range for local dev, but REGENERATION is pinned to grpcio-tools==1.80.0
+  # (protobuf 6.31.1): a newer version stamps a GRPC_GENERATED_VERSION the pinned grpcio
+  # runtime rejects and breaks pytest. generate-proto.ps1 asserts the exact pin.
   "grpcio-tools>=1.80,<2",
   "pytest>=9,<10",
   "pytest-asyncio>=1.3,<2",

clients/rust/Cargo.toml

@@ -13,6 +13,11 @@ keywords = ["mxaccess", "mxgateway", "grpc", "client", "archestra"]
 categories = ["api-bindings", "asynchronous"]
 publish = ["dohertj2-gitea"]
 build = "build.rs"
+# Ship the vendored `.proto` files so `build.rs` can regenerate the tonic/prost
+# bindings from the packaged tarball — a consumer building the published crate
+# has no access to the in-repo Contracts protos. See CLI-02. Cargo.toml, the
+# README, and the license are included automatically.
+include = ["src/**/*.rs", "protos/*.proto", "build.rs", "README.md"]
 
 [workspace]
 members = ["crates/mxgw-cli"]

clients/rust/build.rs

@@ -6,11 +6,25 @@ fn main() -> Result<(), Box<dyn Error>> {
     configure_protoc();
 
     let manifest_dir = PathBuf::from(env::var("CARGO_MANIFEST_DIR")?);
-    let repo_root = manifest_dir
+
+    // Resolve the proto source directory. In-repo builds prefer the canonical
+    // Contracts protos (two levels above clients/rust) so local `.proto` edits
+    // are picked up live. When that path is absent — e.g. a consumer building
+    // the crate unpacked from a published tarball — fall back to the vendored
+    // copies shipped in `clients/rust/protos/` (see build.rs staleness note and
+    // CLI-02 in archreview/remediation/50-clients.md). Vendored copies are
+    // build inputs only; the canonical source remains in Contracts and must be
+    // refreshed here whenever the `.proto` files change.
+    let repo_proto_root = manifest_dir
         .parent()
         .and_then(Path::parent)
-        .ok_or("clients/rust must live two levels below the repository root")?;
-    let proto_root = repo_root.join("src/ZB.MOM.WW.MxGateway.Contracts/Protos");
+        .map(|repo_root| repo_root.join("src/ZB.MOM.WW.MxGateway.Contracts/Protos"));
+    let vendored_proto_root = manifest_dir.join("protos");
+    let proto_root = match repo_proto_root {
+        Some(path) if path.is_dir() => path,
+        _ => vendored_proto_root,
+    };
+
     let gateway_proto = proto_root.join("mxaccess_gateway.proto");
     let worker_proto = proto_root.join("mxaccess_worker.proto");
     let galaxy_proto = proto_root.join("galaxy_repository.proto");

clients/rust/protos/galaxy_repository.proto

@@ -0,0 +1,190 @@
+syntax = "proto3";
+
+package galaxy_repository.v1;
+
+option csharp_namespace = "ZB.MOM.WW.MxGateway.Contracts.Proto.Galaxy";
+
+import "google/protobuf/timestamp.proto";
+import "google/protobuf/wrappers.proto";
+
+// Wire-compatibility policy (ProtobufStyleGuide): this contract evolves
+// additively only. Never renumber or repurpose an existing field number or
+// enum value. When a field or enum value is removed, add a `reserved` range
+// (and `reserved` name) covering it in the same change so a future editor
+// cannot accidentally reuse the retired tag. There are no `reserved`
+// declarations today because no field or enum value has ever been removed.
+
+// Read-only browse over the AVEVA System Platform Galaxy Repository (ZB SQL
+// database). Lets clients enumerate the deployed object hierarchy and each
+// object's dynamic attributes so they know what tag references to subscribe
+// to via the MxAccessGateway service.
+service GalaxyRepository {
+  rpc TestConnection(TestConnectionRequest) returns (TestConnectionReply);
+  rpc GetLastDeployTime(GetLastDeployTimeRequest) returns (GetLastDeployTimeReply);
+  rpc DiscoverHierarchy(DiscoverHierarchyRequest) returns (DiscoverHierarchyReply);
+
+  // Server-stream of deploy events. The server emits the current state immediately
+  // on subscribe (so clients can bootstrap their cache without waiting for the next
+  // deploy), then emits one event each time the gateway's hierarchy cache observes
+  // a new galaxy.time_of_last_deploy. The sequence field is monotonically
+  // increasing per server start; gaps indicate the per-subscriber buffer dropped
+  // older events because the client was too slow.
+  rpc WatchDeployEvents(WatchDeployEventsRequest) returns (stream DeployEvent);
+
+  // Returns the direct children of a parent object (or the root objects when
+  // `parent` is unset). Designed for OPC UA-style lazy expand: clients walk
+  // one level at a time instead of paging the full hierarchy. Filters mirror
+  // DiscoverHierarchy exactly. Backed by the same shared hierarchy cache.
+  rpc BrowseChildren(BrowseChildrenRequest) returns (BrowseChildrenReply);
+}
+
+message TestConnectionRequest {}
+
+message TestConnectionReply {
+  bool ok = 1;
+}
+
+message GetLastDeployTimeRequest {}
+
+message GetLastDeployTimeReply {
+  bool present = 1;
+  google.protobuf.Timestamp time_of_last_deploy = 2;
+}
+
+message DiscoverHierarchyRequest {
+  // Maximum number of objects to return. The server applies its default when
+  // unset and rejects non-positive values.
+  int32 page_size = 1;
+  // Opaque token returned by a previous DiscoverHierarchy response.
+  string page_token = 2;
+  // Optional. When set, return only this object and its descendants.
+  // Empty = full hierarchy.
+  oneof root {
+    int32 root_gobject_id = 3;
+    string root_tag_name = 4;
+    string root_contained_path = 5;
+  }
+  // Optional. Cap on descendant depth from root. Zero returns only the root.
+  // Unset means unlimited depth.
+  google.protobuf.Int32Value max_depth = 6;
+  // Optional object category id filters.
+  repeated int32 category_ids = 7;
+  // Optional case-insensitive substring filters against template names.
+  repeated string template_chain_contains = 8;
+  // Optional anchored, case-insensitive glob over object tag_name.
+  string tag_name_glob = 9;
+  // Optional. Unset or true includes attributes. False returns object skeletons.
+  optional bool include_attributes = 10;
+  // Optional. Return only objects with at least one alarm-bearing attribute.
+  bool alarm_bearing_only = 11;
+  // Optional. Return only objects with at least one historized attribute.
+  bool historized_only = 12;
+}
+
+message DiscoverHierarchyReply {
+  repeated GalaxyObject objects = 1;
+  // Non-empty when another page is available.
+  string next_page_token = 2;
+  // Total number of objects in the cached hierarchy at the time of the call.
+  int32 total_object_count = 3;
+}
+
+message WatchDeployEventsRequest {
+  // Optional. When set, the bootstrap event is suppressed if the cached deploy
+  // time matches this value. Future events are still emitted normally.
+  google.protobuf.Timestamp last_seen_deploy_time = 1;
+}
+
+message DeployEvent {
+  // Monotonically increasing per server start. Gaps indicate dropped events.
+  uint64 sequence = 1;
+  // Server wall-clock when the cache observed the deploy.
+  google.protobuf.Timestamp observed_at = 2;
+  // Galaxy.time_of_last_deploy. Absent only when the Galaxy table reports null.
+  google.protobuf.Timestamp time_of_last_deploy = 3;
+  bool time_of_last_deploy_present = 4;
+  int32 object_count = 5;
+  int32 attribute_count = 6;
+}
+
+message GalaxyObject {
+  int32 gobject_id = 1;
+  string tag_name = 2;
+  string contained_name = 3;
+  string browse_name = 4;
+  int32 parent_gobject_id = 5;
+  bool is_area = 6;
+  int32 category_id = 7;
+  int32 hosted_by_gobject_id = 8;
+  repeated string template_chain = 9;
+  repeated GalaxyAttribute attributes = 10;
+}
+
+message GalaxyAttribute {
+  string attribute_name = 1;
+  string full_tag_reference = 2;
+  // Raw Galaxy SQL `dbo.data_type` identifier, passed through unchanged.
+  // This is NOT a member of `mxaccess_gateway.v1.MxDataType` — Galaxy's
+  // type enumeration is distinct from MXAccess's wire data-type enum and
+  // the two must not be cast or compared. The GalaxyRepository service is
+  // metadata-only and deliberately does not share types with
+  // mxaccess_gateway.proto. See docs/GalaxyRepository.md.
+  int32 mx_data_type = 3;
+  // Human-readable name from Galaxy's `dbo.data_type` table (e.g. "Float",
+  // "Integer", "Boolean"). Free-form Galaxy text; not a stable enum.
+  string data_type_name = 4;
+  bool is_array = 5;
+  int32 array_dimension = 6;
+  bool array_dimension_present = 7;
+  // Raw Galaxy SQL attribute-category identifier, passed through unchanged.
+  // Galaxy-specific; not mapped to any gateway enum. See
+  // docs/GalaxyRepository.md.
+  int32 mx_attribute_category = 8;
+  // Raw Galaxy SQL security-classification identifier, passed through
+  // unchanged. Galaxy-specific; not mapped to any gateway enum. See
+  // docs/GalaxyRepository.md.
+  int32 security_classification = 9;
+  bool is_historized = 10;
+  bool is_alarm = 11;
+}
+
+message BrowseChildrenRequest {
+  // Parent selector. Empty oneof returns root objects (parent_gobject_id == 0).
+  oneof parent {
+    int32 parent_gobject_id = 1;
+    string parent_tag_name = 2;
+    string parent_contained_path = 3;
+  }
+
+  // Maximum number of direct children to return. Server default 500; cap 5000.
+  int32 page_size = 4;
+  // Opaque token returned by a previous BrowseChildren response. Bound to the
+  // cache sequence, parent selector, and the filter set; a mismatch returns
+  // InvalidArgument.
+  string page_token = 5;
+
+  // --- Filter parity with DiscoverHierarchy. AND-combined. ---
+  repeated int32 category_ids = 6;
+  repeated string template_chain_contains = 7;
+  string tag_name_glob = 8;
+  optional bool include_attributes = 9;
+  bool alarm_bearing_only = 10;
+  bool historized_only = 11;
+}
+
+message BrowseChildrenReply {
+  // Direct children matching the filter, sorted areas-first then by
+  // case-insensitive display name (same order as the dashboard tree).
+  repeated GalaxyObject children = 1;
+  // Non-empty when another page of siblings is available.
+  string next_page_token = 2;
+  // Total matching direct children of the parent (post-filter).
+  int32 total_child_count = 3;
+  // Parallel array, indexed with `children`. True when the child has at least
+  // one matching descendant under the same filter set. Lets a UI choose
+  // whether to draw an expand triangle without an extra round trip.
+  repeated bool child_has_children = 4;
+  // Cache sequence this reply was projected from. Clients may pass it back as
+  // part of the page_token contract. Mismatch on the next page -> InvalidArgument.
+  uint64 cache_sequence = 5;
+}

clients/rust/protos/mxaccess_worker.proto

@@ -0,0 +1,132 @@
+syntax = "proto3";
+
+package mxaccess_worker.v1;
+
+option csharp_namespace = "ZB.MOM.WW.MxGateway.Contracts.Proto";
+
+import "google/protobuf/duration.proto";
+import "google/protobuf/timestamp.proto";
+import "mxaccess_gateway.proto";
+
+// Wire-compatibility policy (ProtobufStyleGuide): this contract evolves
+// additively only. Never renumber or repurpose an existing field number or
+// enum value. When a field or enum value is removed, add a `reserved` range
+// (and `reserved` name) covering it in the same change so a future editor
+// cannot accidentally reuse the retired tag. There are no `reserved`
+// declarations today because no field or enum value has ever been removed.
+
+// Gateway-to-worker IPC envelope. Named-pipe framing prepends a little-endian
+// uint32 payload length to this protobuf payload.
+message WorkerEnvelope {
+  uint32 protocol_version = 1;
+  string session_id = 2;
+  uint64 sequence = 3;
+  string correlation_id = 4;
+
+  oneof body {
+    GatewayHello gateway_hello = 10;
+    WorkerHello worker_hello = 11;
+    WorkerReady worker_ready = 12;
+    WorkerCommand worker_command = 13;
+    WorkerCommandReply worker_command_reply = 14;
+    WorkerCancel worker_cancel = 15;
+    WorkerShutdown worker_shutdown = 16;
+    WorkerShutdownAck worker_shutdown_ack = 17;
+    WorkerEvent worker_event = 18;
+    WorkerHeartbeat worker_heartbeat = 19;
+    WorkerFault worker_fault = 20;
+  }
+}
+
+message GatewayHello {
+  uint32 supported_protocol_version = 1;
+  string nonce = 2;
+  string gateway_version = 3;
+}
+
+message WorkerHello {
+  uint32 protocol_version = 1;
+  string nonce = 2;
+  int32 worker_process_id = 3;
+  string worker_version = 4;
+}
+
+message WorkerReady {
+  int32 worker_process_id = 1;
+  string mxaccess_progid = 2;
+  string mxaccess_clsid = 3;
+  google.protobuf.Timestamp ready_timestamp = 4;
+}
+
+message WorkerCommand {
+  mxaccess_gateway.v1.MxCommand command = 1;
+  google.protobuf.Timestamp enqueue_timestamp = 2;
+}
+
+message WorkerCommandReply {
+  mxaccess_gateway.v1.MxCommandReply reply = 1;
+  google.protobuf.Timestamp completed_timestamp = 2;
+}
+
+message WorkerCancel {
+  string reason = 1;
+}
+
+message WorkerShutdown {
+  google.protobuf.Duration grace_period = 1;
+  string reason = 2;
+}
+
+message WorkerShutdownAck {
+  mxaccess_gateway.v1.ProtocolStatus status = 1;
+}
+
+message WorkerEvent {
+  mxaccess_gateway.v1.MxEvent event = 1;
+}
+
+message WorkerHeartbeat {
+  int32 worker_process_id = 1;
+  WorkerState state = 2;
+  google.protobuf.Timestamp last_sta_activity_timestamp = 3;
+  uint32 pending_command_count = 4;
+  uint32 outbound_event_queue_depth = 5;
+  uint64 last_event_sequence = 6;
+  string current_command_correlation_id = 7;
+}
+
+message WorkerFault {
+  WorkerFaultCategory category = 1;
+  string command_method = 2;
+  optional int32 hresult = 3;
+  string exception_type = 4;
+  string diagnostic_message = 5;
+  mxaccess_gateway.v1.ProtocolStatus protocol_status = 6;
+}
+
+enum WorkerState {
+  WORKER_STATE_UNSPECIFIED = 0;
+  WORKER_STATE_STARTING = 1;
+  WORKER_STATE_HANDSHAKING = 2;
+  WORKER_STATE_INITIALIZING_STA = 3;
+  WORKER_STATE_READY = 4;
+  WORKER_STATE_EXECUTING_COMMAND = 5;
+  WORKER_STATE_SHUTTING_DOWN = 6;
+  WORKER_STATE_STOPPED = 7;
+  WORKER_STATE_FAULTED = 8;
+}
+
+enum WorkerFaultCategory {
+  WORKER_FAULT_CATEGORY_UNSPECIFIED = 0;
+  WORKER_FAULT_CATEGORY_INVALID_ARGUMENTS = 1;
+  WORKER_FAULT_CATEGORY_GATEWAY_AUTHENTICATION_FAILED = 2;
+  WORKER_FAULT_CATEGORY_PROTOCOL_MISMATCH = 3;
+  WORKER_FAULT_CATEGORY_PROTOCOL_VIOLATION = 4;
+  WORKER_FAULT_CATEGORY_PIPE_DISCONNECTED = 5;
+  WORKER_FAULT_CATEGORY_MXACCESS_CREATION_FAILED = 6;
+  WORKER_FAULT_CATEGORY_MXACCESS_COMMAND_FAILED = 7;
+  WORKER_FAULT_CATEGORY_MXACCESS_EVENT_CONVERSION_FAILED = 8;
+  WORKER_FAULT_CATEGORY_STA_HUNG = 9;
+  WORKER_FAULT_CATEGORY_QUEUE_OVERFLOW = 10;
+  WORKER_FAULT_CATEGORY_SHUTDOWN_TIMEOUT = 11;
+}

docs/Authentication.md

@@ -73,7 +73,7 @@ The pepper is intentionally not stored alongside the hash: an attacker who exfil
 
 1. Parse the `Authorization` header into a `ParsedApiKey`.
 2. Look up the `ApiKeyRecord` by `KeyId` through `IApiKeyStore.FindByKeyIdAsync`.
-3. Reject revoked records (`RevokedUtc is not null`).
+3. Reject revoked records (`RevokedUtc is not null`) and expired records (`ExpiresUtc` in the past). Expiry is opt-in — keys created without an expiry never expire; an expired key fails opaquely, indistinguishable to the client from any other auth failure.
 4. Hash the presented secret with the configured pepper.
 5. Compare hashes with `CryptographicOperations.FixedTimeEquals` to avoid timing oracles.
 6. Record a `LastUsedUtc` timestamp via `MarkKeyUsedAsync` and return an `ApiKeyIdentity`.
@@ -101,10 +101,44 @@ return ApiKeyVerificationResult.Success(new ApiKeyIdentity(
 `DisplayName`, `Scopes`, and `Constraints`) and is the type downstream
 authorization code consumes.
 
+### Hot-path caching and last-used coalescing
+
+Left unmediated, every authenticated gRPC call costs a SQLite read plus a
+`last_used_utc` **write** (the library verifier couples `MarkKeyUsed` into
+`VerifyAsync`), which makes the auth store the throughput ceiling on the
+bulk-read workload. The gateway layers two decorators over the shared library's
+registrations (in `AuthStoreServiceCollectionExtensions`) — it does not edit the
+library:
+
+- **`CachingApiKeyVerifier`** wraps `IApiKeyVerifier` with an `IMemoryCache`
+  entry per successful verification, keyed on a SHA-256 hash of the presented
+  token (never the plaintext secret). A cache hit within
+  `MxGateway:Security:ApiKeyVerificationCacheSeconds` (default 15 s) returns the
+  cached result without touching the store, so both the read and the coupled
+  write are skipped. Only successes are cached; failures always reach the inner
+  verifier. On a gateway-initiated revoke/rotate/delete the dashboard admin
+  service calls `IApiKeyCacheInvalidator.Invalidate(keyId)`, evicting the cached
+  entry immediately. The short TTL is the backstop for out-of-band mutations
+  (a direct DB edit, or a revoke run by the separate `apikey` CLI process, whose
+  in-memory cache is not the running gateway's cache).
+- **`CoalescingMarkApiKeyStore`** wraps `IApiKeyStore` and forwards at most one
+  `MarkUsed` write per key per `MxGateway:Security:ApiKeyLastUsedCoalesceSeconds`
+  (default 60 s), so even under a cache miss the `last_used_utc` write is bounded
+  to roughly one per key per minute rather than one per RPC. `last_used_utc` is a
+  coarse staleness hint, not an audit record (audit rows are written separately),
+  so bounded staleness of up to one window is acceptable.
+
+`GatewayApiKeyIdentityMapper` additionally memoizes the constraints-JSON
+deserialization by blob, so the per-call parse on the mapped identity collapses to
+a dictionary lookup. Both windows are configurable and may be set to `0` to
+disable the respective mechanism; see [GatewayConfiguration](./GatewayConfiguration.md).
+
 ## Storage
 
 The gateway keeps API key state in a dedicated SQLite database. SQLite is sufficient because credential volume is small, the gateway runs as a single process, and the file is straightforward to back up and rotate independently of the main application data.
 
+The database path is `GatewayOptions.Authentication.SqlitePath`. Its code default is derived from `Environment.GetFolderPath(SpecialFolder.CommonApplicationData)` (`C:\ProgramData\MxGateway\gateway-auth.db` on Windows, `/usr/share/MxGateway/gateway-auth.db` or the container equivalent elsewhere) so the credential store is never written relative to the launch working directory on a non-Windows host. The production hosts pin the explicit Windows path in `appsettings.json`. `GatewayOptionsValidator` rejects a non-rooted (relative) `SqlitePath` so a bad override fails fast at startup rather than scattering the store by launch CWD (SEC-01).
+
 ### Connection factory
 
 `AuthSqliteConnectionFactory` reads `GatewayOptions.Authentication.SqlitePath`, ensures the parent directory exists, and builds a connection string in `ReadWriteCreate` mode so first-run installations can create the file without manual provisioning. Connection pooling is enabled and the connection string carries a non-zero `DefaultTimeout`:
@@ -159,6 +193,8 @@ public static ApiKeyRecord Read(SqliteDataReader reader)
 
 Because `RotateAsync` clears `revoked_utc`, rotating a previously revoked key reactivates it. The dashboard API Keys page therefore offers the Rotate (and Revoke) actions only for keys whose status is `Active`; revoked keys instead show a Delete action that calls `DeleteAsync`, so an operator can permanently remove a revoked row without ever risking un-revocation as a side effect of a rotation.
 
+The dashboard API Keys page also surfaces expiry: each row shows an `Expires` column (`Never` when unset) and a status badge that reads `Expired` (past expiry, red), `Expiring` (within seven days, amber), `Revoked`, or `Active`. This is display-only staleness surfacing; expiry is set at creation time via the `apikey create-key --expires` CLI, not from the dashboard.
+
 ### Audit trail
 
 `SqliteApiKeyAuditStore` (`IApiKeyAuditStore`) appends `ApiKeyAuditEntry` values to the `api_key_audit` table and stamps each row with a UTC timestamp inside the store rather than trusting the caller. `ListRecentAsync` returns the most recent rows ordered by `audit_id` descending and projects them into `ApiKeyAuditRecord`. Rows are kept even after the referenced key is revoked because the audit history is the durable record of administrative action; the `key_id` column is nullable to accommodate non-key-scoped events such as `init-db`.
@@ -192,8 +228,8 @@ The supported subcommands match `ApiKeyAdminCommandKind` exactly:
 | Subcommand | Required options | Behaviour |
 |------------|------------------|-----------|
 | `init-db` | none | Runs the migrator and records an audit entry. |
-| `create-key` | `--key-id`, `--display-name` | Generates a new secret, stores its peppered hash and optional constraints, and prints the assembled `mxgw_<keyId>_<secret>` token. |
-| `list-keys` | none | Lists every stored key with its scopes, constraints, and revocation state. |
+| `create-key` | `--key-id`, `--display-name` | Generates a new secret, stores its peppered hash and optional constraints, and prints the assembled `mxgw_<keyId>_<secret>` token. Optional `--expires` sets an expiry (absolute ISO-8601 UTC, or a relative `<N>d`/`<N>h` from now); omit it for a non-expiring key. |
+| `list-keys` | none | Lists every stored key with its scopes, constraints, revocation state, and expiry (`active`/`expired`/`revoked`). |
 | `revoke-key` | `--key-id` | Sets `revoked_utc` if the key is currently active. |
 | `rotate-key` | `--key-id` | Replaces the secret hash and prints the new token. |
 
@@ -203,6 +239,8 @@ Examples:
 mxgateway apikey init-db
 mxgateway apikey create-key --key-id ops.alice --display-name "Alice (ops)" --scopes read,write
 mxgateway apikey create-key --key-id area1.reader --display-name "Area 1 reader" --scopes invoke:read,metadata:read --read-subtree "Area1/*" --browse-subtree "Area1/*"
+mxgateway apikey create-key --key-id ops.temp --display-name "Temp contractor" --scopes invoke:read --expires 90d
+mxgateway apikey create-key --key-id ops.audit --display-name "Audit window" --scopes metadata:read --expires 2027-01-01T00:00:00Z
 mxgateway apikey list-keys --json
 mxgateway apikey revoke-key --key-id ops.alice
 mxgateway apikey rotate-key --key-id ops.alice

docs/Authorization.md

@@ -89,6 +89,12 @@ The flow is:
 
 The status codes are deliberately distinct: `Unauthenticated` signals "we do not know who you are," and `PermissionDenied` signals "we know who you are, but you cannot do this." Treating the two as the same code would make troubleshooting harder for client implementations.
 
+### Rate limiting the auth surface (SEC-11)
+
+Before the verification store read, the helper checks a cheap in-process per-peer failure counter (`ApiKeyFailureLimiter`). A peer that has accumulated more than `MxGateway:Security:ApiKeyFailureLimit` failed attempts inside the sliding `ApiKeyFailureWindowSeconds` window is short-circuited with `StatusCode.ResourceExhausted` — so online guessing of API-key secrets cannot spend a SQLite read (and, in a naive design, a cache miss) per attempt. The peer is keyed on the presented key id where the token parses, falling back to the transport peer address; keying on key id throttles a single abusive credential without penalizing co-located clients behind a shared NAT. A successful verification resets the peer's counter. The counter is a bounded LRU (`ApiKeyFailureTrackedPeers`) so it cannot grow without limit. `ResourceExhausted` reveals only that throttling is in effect, not whether any particular secret was valid, preserving the opaque-failure property.
+
+The dashboard login surface is throttled independently: `POST /auth/login` carries a fixed-window ASP.NET Core rate-limiter policy keyed per remote IP (`MxGateway:Security:LoginRateLimit*`), rejecting a burst with HTTP 429 before the LDAP bind is relayed to the directory. See [GatewayConfiguration](./GatewayConfiguration.md#security-options).
+
 ## Scope Resolution
 
 `GatewayGrpcScopeResolver` is a stateless singleton that switches on the runtime request type. Top-level RPC requests map directly:
@@ -104,6 +110,7 @@ public string ResolveRequiredScope(object request)
         MxCommandRequest commandRequest => ResolveCommandScope(commandRequest.Command?.Kind ?? MxCommandKind.Unspecified),
         AcknowledgeAlarmRequest => GatewayScopes.InvokeWrite,
         StreamAlarmsRequest => GatewayScopes.EventsRead,
+        QueryActiveAlarmsRequest => GatewayScopes.EventsRead,
         TestConnectionRequest or
         GetLastDeployTimeRequest or
         DiscoverHierarchyRequest or
@@ -113,7 +120,7 @@ public string ResolveRequiredScope(object request)
 }
 ```
 
-The `_ => GatewayScopes.Admin` fallback is intentional: any future request type that the resolver does not recognize fails closed, requiring the strongest scope until the resolver is updated. `AcknowledgeAlarm` is treated as a write — it mutates alarm state, mirroring `MxCommandKind.Write*` — and `StreamAlarms` shares the alarm/event surface with `StreamEvents` and `MxCommandKind.DrainEvents`, so it carries `events:read`. Both alarm RPCs are session-less: the scope check is the only authorization gate, since there is no per-session ownership to enforce.
+The `_ => GatewayScopes.Admin` fallback is intentional: any future request type that the resolver does not recognize fails closed, requiring the strongest scope until the resolver is updated. `AcknowledgeAlarm` is treated as a write — it mutates alarm state, mirroring `MxCommandKind.Write*` — and `StreamAlarms` and `QueryActiveAlarms` share the alarm/event surface with `StreamEvents` and `MxCommandKind.DrainEvents`, so they carry `events:read` (the active-alarm snapshot is the same data reachable through the event surface). All three alarm RPCs are session-less: the scope check is the only authorization gate, since there is no per-session ownership to enforce.
 
 `MxCommandRequest` is special because it multiplexes many MxAccess operations through a single RPC. The resolver inspects the embedded `MxCommandKind` so each operation gets its own scope:
 
@@ -205,7 +212,7 @@ blocking constraint; secured values and raw credentials are never logged.
 |----------|-------|--------------|
 | `SessionOpen` | `session:open` | `OpenSessionRequest` |
 | `SessionClose` | `session:close` | `CloseSessionRequest` |
-| `EventsRead` | `events:read` | `StreamEventsRequest`, `StreamAlarmsRequest`, `MxCommandKind.DrainEvents` |
+| `EventsRead` | `events:read` | `StreamEventsRequest`, `StreamAlarmsRequest`, `QueryActiveAlarmsRequest`, `MxCommandKind.DrainEvents` |
 | `InvokeRead` | `invoke:read` | `MxCommandRequest` for read-style command kinds (`Register`, `AddItem`, `Advise`, `ReadBulk`, and any kind not otherwise mapped) |
 | `InvokeWrite` | `invoke:write` | `AcknowledgeAlarmRequest`, `MxCommandKind.Write`, `MxCommandKind.Write2`, `MxCommandKind.WriteBulk`, `MxCommandKind.Write2Bulk` |
 | `InvokeSecure` | `invoke:secure` | `MxCommandKind.WriteSecured`, `MxCommandKind.WriteSecured2`, `MxCommandKind.WriteSecuredBulk`, `MxCommandKind.WriteSecured2Bulk`, `MxCommandKind.AuthenticateUser` |

docs/ClientProtoGeneration.md

@@ -48,25 +48,55 @@ session.
 ## Descriptor Publishing
 
 Run this command after changing either source `.proto` file or the client proto
-manifest:
+manifest, with the **pinned protoc 34.1** (see [Toolchain Links](./ToolchainLinks.md)):
 
 ```powershell
-scripts/publish-client-proto-inputs.ps1
+pwsh -File scripts/publish-client-proto-inputs.ps1
 ```
 
 The script writes
 `clients/proto/descriptors/mxaccessgw-client-v1.protoset` with imports and
 source information included. The descriptor is a generated artifact; do not edit
-it by hand.
+it by hand. Generating the committed artifact requires the pinned protoc version
+so the checked-in bytes are reproducible; the script fails fast on a version
+mismatch when generating.
 
 Use the check mode in CI or before committing:
 
 ```powershell
-scripts/publish-client-proto-inputs.ps1 -Check
+pwsh -File scripts/publish-client-proto-inputs.ps1 -Check
 ```
 
-`-Check` rebuilds the descriptor in a temporary path and fails when the checked
-in descriptor is stale.
+`-Check` rebuilds the descriptor and fails when the checked-in descriptor is
+stale. The comparison normalizes both the committed and freshly built descriptor
+through the same protoc with `source_code_info` stripped, so it is tolerant of
+protoc-version encoding drift and does not false-fail across protoc releases
+(it warns, rather than fails, when protoc is off the pin).
+
+The gateway test project carries an independent, protoc-free freshness guard:
+`ClientProtoInputTests.Descriptor_ContainsEveryContractMessageAndField` reflects
+over the in-process contract descriptors and fails if any contract message or
+field is missing from the committed protoset. This is the primary CI gate for
+descriptor staleness; a red test means "regenerate and commit the protoset."
+
+### Pinned generator versions
+
+Regeneration is reproducible only with the pinned toolchain. Regenerating with a
+different version silently produces incompatible or noisy output, so the per-client
+scripts assert the pin and resolve tools from `PATH`:
+
+| Generator | Pinned version | Guard |
+|-----------|----------------|-------|
+| protoc (descriptor set) | 34.1 | version assertion in `scripts/publish-client-proto-inputs.ps1` |
+| `Grpc.Tools` (C# `Generated/`) | 2.80.0 (contracts csproj) | `scripts/check-codegen.ps1` git-diff of `Generated/` |
+| `grpcio-tools` (Python) | 1.80.0 (protobuf runtime 6.31.1) | version assertion in `clients/python/generate-proto.ps1` |
+| protobuf / grpc-java (Java) | `protobufVersion` / `grpcVersion` in `clients/java/build.gradle` | `checkGeneratedClean` gradle task |
+
+A newer `grpcio-tools` stamps a `GRPC_GENERATED_VERSION` above the pinned grpcio
+runtime and breaks Python `pytest`; the Java protobuf plugin rewrites
+`MxaccessGateway.java` with spurious protobuf-runtime-version churn on every build
+(revert that one file when no `.proto` changed — see
+[Gateway Testing](./GatewayTesting.md) "Continuous Integration").
 
 ## Output Directories
 

docs/Contracts.md

@@ -97,6 +97,24 @@ behavior.
 Generated C# output is written to `src/ZB.MOM.WW.MxGateway.Contracts/Generated/`. Do not
 hand-edit generated files.
 
+The `Generated/` C# is **tracked and must be committed after any `.proto` change.** The
+contracts project `Compile Remove`s `Generated/**/*.cs` and has `Grpc.Tools` regenerate them,
+but `Grpc.Tools` skips regeneration when the committed output looks up to date. On the net10
+build the freshly regenerated code is compiled, so a stale `Generated/` is invisible there —
+but the **net48 worker** consumes the committed `Generated/` and fails to build with `CS0246`
+on any new type when the checked-in code lags the `.proto`. So after editing a `.proto` you must
+regenerate and commit `Generated/`. If a build does not pick up your proto change, delete the
+stale output to force a full regeneration:
+
+```bash
+rm src/ZB.MOM.WW.MxGateway.Contracts/Generated/*.cs
+dotnet build src/ZB.MOM.WW.MxGateway.Contracts/ZB.MOM.WW.MxGateway.Contracts.csproj
+```
+
+`scripts/check-codegen.ps1` enforces this in CI (it force-regenerates and fails on any
+`git diff` against the committed `Generated/`); the Windows CI job's net48 worker build is the
+definitive guard.
+
 Client generation inputs are published through
 `clients/proto/proto-inputs.json` and the descriptor set under
 `clients/proto/descriptors/`. See
@@ -124,12 +142,25 @@ gateway and test projects:
 dotnet build src/ZB.MOM.WW.MxGateway.slnx
 ```
 
-Regenerate the client descriptor after changing either `.proto` file:
+Regenerate the client descriptor after changing either `.proto` file, using the pinned protoc
+(34.1, see [Toolchain Links](./ToolchainLinks.md)):
 
 ```bash
-powershell -ExecutionPolicy Bypass -File scripts/publish-client-proto-inputs.ps1
+pwsh -File scripts/publish-client-proto-inputs.ps1
 ```
 
+Freshness is guarded two ways so a skipped regeneration cannot ship silently:
+
+- `ClientProtoInputTests.Descriptor_ContainsEveryContractMessageAndField` (gateway test project)
+  reflects over the in-process contract descriptors and fails if any message or field is missing
+  from the committed protoset. It is semantic (symbol presence), needs no protoc, and runs in the
+  Linux CI. A red test means "regenerate and commit the protoset."
+- `pwsh -File scripts/publish-client-proto-inputs.ps1 -Check` rebuilds the descriptor and compares
+  it to the committed one. The comparison normalizes both sides through the same protoc with
+  `source_code_info` stripped, so it does not false-fail across protoc releases.
+- `pwsh scripts/check-codegen.ps1` runs both the descriptor check and the `Generated/`-clean check
+  together; it is the single guard the CI pipeline invokes.
+
 ## Related Documentation
 
 - [Client Proto Generation](./ClientProtoGeneration.md)

docs/GatewayConfiguration.md

@@ -29,7 +29,7 @@ paths, timeouts, queue sizes, enum values, or protocol values are invalid.
       "ShutdownTimeoutSeconds": 10,
       "HeartbeatIntervalSeconds": 5,
       "HeartbeatGraceSeconds": 15,
-      "MaxMessageBytes": 16777216
+      "MaxMessageBytes": 16842752
     },
     "Sessions": {
       "DefaultCommandTimeoutSeconds": 30,
@@ -93,12 +93,15 @@ Environment variables use the normal .NET double-underscore form. For example,
 | Option | Default | Description |
 |--------|---------|-------------|
 | `MxGateway:Authentication:Mode` | `ApiKey` | Selects public gRPC authentication. Supported values are `ApiKey` and `Disabled`. `Disabled` bypasses API-key verification and is for local development only. |
-| `MxGateway:Authentication:SqlitePath` | `C:\ProgramData\MxGateway\gateway-auth.db` | SQLite database path for API-key records and audit rows when API-key authentication is enabled. |
+| `MxGateway:Authentication:SqlitePath` | derived from `CommonApplicationData` (`C:\ProgramData\MxGateway\gateway-auth.db` on Windows, `/usr/share/MxGateway/gateway-auth.db` or the container equivalent elsewhere) | SQLite database path for API-key records and audit rows when API-key authentication is enabled. The code default is built from `Environment.GetFolderPath(SpecialFolder.CommonApplicationData)` so the credential store never lands in the launch working directory on a non-Windows host; the production hosts pin the explicit Windows path in `appsettings.json`, which overrides the code default. |
 | `MxGateway:Authentication:PepperSecretName` | `MxGateway:ApiKeyPepper` | Configuration key used to read the HMAC pepper for API-key secret hashing. The dashboard effective configuration redacts this value. |
 | `MxGateway:Authentication:RunMigrationsOnStartup` | `true` | Runs SQLite auth schema migrations at gateway startup when API-key authentication is enabled. |
 
 When `Mode` is `ApiKey`, `SqlitePath` and `PepperSecretName` must be present.
-`SqlitePath` must be a valid filesystem path.
+`SqlitePath` must be a valid filesystem path and must be **rooted** (absolute):
+the validator rejects a non-rooted path so a relative override cannot silently
+resolve against the working directory and scatter the credential store by launch
+CWD (SEC-01).
 
 ## Worker Options
 
@@ -114,12 +117,16 @@ When `Mode` is `ApiKey`, `SqlitePath` and `PepperSecretName` must be present.
 | `MxGateway:Worker:ShutdownTimeoutSeconds` | `10` | Grace period for worker shutdown before the gateway treats shutdown as failed and may kill the worker process tree. |
 | `MxGateway:Worker:HeartbeatIntervalSeconds` | `5` | Worker heartbeat send interval and gateway heartbeat check cadence input. |
 | `MxGateway:Worker:HeartbeatGraceSeconds` | `15` | Maximum age of the last worker heartbeat before the gateway faults the worker. This must be greater than or equal to `HeartbeatIntervalSeconds`. |
-| `MxGateway:Worker:MaxMessageBytes` | `16777216` | Maximum worker IPC frame payload size in bytes. The validator allows values from `1024` through `268435456`. |
+| `MxGateway:Worker:MaxMessageBytes` | `16842752` | Maximum worker IPC frame payload size in bytes. The validator allows values from `1024` through `268435456`, and additionally requires this to be at least `MxGateway:Protocol:MaxGrpcMessageBytes` plus a 65536-byte (64 KiB) envelope-overhead reserve. The default is the 16 MiB public gRPC cap plus that reserve. The gateway conveys the negotiated value to the worker in the handshake (`GatewayHello.max_frame_bytes`), so the worker frames to the same limit rather than a hard-coded default. |
 
 `StartupProbeRetryAttempts`, `StartupProbeRetryDelayMilliseconds`,
 `PipeConnectAttemptTimeoutMilliseconds`, timeout values, heartbeat values, and
 `MaxMessageBytes` must be positive. `MaxMessageBytes` is intentionally bounded
-to avoid accidental large allocations from malformed or oversized frames.
+to avoid accidental large allocations from malformed or oversized frames. It
+must also stay above `MaxGrpcMessageBytes` by the envelope-overhead reserve so a
+maximally-sized accepted gRPC payload always fits one worker frame once wrapped
+in a `WorkerEnvelope`; otherwise the oversized outbound write would fault the
+whole session. Startup validation fails fast when the headroom is violated.
 
 ## Session Options
 
@@ -177,7 +184,7 @@ events (a "gap") and must re-snapshot; whatever is still retained is replayed.
 | `MxGateway:Dashboard:RecentSessionLimit` | `200` | Maximum number of session summaries projected into each dashboard snapshot. |
 | `MxGateway:Dashboard:ShowTagValues` | `false` | Reserved display control for tag values. The dashboard does not show full tag values by default. |
 | `MxGateway:Dashboard:GroupToRole` | _(empty)_ | LDAP group → dashboard role mapping. Keys are LDAP group names (short CN or full DN — leading-RDN match). Values must be `Admin` (read/write, API-key CRUD) or `Viewer` (read-only). A user whose LDAP groups don't intersect this map cannot sign in; with no mapping at all, only the loopback bypass admits anyone. |
-| `MxGateway:Dashboard:DisableLogin` | `false` | Dev/test only. When `true`, replaces the cookie authentication handler with `DashboardAutoLoginAuthenticationHandler`, which auto-authenticates every dashboard request — including requests from remote browsers, not just loopback — as `AutoLoginUser` holding both `Administrator` and `Viewer` roles. No login form, LDAP bind, or cookie is involved. A loud one-time startup warning is logged. Differs from `AllowAnonymousLocalhost`: `DisableLogin` mints a real authenticated principal (so role-gated write affordances appear), whereas `AllowAnonymousLocalhost` satisfies the authorization requirement on loopback only without minting a principal (write affordances stay hidden). Never enable in production. |
+| `MxGateway:Dashboard:DisableLogin` | `false` | Dev/test only. When `true`, replaces the cookie authentication handler with `DashboardAutoLoginAuthenticationHandler`, which auto-authenticates every dashboard request — including requests from remote browsers, not just loopback — as `AutoLoginUser` holding both `Administrator` and `Viewer` roles. No login form, LDAP bind, or cookie is involved. A loud one-time startup warning is logged. Differs from `AllowAnonymousLocalhost`: `DisableLogin` mints a real authenticated principal (so role-gated write affordances appear), whereas `AllowAnonymousLocalhost` satisfies the authorization requirement on loopback only without minting a principal (write affordances stay hidden). Never enable in production. **Production hard-stop (SEC-04):** when the host runs in the `Production` environment and `DisableLogin` is `true`, startup validation fails and the process aborts — the flag is only accepted outside Production, where the one-time startup warning still fires. |
 | `MxGateway:Dashboard:AutoLoginUser` | `(null)` | Username stamped on the synthetic principal when `DisableLogin` is `true`. Default `(null)` — a null or blank value falls back to `multi-role`. Has no effect when `DisableLogin` is `false`. |
 
 `SnapshotIntervalMilliseconds` must be greater than zero. `RecentFaultLimit`
@@ -215,21 +222,67 @@ When the dashboard is enabled, three hubs are mapped under `/hubs/*`:
   side-effect; the dashboard only sees events while a gRPC client is also
   subscribed to that session.
 
-`GET /hubs/token` (cookie-only) mints a 30-minute data-protected bearer
+`GET /hubs/token` (cookie-only) mints a 5-minute data-protected bearer
 token for the calling user; the Blazor pages use it via
 `DashboardHubConnectionFactory` to authenticate the SignalR connection.
+The factory refreshes the token on every (re)connect, so the short lifetime
+(SEC-05) is transparent to clients. The token is not server-side revocable;
+its short lifetime bounds exposure of a captured token (see
+[GatewayDashboardDesign](./GatewayDashboardDesign.md)).
+
+## LDAP Options (Dashboard Login)
+
+The `MxGateway:Ldap` section configures the LDAP bind used by dashboard `/login`
+(the gRPC API-key model is separate). The shipped defaults are the shared
+dev/test GLAuth posture (`glauth.md`), not a production posture.
+
+| Option | Default | Description |
+|--------|---------|-------------|
+| `MxGateway:Ldap:Enabled` | `true` | Enables LDAP-backed dashboard login. |
+| `MxGateway:Ldap:Server` | `localhost` | LDAP server host. Dev points at the shared GLAuth instance (`10.100.0.35`). |
+| `MxGateway:Ldap:Port` | `3893` | LDAP server port. Must be between `1` and `65535`. |
+| `MxGateway:Ldap:Transport` | `None` | Connection transport: `None` (plaintext), `StartTls` (upgrade), or `Ldaps` (implicit TLS). The dev default is `None` because the shared GLAuth instance has LDAPS disabled and binds send cleartext. **Production hard-stop (SEC-06):** when the host runs in the `Production` environment, `Transport` must not be `None` — startup validation fails otherwise. Deployed hosts must set `Ldaps` or `StartTls`. |
+| `MxGateway:Ldap:AllowInsecure` | `true` | Permits a plaintext bind. Must be `true` when `Transport` is `None`; set `false` (with `Ldaps`/`StartTls`) in production. |
+| `MxGateway:Ldap:SearchBase` | `dc=zb,dc=local` | Search base DN. |
+| `MxGateway:Ldap:ServiceAccountDn` | `cn=serviceaccount,dc=zb,dc=local` | Bind DN for the search account. |
+| `MxGateway:Ldap:ServiceAccountPassword` | `serviceaccount123` | Search-account password. **Dev-only committed value.** On the deployed hosts, do not ship this in `appsettings.json`; supply it out-of-band via the env-var override `MxGateway__Ldap__ServiceAccountPassword` (double-underscore form, as set on the NSSM-wrapped services). The committed `serviceaccount123` is a shared dev credential for the local GLAuth instance and should be rotated; production must use a secret it does not share with dev. |
+| `MxGateway:Ldap:UserNameAttribute` | `cn` | LDAP attribute holding the login user name. |
+| `MxGateway:Ldap:DisplayNameAttribute` | `cn` | LDAP attribute holding the display name. |
+| `MxGateway:Ldap:GroupAttribute` | `memberOf` | LDAP attribute enumerating group membership (mapped to dashboard roles via `MxGateway:Dashboard:GroupToRole`). |
+
+When LDAP is enabled, `Server`, `SearchBase`, `ServiceAccountDn`,
+`ServiceAccountPassword`, and the attribute names must be non-blank, and `Port`
+must be in range. See `glauth.md` for the shared dev instance and the
+dev→production hardening posture.
 
 ## Protocol Options
 
 | Option | Default | Description |
 |--------|---------|-------------|
 | `MxGateway:Protocol:WorkerProtocolVersion` | `1` | Worker IPC protocol version expected by the gateway and worker. This must match `GatewayContractInfo.WorkerProtocolVersion`. |
-| `MxGateway:Protocol:MaxGrpcMessageBytes` | `16777216` | Public gRPC max send and receive message size in bytes. The same default is used by official clients. The validator allows values from `1024` through `268435456`. |
+| `MxGateway:Protocol:MaxGrpcMessageBytes` | `16777216` | Public gRPC max send and receive message size in bytes. The same default is used by official clients. The validator allows values from `1024` through `268435456`, and requires `MxGateway:Worker:MaxMessageBytes` to exceed this by at least the 64 KiB worker-frame envelope reserve (see the Worker options). |
 
 The protocol option is exposed for diagnostics and explicit deployment
 configuration, not for compatibility negotiation. A mismatch fails validation
 at startup.
 
+## Security Options
+
+Bound from `MxGateway:Security`. These knobs tune the authentication hot path
+(SEC-08 verification cache / last-used coalescing) and the auth-surface rate
+limiting (SEC-11). Defaults are safe; leave them unless profiling or a threat
+model requires otherwise.
+
+| Option | Default | Description |
+|--------|---------|-------------|
+| `MxGateway:Security:ApiKeyVerificationCacheSeconds` | `15` | TTL, in seconds, of a cached successful API-key verification. A cache hit within this window skips the per-call SQLite read (and the coupled `last_used` write). Gateway-initiated revoke/rotate/delete invalidate the entry immediately; this TTL is the backstop for out-of-band mutations (a direct DB edit, or a revoke run by the separate `apikey` CLI process). `0` disables the cache. Must be zero or greater. |
+| `MxGateway:Security:ApiKeyLastUsedCoalesceSeconds` | `60` | Coalescing window, in seconds, for the `last_used_utc` write. The library verifier writes `last_used` on every successful verification; this bounds the write to at most one per key per window, so a hammered key does not churn the WAL. `0` forwards every write. Must be zero or greater. |
+| `MxGateway:Security:LoginRateLimitPermitLimit` | `10` | Maximum `POST /auth/login` attempts permitted per remote IP within `LoginRateLimitWindowSeconds` before requests are rejected with HTTP 429. Throttles LDAP credential stuffing before the bind is relayed to the directory. Must be greater than zero. |
+| `MxGateway:Security:LoginRateLimitWindowSeconds` | `60` | Fixed-window length, in seconds, for the per-IP login rate limit. Must be greater than zero. |
+| `MxGateway:Security:ApiKeyFailureLimit` | `10` | Failed API-key verifications, per peer, within `ApiKeyFailureWindowSeconds` that trip the in-process short-circuit. Once tripped, the gRPC auth path rejects further attempts with `ResourceExhausted` **before** the store read; a successful verification resets the peer's counter. The peer is keyed on the presented key id (falling back to the transport address) so a single abusive credential behind a shared NAT is throttled without locking out co-located clients. Must be greater than zero. |
+| `MxGateway:Security:ApiKeyFailureWindowSeconds` | `60` | Sliding-window length, in seconds, over which API-key verification failures are counted per peer. Must be greater than zero. |
+| `MxGateway:Security:ApiKeyFailureTrackedPeers` | `4096` | Maximum distinct peers tracked by the failure counter (a bounded LRU) so a spray of unique peer keys cannot grow memory without limit. Must be greater than zero. |
+
 ## Galaxy Options
 
 | Option | Default | Description |
@@ -238,7 +291,7 @@ at startup.
 | `MxGateway:Galaxy:CommandTimeoutSeconds` | `60` | Per-command SQL timeout for all Galaxy browse RPCs. |
 | `MxGateway:Galaxy:DashboardRefreshIntervalSeconds` | `30` | Interval between background refreshes of the dashboard Galaxy summary cache. SQL is hit at most once per interval regardless of dashboard render rate. |
 | `MxGateway:Galaxy:PersistSnapshot` | `true` | Persists the latest successful Galaxy browse dataset to disk. When `true`, the cache reloads that snapshot at startup so clients can still browse last-known data while the Galaxy database is unreachable. The restored data is served with `Stale` status until a live query confirms it. |
-| `MxGateway:Galaxy:SnapshotCachePath` | `C:\ProgramData\MxGateway\galaxy-snapshot.json` | File path for the persisted Galaxy browse snapshot. Ignored when `PersistSnapshot` is `false`. The snapshot is written atomically (temp file plus rename). |
+| `MxGateway:Galaxy:SnapshotCachePath` | `C:\ProgramData\MxGateway\galaxy-snapshot.json` | File path for the persisted Galaxy browse snapshot. Ignored when `PersistSnapshot` is `false`. The snapshot is written atomically (temp file plus rename). Set an **absolute** path — this option is bound by the shared `ZB.MOM.WW.GalaxyRepository` package (not by `GatewayOptions`), so the gateway validator does not enforce rooting on it; a relative value would resolve against the launch working directory (SEC-01). |
 
 See [Galaxy Repository Browse](./GalaxyRepository.md) for the RPC surface and
 behavior.
@@ -442,7 +495,7 @@ them.
 
 | Option | Default | Purpose |
 |---|---|---|
-| `Tls:SelfSignedCertPath` | `C:\ProgramData\MxGateway\certs\gateway-selfsigned.pfx` | Where the generated certificate is persisted |
+| `Tls:SelfSignedCertPath` | derived from `CommonApplicationData` (`C:\ProgramData\MxGateway\certs\gateway-selfsigned.pfx` on Windows, `/usr/share/MxGateway/certs/gateway-selfsigned.pfx` or the container equivalent elsewhere) | Where the generated certificate is persisted. The code default is built from `Environment.GetFolderPath(SpecialFolder.CommonApplicationData)` so a generated private key never lands in the launch working directory on a non-Windows host (SEC-01). Must be **rooted** (absolute); the validator rejects a non-rooted override. |
 | `Tls:ValidityYears` | `10` | Lifetime of the generated certificate (validated 1–100) |
 | `Tls:AdditionalDnsNames` | `[]` | Extra DNS SANs (e.g. a load-balancer name) |
 | `Tls:RegenerateIfExpired` | `true` | Replace an expired persisted certificate instead of failing |

docs/GatewayDashboardDesign.md

@@ -257,6 +257,15 @@ gated by a confirmation dialog before it reaches `ISessionManager`.
   is killed immediately with no graceful-shutdown attempt. The session is
   removed from the registry and the open-session slot is released either way.
 
+Both actions write a canonical `AuditEvent` through `IAuditWriter` into the
+`audit_event` store (category `SessionAdmin`, actions `dashboard-close-session`
+and `dashboard-kill-worker`) in addition to the operational `ILogger` line — so a
+worker killed mid-production leaves a durable, queryable row rather than only a
+rotatable log entry. The event records the LDAP actor, the session id (`Target`),
+the remote address, and an outcome of `Success`, `Failure`, or `Denied`
+(an unauthorized attempt is still audited as `Denied`). This mirrors the API-key
+management audit path.
+
 ### Workers page
 
 Show:
@@ -436,11 +445,16 @@ Three authorization policies are registered:
   cookie OR a `MxGateway.Dashboard.HubToken` bearer (used by WebSocket upgrades
   where the cookie can't be forwarded).
 
-Two environmental bypasses still apply: `MxGateway:Authentication:Mode = Disabled`
-authorizes every request, and `MxGateway:Dashboard:AllowAnonymousLocalhost`
-(default `true`) authorizes any loopback request without a role check. Remote
-requests always require an authenticated principal carrying at least the
-Viewer role.
+Two environmental bypasses still apply, both scoped to **read-only** access:
+`MxGateway:Authentication:Mode = Disabled` and `MxGateway:Dashboard:AllowAnonymousLocalhost`
+(default `true`, loopback only) each satisfy a requirement that includes the Viewer
+role (`AnyDashboardRole`) but **never** the `AdminOnly` requirement. Destructive/admin
+surfaces (API-key CRUD, session Close, worker Kill) still demand a real `Administrator`
+role claim, so the "anonymous localhost is read-only" contract holds at the policy layer
+rather than only in downstream service re-checks. Remote requests (outside the `Disabled`
+bypass) always require an authenticated principal carrying at least the Viewer role. The
+loopback test trusts `Connection.RemoteIpAddress`; if forwarded-headers middleware is ever
+added upstream, `DashboardAuthorizationHandler.IsLoopbackRequest()` must be revisited.
 
 ### DisableLogin dev bypass
 
@@ -486,9 +500,13 @@ dashboard mints short-lived bearer tokens for the connection:
    and role claims to JSON, encrypts with the ASP.NET Core data-protection
    time-limited protector under purpose
    `ZB.MOM.WW.MxGateway.Dashboard.HubToken.v1`, and returns the protected
-   string. Lifetime is 30 minutes.
+   string. Lifetime is **5 minutes**.
 3. The SignalR client passes the token as either `Authorization: Bearer …` or
-   `?access_token=…` (WebSocket upgrade query string).
+   `?access_token=…` (WebSocket upgrade query string). The query-string form is
+   the standard SignalR carriage for WebSocket upgrades, which cannot attach a
+   custom header; because it is easy to capture (proxy logs, browser history),
+   it must never be request-logged (see the remarks on
+   `HubTokenAuthenticationHandler`).
 4. `HubTokenAuthenticationHandler` validates the protected payload and
    rebuilds the `ClaimsPrincipal` with the carried roles.
 5. The hubs' `[Authorize(Policy = HubClientsPolicy)]` accepts the resulting
@@ -496,7 +514,17 @@ dashboard mints short-lived bearer tokens for the connection:
 
 `DashboardHubConnectionFactory` (scoped to the Blazor circuit) wraps the
 HubConnectionBuilder and supplies a fresh token via `AccessTokenProvider` on
-every (re)connect.
+every (re)connect, so the short 5-minute lifetime is transparent to clients.
+
+Caveat — logout does not revoke outstanding tokens. Logout clears the dashboard
+cookie, but hub bearer tokens are self-contained, data-protection-encrypted, and
+carry no server-side revocation state (no jti denylist). A token captured before
+logout remains valid until it expires, and a role change or key revocation does
+not take effect on an already-issued token until then. The 5-minute lifetime is
+the deliberate mitigation: it bounds that exposure window without the cost of a
+revocation store. Server-side revocation is deferred until per-session hub ACLs
+land (see the per-session-ACL note), at which point tokens gain session/role
+binding and a denylist becomes worthwhile.
 
 ## Configuration
 

docs/GatewayProcessDesign.md

@@ -481,7 +481,9 @@ Internally it owns:
 - pipe stream,
 - read loop,
 - write loop,
+- event write loop,
 - outbound command/control channel serialized by the write loop,
+- unbounded event staging channel drained by the event write loop,
 - bounded inbound event channel,
 - pending command dictionary keyed by correlation id,
 - heartbeat monitor,
@@ -499,15 +501,29 @@ The read loop:
 1. Reads one frame.
 2. Parses `WorkerEnvelope`.
 3. Validates protocol fields.
-4. Dispatches by body type:
+4. Dispatches by body type, **synchronously and without blocking**:
    - `WorkerCommandReply`: completes pending command.
-   - `WorkerEvent`: enqueues event.
+   - `WorkerEvent`: hands the event to the event write loop via a non-blocking staging write.
    - `WorkerHeartbeat`: updates heartbeat timestamp.
    - `WorkerFault`: faults session.
 5. Stops when pipe closes or cancellation is requested.
 
 If the pipe closes while the session is not closing, fault the session.
 
+The read loop never awaits event enqueue. Events are staged to the event write
+loop with a non-blocking write, so a full inbound event channel (a slow or
+absent `StreamEvents` consumer) cannot stall the read loop behind an event and
+delay a command reply or heartbeat (GWC-04). The bounded-channel backpressure
+window (`EventChannelFullModeTimeout`) and the sustained-overflow fault are
+applied by the event write loop, not the read loop.
+
+### Event write loop
+
+The event write loop drains the staging channel and performs the timed write
+into the bounded inbound event channel. When the inbound channel stays full past
+`EventChannelFullModeTimeout` it faults the session (`ProtocolViolation`) — the
+same overflow contract as before, moved off the read loop.
+
 ### Write loop
 
 The write loop serializes all writes to the pipe. No other code should write to

docs/GatewayTesting.md

@@ -408,6 +408,34 @@ Run the gateway test project after shared gateway test infrastructure changes:
 dotnet test src/ZB.MOM.WW.MxGateway.Tests/ZB.MOM.WW.MxGateway.Tests.csproj
 ```
 
+## Continuous Integration
+
+CI runs on Gitea Actions (`.gitea/workflows/ci.yml`; origin is Gitea at
+`gitea.dohertylan.com`) on every push and pull request. The pipeline is split by
+runtime because the x86 Worker cannot build on Linux:
+
+- **`portable`** (Linux runner) — builds `src/ZB.MOM.WW.MxGateway.NonWindows.slnx`,
+  runs the codegen/descriptor freshness guard (`scripts/check-codegen.ps1`), runs the
+  gateway fake-worker tests, and builds/tests the clients that run on Linux: .NET client
+  build, Go (`gofmt` + `go build` + `go test`), Rust (`cargo fmt --check` + `cargo test`
+  + `cargo clippy -D warnings`), and Python (`pytest`).
+- **`java`** (Linux, JDK 17) — `gradle test`. The protobuf gradle plugin rewrites
+  `MxaccessGateway.java` with spurious protobuf-runtime-version churn on every build, so
+  when no `.proto` changed the job reverts that one file (`git checkout`) before asserting
+  the generated tree is clean. The dev Mac has no JRE, so Java verification is CI-only.
+- **`windows`** (self-hosted windev runner) — the only host that builds the **x86 /
+  net48 Worker and Worker.Tests**; these are Windows-only and out of scope for the Linux
+  jobs. This job also proves the net48 build against the committed `Generated/` (the
+  definitive guard for the "regenerate and commit `Generated/`" rule).
+- **`live-mxaccess`** (self-hosted, MXAccess-installed) — scheduled only
+  (`MXGATEWAY_RUN_LIVE_MXACCESS_TESTS=1`); never gates a push.
+
+The freshness guard `scripts/check-codegen.ps1` fails the build when the committed
+client descriptor set or the C# `Generated/` no longer matches the current `.proto`
+sources — the codegen drift class this repo has hit repeatedly (stale client
+descriptors, net48 `CS0246` on unregenerated protos). See
+[Client Proto Generation](./ClientProtoGeneration.md) and [Contracts](./Contracts.md).
+
 ## Related Documentation
 
 - [Cross-Language Smoke Matrix](./CrossLanguageSmokeMatrix.md)

docs/Metrics.md

@@ -44,7 +44,7 @@ All counters are `Counter<long>`. Tag values come from the call sites listed und
 | `mxgateway.faults` | `category` | Faults reported by session, event, or worker code paths. The category is a `SessionManagerErrorCode` or `WorkerClientErrorCode` name. |
 | `mxgateway.workers.killed` | `reason` | Forced terminations of worker processes. |
 | `mxgateway.workers.exited` | `reason` | Clean or fault-driven worker exits. |
-| `mxgateway.heartbeats.failed` | `session_id` | Worker heartbeat misses tracked per session. |
+| `mxgateway.heartbeats.failed` | *(none)* | Aggregate worker heartbeat misses. The exported counter carries **no** `session_id` tag — per-session attribution is unbounded cardinality (every session mints a new time series), so it is kept out of the exporter; use the dashboard snapshot or the log scope for per-session detail. |
 | `mxgateway.grpc.streams.disconnected` | `reason` | Detachments of the dashboard or client gRPC event stream. |
 | `mxgateway.retries.attempted` | `area` | Resilience retries executed by gateway components. |
 
@@ -203,6 +203,18 @@ metrics.RecordEventStreamSend(publicEvent.Family.ToString(), stopwatch.Elapsed);
 
 `Dashboard/DashboardSnapshotService.cs` calls `_metrics.GetSnapshot()` once per `GetSnapshot` invocation and projects it into the dashboard transport types together with the session registry view. The dashboard receives a single, internally consistent snapshot per tick rather than reading individual counters at separate times. See [Gateway Dashboard Design](./GatewayDashboardDesign.md) and [Dashboard Interface Design](./DashboardInterfaceDesign.md) for the projection rules and wire format.
 
+## Auth Store Write Churn
+
+The per-RPC authentication path is a hidden write source: the shared verifier
+refreshes `last_used_utc` on every authenticated call. To keep that off the
+auth-store throughput ceiling, the gateway caches successful verifications for a
+short TTL and coalesces the `last_used_utc` write to at most one per key per
+window (`MxGateway:Security:ApiKeyVerificationCacheSeconds` /
+`ApiKeyLastUsedCoalesceSeconds`, defaults 15 s / 60 s). This bounds WAL churn on
+the bulk-read workload without dropping any metric — auth activity is still
+observable via command-throughput counters and audit rows. See
+[Authentication](./Authentication.md#hot-path-caching-and-last-used-coalescing).
+
 ## Related Documentation
 
 - [Gateway Dashboard Design](./GatewayDashboardDesign.md)

docs/WorkerFrameProtocol.md

@@ -17,8 +17,17 @@ payload_length bytes protobuf WorkerEnvelope
 ```
 
 The reader rejects zero-length payloads and payloads larger than the configured
-maximum before allocating the payload buffer. The default maximum is 16 MiB,
-matching the gateway process design.
+maximum before allocating the payload buffer. The default maximum is the 16 MiB
+public gRPC cap plus a 64 KiB envelope-overhead reserve (16842752 bytes) so a
+maximally-sized accepted gRPC payload always fits one worker frame once wrapped
+in a `WorkerEnvelope`.
+
+The gateway is the source of truth for this maximum: it conveys the negotiated
+value in the handshake as `GatewayHello.max_frame_bytes`, and the worker adopts
+it as its `WorkerFrameProtocolOptions.MaxMessageBytes` instead of a hard-coded
+default. A `max_frame_bytes` of 0 (an older gateway that never set the field)
+means "use the worker's built-in default". This keeps both ends framing to the
+same limit rather than depending on matched compile-time constants.
 
 ## Envelope Validation
 

gateway.md

@@ -424,7 +424,10 @@ Optional diagnostics:
 - `Ping`
 - `GetSessionState`
 - `GetWorkerInfo`
-- `DrainEvents`
+- `DrainEvents` — diagnostic; `max_events` is bounded (the gateway rejects requests
+  above a public ceiling, and the worker caps each reply at its own per-reply limit,
+  treating `max_events = 0` as "the default cap") so one drain cannot pack an
+  unbounded, session-killing reply frame.
 - `ShutdownWorker`
 
 Do not compress MXAccess semantics into generic verbs too early. A command enum

scripts/check-codegen.ps1

@@ -0,0 +1,96 @@
+#!/usr/bin/env pwsh
+# Codegen freshness guard for CI (IPC-01, IPC-19, IPC-20, CLI-02).
+#
+# Three checks, all Linux/macOS-runnable (no Server build, no x86 worker):
+#   1. Published client descriptor set matches the current .proto sources (delegates to
+#      publish-client-proto-inputs.ps1 -Check, which normalizes source_code_info so it is
+#      protoc-version tolerant).
+#   2. The committed C# under Contracts/Generated matches a fresh regeneration. Grpc.Tools is
+#      pinned in the contracts csproj, so a clean checkout regenerates byte-identical output; a
+#      non-empty git diff means a .proto was edited without regenerating and committing Generated/
+#      (which breaks the net48 worker build with CS0246 — see docs/Contracts.md).
+#   3. The Rust crate's vendored protos (clients/rust/protos/*.proto — build inputs that make the
+#      crate buildable outside the repo, CLI-02) are byte-identical to the canonical Contracts
+#      protos. A drift means a .proto was edited without refreshing the vendored copies, which would
+#      publish a stale wire contract to crate consumers while the in-repo build stays correct.
+#
+# The x86 Worker + Worker.Tests are Windows-only and are guarded by the Windows CI job, not here.
+
+[CmdletBinding()]
+param()
+
+Set-StrictMode -Version Latest
+$ErrorActionPreference = 'Stop'
+
+$repoRoot = Resolve-Path (Join-Path $PSScriptRoot '..')
+$generatedDir = Join-Path $repoRoot 'src/ZB.MOM.WW.MxGateway.Contracts/Generated'
+$contractsProject = Join-Path $repoRoot 'src/ZB.MOM.WW.MxGateway.Contracts/ZB.MOM.WW.MxGateway.Contracts.csproj'
+$failures = New-Object System.Collections.Generic.List[string]
+
+Write-Host '== Check 1/2: client descriptor set freshness =='
+try {
+    & (Join-Path $PSScriptRoot 'publish-client-proto-inputs.ps1') -Check
+    if ($LASTEXITCODE -ne 0) {
+        $failures.Add('Client descriptor set is stale (publish-client-proto-inputs.ps1 -Check failed).')
+    }
+}
+catch {
+    $failures.Add("Descriptor freshness check failed: $($_.Exception.Message)")
+}
+
+Write-Host ''
+Write-Host '== Check 2/2: Contracts/Generated matches a fresh regeneration =='
+try {
+    # Force a full regeneration: Grpc.Tools skips regen when the committed .cs look up to date, so
+    # remove them first (the documented "del Generated/*.cs to force regen" trick).
+    if (Test-Path $generatedDir) {
+        Get-ChildItem -Path $generatedDir -Filter '*.cs' -Recurse -File | Remove-Item -Force
+    }
+
+    & dotnet build $contractsProject -c Release --nologo | Out-Host
+    if ($LASTEXITCODE -ne 0) {
+        $failures.Add('Contracts project failed to build during codegen check.')
+    }
+
+    $diff = (& git -C $repoRoot status --porcelain -- 'src/ZB.MOM.WW.MxGateway.Contracts/Generated').Trim()
+    if (-not [string]::IsNullOrEmpty($diff)) {
+        Write-Host $diff
+        $failures.Add('Contracts/Generated differs from a fresh regeneration. Run `dotnet build` on the contracts project and commit Generated/ (required for the net48 worker build).')
+    }
+}
+catch {
+    $failures.Add("Generated codegen check failed: $($_.Exception.Message)")
+}
+
+Write-Host ''
+Write-Host '== Check 3/3: Rust vendored protos match canonical Contracts protos =='
+try {
+    $canonicalProtoDir = Join-Path $repoRoot 'src/ZB.MOM.WW.MxGateway.Contracts/Protos'
+    $vendoredProtoDir = Join-Path $repoRoot 'clients/rust/protos'
+    foreach ($vendored in Get-ChildItem -Path $vendoredProtoDir -Filter '*.proto' -File) {
+        $canonical = Join-Path $canonicalProtoDir $vendored.Name
+        if (-not (Test-Path $canonical)) {
+            $failures.Add("Vendored Rust proto has no canonical counterpart: $($vendored.Name).")
+            continue
+        }
+        $vendoredHash = (Get-FileHash -Algorithm SHA256 $vendored.FullName).Hash
+        $canonicalHash = (Get-FileHash -Algorithm SHA256 $canonical).Hash
+        if ($vendoredHash -ne $canonicalHash) {
+            $failures.Add("Rust vendored proto drifted from canonical: clients/rust/protos/$($vendored.Name). Refresh it from src/ZB.MOM.WW.MxGateway.Contracts/Protos/$($vendored.Name).")
+        }
+    }
+}
+catch {
+    $failures.Add("Rust vendored proto check failed: $($_.Exception.Message)")
+}
+
+Write-Host ''
+if ($failures.Count -gt 0) {
+    Write-Host 'Codegen freshness check FAILED:' -ForegroundColor Red
+    foreach ($failure in $failures) {
+        Write-Host "  - $failure" -ForegroundColor Red
+    }
+    exit 1
+}
+
+Write-Host 'Codegen freshness check passed.' -ForegroundColor Green

scripts/pack-clients.ps1

@@ -187,7 +187,9 @@ function Invoke-PackRust {
         }
 
         Write-Host 'Running cargo package...'
-        & cargo package --no-verify
+        # No --no-verify: the crate vendors its protos (clients/rust/protos) so
+        # the verify build proves it compiles standalone from the tarball (CLI-02).
+        & cargo package
         if ($LASTEXITCODE -ne 0) { throw 'cargo package failed.' }
 
         $packageDir = Join-Path $rustDir 'target/package'
@@ -207,7 +209,7 @@ function Invoke-PackRust {
         Write-Host 'Publishing Rust crate to Gitea...' -ForegroundColor Yellow
         Push-Location (Join-Path $RepoRoot 'clients/rust')
         try {
-            & cargo publish --no-verify --registry dohertj2-gitea
+            & cargo publish --registry dohertj2-gitea
             if ($LASTEXITCODE -ne 0) { throw 'cargo publish failed.' }
         } finally { Pop-Location }
     }

scripts/publish-client-proto-inputs.ps1

@@ -6,23 +6,46 @@ param(
 Set-StrictMode -Version Latest
 $ErrorActionPreference = "Stop"
 
+# Pinned protoc toolchain version used to generate the committed client descriptor set.
+# See docs/ToolchainLinks.md. Generating (committing) the canonical artifact must use this
+# exact version so the checked-in bytes are reproducible. The -Check comparison is made
+# tolerant of protoc-version encoding drift (chiefly source_code_info, see IPC-20) by
+# normalizing both the committed and the freshly built descriptor through the *same* protoc
+# with source info stripped, so it does not false-fail across protoc releases.
+$PinnedProtocVersion = "34.1"
+
 $repoRoot = Resolve-Path (Join-Path $PSScriptRoot "..")
 $protoRoot = Join-Path $repoRoot "src/ZB.MOM.WW.MxGateway.Contracts/Protos"
 $manifestPath = Join-Path $repoRoot "clients/proto/proto-inputs.json"
 $descriptorPath = Join-Path $repoRoot "clients/proto/descriptors/mxaccessgw-client-v1.protoset"
+$protoFiles = @("mxaccess_gateway.proto", "mxaccess_worker.proto", "galaxy_repository.proto")
 
 function Resolve-Protoc {
-    $pathCommand = Get-Command "protoc.exe" -ErrorAction SilentlyContinue
+    # Prefer protoc on PATH (protoc on Linux/macOS, protoc.exe on Windows), then fall back to
+    # the documented winget install location on Windows.
+    foreach ($name in @("protoc", "protoc.exe")) {
+        $pathCommand = Get-Command $name -ErrorAction SilentlyContinue
         if ($null -ne $pathCommand) {
             return $pathCommand.Source
         }
+    }
 
+    if ($env:LOCALAPPDATA) {
         $documentedPath = Join-Path $env:LOCALAPPDATA "Microsoft/WinGet/Packages/Google.Protobuf_Microsoft.Winget.Source_8wekyb3d8bbwe/bin/protoc.exe"
         if (Test-Path $documentedPath) {
             return $documentedPath
         }
+    }
 
-    throw "Could not find protoc.exe. See docs/ToolchainLinks.md for the documented protobuf toolchain path."
+    throw "Could not find protoc on PATH. See docs/ToolchainLinks.md for the documented protobuf toolchain (protoc $PinnedProtocVersion)."
+}
+
+function Get-ProtocVersion {
+    param([string]$Protoc)
+
+    # `protoc --version` prints e.g. "libprotoc 34.1".
+    $raw = (& $Protoc --version) | Select-Object -First 1
+    return ($raw -replace '^libprotoc\s+', '').Trim()
 }
 
 function Ensure-Directory {
@@ -33,7 +56,29 @@ function Ensure-Directory {
     }
 }
 
-function Compare-FileBytes {
+function New-SourceInfoFreeDescriptor {
+    # Re-emits an existing descriptor set with source_code_info stripped, by round-tripping it
+    # through protoc with --descriptor_set_in and *without* --include_source_info. Because both
+    # the committed and freshly built descriptors are normalized through the same protoc binary,
+    # any protoc-version-specific encoding cancels out and the byte comparison is stable.
+    param(
+        [string]$Protoc,
+        [string]$InputDescriptor,
+        [string]$OutputDescriptor
+    )
+
+    & $Protoc `
+        "--descriptor_set_in=$InputDescriptor" `
+        "--include_imports" `
+        "--descriptor_set_out=$OutputDescriptor" `
+        @protoFiles
+
+    if ($LASTEXITCODE -ne 0) {
+        throw "protoc normalization (--descriptor_set_in) failed with exit code $LASTEXITCODE."
+    }
+}
+
+function Test-FileBytesEqual {
     param(
         [string]$ExpectedPath,
         [string]$ActualPath
@@ -66,31 +111,67 @@ foreach ($output in $manifest.generatedOutputs.PSObject.Properties.Value) {
 }
 
 $protoc = Resolve-Protoc
-$outputPath = $descriptorPath
-if ($Check) {
-    $outputPath = Join-Path ([System.IO.Path]::GetTempPath()) ("mxaccessgw-client-v1-" + [System.Guid]::NewGuid().ToString("N") + ".protoset")
-}
+$protocVersion = Get-ProtocVersion $protoc
 
-try {
+if ($Check) {
+    # Version drift no longer produces a false "stale" failure: the comparison is normalized
+    # below. A mismatch is surfaced as a warning so it is visible without blocking the gate.
+    if ($protocVersion -ne $PinnedProtocVersion) {
+        Write-Warning "protoc version '$protocVersion' differs from the pinned '$PinnedProtocVersion'. The freshness comparison is normalized and tolerant of this, but regeneration must use the pinned version (see docs/ClientProtoGeneration.md)."
+    }
+
+    $freshDescriptor = Join-Path ([System.IO.Path]::GetTempPath()) ("mxaccessgw-client-v1-fresh-" + [System.Guid]::NewGuid().ToString("N") + ".protoset")
+    $committedNormalized = Join-Path ([System.IO.Path]::GetTempPath()) ("mxaccessgw-client-v1-committed-" + [System.Guid]::NewGuid().ToString("N") + ".protoset")
+
+    try {
+        # Fresh descriptor from the current .proto sources, source info omitted (already normalized).
         & $protoc `
             "--proto_path=$protoRoot" `
             "--include_imports" `
-        "--include_source_info" `
-        "--descriptor_set_out=$outputPath" `
-        "mxaccess_gateway.proto" `
-        "mxaccess_worker.proto" `
-        "galaxy_repository.proto"
+            "--descriptor_set_out=$freshDescriptor" `
+            @protoFiles
 
         if ($LASTEXITCODE -ne 0) {
             throw "protoc failed with exit code $LASTEXITCODE."
         }
 
-    if ($Check -and -not (Compare-FileBytes -ExpectedPath $descriptorPath -ActualPath $outputPath)) {
-        throw "Client proto descriptor is stale. Run scripts/publish-client-proto-inputs.ps1 and commit the updated descriptor."
+        if (-not (Test-Path $descriptorPath)) {
+            throw "Committed descriptor '$descriptorPath' does not exist. Run scripts/publish-client-proto-inputs.ps1 to create it."
+        }
+
+        # Normalize the committed descriptor (which carries source info) through the same protoc.
+        New-SourceInfoFreeDescriptor -Protoc $protoc -InputDescriptor $descriptorPath -OutputDescriptor $committedNormalized
+
+        if (-not (Test-FileBytesEqual -ExpectedPath $committedNormalized -ActualPath $freshDescriptor)) {
+            throw "Client proto descriptor is stale. Run scripts/publish-client-proto-inputs.ps1 with the pinned protoc ($PinnedProtocVersion) and commit the updated descriptor."
+        }
+
+        Write-Host "Client proto descriptor is up to date."
+    }
+    finally {
+        foreach ($temp in @($freshDescriptor, $committedNormalized)) {
+            if (Test-Path $temp) {
+                Remove-Item -LiteralPath $temp
+            }
+        }
     }
 }
-finally {
-    if ($Check -and (Test-Path $outputPath)) {
-        Remove-Item -LiteralPath $outputPath
+else {
+    # Generating the canonical committed artifact must use the pinned protoc so the bytes are reproducible.
+    if ($protocVersion -ne $PinnedProtocVersion) {
+        throw "protoc version '$protocVersion' does not match the pinned toolchain version '$PinnedProtocVersion'. Install the pinned protoc (see docs/ToolchainLinks.md) before regenerating the committed descriptor, or run with -Check to only verify freshness."
     }
+
+    & $protoc `
+        "--proto_path=$protoRoot" `
+        "--include_imports" `
+        "--include_source_info" `
+        "--descriptor_set_out=$descriptorPath" `
+        @protoFiles
+
+    if ($LASTEXITCODE -ne 0) {
+        throw "protoc failed with exit code $LASTEXITCODE."
+    }
+
+    Write-Host "Wrote client proto descriptor to $descriptorPath (protoc $protocVersion)."
 }

src/ZB.MOM.WW.MxGateway.Contracts/Generated/MxaccessWorker.cs

@@ -44,63 +44,64 @@ namespace ZB.MOM.WW.MxGateway.Contracts.Proto {
             "Y2Nlc3Nfd29ya2VyLnYxLldvcmtlckV2ZW50SAASPwoQd29ya2VyX2hlYXJ0",
             "YmVhdBgTIAEoCzIjLm14YWNjZXNzX3dvcmtlci52MS5Xb3JrZXJIZWFydGJl",
             "YXRIABI3Cgx3b3JrZXJfZmF1bHQYFCABKAsyHy5teGFjY2Vzc193b3JrZXIu",
-            "djEuV29ya2VyRmF1bHRIAEIGCgRib2R5IloKDEdhdGV3YXlIZWxsbxIiChpz",
+            "djEuV29ya2VyRmF1bHRIAEIGCgRib2R5InMKDEdhdGV3YXlIZWxsbxIiChpz",
             "dXBwb3J0ZWRfcHJvdG9jb2xfdmVyc2lvbhgBIAEoDRINCgVub25jZRgCIAEo",
-            "CRIXCg9nYXRld2F5X3ZlcnNpb24YAyABKAkiaQoLV29ya2VySGVsbG8SGAoQ",
-            "cHJvdG9jb2xfdmVyc2lvbhgBIAEoDRINCgVub25jZRgCIAEoCRIZChF3b3Jr",
-            "ZXJfcHJvY2Vzc19pZBgDIAEoBRIWCg53b3JrZXJfdmVyc2lvbhgEIAEoCSKO",
-            "AQoLV29ya2VyUmVhZHkSGQoRd29ya2VyX3Byb2Nlc3NfaWQYASABKAUSFwoP",
-            "bXhhY2Nlc3NfcHJvZ2lkGAIgASgJEhYKDm14YWNjZXNzX2Nsc2lkGAMgASgJ",
-            "EjMKD3JlYWR5X3RpbWVzdGFtcBgEIAEoCzIaLmdvb2dsZS5wcm90b2J1Zi5U",
-            "aW1lc3RhbXAidwoNV29ya2VyQ29tbWFuZBIvCgdjb21tYW5kGAEgASgLMh4u",
-            "bXhhY2Nlc3NfZ2F0ZXdheS52MS5NeENvbW1hbmQSNQoRZW5xdWV1ZV90aW1l",
-            "c3RhbXAYAiABKAsyGi5nb29nbGUucHJvdG9idWYuVGltZXN0YW1wIoEBChJX",
-            "b3JrZXJDb21tYW5kUmVwbHkSMgoFcmVwbHkYASABKAsyIy5teGFjY2Vzc19n",
-            "YXRld2F5LnYxLk14Q29tbWFuZFJlcGx5EjcKE2NvbXBsZXRlZF90aW1lc3Rh",
-            "bXAYAiABKAsyGi5nb29nbGUucHJvdG9idWYuVGltZXN0YW1wIh4KDFdvcmtl",
-            "ckNhbmNlbBIOCgZyZWFzb24YASABKAkiUQoOV29ya2VyU2h1dGRvd24SLwoM",
-            "Z3JhY2VfcGVyaW9kGAEgASgLMhkuZ29vZ2xlLnByb3RvYnVmLkR1cmF0aW9u",
-            "Eg4KBnJlYXNvbhgCIAEoCSJIChFXb3JrZXJTaHV0ZG93bkFjaxIzCgZzdGF0",
-            "dXMYASABKAsyIy5teGFjY2Vzc19nYXRld2F5LnYxLlByb3RvY29sU3RhdHVz",
-            "IjoKC1dvcmtlckV2ZW50EisKBWV2ZW50GAEgASgLMhwubXhhY2Nlc3NfZ2F0",
-            "ZXdheS52MS5NeEV2ZW50IqUCCg9Xb3JrZXJIZWFydGJlYXQSGQoRd29ya2Vy",
-            "X3Byb2Nlc3NfaWQYASABKAUSLgoFc3RhdGUYAiABKA4yHy5teGFjY2Vzc193",
-            "b3JrZXIudjEuV29ya2VyU3RhdGUSPwobbGFzdF9zdGFfYWN0aXZpdHlfdGlt",
-            "ZXN0YW1wGAMgASgLMhouZ29vZ2xlLnByb3RvYnVmLlRpbWVzdGFtcBIdChVw",
-            "ZW5kaW5nX2NvbW1hbmRfY291bnQYBCABKA0SIgoab3V0Ym91bmRfZXZlbnRf",
-            "cXVldWVfZGVwdGgYBSABKA0SGwoTbGFzdF9ldmVudF9zZXF1ZW5jZRgGIAEo",
-            "BBImCh5jdXJyZW50X2NvbW1hbmRfY29ycmVsYXRpb25faWQYByABKAki9AEK",
-            "C1dvcmtlckZhdWx0EjkKCGNhdGVnb3J5GAEgASgOMicubXhhY2Nlc3Nfd29y",
-            "a2VyLnYxLldvcmtlckZhdWx0Q2F0ZWdvcnkSFgoOY29tbWFuZF9tZXRob2QY",
-            "AiABKAkSFAoHaHJlc3VsdBgDIAEoBUgAiAEBEhYKDmV4Y2VwdGlvbl90eXBl",
-            "GAQgASgJEhoKEmRpYWdub3N0aWNfbWVzc2FnZRgFIAEoCRI8Cg9wcm90b2Nv",
-            "bF9zdGF0dXMYBiABKAsyIy5teGFjY2Vzc19nYXRld2F5LnYxLlByb3RvY29s",
-            "U3RhdHVzQgoKCF9ocmVzdWx0KpcCCgtXb3JrZXJTdGF0ZRIcChhXT1JLRVJf",
-            "U1RBVEVfVU5TUEVDSUZJRUQQABIZChVXT1JLRVJfU1RBVEVfU1RBUlRJTkcQ",
-            "ARIcChhXT1JLRVJfU1RBVEVfSEFORFNIQUtJTkcQAhIhCh1XT1JLRVJfU1RB",
-            "VEVfSU5JVElBTElaSU5HX1NUQRADEhYKEldPUktFUl9TVEFURV9SRUFEWRAE",
-            "EiIKHldPUktFUl9TVEFURV9FWEVDVVRJTkdfQ09NTUFORBAFEh4KGldPUktF",
-            "Ul9TVEFURV9TSFVUVElOR19ET1dOEAYSGAoUV09SS0VSX1NUQVRFX1NUT1BQ",
-            "RUQQBxIYChRXT1JLRVJfU1RBVEVfRkFVTFRFRBAIKscEChNXb3JrZXJGYXVs",
-            "dENhdGVnb3J5EiUKIVdPUktFUl9GQVVMVF9DQVRFR09SWV9VTlNQRUNJRklF",
-            "RBAAEisKJ1dPUktFUl9GQVVMVF9DQVRFR09SWV9JTlZBTElEX0FSR1VNRU5U",
-            "UxABEjcKM1dPUktFUl9GQVVMVF9DQVRFR09SWV9HQVRFV0FZX0FVVEhFTlRJ",
-            "Q0FUSU9OX0ZBSUxFRBACEisKJ1dPUktFUl9GQVVMVF9DQVRFR09SWV9QUk9U",
-            "T0NPTF9NSVNNQVRDSBADEiwKKFdPUktFUl9GQVVMVF9DQVRFR09SWV9QUk9U",
-            "T0NPTF9WSU9MQVRJT04QBBIrCidXT1JLRVJfRkFVTFRfQ0FURUdPUllfUElQ",
-            "RV9ESVNDT05ORUNURUQQBRIyCi5XT1JLRVJfRkFVTFRfQ0FURUdPUllfTVhB",
-            "Q0NFU1NfQ1JFQVRJT05fRkFJTEVEEAYSMQotV09SS0VSX0ZBVUxUX0NBVEVH",
-            "T1JZX01YQUNDRVNTX0NPTU1BTkRfRkFJTEVEEAcSOgo2V09SS0VSX0ZBVUxU",
-            "X0NBVEVHT1JZX01YQUNDRVNTX0VWRU5UX0NPTlZFUlNJT05fRkFJTEVEEAgS",
-            "IgoeV09SS0VSX0ZBVUxUX0NBVEVHT1JZX1NUQV9IVU5HEAkSKAokV09SS0VS",
-            "X0ZBVUxUX0NBVEVHT1JZX1FVRVVFX09WRVJGTE9XEAoSKgomV09SS0VSX0ZB",
-            "VUxUX0NBVEVHT1JZX1NIVVRET1dOX1RJTUVPVVQQC0ImqgIjWkIuTU9NLldX",
-            "Lk14R2F0ZXdheS5Db250cmFjdHMuUHJvdG9iBnByb3RvMw=="));
+            "CRIXCg9nYXRld2F5X3ZlcnNpb24YAyABKAkSFwoPbWF4X2ZyYW1lX2J5dGVz",
+            "GAQgASgNImkKC1dvcmtlckhlbGxvEhgKEHByb3RvY29sX3ZlcnNpb24YASAB",
+            "KA0SDQoFbm9uY2UYAiABKAkSGQoRd29ya2VyX3Byb2Nlc3NfaWQYAyABKAUS",
+            "FgoOd29ya2VyX3ZlcnNpb24YBCABKAkijgEKC1dvcmtlclJlYWR5EhkKEXdv",
+            "cmtlcl9wcm9jZXNzX2lkGAEgASgFEhcKD214YWNjZXNzX3Byb2dpZBgCIAEo",
+            "CRIWCg5teGFjY2Vzc19jbHNpZBgDIAEoCRIzCg9yZWFkeV90aW1lc3RhbXAY",
+            "BCABKAsyGi5nb29nbGUucHJvdG9idWYuVGltZXN0YW1wIncKDVdvcmtlckNv",
+            "bW1hbmQSLwoHY29tbWFuZBgBIAEoCzIeLm14YWNjZXNzX2dhdGV3YXkudjEu",
+            "TXhDb21tYW5kEjUKEWVucXVldWVfdGltZXN0YW1wGAIgASgLMhouZ29vZ2xl",
+            "LnByb3RvYnVmLlRpbWVzdGFtcCKBAQoSV29ya2VyQ29tbWFuZFJlcGx5EjIK",
+            "BXJlcGx5GAEgASgLMiMubXhhY2Nlc3NfZ2F0ZXdheS52MS5NeENvbW1hbmRS",
+            "ZXBseRI3ChNjb21wbGV0ZWRfdGltZXN0YW1wGAIgASgLMhouZ29vZ2xlLnBy",
+            "b3RvYnVmLlRpbWVzdGFtcCIeCgxXb3JrZXJDYW5jZWwSDgoGcmVhc29uGAEg",
+            "ASgJIlEKDldvcmtlclNodXRkb3duEi8KDGdyYWNlX3BlcmlvZBgBIAEoCzIZ",
+            "Lmdvb2dsZS5wcm90b2J1Zi5EdXJhdGlvbhIOCgZyZWFzb24YAiABKAkiSAoR",
+            "V29ya2VyU2h1dGRvd25BY2sSMwoGc3RhdHVzGAEgASgLMiMubXhhY2Nlc3Nf",
+            "Z2F0ZXdheS52MS5Qcm90b2NvbFN0YXR1cyI6CgtXb3JrZXJFdmVudBIrCgVl",
+            "dmVudBgBIAEoCzIcLm14YWNjZXNzX2dhdGV3YXkudjEuTXhFdmVudCKlAgoP",
+            "V29ya2VySGVhcnRiZWF0EhkKEXdvcmtlcl9wcm9jZXNzX2lkGAEgASgFEi4K",
+            "BXN0YXRlGAIgASgOMh8ubXhhY2Nlc3Nfd29ya2VyLnYxLldvcmtlclN0YXRl",
+            "Ej8KG2xhc3Rfc3RhX2FjdGl2aXR5X3RpbWVzdGFtcBgDIAEoCzIaLmdvb2ds",
+            "ZS5wcm90b2J1Zi5UaW1lc3RhbXASHQoVcGVuZGluZ19jb21tYW5kX2NvdW50",
+            "GAQgASgNEiIKGm91dGJvdW5kX2V2ZW50X3F1ZXVlX2RlcHRoGAUgASgNEhsK",
+            "E2xhc3RfZXZlbnRfc2VxdWVuY2UYBiABKAQSJgoeY3VycmVudF9jb21tYW5k",
+            "X2NvcnJlbGF0aW9uX2lkGAcgASgJIvQBCgtXb3JrZXJGYXVsdBI5CghjYXRl",
+            "Z29yeRgBIAEoDjInLm14YWNjZXNzX3dvcmtlci52MS5Xb3JrZXJGYXVsdENh",
+            "dGVnb3J5EhYKDmNvbW1hbmRfbWV0aG9kGAIgASgJEhQKB2hyZXN1bHQYAyAB",
+            "KAVIAIgBARIWCg5leGNlcHRpb25fdHlwZRgEIAEoCRIaChJkaWFnbm9zdGlj",
+            "X21lc3NhZ2UYBSABKAkSPAoPcHJvdG9jb2xfc3RhdHVzGAYgASgLMiMubXhh",
+            "Y2Nlc3NfZ2F0ZXdheS52MS5Qcm90b2NvbFN0YXR1c0IKCghfaHJlc3VsdCqX",
+            "AgoLV29ya2VyU3RhdGUSHAoYV09SS0VSX1NUQVRFX1VOU1BFQ0lGSUVEEAAS",
+            "GQoVV09SS0VSX1NUQVRFX1NUQVJUSU5HEAESHAoYV09SS0VSX1NUQVRFX0hB",
+            "TkRTSEFLSU5HEAISIQodV09SS0VSX1NUQVRFX0lOSVRJQUxJWklOR19TVEEQ",
+            "AxIWChJXT1JLRVJfU1RBVEVfUkVBRFkQBBIiCh5XT1JLRVJfU1RBVEVfRVhF",
+            "Q1VUSU5HX0NPTU1BTkQQBRIeChpXT1JLRVJfU1RBVEVfU0hVVFRJTkdfRE9X",
+            "ThAGEhgKFFdPUktFUl9TVEFURV9TVE9QUEVEEAcSGAoUV09SS0VSX1NUQVRF",
+            "X0ZBVUxURUQQCCrHBAoTV29ya2VyRmF1bHRDYXRlZ29yeRIlCiFXT1JLRVJf",
+            "RkFVTFRfQ0FURUdPUllfVU5TUEVDSUZJRUQQABIrCidXT1JLRVJfRkFVTFRf",
+            "Q0FURUdPUllfSU5WQUxJRF9BUkdVTUVOVFMQARI3CjNXT1JLRVJfRkFVTFRf",
+            "Q0FURUdPUllfR0FURVdBWV9BVVRIRU5USUNBVElPTl9GQUlMRUQQAhIrCidX",
+            "T1JLRVJfRkFVTFRfQ0FURUdPUllfUFJPVE9DT0xfTUlTTUFUQ0gQAxIsCihX",
+            "T1JLRVJfRkFVTFRfQ0FURUdPUllfUFJPVE9DT0xfVklPTEFUSU9OEAQSKwon",
+            "V09SS0VSX0ZBVUxUX0NBVEVHT1JZX1BJUEVfRElTQ09OTkVDVEVEEAUSMgou",
+            "V09SS0VSX0ZBVUxUX0NBVEVHT1JZX01YQUNDRVNTX0NSRUFUSU9OX0ZBSUxF",
+            "RBAGEjEKLVdPUktFUl9GQVVMVF9DQVRFR09SWV9NWEFDQ0VTU19DT01NQU5E",
+            "X0ZBSUxFRBAHEjoKNldPUktFUl9GQVVMVF9DQVRFR09SWV9NWEFDQ0VTU19F",
+            "VkVOVF9DT05WRVJTSU9OX0ZBSUxFRBAIEiIKHldPUktFUl9GQVVMVF9DQVRF",
+            "R09SWV9TVEFfSFVORxAJEigKJFdPUktFUl9GQVVMVF9DQVRFR09SWV9RVUVV",
+            "RV9PVkVSRkxPVxAKEioKJldPUktFUl9GQVVMVF9DQVRFR09SWV9TSFVURE9X",
+            "Tl9USU1FT1VUEAtCJqoCI1pCLk1PTS5XVy5NeEdhdGV3YXkuQ29udHJhY3Rz",
+            "LlByb3RvYgZwcm90bzM="));
       descriptor = pbr::FileDescriptor.FromGeneratedCode(descriptorData,
           new pbr::FileDescriptor[] { global::Google.Protobuf.WellKnownTypes.DurationReflection.Descriptor, global::Google.Protobuf.WellKnownTypes.TimestampReflection.Descriptor, global::ZB.MOM.WW.MxGateway.Contracts.Proto.MxaccessGatewayReflection.Descriptor, },
           new pbr::GeneratedClrTypeInfo(new[] {typeof(global::ZB.MOM.WW.MxGateway.Contracts.Proto.WorkerState), typeof(global::ZB.MOM.WW.MxGateway.Contracts.Proto.WorkerFaultCategory), }, null, new pbr::GeneratedClrTypeInfo[] {
             new pbr::GeneratedClrTypeInfo(typeof(global::ZB.MOM.WW.MxGateway.Contracts.Proto.WorkerEnvelope), global::ZB.MOM.WW.MxGateway.Contracts.Proto.WorkerEnvelope.Parser, new[]{ "ProtocolVersion", "SessionId", "Sequence", "CorrelationId", "GatewayHello", "WorkerHello", "WorkerReady", "WorkerCommand", "WorkerCommandReply", "WorkerCancel", "WorkerShutdown", "WorkerShutdownAck", "WorkerEvent", "WorkerHeartbeat", "WorkerFault" }, new[]{ "Body" }, null, null, null),
-            new pbr::GeneratedClrTypeInfo(typeof(global::ZB.MOM.WW.MxGateway.Contracts.Proto.GatewayHello), global::ZB.MOM.WW.MxGateway.Contracts.Proto.GatewayHello.Parser, new[]{ "SupportedProtocolVersion", "Nonce", "GatewayVersion" }, null, null, null, null),
+            new pbr::GeneratedClrTypeInfo(typeof(global::ZB.MOM.WW.MxGateway.Contracts.Proto.GatewayHello), global::ZB.MOM.WW.MxGateway.Contracts.Proto.GatewayHello.Parser, new[]{ "SupportedProtocolVersion", "Nonce", "GatewayVersion", "MaxFrameBytes" }, null, null, null, null),
             new pbr::GeneratedClrTypeInfo(typeof(global::ZB.MOM.WW.MxGateway.Contracts.Proto.WorkerHello), global::ZB.MOM.WW.MxGateway.Contracts.Proto.WorkerHello.Parser, new[]{ "ProtocolVersion", "Nonce", "WorkerProcessId", "WorkerVersion" }, null, null, null, null),
             new pbr::GeneratedClrTypeInfo(typeof(global::ZB.MOM.WW.MxGateway.Contracts.Proto.WorkerReady), global::ZB.MOM.WW.MxGateway.Contracts.Proto.WorkerReady.Parser, new[]{ "WorkerProcessId", "MxaccessProgid", "MxaccessClsid", "ReadyTimestamp" }, null, null, null, null),
             new pbr::GeneratedClrTypeInfo(typeof(global::ZB.MOM.WW.MxGateway.Contracts.Proto.WorkerCommand), global::ZB.MOM.WW.MxGateway.Contracts.Proto.WorkerCommand.Parser, new[]{ "Command", "EnqueueTimestamp" }, null, null, null, null),
@@ -1108,6 +1109,7 @@ namespace ZB.MOM.WW.MxGateway.Contracts.Proto {
       supportedProtocolVersion_ = other.supportedProtocolVersion_;
       nonce_ = other.nonce_;
       gatewayVersion_ = other.gatewayVersion_;
+      maxFrameBytes_ = other.maxFrameBytes_;
       _unknownFields = pb::UnknownFieldSet.Clone(other._unknownFields);
     }
 
@@ -1153,6 +1155,25 @@ namespace ZB.MOM.WW.MxGateway.Contracts.Proto {
       }
     }
 
+    /// <summary>Field number for the "max_frame_bytes" field.</summary>
+    public const int MaxFrameBytesFieldNumber = 4;
+    private uint maxFrameBytes_;
+    /// <summary>
+    /// Maximum worker-frame payload size, in bytes, negotiated by the gateway from its
+    /// configured pipe limit. The worker adopts this as its frame-protocol MaxMessageBytes
+    /// instead of a hard-coded default; 0 (an older gateway that never set the field) means
+    /// "use the worker's built-in default". Sits above the public gRPC cap by an
+    /// envelope-overhead margin so an accepted gRPC payload always fits one worker frame.
+    /// </summary>
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public uint MaxFrameBytes {
+      get { return maxFrameBytes_; }
+      set {
+        maxFrameBytes_ = value;
+      }
+    }
+
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
     public override bool Equals(object other) {
@@ -1171,6 +1192,7 @@ namespace ZB.MOM.WW.MxGateway.Contracts.Proto {
       if (SupportedProtocolVersion != other.SupportedProtocolVersion) return false;
       if (Nonce != other.Nonce) return false;
       if (GatewayVersion != other.GatewayVersion) return false;
+      if (MaxFrameBytes != other.MaxFrameBytes) return false;
       return Equals(_unknownFields, other._unknownFields);
     }
 
@@ -1181,6 +1203,7 @@ namespace ZB.MOM.WW.MxGateway.Contracts.Proto {
       if (SupportedProtocolVersion != 0) hash ^= SupportedProtocolVersion.GetHashCode();
       if (Nonce.Length != 0) hash ^= Nonce.GetHashCode();
       if (GatewayVersion.Length != 0) hash ^= GatewayVersion.GetHashCode();
+      if (MaxFrameBytes != 0) hash ^= MaxFrameBytes.GetHashCode();
       if (_unknownFields != null) {
         hash ^= _unknownFields.GetHashCode();
       }
@@ -1211,6 +1234,10 @@ namespace ZB.MOM.WW.MxGateway.Contracts.Proto {
         output.WriteRawTag(26);
         output.WriteString(GatewayVersion);
       }
+      if (MaxFrameBytes != 0) {
+        output.WriteRawTag(32);
+        output.WriteUInt32(MaxFrameBytes);
+      }
       if (_unknownFields != null) {
         _unknownFields.WriteTo(output);
       }
@@ -1233,6 +1260,10 @@ namespace ZB.MOM.WW.MxGateway.Contracts.Proto {
         output.WriteRawTag(26);
         output.WriteString(GatewayVersion);
       }
+      if (MaxFrameBytes != 0) {
+        output.WriteRawTag(32);
+        output.WriteUInt32(MaxFrameBytes);
+      }
       if (_unknownFields != null) {
         _unknownFields.WriteTo(ref output);
       }
@@ -1252,6 +1283,9 @@ namespace ZB.MOM.WW.MxGateway.Contracts.Proto {
       if (GatewayVersion.Length != 0) {
         size += 1 + pb::CodedOutputStream.ComputeStringSize(GatewayVersion);
       }
+      if (MaxFrameBytes != 0) {
+        size += 1 + pb::CodedOutputStream.ComputeUInt32Size(MaxFrameBytes);
+      }
       if (_unknownFields != null) {
         size += _unknownFields.CalculateSize();
       }
@@ -1273,6 +1307,9 @@ namespace ZB.MOM.WW.MxGateway.Contracts.Proto {
       if (other.GatewayVersion.Length != 0) {
         GatewayVersion = other.GatewayVersion;
       }
+      if (other.MaxFrameBytes != 0) {
+        MaxFrameBytes = other.MaxFrameBytes;
+      }
       _unknownFields = pb::UnknownFieldSet.MergeFrom(_unknownFields, other._unknownFields);
     }
 
@@ -1304,6 +1341,10 @@ namespace ZB.MOM.WW.MxGateway.Contracts.Proto {
             GatewayVersion = input.ReadString();
             break;
           }
+          case 32: {
+            MaxFrameBytes = input.ReadUInt32();
+            break;
+          }
         }
       }
     #endif
@@ -1335,6 +1376,10 @@ namespace ZB.MOM.WW.MxGateway.Contracts.Proto {
             GatewayVersion = input.ReadString();
             break;
           }
+          case 32: {
+            MaxFrameBytes = input.ReadUInt32();
+            break;
+          }
         }
       }
     }

src/ZB.MOM.WW.MxGateway.Contracts/Protos/mxaccess_worker.proto

@@ -42,6 +42,12 @@ message GatewayHello {
   uint32 supported_protocol_version = 1;
   string nonce = 2;
   string gateway_version = 3;
+  // Maximum worker-frame payload size, in bytes, negotiated by the gateway from its
+  // configured pipe limit. The worker adopts this as its frame-protocol MaxMessageBytes
+  // instead of a hard-coded default; 0 (an older gateway that never set the field) means
+  // "use the worker's built-in default". Sits above the public gRPC cap by an
+  // envelope-overhead margin so an accepted gRPC payload always fits one worker frame.
+  uint32 max_frame_bytes = 4;
 }
 
 message WorkerHello {

src/ZB.MOM.WW.MxGateway.Contracts/ZB.MOM.WW.MxGateway.Contracts.csproj

@@ -23,6 +23,13 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <!-- Generated\**\*.cs is Compile-Removed and regenerated by Grpc.Tools into the TRACKED Generated
+         folder. It MUST be committed after any .proto change: Grpc.Tools skips regeneration when the
+         committed output looks up to date, so on net10 the freshly regenerated code compiles (drift is
+         invisible) while the net48 worker, which consumes the COMMITTED Generated\*.cs, fails with
+         CS0246 on new types. Regenerate + commit after editing a .proto; if a build does not pick up
+         the change, delete Generated\*.cs to force a full regen. scripts/check-codegen.ps1 enforces
+         this in CI. See docs/Contracts.md. -->
     <Compile Remove="Generated\**\*.cs" />
     <Protobuf Include="Protos\mxaccess_gateway.proto" ProtoRoot="Protos" OutputDir="Generated" GrpcOutputDir="Generated" GrpcServices="Both" />
     <Protobuf Include="Protos\mxaccess_worker.proto" ProtoRoot="Protos" OutputDir="Generated" GrpcServices="None" />

src/ZB.MOM.WW.MxGateway.IntegrationTests/ZB.MOM.WW.MxGateway.IntegrationTests.csproj

@@ -22,8 +22,8 @@
     (IntegrationTests-028).
   -->
   <ItemGroup>
-    <PackageReference Include="ZB.MOM.WW.Auth.Abstractions" Version="0.1.2" />
-    <PackageReference Include="ZB.MOM.WW.Auth.Ldap" Version="0.1.2" />
+    <PackageReference Include="ZB.MOM.WW.Auth.Abstractions" Version="0.1.4" />
+    <PackageReference Include="ZB.MOM.WW.Auth.Ldap" Version="0.1.4" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="10.0.7" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Binder" Version="10.0.7" />
   </ItemGroup>

src/ZB.MOM.WW.MxGateway.Server/Configuration/AuthenticationOptions.cs

@@ -5,8 +5,18 @@ public sealed class AuthenticationOptions
     /// <summary>Gets the authentication mode.</summary>
     public AuthenticationMode Mode { get; init; } = AuthenticationMode.ApiKey;
 
-    /// <summary>Gets the SQLite database path for authentication credentials.</summary>
-    public string SqlitePath { get; init; } = @"C:\ProgramData\MxGateway\gateway-auth.db";
+    /// <summary>
+    /// Gets the SQLite database path for authentication credentials. The default is
+    /// derived from <see cref="Environment.SpecialFolder.CommonApplicationData"/>
+    /// (<c>C:\ProgramData</c> on Windows, <c>/usr/share</c> or the container equivalent
+    /// elsewhere) so the credential store never lands in the launch working directory on a
+    /// non-Windows host. The production hosts override this with an explicit path in
+    /// <c>appsettings.json</c>; the validator rejects a non-rooted override.
+    /// </summary>
+    public string SqlitePath { get; init; } = Path.Combine(
+        Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData),
+        "MxGateway",
+        "gateway-auth.db");
 
     /// <summary>Gets the secret manager name for API key pepper.</summary>
     public string PepperSecretName { get; init; } = "MxGateway:ApiKeyPepper";

src/ZB.MOM.WW.MxGateway.Server/Configuration/GatewayConfigurationServiceCollectionExtensions.cs

@@ -1,4 +1,7 @@
 using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection.Extensions;
+using Microsoft.Extensions.FileProviders;
+using Microsoft.Extensions.Hosting;
 using ZB.MOM.WW.Configuration;
 
 namespace ZB.MOM.WW.MxGateway.Server.Configuration;
@@ -12,6 +15,14 @@ public static class GatewayConfigurationServiceCollectionExtensions
     public static IServiceCollection AddGatewayConfiguration(
         this IServiceCollection services, IConfiguration configuration)
     {
+        // GatewayOptionsValidator depends on IHostEnvironment to gate the production-only rules
+        // (SEC-04/06). The real host and the apikey CLI both build through WebApplicationBuilder,
+        // which registers IHostEnvironment before this call — so TryAdd is a no-op there. Minimal
+        // containers (unit tests, tooling) have none; fall back to a non-production environment so
+        // the validator still activates and the production guards stay off outside a real
+        // deployment (the fail-fast guards only make sense against a real host environment).
+        services.TryAddSingleton<IHostEnvironment>(new FallbackHostEnvironment());
+
         services.AddValidatedOptions<GatewayOptions, GatewayOptionsValidator>(
             configuration, GatewayOptions.SectionName);
 
@@ -19,4 +30,19 @@ public static class GatewayConfigurationServiceCollectionExtensions
 
         return services;
     }
+
+    /// <summary>
+    /// Non-production <see cref="IHostEnvironment"/> used only when no real host registered one
+    /// (minimal test/tooling containers). The real host's registration always wins via TryAdd.
+    /// </summary>
+    private sealed class FallbackHostEnvironment : IHostEnvironment
+    {
+        public string EnvironmentName { get; set; } = Environments.Development;
+
+        public string ApplicationName { get; set; } = typeof(FallbackHostEnvironment).Assembly.GetName().Name ?? "MxGateway";
+
+        public string ContentRootPath { get; set; } = AppContext.BaseDirectory;
+
+        public IFileProvider ContentRootFileProvider { get; set; } = new NullFileProvider();
+    }
 }

src/ZB.MOM.WW.MxGateway.Server/Configuration/GatewayOptions.cs

@@ -46,4 +46,10 @@ public sealed class GatewayOptions
 
     /// <summary>Gets self-signed TLS certificate auto-generation options.</summary>
     public TlsOptions Tls { get; init; } = new();
+
+    /// <summary>
+    /// Gets security hot-path options (API-key verification cache / last-used coalescing and
+    /// login / API-key rate limiting).
+    /// </summary>
+    public SecurityOptions Security { get; init; } = new();
 }

src/ZB.MOM.WW.MxGateway.Server/Configuration/GatewayOptionsValidator.cs

@@ -1,6 +1,7 @@
 using ZB.MOM.WW.Auth.Abstractions.Ldap;
 using ZB.MOM.WW.Configuration;
 using ZB.MOM.WW.MxGateway.Contracts;
+using ZB.MOM.WW.MxGateway.Server.Workers;
 
 namespace ZB.MOM.WW.MxGateway.Server.Configuration;
 
@@ -9,18 +10,83 @@ public sealed class GatewayOptionsValidator : OptionsValidatorBase<GatewayOption
     private const int MinimumMaxMessageBytes = 1024;
     private const int MaximumMaxMessageBytes = 256 * 1024 * 1024;
 
+    // Whether the host is running in the Production environment. Drives the production-only
+    // hard-stops (dashboard login disabled, plaintext LDAP transport) that must abort startup
+    // rather than merely warn. Non-production hosts keep the permissive dev posture.
+    private readonly bool _isProduction;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="GatewayOptionsValidator"/> class for the
+    /// dependency-injection path, deriving the production posture from the host environment.
+    /// </summary>
+    /// <param name="environment">The host environment.</param>
+    public GatewayOptionsValidator(IHostEnvironment environment)
+    {
+        ArgumentNullException.ThrowIfNull(environment);
+        _isProduction = environment.IsProduction();
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="GatewayOptionsValidator"/> class for unit
+    /// tests and non-DI callers. Defaults to a non-production posture so the production-only
+    /// hard-stops do not fire; pass <see langword="true"/> to exercise them.
+    /// </summary>
+    /// <param name="isProduction">Whether to treat the host as running in Production.</param>
+    internal GatewayOptionsValidator(bool isProduction = false)
+    {
+        _isProduction = isProduction;
+    }
+
     /// <inheritdoc />
     protected override void Validate(ValidationBuilder builder, GatewayOptions options)
     {
         ValidateAuthentication(options.Authentication, builder);
-        ValidateLdap(options.Ldap, builder);
+        ValidateLdap(options.Ldap, builder, _isProduction);
         ValidateWorker(options.Worker, builder);
         ValidateSessions(options.Sessions, builder);
         ValidateEvents(options.Events, builder);
-        ValidateDashboard(options.Dashboard, builder);
+        ValidateDashboard(options.Dashboard, builder, _isProduction);
         ValidateProtocol(options.Protocol, builder);
+        ValidateFrameSizeHeadroom(options.Worker, options.Protocol, builder);
         ValidateAlarms(options.Alarms, builder);
         ValidateTls(options.Tls, builder);
+        ValidateSecurity(options.Security, builder);
+    }
+
+    private static void ValidateSecurity(SecurityOptions options, ValidationBuilder builder)
+    {
+        // Cache/coalesce windows may be 0 (disables that mechanism); negatives are invalid.
+        AddIfNegative(
+            options.ApiKeyVerificationCacheSeconds,
+            "MxGateway:Security:ApiKeyVerificationCacheSeconds must be greater than or equal to zero (0 disables the verification cache).",
+            builder);
+        AddIfNegative(
+            options.ApiKeyLastUsedCoalesceSeconds,
+            "MxGateway:Security:ApiKeyLastUsedCoalesceSeconds must be greater than or equal to zero (0 forwards every last_used write).",
+            builder);
+
+        // Rate-limit knobs must be positive: a zero permit/window/limit is a misconfiguration that
+        // would either reject every request or divide by zero rather than express an intent.
+        AddIfNotPositive(
+            options.LoginRateLimitPermitLimit,
+            "MxGateway:Security:LoginRateLimitPermitLimit must be greater than zero.",
+            builder);
+        AddIfNotPositive(
+            options.LoginRateLimitWindowSeconds,
+            "MxGateway:Security:LoginRateLimitWindowSeconds must be greater than zero.",
+            builder);
+        AddIfNotPositive(
+            options.ApiKeyFailureLimit,
+            "MxGateway:Security:ApiKeyFailureLimit must be greater than zero.",
+            builder);
+        AddIfNotPositive(
+            options.ApiKeyFailureWindowSeconds,
+            "MxGateway:Security:ApiKeyFailureWindowSeconds must be greater than zero.",
+            builder);
+        AddIfNotPositive(
+            options.ApiKeyFailureTrackedPeers,
+            "MxGateway:Security:ApiKeyFailureTrackedPeers must be greater than zero.",
+            builder);
     }
 
     private static void ValidateAuthentication(AuthenticationOptions options, ValidationBuilder builder)
@@ -41,6 +107,10 @@ public sealed class GatewayOptionsValidator : OptionsValidatorBase<GatewayOption
                 options.SqlitePath,
                 "MxGateway:Authentication:SqlitePath must be a valid filesystem path.",
                 builder);
+            AddIfNotRooted(
+                options.SqlitePath,
+                "MxGateway:Authentication:SqlitePath must be an absolute (rooted) path so the credential store never lands in the launch working directory.",
+                builder);
             AddIfBlank(
                 options.PepperSecretName,
                 "MxGateway:Authentication:PepperSecretName is required when API-key authentication is enabled.",
@@ -48,7 +118,7 @@ public sealed class GatewayOptionsValidator : OptionsValidatorBase<GatewayOption
         }
     }
 
-    private static void ValidateLdap(LdapOptions options, ValidationBuilder builder)
+    private static void ValidateLdap(LdapOptions options, ValidationBuilder builder, bool isProduction)
     {
         if (!options.Enabled)
         {
@@ -83,6 +153,16 @@ public sealed class GatewayOptionsValidator : OptionsValidatorBase<GatewayOption
         {
             builder.Add("MxGateway:Ldap:AllowInsecure must be true when Transport is None (plaintext).");
         }
+
+        // Production hard-stop: plaintext LDAP binds send the operator's password in the clear.
+        // The permissive dev default (Transport=None against the shared GLAuth instance) is
+        // acceptable off-production but must never ship to a Production host. Deployed hosts must
+        // set Transport=Ldaps/StartTls; see docs/GatewayConfiguration.md and glauth.md.
+        if (isProduction && options.Transport == LdapTransport.None)
+        {
+            builder.Add(
+                "MxGateway:Ldap:Transport must not be None (plaintext) in the Production environment; use Ldaps or StartTls.");
+        }
     }
 
     private static void ValidateWorker(WorkerOptions options, ValidationBuilder builder)
@@ -224,8 +304,19 @@ public sealed class GatewayOptionsValidator : OptionsValidatorBase<GatewayOption
             $"MxGateway:Events:MaxSparseArrayLength must be between 1 and {Array.MaxLength}.");
     }
 
-    private static void ValidateDashboard(DashboardOptions options, ValidationBuilder builder)
+    private static void ValidateDashboard(DashboardOptions options, ValidationBuilder builder, bool isProduction)
     {
+        // Production hard-stop: DisableLogin swaps in an auto-login handler that authenticates
+        // EVERY request (remote included) as AutoLoginUser holding both roles, turning the whole
+        // dashboard — API-key CRUD and worker Kill included — into an unauthenticated admin
+        // surface on a 0.0.0.0-bound port. It is a dev/test-only convenience; abort startup if it
+        // is set in Production. Non-production hosts keep the existing runtime warning.
+        if (isProduction && options.DisableLogin)
+        {
+            builder.Add(
+                "MxGateway:Dashboard:DisableLogin must not be true in the Production environment; it disables all dashboard authentication.");
+        }
+
         // GroupToRole shape is validated even when the dashboard is disabled so
         // misconfiguration surfaces at startup; emptiness is allowed, with the
         // consequence that no LDAP user can sign in (login returns "no roles
@@ -348,6 +439,10 @@ public sealed class GatewayOptionsValidator : OptionsValidatorBase<GatewayOption
             options.SelfSignedCertPath,
             "MxGateway:Tls:SelfSignedCertPath must be a valid filesystem path.",
             builder);
+        AddIfNotRooted(
+            options.SelfSignedCertPath,
+            "MxGateway:Tls:SelfSignedCertPath must be an absolute (rooted) path so the generated private key never lands in the launch working directory.",
+            builder);
 
         foreach (string dns in options.AdditionalDnsNames)
         {
@@ -373,6 +468,35 @@ public sealed class GatewayOptionsValidator : OptionsValidatorBase<GatewayOption
         }
     }
 
+    // The worker-frame (pipe) maximum must stay above the public gRPC cap by the envelope-overhead
+    // reserve, otherwise a maximally-sized accepted gRPC payload does not fit one worker frame once
+    // wrapped in a WorkerEnvelope and the outbound write faults the whole session (IPC-03). Fail fast
+    // at startup rather than mid-traffic. Only checked when both knobs are themselves in range so the
+    // message is not doubled up with the individual range errors.
+    private static void ValidateFrameSizeHeadroom(
+        WorkerOptions worker,
+        ProtocolOptions protocol,
+        ValidationBuilder builder)
+    {
+        bool workerInRange = worker.MaxMessageBytes is >= MinimumMaxMessageBytes and <= MaximumMaxMessageBytes;
+        bool grpcInRange = protocol.MaxGrpcMessageBytes is >= MinimumMaxMessageBytes and <= MaximumMaxMessageBytes;
+        if (!workerInRange || !grpcInRange)
+        {
+            return;
+        }
+
+        long requiredWorkerMax =
+            (long)protocol.MaxGrpcMessageBytes + WorkerFrameProtocolOptions.EnvelopeOverheadReserveBytes;
+        if (worker.MaxMessageBytes < requiredWorkerMax)
+        {
+            builder.Add(
+                $"MxGateway:Worker:MaxMessageBytes ({worker.MaxMessageBytes}) must be at least "
+                + $"MxGateway:Protocol:MaxGrpcMessageBytes ({protocol.MaxGrpcMessageBytes}) plus the "
+                + $"{WorkerFrameProtocolOptions.EnvelopeOverheadReserveBytes}-byte worker-frame envelope reserve "
+                + $"(>= {requiredWorkerMax}).");
+        }
+    }
+
     private static void AddIfBlank(string? value, string message, ValidationBuilder builder)
     {
         builder.RequireThat(!string.IsNullOrWhiteSpace(value), message);
@@ -388,6 +512,53 @@ public sealed class GatewayOptionsValidator : OptionsValidatorBase<GatewayOption
         builder.RequireThat(value >= 0, message);
     }
 
+    private static void AddIfNotRooted(string? value, string message, ValidationBuilder builder)
+    {
+        // Security-sensitive paths (the auth DB, the self-signed private key) must be absolute:
+        // a non-rooted value silently resolves against the launch working directory, so the store
+        // moves with the CWD and can leak into the source tree. Reject rather than auto-root —
+        // silent relocation of a credential store is worse than a boot error. Blank is handled by
+        // AddIfBlank; an empty value is not treated as non-rooted here.
+        if (string.IsNullOrWhiteSpace(value))
+        {
+            return;
+        }
+
+        if (!IsRootedForAnyPlatform(value))
+        {
+            builder.Add(message);
+        }
+    }
+
+    /// <summary>
+    /// Determines whether <paramref name="value"/> is an absolute path for <em>any</em> platform,
+    /// not just the host running the validator. This matters on the macOS dev box, where the
+    /// production <c>appsettings.json</c> ships Windows-absolute paths (<c>C:\ProgramData\...</c>)
+    /// that <see cref="Path.IsPathRooted(string)"/> reports as non-rooted on Unix. The intent of the
+    /// rooting check is to reject bare filenames that resolve against the launch working directory,
+    /// so a valid Windows drive-qualified or UNC path must pass regardless of the current OS.
+    /// </summary>
+    private static bool IsRootedForAnyPlatform(string value)
+    {
+        // Rooted on the current OS (Unix "/...", or a Windows drive/UNC path when on Windows).
+        if (Path.IsPathRooted(value))
+        {
+            return true;
+        }
+
+        // Windows drive-qualified path ("C:\..." or "C:/...") checked on a non-Windows host.
+        if (value.Length >= 3
+            && char.IsLetter(value[0])
+            && value[1] == ':'
+            && (value[2] == '\\' || value[2] == '/'))
+        {
+            return true;
+        }
+
+        // Windows UNC path ("\\server\share") checked on a non-Windows host.
+        return value.StartsWith(@"\\", StringComparison.Ordinal);
+    }
+
     private static void AddIfInvalidPath(string? value, string message, ValidationBuilder builder)
     {
         if (string.IsNullOrWhiteSpace(value))

src/ZB.MOM.WW.MxGateway.Server/Configuration/SecurityOptions.cs

@@ -0,0 +1,65 @@
+namespace ZB.MOM.WW.MxGateway.Server.Configuration;
+
+/// <summary>
+/// Security hot-path options bound from <c>MxGateway:Security</c>. Groups the API-key verification
+/// cache and <c>last_used</c> write-coalescing knobs (SEC-08) with the login and API-key
+/// rate-limiting knobs (SEC-11). Defaults preserve safe, low-overhead behaviour without requiring
+/// operators to configure anything.
+/// </summary>
+public sealed class SecurityOptions
+{
+    /// <summary>The configuration sub-section this binds from.</summary>
+    public const string SectionName = "MxGateway:Security";
+
+    /// <summary>
+    /// Gets the time-to-live, in seconds, of a cached successful API-key verification. A cache hit
+    /// within this window skips the per-call SQLite read (and the library verifier's coupled
+    /// <c>last_used</c> write). Explicit invalidation on gateway-initiated revoke/rotate is the
+    /// primary correctness mechanism; this short TTL is the backstop for out-of-band mutations.
+    /// Set to <c>0</c> to disable caching. Default is 15 seconds.
+    /// </summary>
+    public int ApiKeyVerificationCacheSeconds { get; init; } = 15;
+
+    /// <summary>
+    /// Gets the coalescing window, in seconds, for the <c>last_used_utc</c> write. The library
+    /// verifier couples the write into every verification; this decorator forwards at most one
+    /// <c>MarkUsed</c> per key per window, so a hammered key produces at most one write per window
+    /// rather than one per authenticated RPC. Set to <c>0</c> to forward every write. Default is
+    /// 60 seconds (at most one write per key per minute).
+    /// </summary>
+    public int ApiKeyLastUsedCoalesceSeconds { get; init; } = 60;
+
+    /// <summary>
+    /// Gets the maximum number of <c>POST /auth/login</c> attempts permitted per remote IP within
+    /// <see cref="LoginRateLimitWindowSeconds"/> before requests are rejected with HTTP 429. Default
+    /// is 10.
+    /// </summary>
+    public int LoginRateLimitPermitLimit { get; init; } = 10;
+
+    /// <summary>
+    /// Gets the fixed-window length, in seconds, for the <c>POST /auth/login</c> per-IP rate limit.
+    /// Default is 60 seconds.
+    /// </summary>
+    public int LoginRateLimitWindowSeconds { get; init; } = 60;
+
+    /// <summary>
+    /// Gets the number of consecutive failed API-key verifications, per peer, within
+    /// <see cref="ApiKeyFailureWindowSeconds"/> that trips the in-process short-circuit. Once tripped,
+    /// the gRPC auth path rejects further attempts before the store read; a successful verification
+    /// resets the peer's counter. Default is 10.
+    /// </summary>
+    public int ApiKeyFailureLimit { get; init; } = 10;
+
+    /// <summary>
+    /// Gets the sliding-window length, in seconds, over which API-key verification failures are
+    /// counted per peer. Default is 60 seconds.
+    /// </summary>
+    public int ApiKeyFailureWindowSeconds { get; init; } = 60;
+
+    /// <summary>
+    /// Gets the maximum number of distinct peers tracked by the API-key failure counter. The counter
+    /// is a bounded LRU so a spray of unique peer keys cannot grow memory without limit. Default is
+    /// 4096.
+    /// </summary>
+    public int ApiKeyFailureTrackedPeers { get; init; } = 4096;
+}

src/ZB.MOM.WW.MxGateway.Server/Configuration/TlsOptions.cs

@@ -7,9 +7,19 @@ namespace ZB.MOM.WW.MxGateway.Server.Configuration;
 /// </summary>
 public sealed class TlsOptions
 {
-    /// <summary>Path to the persisted self-signed PFX. Reused across restarts.</summary>
-    public string SelfSignedCertPath { get; init; } =
-        @"C:\ProgramData\MxGateway\certs\gateway-selfsigned.pfx";
+    /// <summary>
+    /// Path to the persisted self-signed PFX. Reused across restarts. The default is derived
+    /// from <see cref="Environment.SpecialFolder.CommonApplicationData"/> (<c>C:\ProgramData</c>
+    /// on Windows, <c>/usr/share</c> or the container equivalent elsewhere) so a generated
+    /// private key never lands in the launch working directory on a non-Windows host. The
+    /// production hosts override this with an explicit path; the validator rejects a non-rooted
+    /// override.
+    /// </summary>
+    public string SelfSignedCertPath { get; init; } = Path.Combine(
+        Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData),
+        "MxGateway",
+        "certs",
+        "gateway-selfsigned.pfx");
 
     /// <summary>Lifetime in years of a freshly generated certificate.</summary>
     public int ValidityYears { get; init; } = 10;

src/ZB.MOM.WW.MxGateway.Server/Configuration/WorkerOptions.cs

@@ -33,6 +33,14 @@ public sealed class WorkerOptions
     /// <summary>The grace period in seconds after a heartbeat before considering the worker unresponsive.</summary>
     public int HeartbeatGraceSeconds { get; init; } = 15;
 
-    /// <summary>The maximum message size in bytes for IPC communication.</summary>
-    public int MaxMessageBytes { get; init; } = 16 * 1024 * 1024;
+    /// <summary>
+    /// The maximum worker-frame (pipe) message size in bytes. Must stay at least
+    /// <see cref="Workers.WorkerFrameProtocolOptions.EnvelopeOverheadReserveBytes"/> above
+    /// <see cref="ProtocolOptions.MaxGrpcMessageBytes"/> so a maximally-sized accepted gRPC payload
+    /// still fits one worker frame (IPC-03); the gateway conveys this value to the worker in the
+    /// handshake (<c>GatewayHello.max_frame_bytes</c>, IPC-02). Default is the 16 MB public gRPC cap
+    /// plus that reserve.
+    /// </summary>
+    public int MaxMessageBytes { get; init; } =
+        (16 * 1024 * 1024) + Workers.WorkerFrameProtocolOptions.EnvelopeOverheadReserveBytes;
 }

src/ZB.MOM.WW.MxGateway.Server/Dashboard/Components/Pages/ApiKeysPage.razor

@@ -164,6 +164,7 @@ else
                             <th scope="col">Constraints</th>
                             <th scope="col">Created</th>
                             <th scope="col">Last Used</th>
+                            <th scope="col">Expires</th>
                             @if (CanManageApiKeys)
                             {
                                 <th scope="col">Actions</th>
@@ -175,12 +176,13 @@ else
                         {
                             <tr>
                                 <td><code>@key.KeyId</code></td>
-                                <td><StatusBadge Text="@(key.RevokedUtc is null ? "Active" : "Revoked")" /></td>
+                                <td><StatusBadge Text="@KeyStatus(key)" /></td>
                                 <td>@DashboardDisplay.Text(key.DisplayName)</td>
                                 <td>@DashboardDisplay.Text(string.Join(", ", key.Scopes.Order(StringComparer.Ordinal)))</td>
                                 <td>@DashboardDisplay.Text(ConstraintText(key.Constraints))</td>
                                 <td>@DashboardDisplay.DateTime(key.CreatedUtc)</td>
                                 <td>@DashboardDisplay.DateTime(key.LastUsedUtc)</td>
+                                <td>@(key.ExpiresUtc is null ? "Never" : DashboardDisplay.DateTime(key.ExpiresUtc))</td>
                                 @if (CanManageApiKeys)
                                 {
                                     <td>
@@ -468,6 +470,35 @@ else
         }
     }
 
+    // Window before an expiry within which a key is flagged as "Expiring" (warn) rather than "Active".
+    private static readonly TimeSpan ExpiringSoonWindow = TimeSpan.FromDays(7);
+
+    // Status vocabulary understood by StatusBadge: Revoked wins over expiry; a past expiry is Expired
+    // (bad), an expiry inside ExpiringSoonWindow is Expiring (warn), otherwise Active (SEC-10).
+    private static string KeyStatus(DashboardApiKeySummary key)
+    {
+        if (key.RevokedUtc is not null)
+        {
+            return "Revoked";
+        }
+
+        if (key.ExpiresUtc is { } expiresAt)
+        {
+            DateTimeOffset now = DateTimeOffset.UtcNow;
+            if (expiresAt <= now)
+            {
+                return "Expired";
+            }
+
+            if (expiresAt - now <= ExpiringSoonWindow)
+            {
+                return "Expiring";
+            }
+        }
+
+        return "Active";
+    }
+
     private static string ConstraintText(ApiKeyConstraints constraints)
     {
         if (constraints.IsEmpty)

src/ZB.MOM.WW.MxGateway.Server/Dashboard/Components/Shared/StatusBadge.razor

@@ -9,8 +9,8 @@
     {
         "Ready" or "Healthy" or "Active" => StatusState.Ok,
         "Creating" or "StartingWorker" or "WaitingForPipe" or "InitializingWorker" or "Closing"
-            or "Stale" or "Degraded" => StatusState.Warn,
-        "Faulted" or "Unavailable" => StatusState.Bad,
+            or "Stale" or "Degraded" or "Expiring" => StatusState.Warn,
+        "Faulted" or "Unavailable" or "Expired" => StatusState.Bad,
         _ => StatusState.Idle,
     };
 }

src/ZB.MOM.WW.MxGateway.Server/Dashboard/DashboardApiKeyManagementService.cs

@@ -15,7 +15,8 @@ public sealed class DashboardApiKeyManagementService(
     ApiKeyAdminCommands adminCommands,
     IApiKeyAdminStore adminStore,
     IAuditWriter auditWriter,
-    IHttpContextAccessor httpContextAccessor) : IDashboardApiKeyManagementService
+    IHttpContextAccessor httpContextAccessor,
+    IApiKeyCacheInvalidator? cacheInvalidator = null) : IDashboardApiKeyManagementService
 {
     private const string UnauthorizedMessage = "Sign in with an authorized LDAP account to manage API keys.";
     private const string PepperUnavailableMarker = "pepper unavailable";
@@ -100,6 +101,10 @@ public sealed class DashboardApiKeyManagementService(
             .RevokeKeyAsync(normalizedKeyId, RemoteAddress(), cancellationToken)
             .ConfigureAwait(false);
 
+        // SEC-08: drop any cached verification for this key in THIS gateway process so the revoke
+        // takes effect immediately rather than after the verification-cache TTL elapses.
+        cacheInvalidator?.Invalidate(normalizedKeyId);
+
         await WriteDashboardAuditAsync(
                 user,
                 normalizedKeyId,
@@ -138,6 +143,10 @@ public sealed class DashboardApiKeyManagementService(
                 .RotateKeyAsync(normalizedKeyId, RemoteAddress(), cancellationToken)
                 .ConfigureAwait(false);
 
+            // SEC-08: the old secret's cached verification must not outlive the rotate — evict it so
+            // the superseded secret stops authenticating within this process immediately.
+            cacheInvalidator?.Invalidate(normalizedKeyId);
+
             bool succeeded = rotated.Token is not null;
 
             await WriteDashboardAuditAsync(
@@ -182,6 +191,10 @@ public sealed class DashboardApiKeyManagementService(
             .DeleteAsync(normalizedKeyId, cancellationToken)
             .ConfigureAwait(false);
 
+        // SEC-08: a deleted key is only reachable after a prior revoke, but evict defensively so no
+        // cached verification survives the delete.
+        cacheInvalidator?.Invalidate(normalizedKeyId);
+
         await WriteDashboardAuditAsync(
                 user,
                 normalizedKeyId,

src/ZB.MOM.WW.MxGateway.Server/Dashboard/DashboardApiKeySummary.cs

@@ -9,4 +9,5 @@ public sealed record DashboardApiKeySummary(
     ApiKeyConstraints Constraints,
     DateTimeOffset CreatedUtc,
     DateTimeOffset? LastUsedUtc,
-    DateTimeOffset? RevokedUtc);
+    DateTimeOffset? RevokedUtc,
+    DateTimeOffset? ExpiresUtc = null);

src/ZB.MOM.WW.MxGateway.Server/Dashboard/DashboardAuthorizationHandler.cs

@@ -11,6 +11,18 @@ namespace ZB.MOM.WW.MxGateway.Server.Dashboard;
 /// (b) authentication is fully disabled, or (c) the request is from loopback
 /// and <c>MxGateway:Dashboard:AllowAnonymousLocalhost</c> is on.
 /// </summary>
+/// <remarks>
+/// The environment bypasses in (b) and (c) grant <em>read-only</em> access only: they
+/// satisfy a requirement that includes <see cref="DashboardRoles.Viewer"/> (i.e.
+/// <see cref="DashboardAuthorizationRequirement.AnyDashboardRole"/>) but never the
+/// <see cref="DashboardAuthorizationRequirement.AdminOnly"/> requirement. Destructive/admin
+/// surfaces still require a real Admin role claim, preserving the documented
+/// "anonymous localhost is read-only" contract at the policy layer rather than by accident
+/// in downstream service re-checks. The loopback test trusts
+/// <c>Connection.RemoteIpAddress</c>; if forwarded-headers middleware is ever added upstream,
+/// <see cref="IsLoopbackRequest"/> must be revisited so a spoofed <c>X-Forwarded-For</c>
+/// cannot masquerade as loopback.
+/// </remarks>
 public sealed class DashboardAuthorizationHandler(
     IHttpContextAccessor httpContextAccessor,
     IOptions<GatewayOptions> options) : AuthorizationHandler<DashboardAuthorizationRequirement>
@@ -22,14 +34,18 @@ public sealed class DashboardAuthorizationHandler(
     {
         GatewayOptions gatewayOptions = options.Value;
 
-        if (gatewayOptions.Authentication.Mode == AuthenticationMode.Disabled)
+        // Environment bypasses are read-only: they satisfy the Viewer requirement
+        // (AnyDashboardRole) but never AdminOnly, which lacks Viewer in RequiredRoles.
+        bool grantsReadOnly = requirement.RequiredRoles.Contains(DashboardRoles.Viewer);
+
+        if (grantsReadOnly && gatewayOptions.Authentication.Mode == AuthenticationMode.Disabled)
         {
             context.Succeed(requirement);
 
             return Task.CompletedTask;
         }
 
-        if (gatewayOptions.Dashboard.AllowAnonymousLocalhost && IsLoopbackRequest())
+        if (grantsReadOnly && gatewayOptions.Dashboard.AllowAnonymousLocalhost && IsLoopbackRequest())
         {
             context.Succeed(requirement);
 

src/ZB.MOM.WW.MxGateway.Server/Dashboard/DashboardEndpointRouteBuilderExtensions.cs

@@ -1,4 +1,5 @@
 using System.Text.Encodings.Web;
+using System.Threading.RateLimiting;
 using Microsoft.AspNetCore.Antiforgery;
 using Microsoft.AspNetCore.Authentication;
 using ZB.MOM.WW.MxGateway.Server.Configuration;
@@ -10,6 +11,41 @@ namespace ZB.MOM.WW.MxGateway.Server.Dashboard;
 /// <summary>Endpoint extensions for registering the gateway dashboard routes.</summary>
 public static class DashboardEndpointRouteBuilderExtensions
 {
+    /// <summary>
+    /// The named rate-limiter policy applied to the <c>POST /auth/login</c> route (SEC-11). Registered
+    /// in <c>GatewayApplication</c> via <see cref="GetLoginRateLimitPartition"/>.
+    /// </summary>
+    internal const string LoginRateLimiterPolicy = "dashboard-login";
+
+    /// <summary>
+    /// Builds the fixed-window rate-limit partition for a login request, keyed on the remote IP.
+    /// Shared by the production policy registration and the tests so both exercise identical limits.
+    /// </summary>
+    /// <param name="httpContext">The inbound request.</param>
+    /// <param name="security">The bound security options carrying the login-limit knobs.</param>
+    /// <returns>The per-IP fixed-window partition.</returns>
+    internal static RateLimitPartition<string> GetLoginRateLimitPartition(
+        HttpContext httpContext,
+        SecurityOptions security)
+    {
+        string partitionKey = httpContext.Connection.RemoteIpAddress?.ToString() ?? "unknown";
+        return RateLimitPartition.GetFixedWindowLimiter(
+            partitionKey,
+            _ => new FixedWindowRateLimiterOptions
+            {
+                PermitLimit = security.LoginRateLimitPermitLimit,
+                Window = TimeSpan.FromSeconds(security.LoginRateLimitWindowSeconds),
+                QueueLimit = 0,
+                AutoReplenishment = true,
+            });
+    }
+
+    // Test seam: a standalone partitioned limiter over the production partition logic, so a test can
+    // acquire leases and assert the (permit+1)th is rejected without an HTTP server.
+    internal static PartitionedRateLimiter<HttpContext> CreateLoginRateLimiter(SecurityOptions security)
+        => PartitionedRateLimiter.Create<HttpContext, string>(
+            ctx => GetLoginRateLimitPartition(ctx, security));
+
     /// <summary>Maps all gateway dashboard routes including login, logout, and Razor components.</summary>
     /// <param name="endpoints">The endpoint route builder.</param>
     /// <returns>The route builder for chaining.</returns>
@@ -40,6 +76,8 @@ public static class DashboardEndpointRouteBuilderExtensions
                 (HttpContext httpContext, IAntiforgery antiforgery, IDashboardAuthenticator authenticator) =>
                     PostLoginAsync(httpContext, antiforgery, authenticator))
             .AllowAnonymous()
+            // SEC-11: throttle credential stuffing before the LDAP bind is relayed to the directory.
+            .RequireRateLimiting(LoginRateLimiterPolicy)
             .WithName("DashboardLoginPost");
 
         endpoints.MapPost(

src/ZB.MOM.WW.MxGateway.Server/Dashboard/DashboardSessionAdminService.cs

@@ -1,6 +1,8 @@
 using System.Security.Claims;
+using System.Text.Json;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Abstractions;
+using ZB.MOM.WW.Audit;
 using ZB.MOM.WW.MxGateway.Server.Sessions;
 
 namespace ZB.MOM.WW.MxGateway.Server.Dashboard;
@@ -8,21 +10,35 @@ namespace ZB.MOM.WW.MxGateway.Server.Dashboard;
 /// <summary>
 /// Default implementation of <see cref="IDashboardSessionAdminService"/>: gates
 /// destructive session actions on the <see cref="DashboardRoles.Admin"/> role,
-/// audit-logs successful operations, and converts <see cref="SessionManagerException"/>
-/// (and any other unexpected exceptions) into <see cref="DashboardSessionAdminResult.Fail(string)"/>
-/// so the Blazor pages never see a raw exception.
+/// records each attempt as a canonical <see cref="AuditEvent"/> through <see cref="IAuditWriter"/>
+/// (in addition to the operational <see cref="ILogger"/> line), and converts
+/// <see cref="SessionManagerException"/> (and any other unexpected exceptions) into
+/// <see cref="DashboardSessionAdminResult.Fail(string)"/> so the Blazor pages never see a raw exception.
 /// </summary>
 /// <remarks>
 ///     The constant <c>dashboard-admin-kill</c> is the reason passed to
 ///     <see cref="ISessionManager.KillWorkerAsync"/> and forwarded as the
 ///     <c>reason</c> tag on the <c>mxgateway.workers.killed</c> counter and in
-///     the worker-kill audit log entries.
+///     the worker-kill audit log entries. Destructive dashboard actions write durable,
+///     queryable audit rows (actions <c>dashboard-close-session</c> / <c>dashboard-kill-worker</c>)
+///     to the canonical <c>audit_event</c> store, mirroring the API-key management path so a
+///     worker killed mid-production is not visible only in a rotatable <see cref="ILogger"/> line.
 /// </remarks>
 public sealed class DashboardSessionAdminService(
     ISessionManager sessionManager,
     IHttpContextAccessor httpContextAccessor,
+    IAuditWriter auditWriter,
     ILogger<DashboardSessionAdminService>? logger = null) : IDashboardSessionAdminService
 {
+    /// <summary>Canonical <see cref="AuditEvent.Category"/> for dashboard session-admin actions.</summary>
+    internal const string SessionAdminCategory = "SessionAdmin";
+
+    /// <summary>Canonical <see cref="AuditEvent.Action"/> for a dashboard session close.</summary>
+    internal const string CloseSessionAction = "dashboard-close-session";
+
+    /// <summary>Canonical <see cref="AuditEvent.Action"/> for a dashboard worker kill.</summary>
+    internal const string KillWorkerAction = "dashboard-kill-worker";
+
     private const string UnauthorizedMessage = "Sign in as an Admin to close sessions or kill workers.";
     private const string KillReason = "dashboard-admin-kill";
 
@@ -46,6 +62,8 @@ public sealed class DashboardSessionAdminService(
     {
         if (!CanManage(user))
         {
+            await WriteAuditAsync(user, CloseSessionAction, sessionId, AuditOutcome.Denied, "unauthorized", cancellationToken)
+                .ConfigureAwait(false);
             return DashboardSessionAdminResult.Fail(UnauthorizedMessage);
         }
 
@@ -68,6 +86,15 @@ public sealed class DashboardSessionAdminService(
                 ResolveRemoteAddress(),
                 result.AlreadyClosed);
 
+            await WriteAuditAsync(
+                    user,
+                    CloseSessionAction,
+                    sessionId,
+                    AuditOutcome.Success,
+                    result.AlreadyClosed ? "alreadyClosed" : "closed",
+                    cancellationToken)
+                .ConfigureAwait(false);
+
             return DashboardSessionAdminResult.Success(
                 result.AlreadyClosed
                     ? $"Session {sessionId} was already closed."
@@ -75,6 +102,8 @@ public sealed class DashboardSessionAdminService(
         }
         catch (SessionManagerException exception) when (exception.ErrorCode == SessionManagerErrorCode.SessionNotFound)
         {
+            await WriteAuditAsync(user, CloseSessionAction, sessionId, AuditOutcome.Failure, "not-found", cancellationToken)
+                .ConfigureAwait(false);
             return DashboardSessionAdminResult.Fail($"Session {sessionId} was not found.");
         }
         catch (SessionManagerException exception)
@@ -84,6 +113,8 @@ public sealed class DashboardSessionAdminService(
                 "Dashboard admin {Actor} close failed for session {SessionId}.",
                 actor,
                 sessionId);
+            await WriteAuditAsync(user, CloseSessionAction, sessionId, AuditOutcome.Failure, exception.Message, cancellationToken)
+                .ConfigureAwait(false);
             return DashboardSessionAdminResult.Fail(
                 $"Close failed: {exception.Message}");
         }
@@ -98,6 +129,8 @@ public sealed class DashboardSessionAdminService(
                 "Dashboard admin {Actor} close failed unexpectedly for session {SessionId}.",
                 actor,
                 sessionId);
+            await WriteAuditAsync(user, CloseSessionAction, sessionId, AuditOutcome.Failure, "unexpected", cancellationToken)
+                .ConfigureAwait(false);
             return DashboardSessionAdminResult.Fail(
                 $"Close failed unexpectedly for session {sessionId}. See the gateway log for details.");
         }
@@ -111,6 +144,8 @@ public sealed class DashboardSessionAdminService(
     {
         if (!CanManage(user))
         {
+            await WriteAuditAsync(user, KillWorkerAction, sessionId, AuditOutcome.Denied, "unauthorized", cancellationToken)
+                .ConfigureAwait(false);
             return DashboardSessionAdminResult.Fail(UnauthorizedMessage);
         }
 
@@ -133,6 +168,15 @@ public sealed class DashboardSessionAdminService(
                 ResolveRemoteAddress(),
                 result.AlreadyClosed);
 
+            await WriteAuditAsync(
+                    user,
+                    KillWorkerAction,
+                    sessionId,
+                    AuditOutcome.Success,
+                    result.AlreadyClosed ? "alreadyClosed" : "killed",
+                    cancellationToken)
+                .ConfigureAwait(false);
+
             return DashboardSessionAdminResult.Success(
                 result.AlreadyClosed
                     ? $"Session {sessionId} was already closed."
@@ -140,6 +184,8 @@ public sealed class DashboardSessionAdminService(
         }
         catch (SessionManagerException exception) when (exception.ErrorCode == SessionManagerErrorCode.SessionNotFound)
         {
+            await WriteAuditAsync(user, KillWorkerAction, sessionId, AuditOutcome.Failure, "not-found", cancellationToken)
+                .ConfigureAwait(false);
             return DashboardSessionAdminResult.Fail($"Session {sessionId} was not found.");
         }
         catch (SessionManagerException exception)
@@ -149,6 +195,8 @@ public sealed class DashboardSessionAdminService(
                 "Dashboard admin {Actor} kill failed for session {SessionId}.",
                 actor,
                 sessionId);
+            await WriteAuditAsync(user, KillWorkerAction, sessionId, AuditOutcome.Failure, exception.Message, cancellationToken)
+                .ConfigureAwait(false);
             return DashboardSessionAdminResult.Fail(
                 $"Kill failed: {exception.Message}");
         }
@@ -163,6 +211,8 @@ public sealed class DashboardSessionAdminService(
                 "Dashboard admin {Actor} kill failed unexpectedly for session {SessionId}.",
                 actor,
                 sessionId);
+            await WriteAuditAsync(user, KillWorkerAction, sessionId, AuditOutcome.Failure, "unexpected", cancellationToken)
+                .ConfigureAwait(false);
             return DashboardSessionAdminResult.Fail(
                 $"Kill failed unexpectedly for session {sessionId}. See the gateway log for details.");
         }
@@ -177,4 +227,51 @@ public sealed class DashboardSessionAdminService(
     {
         return httpContextAccessor.HttpContext?.Connection.RemoteIpAddress?.ToString();
     }
+
+    /// <summary>
+    /// Writes a canonical <see cref="AuditEvent"/> for a dashboard session-admin action through the
+    /// best-effort <see cref="IAuditWriter"/> (failures are swallowed/logged by the writer, so this
+    /// never throws and never masks the operation result). <see cref="AuditEvent.Actor"/> is the LDAP
+    /// operator, <see cref="AuditEvent.Target"/> the session id, and <paramref name="detail"/> is wrapped
+    /// as the <c>detail</c> field of the JSON extension bag.
+    /// </summary>
+    private async Task WriteAuditAsync(
+        ClaimsPrincipal user,
+        string action,
+        string sessionId,
+        AuditOutcome outcome,
+        string? detail,
+        CancellationToken cancellationToken)
+    {
+        AuditEvent auditEvent = new()
+        {
+            EventId = Guid.NewGuid(),
+            OccurredAtUtc = DateTimeOffset.UtcNow,
+            Actor = ResolveActor(user),
+            Action = action,
+            Outcome = outcome,
+            Category = SessionAdminCategory,
+            Target = sessionId,
+            SourceNode = ResolveRemoteAddress(),
+            CorrelationId = ParseCorrelationId(),
+            DetailsJson = WrapDetail(detail),
+        };
+
+        await auditWriter.WriteAsync(auditEvent, cancellationToken).ConfigureAwait(false);
+    }
+
+    /// <summary>
+    /// Derives a correlation id from the request trace identifier when it is a well-formed GUID;
+    /// otherwise null (the default <c>HttpContext.TraceIdentifier</c> is the connection:request form,
+    /// not a GUID, so it correlates to null rather than fabricating one).
+    /// </summary>
+    private Guid? ParseCorrelationId() =>
+        Guid.TryParse(httpContextAccessor.HttpContext?.TraceIdentifier, out Guid correlationId)
+            ? correlationId
+            : null;
+
+    private static string? WrapDetail(string? detail) =>
+        detail is null
+            ? null
+            : JsonSerializer.Serialize(new Dictionary<string, string> { ["detail"] = detail });
 }

src/ZB.MOM.WW.MxGateway.Server/Dashboard/DashboardSnapshotService.cs

@@ -273,7 +273,8 @@ public sealed class DashboardSnapshotService : IDashboardSnapshotService
                     Constraints: ApiKeyConstraintSerializer.Deserialize(key.ConstraintsJson),
                     CreatedUtc: key.CreatedUtc,
                     LastUsedUtc: key.LastUsedUtc,
-                    RevokedUtc: key.RevokedUtc))
+                    RevokedUtc: key.RevokedUtc,
+                    ExpiresUtc: key.ExpiresUtc))
                 .ToArray();
 
             Volatile.Write(ref _apiKeySummaries, summaries);

src/ZB.MOM.WW.MxGateway.Server/Dashboard/HubTokenAuthenticationHandler.cs

@@ -10,6 +10,16 @@ namespace ZB.MOM.WW.MxGateway.Server.Dashboard;
 /// string (used by WebSocket upgrade requests that can't carry custom headers)
 /// and validating it via <see cref="HubTokenService"/>.
 /// </summary>
+/// <remarks>
+/// Carrying the token in the <c>?access_token=</c> query string is the standard SignalR pattern:
+/// the WebSocket upgrade handshake cannot attach a custom <c>Authorization</c> header, so the JS
+/// client appends the token to the URL. Because a query string is far easier to capture than a
+/// header (proxy access logs, browser history, <c>Referer</c>), this value must NEVER be
+/// request-logged. Serilog HTTP request logging is intentionally not enabled; if it is ever added,
+/// scrub the <c>access_token</c> query parameter before the URL reaches a sink. The short token
+/// lifetime (<see cref="HubTokenService.TokenLifetime"/>) is the backstop that bounds exposure of a
+/// leaked token.
+/// </remarks>
 public sealed class HubTokenAuthenticationHandler : AuthenticationHandler<AuthenticationSchemeOptions>
 {
     private readonly HubTokenService _tokens;

src/ZB.MOM.WW.MxGateway.Server/Dashboard/HubTokenService.cs

@@ -26,7 +26,15 @@ namespace ZB.MOM.WW.MxGateway.Server.Dashboard;
 public sealed class HubTokenService
 {
     private const string ProtectorPurpose = "ZB.MOM.WW.MxGateway.Dashboard.HubToken.v1";
-    private static readonly TimeSpan TokenLifetime = TimeSpan.FromMinutes(30);
+
+    // Hub bearer tokens are single-purpose, data-protection-encrypted, and NOT server-side
+    // revocable. A short lifetime bounds the exposure window of a token captured from a proxy
+    // or log after logout (the cookie is cleared on logout, but outstanding tokens are not), and
+    // bounds how long a stale role set survives a role change. Five minutes is transparent to
+    // clients because DashboardHubConnectionFactory mints a fresh token on every (re)connect;
+    // see docs/GatewayDashboardDesign.md. Heavier jti-denylist revocation is deliberately
+    // deferred until per-session hub ACLs land (SEC-25), when tokens gain session binding.
+    internal static readonly TimeSpan TokenLifetime = TimeSpan.FromMinutes(5);
 
     private readonly ITimeLimitedDataProtector _protector;
 
@@ -41,14 +49,24 @@ public sealed class HubTokenService
     /// <summary>Issues a bearer token carrying the user's identity and roles.</summary>
     /// <param name="user">The claims principal representing the user.</param>
     /// <returns>The data-protected bearer token string.</returns>
-    public string Issue(ClaimsPrincipal user)
+    public string Issue(ClaimsPrincipal user) => Issue(user, TokenLifetime);
+
+    /// <summary>
+    /// Issues a bearer token that expires after the supplied lifetime. Test seam so a caller can
+    /// mint an already-expired token deterministically without wall-clock delay; production callers
+    /// use <see cref="Issue(ClaimsPrincipal)"/> and get <see cref="TokenLifetime"/>.
+    /// </summary>
+    /// <param name="user">The claims principal representing the user.</param>
+    /// <param name="lifetime">The lifetime applied to the token; a non-positive value yields an already-expired token.</param>
+    /// <returns>The data-protected bearer token string.</returns>
+    internal string Issue(ClaimsPrincipal user, TimeSpan lifetime)
     {
         ArgumentNullException.ThrowIfNull(user);
         HubTokenPayload payload = new(
             user.Identity?.Name,
             user.FindFirstValue(ClaimTypes.NameIdentifier),
             [.. user.FindAll(ClaimTypes.Role).Select(c => c.Value)]);
-        return _protector.Protect(JsonSerializer.Serialize(payload), TokenLifetime);
+        return _protector.Protect(JsonSerializer.Serialize(payload), lifetime);
     }
 
     /// <summary>Validates a token and returns the equivalent claims principal; null when invalid or expired.</summary>

src/ZB.MOM.WW.MxGateway.Server/GatewayApplication.cs

@@ -41,6 +41,9 @@ public static class GatewayApplication
         app.UseStaticFiles();
         app.UseAuthentication();
         app.UseAuthorization();
+        // SEC-11: the rate limiter must run after routing has selected the endpoint (so its
+        // RequireRateLimiting policy metadata is visible) and before the endpoint executes.
+        app.UseRateLimiter();
         app.UseAntiforgery();
         app.MapGatewayEndpoints();
 
@@ -68,6 +71,7 @@ public static class GatewayApplication
         builder.Services.AddGatewayConfiguration(builder.Configuration);
         builder.Services.AddSqliteAuthStore(builder.Configuration);
         builder.Services.AddGatewayGrpcAuthorization();
+        AddLoginRateLimiter(builder);
         builder.Services.AddHealthChecks()
             .AddTypeActivatedCheck<AuthStoreHealthCheck>(
                 "auth-store",
@@ -101,6 +105,26 @@ public static class GatewayApplication
         return builder;
     }
 
+    // SEC-11: register the named fixed-window rate-limiter policy applied to POST /auth/login. The
+    // limit knobs are read from MxGateway:Security at startup; the per-request partition is keyed on
+    // the remote IP (see DashboardEndpointRouteBuilderExtensions.GetLoginRateLimitPartition).
+    private static void AddLoginRateLimiter(WebApplicationBuilder builder)
+    {
+        SecurityOptions security =
+            builder.Configuration.GetSection(SecurityOptions.SectionName).Get<SecurityOptions>()
+            ?? new SecurityOptions();
+
+        builder.Services.AddRateLimiter(options =>
+        {
+            options.RejectionStatusCode = StatusCodes.Status429TooManyRequests;
+            options.AddPolicy(
+                DashboardEndpointRouteBuilderExtensions.LoginRateLimiterPolicy,
+                httpContext => DashboardEndpointRouteBuilderExtensions.GetLoginRateLimitPartition(
+                    httpContext,
+                    security));
+        });
+    }
+
     private static void ConfigureSelfSignedTls(WebApplicationBuilder builder)
     {
         if (!Security.Tls.KestrelTlsInspector.RequiresGeneratedCertificate(builder.Configuration))

src/ZB.MOM.WW.MxGateway.Server/Grpc/MxAccessGatewayService.cs

@@ -946,6 +946,7 @@ public sealed class MxAccessGatewayService(
             WorkerClientErrorCode.GatewayShutdown => StatusCode.Cancelled,
             WorkerClientErrorCode.InvalidState => StatusCode.FailedPrecondition,
             WorkerClientErrorCode.ProtocolViolation => StatusCode.Internal,
+            WorkerClientErrorCode.CommandTooLarge => StatusCode.ResourceExhausted,
             _ => StatusCode.Unavailable,
         };
 

src/ZB.MOM.WW.MxGateway.Server/Grpc/MxAccessGrpcRequestValidator.cs

@@ -5,6 +5,13 @@ namespace ZB.MOM.WW.MxGateway.Server.Grpc;
 
 public sealed class MxAccessGrpcRequestValidator
 {
+    // Upper bound on a single DrainEvents request. DrainEvents is a diagnostics RPC that returns
+    // buffered events in one non-streaming reply, so an unbounded max_events could pack the whole
+    // queue into a session-killing frame (IPC-04). The worker independently caps each reply at its
+    // own MaxDrainEventsPerReply; this public bound rejects an obviously-abusive request loudly at
+    // the boundary. max_events = 0 is allowed and means "the worker's default batch cap".
+    private const uint MaxDrainEventsPerRequest = 10_000;
+
     /// <summary>Validates an open session request.</summary>
     /// <param name="request">The request to validate.</param>
     public void ValidateOpenSession(OpenSessionRequest request)
@@ -69,6 +76,14 @@ public sealed class MxAccessGrpcRequestValidator
             throw InvalidArgument(
                 $"Command kind {command.Kind} requires payload {expectedPayload} but received {command.PayloadCase}.");
         }
+
+        // The payload case now matches the kind, so command.DrainEvents is non-null here.
+        if (command.Kind is MxCommandKind.DrainEvents && command.DrainEvents.MaxEvents > MaxDrainEventsPerRequest)
+        {
+            throw InvalidArgument(
+                $"DrainEvents max_events ({command.DrainEvents.MaxEvents}) must not exceed {MaxDrainEventsPerRequest}; "
+                + "use 0 to request the worker default batch cap.");
+        }
     }
 
     private static MxCommand.PayloadOneofCase ExpectedPayload(MxCommandKind kind)

src/ZB.MOM.WW.MxGateway.Server/Metrics/GatewayMetrics.cs

@@ -351,7 +351,11 @@ public sealed class GatewayMetrics : IDisposable
             _heartbeatFailures++;
         }
 
-        _heartbeatFailuresCounter.Add(1, new KeyValuePair<string, object?>("session_id", sessionId));
+        // Exported without a session_id tag: per-session attribution is unbounded cardinality
+        // (every session ever opened mints a new exporter time series, bloating Prometheus/OTLP
+        // storage on long-running gateways). Per-session detail stays available via the dashboard
+        // snapshot and the log scope; the exported counter tracks only the aggregate.
+        _heartbeatFailuresCounter.Add(1);
     }
 
     /// <summary>

src/ZB.MOM.WW.MxGateway.Server/Security/Authentication/ApiKeyAdminCliRunner.cs

@@ -67,6 +67,7 @@ public sealed class ApiKeyAdminCliRunner(ApiKeyAdminCommands commands)
                 Required(command.DisplayName),
                 command.Scopes,
                 ApiKeyConstraintSerializer.Serialize(command.Constraints),
+                command.ExpiresUtc,
                 remoteAddress: null,
                 cancellationToken)
             .ConfigureAwait(false);
@@ -134,8 +135,16 @@ public sealed class ApiKeyAdminCliRunner(ApiKeyAdminCommands commands)
 
         foreach (ApiKeyAdminListedKey key in result.Keys)
         {
-            string revoked = key.RevokedUtc is null ? "active" : "revoked";
-            await output.WriteLineAsync($"{key.KeyId}\t{key.DisplayName}\t{revoked}\t{string.Join(',', key.Scopes)}")
+            string status = key.RevokedUtc is not null
+                ? "revoked"
+                : key.ExpiresUtc is { } expiresAt && expiresAt <= DateTimeOffset.UtcNow
+                    ? "expired"
+                    : "active";
+            string expiry = key.ExpiresUtc is { } expires
+                ? expires.ToUniversalTime().ToString("u", System.Globalization.CultureInfo.InvariantCulture)
+                : "-";
+            await output.WriteLineAsync(
+                    $"{key.KeyId}\t{key.DisplayName}\t{status}\t{expiry}\t{string.Join(',', key.Scopes)}")
                 .ConfigureAwait(false);
         }
     }
@@ -150,7 +159,8 @@ public sealed class ApiKeyAdminCliRunner(ApiKeyAdminCommands commands)
             Constraints: ApiKeyConstraintSerializer.Deserialize(key.ConstraintsJson),
             CreatedUtc: key.CreatedUtc,
             LastUsedUtc: key.LastUsedUtc,
-            RevokedUtc: key.RevokedUtc);
+            RevokedUtc: key.RevokedUtc,
+            ExpiresUtc: key.ExpiresUtc);
     }
 
     private static string Required(string? value)

src/ZB.MOM.WW.MxGateway.Server/Security/Authentication/ApiKeyAdminCommand.cs

@@ -8,4 +8,5 @@ public sealed record ApiKeyAdminCommand(
     string? KeyId,
     string? DisplayName,
     IReadOnlySet<string> Scopes,
-    ApiKeyConstraints Constraints);
+    ApiKeyConstraints Constraints,
+    DateTimeOffset? ExpiresUtc = null);

src/ZB.MOM.WW.MxGateway.Server/Security/Authentication/ApiKeyAdminCommandLineParser.cs

@@ -82,9 +82,11 @@ public static class ApiKeyAdminCommandLineParser
         string? displayName = GetOption(options, "display-name");
         IReadOnlySet<string> scopes = ParseScopes(GetOption(options, "scopes"));
         ApiKeyConstraints constraints;
+        DateTimeOffset? expiresUtc;
         try
         {
             constraints = ParseConstraints(options);
+            expiresUtc = ParseExpiry(GetOption(options, "expires"));
         }
         catch (FormatException exception)
         {
@@ -111,7 +113,8 @@ public static class ApiKeyAdminCommandLineParser
             KeyId: keyId,
             DisplayName: displayName,
             Scopes: scopes,
-            Constraints: constraints));
+            Constraints: constraints,
+            ExpiresUtc: expiresUtc));
     }
 
     private static bool TryParseKind(string value, out ApiKeyAdminCommandKind kind)
@@ -233,6 +236,42 @@ public static class ApiKeyAdminCommandLineParser
             ReadHistorizedOnly: HasFlag(options, "read-historized-only"));
     }
 
+    // Parses the optional --expires value into an absolute UTC expiry (SEC-10). Accepts a relative
+    // "<N>d"/"<N>h" duration from now (operator-friendly) or an absolute ISO-8601 instant/date
+    // (assumed UTC). Null/blank means no expiry — expiry stays opt-in, preserving prior behaviour.
+    private static DateTimeOffset? ParseExpiry(string? value)
+    {
+        if (string.IsNullOrWhiteSpace(value))
+        {
+            return null;
+        }
+
+        string trimmed = value.Trim();
+        char unit = char.ToLowerInvariant(trimmed[^1]);
+        if (unit is 'd' or 'h'
+            && int.TryParse(
+                trimmed[..^1],
+                System.Globalization.NumberStyles.None,
+                System.Globalization.CultureInfo.InvariantCulture,
+                out int amount))
+        {
+            TimeSpan offset = unit == 'd' ? TimeSpan.FromDays(amount) : TimeSpan.FromHours(amount);
+            return DateTimeOffset.UtcNow + offset;
+        }
+
+        if (DateTimeOffset.TryParse(
+                trimmed,
+                System.Globalization.CultureInfo.InvariantCulture,
+                System.Globalization.DateTimeStyles.AssumeUniversal | System.Globalization.DateTimeStyles.AdjustToUniversal,
+                out DateTimeOffset parsed))
+        {
+            return parsed;
+        }
+
+        throw new FormatException(
+            "--expires must be a relative duration ('<N>d' or '<N>h') or an absolute ISO-8601 UTC timestamp.");
+    }
+
     private static int? ParseNullableInt(string? value)
     {
         if (string.IsNullOrWhiteSpace(value))

src/ZB.MOM.WW.MxGateway.Server/Security/Authentication/ApiKeyAdminListedKey.cs

@@ -8,4 +8,5 @@ public sealed record ApiKeyAdminListedKey(
     ApiKeyConstraints Constraints,
     DateTimeOffset CreatedUtc,
     DateTimeOffset? LastUsedUtc,
-    DateTimeOffset? RevokedUtc);
+    DateTimeOffset? RevokedUtc,
+    DateTimeOffset? ExpiresUtc = null);

src/ZB.MOM.WW.MxGateway.Server/Security/Authentication/AuthStoreServiceCollectionExtensions.cs

@@ -1,4 +1,6 @@
+using Microsoft.Extensions.Caching.Memory;
 using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Extensions.Options;
 using ZB.MOM.WW.Audit;
 using ZB.MOM.WW.Auth.Abstractions.ApiKeys;
@@ -6,6 +8,7 @@ using ZB.MOM.WW.Auth.ApiKeys;
 using ZB.MOM.WW.Auth.ApiKeys.Admin;
 using ZB.MOM.WW.Auth.ApiKeys.DependencyInjection;
 using ZB.MOM.WW.Auth.ApiKeys.Sqlite;
+using ZB.MOM.WW.MxGateway.Server.Configuration;
 using ZB.MOM.WW.MxGateway.Server.Security.Audit;
 
 namespace ZB.MOM.WW.MxGateway.Server.Security.Authentication;
@@ -66,6 +69,34 @@ public static class AuthStoreServiceCollectionExtensions
         // migrator and the migration hosted service.
         services.AddZbApiKeyAuth(effectiveConfig, AuthenticationSectionPath);
 
+        // SEC-08 hot-path decorators. Every gRPC call previously did a SQLite read plus a
+        // last_used_utc WRITE via IApiKeyVerifier.VerifyAsync (the library verifier couples the
+        // mark into verification). Two gateway-side decorators cut that cost without editing the
+        // external library:
+        //   * CoalescingMarkApiKeyStore wraps the library's IApiKeyStore and coalesces the
+        //     last_used write to at most one per key per MxGateway:Security window (default 60s),
+        //     so the library verifier's per-call mark no longer churns the WAL.
+        //   * CachingApiKeyVerifier wraps the library's IApiKeyVerifier with a short-TTL memory
+        //     cache (MxGateway:Security:ApiKeyVerificationCacheSeconds, default 15s) keyed on a
+        //     SHA-256 hash of the presented token, so a cache hit skips the store read entirely.
+        // Invalidation of a cached verification on a gateway-initiated revoke/rotate/delete is
+        // wired at the dashboard admin call site (DashboardApiKeyManagementService) via
+        // IApiKeyCacheInvalidator; the short TTL is the backstop for out-of-band mutations.
+        // Read the security knobs straight off IConfiguration rather than IOptions<GatewayOptions>:
+        // touching IOptions<GatewayOptions>.Value would force the whole-options validation pipeline
+        // (which needs IHostEnvironment) at auth-store resolution, breaking the bare-DI auth tests.
+        // GatewayOptions is still validated at startup, which covers these same values.
+        SecurityOptions security = configuration.GetSection(SecurityOptions.SectionName).Get<SecurityOptions>()
+            ?? new SecurityOptions();
+        services.AddMemoryCache();
+        DecorateSingleton<IApiKeyStore>(
+            services,
+            (sp, inner) => new CoalescingMarkApiKeyStore(
+                inner,
+                security,
+                sp.GetService<TimeProvider>() ?? TimeProvider.System));
+        DecorateVerifierWithCache(services, security);
+
         services.AddSingleton(sp =>
             new SqliteCanonicalAuditStore(sp.GetRequiredService<AuthSqliteConnectionFactory>()));
         // Resolve the logger defensively: the production host always registers ILogger<T>, but the
@@ -103,4 +134,58 @@ public static class AuthStoreServiceCollectionExtensions
 
         return services;
     }
+
+    /// <summary>
+    /// Replaces the last registration of <typeparamref name="TService"/> with a singleton that wraps
+    /// it. The wrapped (inner) service is created once, preserving singleton semantics. Used to layer
+    /// the SEC-08 store decorator over the external library's registration without editing it.
+    /// </summary>
+    private static void DecorateSingleton<TService>(
+        IServiceCollection services,
+        Func<IServiceProvider, TService, TService> decorator)
+        where TService : class
+    {
+        Func<IServiceProvider, TService> innerFactory = CaptureInnerFactory<TService>(services);
+        services.AddSingleton(sp => decorator(sp, innerFactory(sp)));
+    }
+
+    // Wraps the library's IApiKeyVerifier with CachingApiKeyVerifier and exposes the same instance
+    // as IApiKeyCacheInvalidator so admin call sites can drop cached verifications on revoke/rotate.
+    private static void DecorateVerifierWithCache(IServiceCollection services, SecurityOptions security)
+    {
+        Func<IServiceProvider, IApiKeyVerifier> innerFactory = CaptureInnerFactory<IApiKeyVerifier>(services);
+        services.AddSingleton(sp => new CachingApiKeyVerifier(
+            innerFactory(sp),
+            sp.GetRequiredService<IMemoryCache>(),
+            security));
+        services.AddSingleton<IApiKeyVerifier>(sp => sp.GetRequiredService<CachingApiKeyVerifier>());
+        services.AddSingleton<IApiKeyCacheInvalidator>(sp => sp.GetRequiredService<CachingApiKeyVerifier>());
+    }
+
+    // Removes the current last registration of TService and returns a factory that materialises that
+    // original implementation exactly once when first resolved. The removed descriptor may be a
+    // type, factory or instance registration.
+    private static Func<IServiceProvider, TService> CaptureInnerFactory<TService>(IServiceCollection services)
+        where TService : class
+    {
+        ServiceDescriptor descriptor = services.LastOrDefault(d => d.ServiceType == typeof(TService))
+            ?? throw new InvalidOperationException(
+                $"No existing registration for {typeof(TService)} to decorate; register the library provider first.");
+        services.Remove(descriptor);
+
+        if (descriptor.ImplementationInstance is TService instance)
+        {
+            return _ => instance;
+        }
+
+        if (descriptor.ImplementationFactory is not null)
+        {
+            return sp => (TService)descriptor.ImplementationFactory(sp);
+        }
+
+        Type implementationType = descriptor.ImplementationType
+            ?? throw new InvalidOperationException(
+                $"Registration for {typeof(TService)} has no implementation type, factory or instance to decorate.");
+        return sp => (TService)ActivatorUtilities.CreateInstance(sp, implementationType);
+    }
 }

src/ZB.MOM.WW.MxGateway.Server/Security/Authentication/CachingApiKeyVerifier.cs

@@ -0,0 +1,159 @@
+using System.Collections.Concurrent;
+using System.Security.Cryptography;
+using System.Text;
+using Microsoft.Extensions.Caching.Memory;
+using ZB.MOM.WW.Auth.Abstractions.ApiKeys;
+using ZB.MOM.WW.MxGateway.Server.Configuration;
+
+namespace ZB.MOM.WW.MxGateway.Server.Security.Authentication;
+
+/// <summary>
+/// Lets gateway-side admin call sites drop a cached API-key verification when they revoke, rotate
+/// or delete a key, so a mutation applied through the running gateway process takes effect
+/// immediately rather than after the cache TTL elapses.
+/// </summary>
+public interface IApiKeyCacheInvalidator
+{
+    /// <summary>Removes every cached verification for the given key id.</summary>
+    /// <param name="keyId">The key id whose cached verifications should be dropped.</param>
+    void Invalidate(string keyId);
+}
+
+/// <summary>
+/// An <see cref="IApiKeyVerifier"/> decorator that caches successful verifications for a short,
+/// configurable TTL (<see cref="SecurityOptions.ApiKeyVerificationCacheSeconds"/>), keyed on a
+/// SHA-256 hash of the presented token. A cache hit returns the cached result without calling the
+/// inner (library) verifier, so it avoids both the per-call SQLite read and the <c>last_used</c>
+/// write the library verifier couples into <see cref="IApiKeyVerifier.VerifyAsync"/>.
+/// </summary>
+/// <remarks>
+/// <para>
+/// Only successful verifications are cached. Failures and unparseable headers always fall through
+/// to the inner verifier — caching a failure risks pinning a transiently-wrong negative, and the
+/// SEC-11 per-peer failure counter (not this cache) is what bounds brute-force cost.
+/// </para>
+/// <para>
+/// The cache key is the hex SHA-256 of the presented token (which embeds both the key id and the
+/// secret). Hashing means the plaintext secret is never stored in memory. The hash is a cache index
+/// only; the authentic constant-time secret comparison remains inside the inner verifier, reached
+/// on every cache miss.
+/// </para>
+/// <para>
+/// Correctness on mutation is provided by two mechanisms: gateway-initiated revoke/rotate/delete
+/// call <see cref="Invalidate"/> directly (see <c>DashboardApiKeyManagementService</c>), and the
+/// short TTL is the backstop for out-of-band mutations (a direct DB edit, or a revoke issued by the
+/// separate <c>apikey</c> CLI process, whose in-memory cache is not this process's cache).
+/// </para>
+/// </remarks>
+public sealed class CachingApiKeyVerifier : IApiKeyVerifier, IApiKeyCacheInvalidator
+{
+    private const string CacheKeyPrefix = "mxgw:apikeyverif:";
+
+    private readonly IApiKeyVerifier _inner;
+    private readonly IMemoryCache _cache;
+    private readonly TimeSpan _ttl;
+
+    // keyId -> set of cache keys currently held for that id, so a revoke/rotate can evict every
+    // secret variant (e.g. an old secret still within TTL after a rotate).
+    private readonly ConcurrentDictionary<string, ConcurrentDictionary<string, byte>> _keyIdIndex =
+        new(StringComparer.Ordinal);
+
+    /// <summary>Initializes a new instance of the <see cref="CachingApiKeyVerifier"/> class.</summary>
+    /// <param name="inner">The wrapped verifier (the library verifier) reached on a cache miss.</param>
+    /// <param name="cache">The shared memory cache.</param>
+    /// <param name="security">Security options carrying the verification-cache TTL.</param>
+    public CachingApiKeyVerifier(IApiKeyVerifier inner, IMemoryCache cache, SecurityOptions security)
+        : this(
+            inner,
+            cache,
+            TimeSpan.FromSeconds((security ?? throw new ArgumentNullException(nameof(security)))
+                .ApiKeyVerificationCacheSeconds))
+    {
+    }
+
+    // Test/explicit-TTL seam.
+    internal CachingApiKeyVerifier(IApiKeyVerifier inner, IMemoryCache cache, TimeSpan ttl)
+    {
+        ArgumentNullException.ThrowIfNull(inner);
+        ArgumentNullException.ThrowIfNull(cache);
+        _inner = inner;
+        _cache = cache;
+        _ttl = ttl;
+    }
+
+    /// <inheritdoc />
+    public async Task<ApiKeyVerification> VerifyAsync(string authorizationHeader, CancellationToken ct)
+    {
+        if (_ttl <= TimeSpan.Zero || !TryComputeCacheKey(authorizationHeader, out string cacheKey))
+        {
+            return await _inner.VerifyAsync(authorizationHeader, ct).ConfigureAwait(false);
+        }
+
+        if (_cache.TryGetValue(cacheKey, out ApiKeyVerification? cached) && cached is not null)
+        {
+            return cached;
+        }
+
+        ApiKeyVerification result = await _inner.VerifyAsync(authorizationHeader, ct).ConfigureAwait(false);
+
+        if (result.Succeeded && result.Identity is not null)
+        {
+            _cache.Set(cacheKey, result, new MemoryCacheEntryOptions
+            {
+                AbsoluteExpirationRelativeToNow = _ttl,
+            });
+            IndexCacheKey(result.Identity.KeyId, cacheKey);
+        }
+
+        return result;
+    }
+
+    /// <inheritdoc />
+    public void Invalidate(string keyId)
+    {
+        if (string.IsNullOrEmpty(keyId))
+        {
+            return;
+        }
+
+        if (_keyIdIndex.TryRemove(keyId, out ConcurrentDictionary<string, byte>? cacheKeys))
+        {
+            foreach (string cacheKey in cacheKeys.Keys)
+            {
+                _cache.Remove(cacheKey);
+            }
+        }
+    }
+
+    private void IndexCacheKey(string keyId, string cacheKey)
+    {
+        ConcurrentDictionary<string, byte> set = _keyIdIndex.GetOrAdd(
+            keyId,
+            static _ => new ConcurrentDictionary<string, byte>(StringComparer.Ordinal));
+        set.TryAdd(cacheKey, 0);
+    }
+
+    private static bool TryComputeCacheKey(string? authorizationHeader, out string cacheKey)
+    {
+        cacheKey = string.Empty;
+        if (string.IsNullOrEmpty(authorizationHeader))
+        {
+            return false;
+        }
+
+        ReadOnlySpan<char> header = authorizationHeader.AsSpan().Trim();
+        const string bearer = "Bearer ";
+        ReadOnlySpan<char> token = header.StartsWith(bearer, StringComparison.OrdinalIgnoreCase)
+            ? header[bearer.Length..].Trim()
+            : header;
+
+        if (token.IsEmpty)
+        {
+            return false;
+        }
+
+        byte[] hash = SHA256.HashData(Encoding.UTF8.GetBytes(token.ToString()));
+        cacheKey = CacheKeyPrefix + Convert.ToHexString(hash);
+        return true;
+    }
+}

src/ZB.MOM.WW.MxGateway.Server/Security/Authentication/CoalescingMarkApiKeyStore.cs

@@ -0,0 +1,101 @@
+using System.Collections.Concurrent;
+using ZB.MOM.WW.Auth.Abstractions.ApiKeys;
+using ZB.MOM.WW.MxGateway.Server.Configuration;
+
+namespace ZB.MOM.WW.MxGateway.Server.Security.Authentication;
+
+/// <summary>
+/// An <see cref="IApiKeyStore"/> decorator that coalesces <see cref="MarkUsedAsync"/> writes to at
+/// most one per key per <see cref="SecurityOptions.ApiKeyLastUsedCoalesceSeconds"/> window. Lookups
+/// pass through unchanged.
+/// </summary>
+/// <remarks>
+/// The library verifier couples the <c>last_used_utc</c> write into every successful verification
+/// by calling <see cref="IApiKeyStore.MarkUsedAsync"/>. On the bulk-read hot path that turns a
+/// per-RPC database write into the throughput ceiling. This decorator sits under the library
+/// verifier: it forwards the first mark for a key, then drops subsequent marks until the window
+/// elapses, so <c>last_used_utc</c> is refreshed at most once per key per window while the read
+/// path stays correct. <c>last_used_utc</c> is a coarse staleness indicator, not an audit record
+/// (audit rows are written separately), so bounded staleness of up to one window is acceptable.
+/// </remarks>
+public sealed class CoalescingMarkApiKeyStore : IApiKeyStore
+{
+    private readonly IApiKeyStore _inner;
+    private readonly TimeSpan _window;
+    private readonly TimeProvider _clock;
+
+    // keyId -> UtcTicks of the last forwarded mark. Bounded by the number of API keys, which is
+    // small; no eviction needed.
+    private readonly ConcurrentDictionary<string, long> _lastMarkedTicks = new(StringComparer.Ordinal);
+
+    /// <summary>Initializes a new instance of the <see cref="CoalescingMarkApiKeyStore"/> class.</summary>
+    /// <param name="inner">The wrapped store.</param>
+    /// <param name="security">Security options carrying the coalescing window.</param>
+    /// <param name="clock">The time provider.</param>
+    public CoalescingMarkApiKeyStore(IApiKeyStore inner, SecurityOptions security, TimeProvider clock)
+        : this(
+            inner,
+            TimeSpan.FromSeconds((security ?? throw new ArgumentNullException(nameof(security)))
+                .ApiKeyLastUsedCoalesceSeconds),
+            clock)
+    {
+    }
+
+    // Test/explicit-window seam.
+    internal CoalescingMarkApiKeyStore(IApiKeyStore inner, TimeSpan window, TimeProvider clock)
+    {
+        ArgumentNullException.ThrowIfNull(inner);
+        ArgumentNullException.ThrowIfNull(clock);
+        _inner = inner;
+        _window = window;
+        _clock = clock;
+    }
+
+    /// <inheritdoc />
+    public Task<ApiKeyRecord?> FindByKeyIdAsync(string keyId, CancellationToken ct)
+        => _inner.FindByKeyIdAsync(keyId, ct);
+
+    /// <inheritdoc />
+    public Task<ApiKeyRecord?> FindActiveByKeyIdAsync(string keyId, CancellationToken ct)
+        => _inner.FindActiveByKeyIdAsync(keyId, ct);
+
+    /// <inheritdoc />
+    public Task MarkUsedAsync(string keyId, DateTimeOffset whenUtc, CancellationToken ct)
+    {
+        ArgumentNullException.ThrowIfNull(keyId);
+
+        if (_window <= TimeSpan.Zero)
+        {
+            return _inner.MarkUsedAsync(keyId, whenUtc, ct);
+        }
+
+        long now = _clock.GetUtcNow().UtcTicks;
+
+        while (true)
+        {
+            if (_lastMarkedTicks.TryGetValue(keyId, out long last))
+            {
+                if (now - last < _window.Ticks)
+                {
+                    // Within the coalescing window — drop the write.
+                    return Task.CompletedTask;
+                }
+
+                if (_lastMarkedTicks.TryUpdate(keyId, now, last))
+                {
+                    return _inner.MarkUsedAsync(keyId, whenUtc, ct);
+                }
+
+                // Lost the race to another writer; re-evaluate.
+                continue;
+            }
+
+            if (_lastMarkedTicks.TryAdd(keyId, now))
+            {
+                return _inner.MarkUsedAsync(keyId, whenUtc, ct);
+            }
+
+            // Lost the race to another writer; re-evaluate.
+        }
+    }
+}

src/ZB.MOM.WW.MxGateway.Server/Security/Authentication/GatewayApiKeyIdentityMapper.cs

@@ -1,3 +1,5 @@
+using System.Collections.Concurrent;
+
 using LibApiKeyIdentity = ZB.MOM.WW.Auth.Abstractions.ApiKeys.ApiKeyIdentity;
 
 namespace ZB.MOM.WW.MxGateway.Server.Security.Authentication;
@@ -17,6 +19,36 @@ namespace ZB.MOM.WW.MxGateway.Server.Security.Authentication;
 /// </remarks>
 public static class GatewayApiKeyIdentityMapper
 {
+    // SEC-08: memoize the constraints deserialization keyed by the raw JSON blob so the per-call
+    // JSON parse on the auth hot path collapses to a dictionary lookup. Distinct blobs are bounded
+    // by the number of API keys (small); ApiKeyConstraints is an immutable record, so a parsed
+    // instance is safe to share across callers. The cap is a defensive backstop against a pathological
+    // spread of distinct blobs — past it, we simply parse without caching rather than grow unbounded.
+    private const int MaxCachedConstraintBlobs = 1024;
+    private static readonly ConcurrentDictionary<string, ApiKeyConstraints> ConstraintCache =
+        new(StringComparer.Ordinal);
+
+    private static ApiKeyConstraints DeserializeConstraints(string? constraintsJson)
+    {
+        if (string.IsNullOrWhiteSpace(constraintsJson))
+        {
+            return ApiKeyConstraints.Empty;
+        }
+
+        if (ConstraintCache.TryGetValue(constraintsJson, out ApiKeyConstraints? cached))
+        {
+            return cached;
+        }
+
+        ApiKeyConstraints parsed = ApiKeyConstraintSerializer.Deserialize(constraintsJson);
+        if (ConstraintCache.Count < MaxCachedConstraintBlobs)
+        {
+            ConstraintCache.TryAdd(constraintsJson, parsed);
+        }
+
+        return parsed;
+    }
+
     /// <summary>
     /// Converts a shared API-key identity into the gateway identity, deserializing the opaque
     /// constraints JSON into <see cref="ApiKeyConstraints"/>.
@@ -38,6 +70,6 @@ public static class GatewayApiKeyIdentityMapper
             KeyPrefix: "mxgw",
             DisplayName: identity.DisplayName,
             Scopes: identity.Scopes,
-            Constraints: ApiKeyConstraintSerializer.Deserialize(constraintsJson));
+            Constraints: DeserializeConstraints(constraintsJson));
     }
 }

src/ZB.MOM.WW.MxGateway.Server/Security/Authorization/ApiKeyFailureLimiter.cs

@@ -0,0 +1,152 @@
+using System.Collections.Concurrent;
+using ZB.MOM.WW.MxGateway.Server.Configuration;
+
+namespace ZB.MOM.WW.MxGateway.Server.Security.Authorization;
+
+/// <summary>
+/// Cheap, in-process per-peer sliding-window failure counter for the gRPC auth path (SEC-11). It is
+/// checked BEFORE the API-key verification store read and short-circuits a peer that has exceeded
+/// <see cref="SecurityOptions.ApiKeyFailureLimit"/> failed attempts within
+/// <see cref="SecurityOptions.ApiKeyFailureWindowSeconds"/>; a successful verification resets the
+/// peer's counter.
+/// </summary>
+/// <remarks>
+/// <para>
+/// The peer key is the API key id when the presented token parses, falling back to the transport
+/// peer address otherwise. Keying on key id (per the NAT caveat in <c>glauth.md</c>) means a single
+/// abusive credential behind a shared NAT is throttled without locking out unrelated clients on the
+/// same address.
+/// </para>
+/// <para>
+/// The tracked-peer set is a bounded LRU (<see cref="SecurityOptions.ApiKeyFailureTrackedPeers"/>) so
+/// a spray of unique peer keys cannot grow memory without limit. Successful peers are removed on
+/// reset, so in steady state the map holds only peers with recent failures — the common success path
+/// is a lock-free dictionary miss.
+/// </para>
+/// </remarks>
+public sealed class ApiKeyFailureLimiter
+{
+    private readonly int _limit;
+    private readonly long _windowTicks;
+    private readonly int _maxPeers;
+    private readonly TimeProvider _clock;
+
+    private readonly ConcurrentDictionary<string, PeerState> _peers = new(StringComparer.Ordinal);
+
+    /// <summary>Initializes a new instance of the <see cref="ApiKeyFailureLimiter"/> class.</summary>
+    /// <param name="security">Security options carrying the failure-limit knobs.</param>
+    /// <param name="clock">The time provider.</param>
+    public ApiKeyFailureLimiter(SecurityOptions security, TimeProvider clock)
+        : this(
+            (security ?? throw new ArgumentNullException(nameof(security))).ApiKeyFailureLimit,
+            TimeSpan.FromSeconds(security.ApiKeyFailureWindowSeconds),
+            security.ApiKeyFailureTrackedPeers,
+            clock)
+    {
+    }
+
+    // Test/explicit seam.
+    internal ApiKeyFailureLimiter(int limit, TimeSpan window, int maxPeers, TimeProvider clock)
+    {
+        ArgumentNullException.ThrowIfNull(clock);
+        _limit = limit;
+        _windowTicks = window.Ticks;
+        _maxPeers = maxPeers;
+        _clock = clock;
+    }
+
+    /// <summary>Returns whether the peer has reached the failure limit within the current window.</summary>
+    /// <param name="peer">The peer key (key id or peer address).</param>
+    /// <returns><see langword="true"/> when the peer should be short-circuited.</returns>
+    public bool IsBlocked(string peer)
+    {
+        ArgumentNullException.ThrowIfNull(peer);
+        if (_limit <= 0)
+        {
+            return false;
+        }
+
+        if (!_peers.TryGetValue(peer, out PeerState? state))
+        {
+            return false;
+        }
+
+        long now = _clock.GetUtcNow().UtcTicks;
+        lock (state)
+        {
+            Prune(state, now);
+            return state.FailureTicks.Count >= _limit;
+        }
+    }
+
+    /// <summary>Records a failed verification attempt for the peer.</summary>
+    /// <param name="peer">The peer key (key id or peer address).</param>
+    public void RecordFailure(string peer)
+    {
+        ArgumentNullException.ThrowIfNull(peer);
+        if (_limit <= 0)
+        {
+            return;
+        }
+
+        long now = _clock.GetUtcNow().UtcTicks;
+        PeerState state = _peers.GetOrAdd(peer, static _ => new PeerState());
+        lock (state)
+        {
+            Prune(state, now);
+            state.FailureTicks.Enqueue(now);
+            state.LastActivityTicks = now;
+        }
+
+        EvictIfOverCapacity();
+    }
+
+    /// <summary>Clears the peer's failure count after a successful verification.</summary>
+    /// <param name="peer">The peer key (key id or peer address).</param>
+    public void Reset(string peer)
+    {
+        ArgumentNullException.ThrowIfNull(peer);
+        _peers.TryRemove(peer, out _);
+    }
+
+    private void Prune(PeerState state, long now)
+    {
+        while (state.FailureTicks.Count > 0 && now - state.FailureTicks.Peek() >= _windowTicks)
+        {
+            state.FailureTicks.Dequeue();
+        }
+    }
+
+    private void EvictIfOverCapacity()
+    {
+        // Best-effort eviction: only runs when the map exceeds the cap (rare, since only peers with
+        // recent failures are tracked). Removes the least-recently-active peer. Racy under
+        // concurrency, which is acceptable for a bound rather than an exact policy.
+        while (_peers.Count > _maxPeers)
+        {
+            string? oldest = null;
+            long oldestTicks = long.MaxValue;
+            foreach (KeyValuePair<string, PeerState> entry in _peers)
+            {
+                long activity = Volatile.Read(ref entry.Value.LastActivityTicks);
+                if (activity < oldestTicks)
+                {
+                    oldestTicks = activity;
+                    oldest = entry.Key;
+                }
+            }
+
+            if (oldest is null || !_peers.TryRemove(oldest, out _))
+            {
+                break;
+            }
+        }
+    }
+
+    private sealed class PeerState
+    {
+        public Queue<long> FailureTicks { get; } = new();
+
+        public long LastActivityTicks;
+    }
+}

src/ZB.MOM.WW.MxGateway.Server/Security/Authorization/GatewayGrpcAuthorizationInterceptor.cs

@@ -15,7 +15,8 @@ public sealed class GatewayGrpcAuthorizationInterceptor(
     IApiKeyVerifier apiKeyVerifier,
     GatewayGrpcScopeResolver scopeResolver,
     IGatewayRequestIdentityAccessor identityAccessor,
-    IOptions<GatewayOptions> options) : Interceptor
+    IOptions<GatewayOptions> options,
+    ApiKeyFailureLimiter failureLimiter) : Interceptor
 {
     /// <inheritdoc />
     public override async Task<TResponse> UnaryServerHandler<TRequest, TResponse>(
@@ -63,6 +64,19 @@ public sealed class GatewayGrpcAuthorizationInterceptor(
 
         string? authorizationHeader = context.RequestHeaders.GetValue("authorization");
 
+        // SEC-11: short-circuit a peer that has already failed too many times inside the sliding
+        // window BEFORE the verification store read, so online guessing cannot spend a SQLite read
+        // per attempt. The peer key prefers the presented key id over the transport address (NAT
+        // caveat). ResourceExhausted signals throttling without revealing whether any particular
+        // secret was valid.
+        string peerKey = ResolvePeerKey(authorizationHeader, context);
+        if (failureLimiter.IsBlocked(peerKey))
+        {
+            throw new RpcException(new Status(
+                StatusCode.ResourceExhausted,
+                "Too many authentication attempts. Try again later."));
+        }
+
         // The shared verifier owns parse + pepper + lookup + revocation + constant-time compare,
         // returning a discriminated failure rather than throwing. Every authentication failure maps
         // to Unauthenticated with an opaque message; the client never learns which stage failed.
@@ -72,11 +86,16 @@ public sealed class GatewayGrpcAuthorizationInterceptor(
 
         if (!verification.Succeeded || verification.Identity is null)
         {
+            failureLimiter.RecordFailure(peerKey);
             throw new RpcException(new Status(
                 StatusCode.Unauthenticated,
                 "Missing or invalid API key."));
         }
 
+        // Successful authentication clears the peer's failure count so a legitimate client that
+        // fat-fingered a few attempts is not penalised once it recovers.
+        failureLimiter.Reset(peerKey);
+
         ApiKeyIdentity identity = GatewayApiKeyIdentityMapper.ToGatewayIdentity(verification.Identity);
 
         string requiredScope = scopeResolver.ResolveRequiredScope(request);
@@ -89,4 +108,30 @@ public sealed class GatewayGrpcAuthorizationInterceptor(
 
         return identity;
     }
+
+    // Resolves the failure-limiter partition key: the presented key id (token shape
+    // mxgw_<keyId>_<secret>) when the header parses, otherwise the transport peer address. Keying on
+    // key id throttles a single abusive credential without locking out co-located clients behind NAT.
+    private static string ResolvePeerKey(string? authorizationHeader, ServerCallContext context)
+    {
+        if (!string.IsNullOrWhiteSpace(authorizationHeader))
+        {
+            ReadOnlySpan<char> header = authorizationHeader.AsSpan().Trim();
+            const string bearer = "Bearer ";
+            ReadOnlySpan<char> token = header.StartsWith(bearer, StringComparison.OrdinalIgnoreCase)
+                ? header[bearer.Length..].Trim()
+                : header;
+
+            // mxgw_<keyId>_<secret>: the key id is the second underscore-delimited segment. The
+            // secret may itself contain underscores, but the key id is unaffected.
+            string tokenText = token.ToString();
+            string[] parts = tokenText.Split('_');
+            if (parts.Length >= 3 && parts[0].Length > 0 && parts[1].Length > 0)
+            {
+                return "key:" + parts[1];
+            }
+        }
+
+        return "peer:" + context.Peer;
+    }
 }

src/ZB.MOM.WW.MxGateway.Server/Security/Authorization/GatewayGrpcScopeResolver.cs

@@ -20,6 +20,7 @@ public sealed class GatewayGrpcScopeResolver
             MxCommandRequest commandRequest => ResolveCommandScope(commandRequest.Command?.Kind ?? MxCommandKind.Unspecified),
             AcknowledgeAlarmRequest => GatewayScopes.InvokeWrite,
             StreamAlarmsRequest => GatewayScopes.EventsRead,
+            QueryActiveAlarmsRequest => GatewayScopes.EventsRead,
             TestConnectionRequest or
             GetLastDeployTimeRequest or
             DiscoverHierarchyRequest or

src/ZB.MOM.WW.MxGateway.Server/Security/Authorization/GrpcAuthorizationServiceCollectionExtensions.cs

@@ -19,6 +19,13 @@ public static class GrpcAuthorizationServiceCollectionExtensions
         services.AddSingleton<GatewayGrpcScopeResolver>();
         services.AddSingleton<IGatewayRequestIdentityAccessor, GatewayRequestIdentityAccessor>();
         services.AddSingleton<IConstraintEnforcer, ConstraintEnforcer>();
+        // SEC-11 per-peer failure counter, checked before the verification store read. Bind the knobs
+        // from IConfiguration directly (not IOptions<GatewayOptions>) to avoid coupling this
+        // registration to the whole-options validation pipeline.
+        services.AddSingleton(sp => new ApiKeyFailureLimiter(
+            sp.GetRequiredService<IConfiguration>().GetSection(SecurityOptions.SectionName).Get<SecurityOptions>()
+                ?? new SecurityOptions(),
+            sp.GetService<TimeProvider>() ?? TimeProvider.System));
         services.AddSingleton<GatewayGrpcAuthorizationInterceptor>();
         services
             .AddOptions<global::Grpc.AspNetCore.Server.GrpcServiceOptions>()

src/ZB.MOM.WW.MxGateway.Server/Security/Tls/SelfSignedCertificateProvider.cs

@@ -163,7 +163,15 @@ public sealed class SelfSignedCertificateProvider
             // temp file empty, harden its permissions, and only then write the PFX into
             // the already-protected file. The temp path is in the same directory as the
             // target so the Move is atomic and preserves the hardened DACL/mode.
-            string temp = path + ".tmp";
+            //
+            // The temp name carries a unique suffix rather than a fixed "<path>.tmp": two
+            // processes (or two parallel callers) generating to the same target must not
+            // collide on one temp file. On Windows a fixed name makes the second writer's
+            // File.Create/Move fail with "the process cannot access the file ... because it
+            // is being used by another process"; a unique name lets each generation stage
+            // independently, and the final atomic Move (last-writer-wins) still yields a
+            // valid, equivalent certificate at the shared path.
+            string temp = $"{path}.{Guid.NewGuid():N}.tmp";
             using (File.Create(temp)) { }
             HardenPermissions(temp);
 

src/ZB.MOM.WW.MxGateway.Server/Workers/WorkerClient.cs

@@ -24,6 +24,13 @@ public sealed class WorkerClient : IWorkerClient
     private readonly WorkerFrameWriter _writer;
     private readonly Channel<WorkerEnvelope> _outboundEnvelopes;
     private readonly Channel<WorkerEvent> _events;
+
+    // Staging hand-off between the read loop and the dedicated event writer. The read loop writes
+    // here with a non-blocking TryWrite so a full consumer channel (_events) can never stall the read
+    // loop behind an event — replies and heartbeats keep flowing (GWC-04). Unbounded, but only fills
+    // during the bounded EventChannelFullModeTimeout window before EventWriteLoopAsync faults on a
+    // sustained backlog, after which the read loop stops.
+    private readonly Channel<WorkerEvent> _eventStaging;
     private readonly ConcurrentDictionary<string, PendingCommand> _pendingCommands = new(StringComparer.Ordinal);
     private readonly SemaphoreSlim _pendingCommandSlots;
     private readonly CancellationTokenSource _stopCts = new();
@@ -35,6 +42,7 @@ public sealed class WorkerClient : IWorkerClient
     private int _eventsReaderClaimed;
     private Task? _readLoopTask;
     private Task? _writeLoopTask;
+    private Task? _eventWriteLoopTask;
     private Task? _heartbeatLoopTask;
     private bool _workerStartRecorded;
     private bool _disposed;
@@ -82,6 +90,14 @@ public sealed class WorkerClient : IWorkerClient
                 FullMode = BoundedChannelFullMode.Wait,
                 AllowSynchronousContinuations = false,
             });
+        _eventStaging = Channel.CreateUnbounded<WorkerEvent>(
+            new UnboundedChannelOptions
+            {
+                // The read loop is the only writer; EventWriteLoopAsync is the only reader.
+                SingleReader = true,
+                SingleWriter = true,
+                AllowSynchronousContinuations = false,
+            });
         _lastHeartbeatAt = _timeProvider.GetUtcNow();
     }
 
@@ -144,6 +160,7 @@ public sealed class WorkerClient : IWorkerClient
         MarkReady(readyEnvelope.WorkerReady);
 
         _readLoopTask = Task.Run(ReadLoopAsync);
+        _eventWriteLoopTask = Task.Run(EventWriteLoopAsync);
         _heartbeatLoopTask = Task.Run(HeartbeatLoopAsync);
     }
 
@@ -187,7 +204,23 @@ public sealed class WorkerClient : IWorkerClient
 
         try
         {
-            await EnqueueAsync(CreateCommandEnvelope(correlationId, command), cancellationToken).ConfigureAwait(false);
+            WorkerEnvelope commandEnvelope = CreateCommandEnvelope(correlationId, command);
+
+            // Reject an oversized command at the enqueue boundary so only this correlation fails
+            // (ResourceExhausted) rather than the frame reaching the write loop and faulting the whole
+            // session (IPC-03). Command envelopes are the only gateway-authored outbound payload whose
+            // size the caller controls; checking here keeps a MessageTooLarge in the write loop a
+            // genuine desync signal.
+            int envelopeSize = commandEnvelope.CalculateSize();
+            if (envelopeSize > _connection.FrameOptions.MaxMessageBytes)
+            {
+                throw new WorkerClientException(
+                    WorkerClientErrorCode.CommandTooLarge,
+                    $"Worker command {method} serializes to {envelopeSize} bytes, exceeding the negotiated "
+                    + $"worker-frame maximum of {_connection.FrameOptions.MaxMessageBytes} bytes.");
+            }
+
+            await EnqueueAsync(commandEnvelope, cancellationToken).ConfigureAwait(false);
             using CancellationTokenSource timeoutCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
             Task timeoutTask = Task.Delay(timeout, timeoutCts.Token);
             Task<WorkerCommandReply> replyTask = pendingCommand.Task;
@@ -328,6 +361,7 @@ public sealed class WorkerClient : IWorkerClient
         KillOwnedProcess("Dispose");
         _stopCts.Cancel();
         _outboundEnvelopes.Writer.TryComplete();
+        _eventStaging.Writer.TryComplete();
         _events.Writer.TryComplete();
         CompletePendingCommands(
             new WorkerClientException(
@@ -382,7 +416,7 @@ public sealed class WorkerClient : IWorkerClient
             while (!_stopCts.IsCancellationRequested)
             {
                 WorkerEnvelope envelope = await _reader.ReadAsync(_stopCts.Token).ConfigureAwait(false);
-                await DispatchEnvelopeAsync(envelope, _stopCts.Token).ConfigureAwait(false);
+                DispatchEnvelope(envelope);
             }
         }
         catch (OperationCanceledException) when (_stopCts.IsCancellationRequested || IsTerminalState())
@@ -481,12 +515,14 @@ public sealed class WorkerClient : IWorkerClient
         return true;
     }
 
-    /// <summary>Routes received envelope to appropriate handler.</summary>
+    /// <summary>
+    ///     Routes a received envelope to its handler. Every branch dispatches synchronously and
+    ///     immediately — the event branch only stages the event for the dedicated writer — so a full
+    ///     event channel can never delay a command reply, heartbeat, fault, or shutdown ack behind an
+    ///     event backlog (GWC-04).
+    /// </summary>
     /// <param name="envelope">The envelope to dispatch.</param>
-    /// <param name="cancellationToken">Cancellation token.</param>
-    private async Task DispatchEnvelopeAsync(
-        WorkerEnvelope envelope,
-        CancellationToken cancellationToken)
+    private void DispatchEnvelope(WorkerEnvelope envelope)
     {
         switch (envelope.BodyCase)
         {
@@ -494,7 +530,7 @@ public sealed class WorkerClient : IWorkerClient
                 CompleteCommand(envelope);
                 break;
             case WorkerEnvelope.BodyOneofCase.WorkerEvent:
-                await EnqueueWorkerEventAsync(envelope.WorkerEvent, cancellationToken).ConfigureAwait(false);
+                StageWorkerEvent(envelope.WorkerEvent);
                 break;
             case WorkerEnvelope.BodyOneofCase.WorkerHeartbeat:
                 MarkHeartbeat(envelope.WorkerHeartbeat);
@@ -517,6 +553,45 @@ public sealed class WorkerClient : IWorkerClient
         }
     }
 
+    /// <summary>
+    ///     Hands a received worker event to the dedicated event writer without blocking the read loop.
+    ///     The staging channel is unbounded and this is the only writer, so <c>TryWrite</c> always
+    ///     succeeds unless the channel has been completed during shutdown — in which case the event is
+    ///     safely dropped because the client is closing. Backpressure and the sustained-overflow fault
+    ///     are applied by <see cref="EventWriteLoopAsync"/> against the bounded consumer channel,
+    ///     off the read loop (GWC-04).
+    /// </summary>
+    /// <param name="workerEvent">The event received from the worker.</param>
+    private void StageWorkerEvent(WorkerEvent workerEvent)
+    {
+        if (workerEvent.Event is not null)
+        {
+            _metrics?.EventReceived(SessionId, workerEvent.Event.Family.ToString());
+        }
+
+        _eventStaging.Writer.TryWrite(workerEvent);
+    }
+
+    /// <summary>
+    ///     Drains staged worker events and applies the bounded-channel backpressure (and
+    ///     sustained-overflow fault) on a dedicated task, so the timed <see cref="Channel"/> write
+    ///     never runs on the read loop (GWC-04). Mirrors <see cref="WriteLoopAsync"/> for events.
+    /// </summary>
+    private async Task EventWriteLoopAsync()
+    {
+        try
+        {
+            await foreach (WorkerEvent workerEvent in
+                _eventStaging.Reader.ReadAllAsync(_stopCts.Token).ConfigureAwait(false))
+            {
+                await EnqueueWorkerEventAsync(workerEvent, _stopCts.Token).ConfigureAwait(false);
+            }
+        }
+        catch (OperationCanceledException) when (_stopCts.IsCancellationRequested || IsTerminalState())
+        {
+        }
+    }
+
     /// <summary>
     ///     Enqueues a worker event for client consumption. The channel is
     ///     configured with <see cref="BoundedChannelFullMode.Wait"/>
@@ -536,11 +611,6 @@ public sealed class WorkerClient : IWorkerClient
         WorkerEvent workerEvent,
         CancellationToken cancellationToken)
     {
-        if (workerEvent.Event is not null)
-        {
-            _metrics?.EventReceived(SessionId, workerEvent.Event.Family.ToString());
-        }
-
         if (_events.Writer.TryWrite(workerEvent))
         {
             int queueDepth = Interlocked.Increment(ref _eventQueueDepth);
@@ -731,6 +801,7 @@ public sealed class WorkerClient : IWorkerClient
 
         _stopCts.Cancel();
         _outboundEnvelopes.Writer.TryComplete();
+        _eventStaging.Writer.TryComplete();
         _events.Writer.TryComplete();
         CompletePendingCommands(
             new WorkerClientException(
@@ -764,6 +835,7 @@ public sealed class WorkerClient : IWorkerClient
 
         _stopCts.Cancel();
         _outboundEnvelopes.Writer.TryComplete(fault);
+        _eventStaging.Writer.TryComplete(fault);
         _events.Writer.TryComplete(fault);
         KillOwnedProcess(errorCode.ToString());
         CompletePendingCommands(fault);
@@ -910,6 +982,10 @@ public sealed class WorkerClient : IWorkerClient
                 SupportedProtocolVersion = _connection.FrameOptions.ProtocolVersion,
                 Nonce = _connection.Nonce,
                 GatewayVersion = typeof(GatewayContractInfo).Assembly.GetName().Version?.ToString() ?? GatewayVersionFallback,
+
+                // Convey the negotiated worker-frame maximum so the worker adopts it instead of a
+                // hard-coded default (IPC-02). Sits above the public gRPC cap by the envelope reserve.
+                MaxFrameBytes = (uint)_connection.FrameOptions.MaxMessageBytes,
             });
     }
 
@@ -985,7 +1061,7 @@ public sealed class WorkerClient : IWorkerClient
     /// <param name="cancellationToken">Cancellation token.</param>
     private async Task WaitForBackgroundTasksAsync(CancellationToken cancellationToken)
     {
-        Task[] tasks = new[] { _readLoopTask, _writeLoopTask, _heartbeatLoopTask }
+        Task[] tasks = new[] { _readLoopTask, _writeLoopTask, _eventWriteLoopTask, _heartbeatLoopTask }
             .Where(task => task is not null)
             .Cast<Task>()
             .ToArray();

src/ZB.MOM.WW.MxGateway.Server/Workers/WorkerClientErrorCode.cs

@@ -12,4 +12,9 @@ public enum WorkerClientErrorCode
     GatewayShutdown,
     WriteFailed,
     PendingCommandLimitExceeded,
+
+    // The serialized command envelope exceeds the negotiated worker-frame maximum. Rejected at the
+    // enqueue boundary so only the offending command fails (mapped to ResourceExhausted) instead of
+    // the oversized frame reaching the write loop and faulting the whole session (IPC-03).
+    CommandTooLarge,
 }

src/ZB.MOM.WW.MxGateway.Server/Workers/WorkerFrameProtocolOptions.cs

@@ -10,6 +10,15 @@ public sealed class WorkerFrameProtocolOptions
     /// <summary>Default maximum message size in bytes (16 MB).</summary>
     public const int DefaultMaxMessageBytes = 16 * 1024 * 1024;
 
+    /// <summary>
+    /// Byte margin the worker-frame (pipe) maximum must keep above the public gRPC message cap so a
+    /// gRPC payload accepted at the public boundary always fits inside one worker frame once wrapped
+    /// in a <c>WorkerEnvelope</c> (correlation id, timestamps, oneof framing). Without this headroom
+    /// the pipe max equals the gRPC max and a maximally-sized accepted request faults the whole
+    /// session on the outbound write (IPC-03). 64 KiB is far larger than the fixed envelope overhead.
+    /// </summary>
+    public const int EnvelopeOverheadReserveBytes = 64 * 1024;
+
     /// <summary>
     /// Initializes worker frame protocol options with a session ID.
     /// </summary>

src/ZB.MOM.WW.MxGateway.Server/ZB.MOM.WW.MxGateway.Server.csproj

@@ -6,10 +6,10 @@
 
   <ItemGroup>
     <PackageReference Include="Grpc.AspNetCore" Version="2.76.0" />
-    <PackageReference Include="ZB.MOM.WW.Auth.Abstractions" Version="0.1.2" />
-    <PackageReference Include="ZB.MOM.WW.Auth.Ldap" Version="0.1.2" />
-    <PackageReference Include="ZB.MOM.WW.Auth.ApiKeys" Version="0.1.2" />
-    <PackageReference Include="ZB.MOM.WW.Auth.AspNetCore" Version="0.1.2" />
+    <PackageReference Include="ZB.MOM.WW.Auth.Abstractions" Version="0.1.4" />
+    <PackageReference Include="ZB.MOM.WW.Auth.Ldap" Version="0.1.4" />
+    <PackageReference Include="ZB.MOM.WW.Auth.ApiKeys" Version="0.1.4" />
+    <PackageReference Include="ZB.MOM.WW.Auth.AspNetCore" Version="0.1.4" />
     <PackageReference Include="ZB.MOM.WW.Audit" Version="0.1.0" />
     <PackageReference Include="ZB.MOM.WW.Theme" Version="0.3.1" />
     <PackageReference Include="ZB.MOM.WW.Configuration" Version="0.1.0" />

src/ZB.MOM.WW.MxGateway.Server/appsettings.json

@@ -38,7 +38,7 @@
       "ShutdownTimeoutSeconds": 10,
       "HeartbeatIntervalSeconds": 5,
       "HeartbeatGraceSeconds": 15,
-      "MaxMessageBytes": 16777216
+      "MaxMessageBytes": 16842752
     },
     "Sessions": {
       "DefaultCommandTimeoutSeconds": 30,

src/ZB.MOM.WW.MxGateway.Tests/Configuration/GatewayOptionsTests.cs

@@ -14,7 +14,15 @@ public sealed class GatewayOptionsTests
         GatewayOptions options = BindOptions(new Dictionary<string, string?>());
 
         Assert.Equal(AuthenticationMode.ApiKey, options.Authentication.Mode);
-        Assert.Equal(@"C:\ProgramData\MxGateway\gateway-auth.db", options.Authentication.SqlitePath);
+        // SEC-01: the default is derived from CommonApplicationData (C:\ProgramData on Windows,
+        // /usr/share on Unix) rather than a Windows literal, so assert against the same derivation
+        // to stay platform-correct.
+        Assert.Equal(
+            Path.Combine(
+                Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData),
+                "MxGateway",
+                "gateway-auth.db"),
+            options.Authentication.SqlitePath);
         Assert.Equal("MxGateway:ApiKeyPepper", options.Authentication.PepperSecretName);
         Assert.True(options.Authentication.RunMigrationsOnStartup);
 
@@ -27,7 +35,8 @@ public sealed class GatewayOptionsTests
         Assert.Equal(10, options.Worker.ShutdownTimeoutSeconds);
         Assert.Equal(5, options.Worker.HeartbeatIntervalSeconds);
         Assert.Equal(15, options.Worker.HeartbeatGraceSeconds);
-        Assert.Equal(16 * 1024 * 1024, options.Worker.MaxMessageBytes);
+        // 16 MiB public gRPC cap plus the 64 KiB worker-frame envelope reserve (IPC-03 headroom).
+        Assert.Equal((16 * 1024 * 1024) + (64 * 1024), options.Worker.MaxMessageBytes);
 
         Assert.Equal(30, options.Sessions.DefaultCommandTimeoutSeconds);
         Assert.Equal(64, options.Sessions.MaxSessions);

src/ZB.MOM.WW.MxGateway.Tests/Configuration/GatewayOptionsValidatorTests.cs

@@ -1,5 +1,6 @@
 using Microsoft.Extensions.Options;
 using ZB.MOM.WW.MxGateway.Server.Configuration;
+using LdapTransport = ZB.MOM.WW.Auth.Abstractions.Ldap.LdapTransport;
 
 namespace ZB.MOM.WW.MxGateway.Tests.Configuration;
 
@@ -548,4 +549,272 @@ public sealed class GatewayOptionsValidatorTests
         ValidateOptionsResult result = new GatewayOptionsValidator().Validate(null, options);
         Assert.True(result.Succeeded);
     }
+
+    // -------------------------------------------------------------------------
+    // SEC-01: security-sensitive paths must be rooted (absolute)
+    // -------------------------------------------------------------------------
+
+    private static GatewayOptions CloneWithAuthentication(GatewayOptions source, AuthenticationOptions authentication)
+        => new()
+        {
+            Authentication = authentication,
+            Ldap = source.Ldap,
+            Worker = source.Worker,
+            Sessions = source.Sessions,
+            Events = source.Events,
+            Dashboard = source.Dashboard,
+            Protocol = source.Protocol,
+            Alarms = source.Alarms,
+            Tls = source.Tls,
+        };
+
+    /// <summary>Verifies the default (CommonApplicationData-derived) auth DB path is rooted and passes validation.</summary>
+    [Fact]
+    public void Validate_Succeeds_WithDefaultRootedSqlitePath()
+    {
+        // The default AuthenticationOptions.SqlitePath is derived from CommonApplicationData,
+        // which is rooted on every host OS.
+        ValidateOptionsResult result = new GatewayOptionsValidator().Validate(null, ValidOptions());
+        Assert.True(result.Succeeded);
+    }
+
+    /// <summary>Verifies a non-rooted <see cref="AuthenticationOptions.SqlitePath"/> fails validation.</summary>
+    [Fact]
+    public void Validate_Fails_WhenSqlitePathNotRooted()
+    {
+        GatewayOptions options = CloneWithAuthentication(
+            ValidOptions(),
+            new AuthenticationOptions { SqlitePath = "gateway-auth.db" });
+        ValidateOptionsResult result = new GatewayOptionsValidator().Validate(null, options);
+        Assert.True(result.Failed);
+        Assert.Contains(
+            result.Failures!,
+            f => f.Contains("MxGateway:Authentication:SqlitePath") && f.Contains("rooted"));
+    }
+
+    /// <summary>Verifies a non-rooted <see cref="TlsOptions.SelfSignedCertPath"/> fails validation.</summary>
+    [Fact]
+    public void Validate_Fails_WhenSelfSignedCertPathNotRooted()
+    {
+        GatewayOptions options = CloneWithTls(
+            ValidOptions(),
+            new TlsOptions { SelfSignedCertPath = "gateway-selfsigned.pfx" });
+        ValidateOptionsResult result = new GatewayOptionsValidator().Validate(null, options);
+        Assert.True(result.Failed);
+        Assert.Contains(
+            result.Failures!,
+            f => f.Contains("MxGateway:Tls:SelfSignedCertPath") && f.Contains("rooted"));
+    }
+
+    // -------------------------------------------------------------------------
+    // SEC-04: DisableLogin production guard
+    // -------------------------------------------------------------------------
+
+    private static GatewayOptions CloneWithDashboard(GatewayOptions source, DashboardOptions dashboard)
+        => new()
+        {
+            Authentication = source.Authentication,
+            Ldap = source.Ldap,
+            Worker = source.Worker,
+            Sessions = source.Sessions,
+            Events = source.Events,
+            Dashboard = dashboard,
+            Protocol = source.Protocol,
+            Alarms = source.Alarms,
+            Tls = source.Tls,
+        };
+
+    /// <summary>Verifies <see cref="DashboardOptions.DisableLogin"/> set to <see langword="true"/> aborts startup in Production.</summary>
+    [Fact]
+    public void Validate_Fails_WhenDisableLoginTrueInProduction()
+    {
+        GatewayOptions options = CloneWithDashboard(
+            ValidOptions(),
+            new DashboardOptions { DisableLogin = true });
+        ValidateOptionsResult result = new GatewayOptionsValidator(isProduction: true).Validate(null, options);
+        Assert.True(result.Failed);
+        Assert.Contains(
+            result.Failures!,
+            f => f.Contains("MxGateway:Dashboard:DisableLogin") && f.Contains("Production"));
+    }
+
+    /// <summary>Verifies <see cref="DashboardOptions.DisableLogin"/> set to <see langword="true"/> is accepted outside Production.</summary>
+    [Fact]
+    public void Validate_Succeeds_WhenDisableLoginTrueInDevelopment()
+    {
+        GatewayOptions options = CloneWithDashboard(
+            ValidOptions(),
+            new DashboardOptions { DisableLogin = true });
+        ValidateOptionsResult result = new GatewayOptionsValidator(isProduction: false).Validate(null, options);
+        Assert.True(result.Succeeded);
+    }
+
+    // -------------------------------------------------------------------------
+    // SEC-06: LDAP plaintext transport production guard
+    // -------------------------------------------------------------------------
+
+    /// <summary>Verifies plaintext LDAP transport (None) aborts startup in Production.</summary>
+    [Fact]
+    public void Validate_Fails_WhenLdapTransportNoneInProduction()
+    {
+        // The class default LDAP options ship Transport=None + AllowInsecure=true (dev posture).
+        ValidateOptionsResult result = new GatewayOptionsValidator(isProduction: true).Validate(null, ValidOptions());
+        Assert.True(result.Failed);
+        Assert.Contains(
+            result.Failures!,
+            f => f.Contains("MxGateway:Ldap:Transport") && f.Contains("Production"));
+    }
+
+    /// <summary>Verifies plaintext LDAP transport (None) is accepted outside Production.</summary>
+    [Fact]
+    public void Validate_Succeeds_WhenLdapTransportNoneInDevelopment()
+    {
+        ValidateOptionsResult result = new GatewayOptionsValidator(isProduction: false).Validate(null, ValidOptions());
+        Assert.True(result.Succeeded);
+    }
+
+    /// <summary>Verifies secure LDAP transport (Ldaps) passes validation in Production.</summary>
+    [Fact]
+    public void Validate_Succeeds_WhenLdapTransportLdapsInProduction()
+    {
+        GatewayOptions options = CloneWithLdap(
+            ValidOptions(),
+            new LdapOptions { Enabled = true, Transport = LdapTransport.Ldaps, AllowInsecure = false });
+        ValidateOptionsResult result = new GatewayOptionsValidator(isProduction: true).Validate(null, options);
+        Assert.True(result.Succeeded);
+    }
+
+    // ---- SEC-11: MxGateway:Security validation ----
+
+    private static GatewayOptions WithSecurity(SecurityOptions security) => new() { Security = security };
+
+    /// <summary>Verifies the default security options pass validation.</summary>
+    [Fact]
+    public void Validate_Succeeds_WithDefaultSecurityOptions()
+    {
+        ValidateOptionsResult result = new GatewayOptionsValidator().Validate(null, WithSecurity(new SecurityOptions()));
+        Assert.True(result.Succeeded);
+    }
+
+    /// <summary>Verifies a zero verification-cache TTL is allowed (disables caching).</summary>
+    [Fact]
+    public void Validate_Succeeds_WhenVerificationCacheSecondsZero()
+    {
+        ValidateOptionsResult result = new GatewayOptionsValidator().Validate(
+            null,
+            WithSecurity(new SecurityOptions { ApiKeyVerificationCacheSeconds = 0 }));
+        Assert.True(result.Succeeded);
+    }
+
+    /// <summary>Verifies a negative verification-cache TTL fails validation.</summary>
+    [Fact]
+    public void Validate_Fails_WhenVerificationCacheSecondsNegative()
+    {
+        ValidateOptionsResult result = new GatewayOptionsValidator().Validate(
+            null,
+            WithSecurity(new SecurityOptions { ApiKeyVerificationCacheSeconds = -1 }));
+        Assert.True(result.Failed);
+        Assert.Contains(result.Failures!, f => f.Contains("ApiKeyVerificationCacheSeconds"));
+    }
+
+    /// <summary>Verifies a negative last-used coalesce window fails validation.</summary>
+    [Fact]
+    public void Validate_Fails_WhenLastUsedCoalesceSecondsNegative()
+    {
+        ValidateOptionsResult result = new GatewayOptionsValidator().Validate(
+            null,
+            WithSecurity(new SecurityOptions { ApiKeyLastUsedCoalesceSeconds = -5 }));
+        Assert.True(result.Failed);
+        Assert.Contains(result.Failures!, f => f.Contains("ApiKeyLastUsedCoalesceSeconds"));
+    }
+
+    /// <summary>Verifies a zero login rate-limit permit fails validation.</summary>
+    [Fact]
+    public void Validate_Fails_WhenLoginRateLimitPermitLimitZero()
+    {
+        ValidateOptionsResult result = new GatewayOptionsValidator().Validate(
+            null,
+            WithSecurity(new SecurityOptions { LoginRateLimitPermitLimit = 0 }));
+        Assert.True(result.Failed);
+        Assert.Contains(result.Failures!, f => f.Contains("LoginRateLimitPermitLimit"));
+    }
+
+    /// <summary>Verifies a zero login rate-limit window fails validation.</summary>
+    [Fact]
+    public void Validate_Fails_WhenLoginRateLimitWindowSecondsZero()
+    {
+        ValidateOptionsResult result = new GatewayOptionsValidator().Validate(
+            null,
+            WithSecurity(new SecurityOptions { LoginRateLimitWindowSeconds = 0 }));
+        Assert.True(result.Failed);
+        Assert.Contains(result.Failures!, f => f.Contains("LoginRateLimitWindowSeconds"));
+    }
+
+    /// <summary>Verifies a zero API-key failure limit fails validation.</summary>
+    [Fact]
+    public void Validate_Fails_WhenApiKeyFailureLimitZero()
+    {
+        ValidateOptionsResult result = new GatewayOptionsValidator().Validate(
+            null,
+            WithSecurity(new SecurityOptions { ApiKeyFailureLimit = 0 }));
+        Assert.True(result.Failed);
+        Assert.Contains(result.Failures!, f => f.Contains("ApiKeyFailureLimit"));
+    }
+
+    /// <summary>Verifies a zero tracked-peer cap fails validation.</summary>
+    [Fact]
+    public void Validate_Fails_WhenApiKeyFailureTrackedPeersZero()
+    {
+        ValidateOptionsResult result = new GatewayOptionsValidator().Validate(
+            null,
+            WithSecurity(new SecurityOptions { ApiKeyFailureTrackedPeers = 0 }));
+        Assert.True(result.Failed);
+        Assert.Contains(result.Failures!, f => f.Contains("ApiKeyFailureTrackedPeers"));
+    }
+
+    private static GatewayOptions WithWorkerAndProtocol(WorkerOptions worker, ProtocolOptions protocol)
+    {
+        GatewayOptions source = ValidOptions();
+        return new GatewayOptions
+        {
+            Authentication = source.Authentication,
+            Ldap = source.Ldap,
+            Worker = worker,
+            Sessions = source.Sessions,
+            Events = source.Events,
+            Dashboard = source.Dashboard,
+            Protocol = protocol,
+            Alarms = source.Alarms,
+            Tls = source.Tls,
+        };
+    }
+
+    /// <summary>
+    /// Verifies the default worker-frame maximum keeps the required envelope-overhead reserve above
+    /// the default public gRPC cap, so a stock configuration passes the IPC-03 headroom check.
+    /// </summary>
+    [Fact]
+    public void Validate_Succeeds_WhenWorkerFrameMaxHasEnvelopeHeadroom()
+    {
+        ValidateOptionsResult result = new GatewayOptionsValidator().Validate(null, ValidOptions());
+        Assert.True(result.Succeeded);
+    }
+
+    /// <summary>
+    /// Verifies that a worker-frame maximum equal to the gRPC cap (zero headroom) fails validation:
+    /// a maximally-sized accepted gRPC payload would not fit one worker frame once wrapped in a
+    /// WorkerEnvelope, faulting the whole session on the outbound write (IPC-03).
+    /// </summary>
+    [Fact]
+    public void Validate_Fails_WhenWorkerFrameMaxEqualsGrpcMaxWithoutHeadroom()
+    {
+        const int grpcMax = 16 * 1024 * 1024;
+        ValidateOptionsResult result = new GatewayOptionsValidator().Validate(
+            null,
+            WithWorkerAndProtocol(
+                new WorkerOptions { MaxMessageBytes = grpcMax },
+                new ProtocolOptions { MaxGrpcMessageBytes = grpcMax }));
+        Assert.True(result.Failed);
+        Assert.Contains(result.Failures!, f => f.Contains("MaxMessageBytes") && f.Contains("reserve"));
+    }
 }

src/ZB.MOM.WW.MxGateway.Tests/Contracts/ClientProtoInputTests.cs

@@ -1,5 +1,6 @@
 using System.Text.Json;
 using Google.Protobuf;
+using Google.Protobuf.Reflection;
 using ZB.MOM.WW.MxGateway.Contracts;
 using ZB.MOM.WW.MxGateway.Contracts.Proto;
 
@@ -7,6 +8,102 @@ namespace ZB.MOM.WW.MxGateway.Tests.Contracts;
 
 public sealed class ClientProtoInputTests
 {
+    /// <summary>
+    /// Guards the published client descriptor set against silent staleness (IPC-01). Every message
+    /// and field compiled into the in-process contract (which the build regenerates from the current
+    /// <c>.proto</c> sources) must appear in the committed protoset. A missing symbol means the
+    /// descriptor was not regenerated after a proto change; run
+    /// <c>scripts/publish-client-proto-inputs.ps1</c> and commit the refreshed protoset.
+    /// The check is semantic (symbol presence) rather than byte-wise, so it is independent of protoc
+    /// version and does not require protoc on the test runner.
+    /// </summary>
+    [Fact]
+    public void Descriptor_ContainsEveryContractMessageAndField()
+    {
+        DirectoryInfo repositoryRoot = FindRepositoryRoot();
+        string descriptorPath = Path.Combine(
+            repositoryRoot.FullName,
+            "clients",
+            "proto",
+            "descriptors",
+            "mxaccessgw-client-v1.protoset");
+
+        Assert.True(File.Exists(descriptorPath), $"Expected descriptor set '{descriptorPath}' to exist.");
+
+        FileDescriptorSet descriptorSet = FileDescriptorSet.Parser.ParseFrom(File.ReadAllBytes(descriptorPath));
+
+        HashSet<string> publishedMessages = new(StringComparer.Ordinal);
+        HashSet<string> publishedFields = new(StringComparer.Ordinal);
+        foreach (FileDescriptorProto file in descriptorSet.File)
+        {
+            foreach (DescriptorProto message in file.MessageType)
+            {
+                CollectPublishedSymbols(file.Package, message, publishedMessages, publishedFields);
+            }
+        }
+
+        List<string> missing = [];
+        foreach (FileDescriptor file in new[] { MxaccessGatewayReflection.Descriptor, MxaccessWorkerReflection.Descriptor })
+        {
+            foreach (MessageDescriptor message in file.MessageTypes)
+            {
+                CollectMissingContractSymbols(message, publishedMessages, publishedFields, missing);
+            }
+        }
+
+        Assert.True(
+            missing.Count == 0,
+            "Published client descriptor is stale; regenerate with scripts/publish-client-proto-inputs.ps1 and commit. "
+                + "Missing symbols: "
+                + string.Join(", ", missing));
+    }
+
+    private static void CollectPublishedSymbols(
+        string package,
+        DescriptorProto message,
+        HashSet<string> messages,
+        HashSet<string> fields)
+    {
+        string fullName = string.IsNullOrEmpty(package) ? message.Name : package + "." + message.Name;
+        messages.Add(fullName);
+
+        foreach (FieldDescriptorProto field in message.Field)
+        {
+            fields.Add(fullName + "/" + field.Name);
+        }
+
+        foreach (DescriptorProto nested in message.NestedType)
+        {
+            CollectPublishedSymbols(fullName, nested, messages, fields);
+        }
+    }
+
+    private static void CollectMissingContractSymbols(
+        MessageDescriptor message,
+        HashSet<string> publishedMessages,
+        HashSet<string> publishedFields,
+        List<string> missing)
+    {
+        if (!publishedMessages.Contains(message.FullName))
+        {
+            missing.Add(message.FullName);
+        }
+
+        foreach (FieldDescriptor field in message.Fields.InDeclarationOrder())
+        {
+            string key = message.FullName + "/" + field.Name;
+            if (!publishedFields.Contains(key))
+            {
+                missing.Add(key);
+            }
+        }
+
+        foreach (MessageDescriptor nested in message.NestedTypes)
+        {
+            CollectMissingContractSymbols(nested, publishedMessages, publishedFields, missing);
+        }
+    }
+
     /// <summary>Verifies that the proto inputs manifest declares current protocol versions and existing source files.</summary>
     [Fact]
     public void Manifest_DeclaresCurrentProtocolVersionsAndExistingInputs()

src/ZB.MOM.WW.MxGateway.Tests/Diagnostics/AuthStoreHealthCheckTests.cs

@@ -1,6 +1,7 @@
 using Microsoft.Extensions.Diagnostics.HealthChecks;
 using ZB.MOM.WW.Auth.ApiKeys.Sqlite;
 using ZB.MOM.WW.MxGateway.Server.Diagnostics;
+using ZB.MOM.WW.MxGateway.Tests.Security.Authentication;
 
 namespace ZB.MOM.WW.MxGateway.Tests.Diagnostics;
 
@@ -17,15 +18,15 @@ public sealed class AuthStoreHealthCheckTests
     [Fact]
     public async Task Healthy_WhenStoreReachable()
     {
-        var path = Path.Combine(Path.GetTempPath(), $"authcheck-{Guid.NewGuid():N}.db");
-        try
-        {
-            var check = new AuthStoreHealthCheck(FactoryFor(path));
+        // Open a real SQLite file via the health check. TempDatabaseDirectory clears the
+        // Microsoft.Data.Sqlite connection pool on dispose before deleting the file; without
+        // that the pool keeps the .db handle open and the delete throws "used by another
+        // process" on Windows (a latent full-suite flake — the file opens fine on macOS).
+        using TempDatabaseDirectory directory = TempDatabaseDirectory.Create("authcheck");
+        var check = new AuthStoreHealthCheck(FactoryFor(directory.DatabasePath()));
         var result = await check.CheckHealthAsync(new HealthCheckContext());
         Assert.Equal(HealthStatus.Healthy, result.Status);
     }
-        finally { if (File.Exists(path)) File.Delete(path); }
-    }
 
     /// <summary>The health check reports unhealthy when the database path cannot be opened.</summary>
     /// <returns>A task that represents the asynchronous operation.</returns>

src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardAuthorizationHandlerTests.cs

@@ -128,11 +128,58 @@ public sealed class DashboardAuthorizationHandlerTests
         Assert.False(context.HasSucceeded);
     }
 
+    /// <summary>
+    /// Verifies that the anonymous-localhost bypass is read-only: a loopback request with
+    /// <c>AllowAnonymousLocalhost</c> on is denied the <see cref="DashboardAuthorizationRequirement.AdminOnly"/>
+    /// requirement, so destructive/admin surfaces are never reachable without a real Admin role.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task HandleAsync_AnonymousLocalhostAllowed_DoesNotSatisfyAdminPolicy()
+    {
+        AuthorizationHandlerContext context = await AuthorizeAsync(
+            new ClaimsPrincipal(new ClaimsIdentity()),
+            IPAddress.Loopback,
+            allowAnonymousLocalhost: true,
+            DashboardAuthorizationRequirement.AdminOnly);
+
+        Assert.False(context.HasSucceeded);
+    }
+
+    /// <summary>
+    /// Verifies that with authentication fully disabled the environment bypass stays read-only:
+    /// a remote request satisfies <see cref="DashboardAuthorizationRequirement.AnyDashboardRole"/>
+    /// (Viewer) but is denied <see cref="DashboardAuthorizationRequirement.AdminOnly"/>.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task HandleAsync_AuthenticationDisabled_GrantsViewerButNotAdmin()
+    {
+        AuthorizationHandlerContext viewerContext = await AuthorizeAsync(
+            new ClaimsPrincipal(new ClaimsIdentity()),
+            IPAddress.Parse("10.0.0.5"),
+            allowAnonymousLocalhost: false,
+            DashboardAuthorizationRequirement.AnyDashboardRole,
+            authenticationMode: AuthenticationMode.Disabled);
+
+        Assert.True(viewerContext.HasSucceeded);
+
+        AuthorizationHandlerContext adminContext = await AuthorizeAsync(
+            new ClaimsPrincipal(new ClaimsIdentity()),
+            IPAddress.Parse("10.0.0.5"),
+            allowAnonymousLocalhost: false,
+            DashboardAuthorizationRequirement.AdminOnly,
+            authenticationMode: AuthenticationMode.Disabled);
+
+        Assert.False(adminContext.HasSucceeded);
+    }
+
     private static async Task<AuthorizationHandlerContext> AuthorizeAsync(
         ClaimsPrincipal principal,
         IPAddress remoteAddress,
         bool allowAnonymousLocalhost,
-        DashboardAuthorizationRequirement requirement)
+        DashboardAuthorizationRequirement requirement,
+        AuthenticationMode authenticationMode = AuthenticationMode.ApiKey)
     {
         DefaultHttpContext httpContext = new();
         httpContext.Connection.RemoteIpAddress = remoteAddress;
@@ -140,6 +187,10 @@ public sealed class DashboardAuthorizationHandlerTests
             new HttpContextAccessor { HttpContext = httpContext },
             Options.Create(new GatewayOptions
             {
+                Authentication = new AuthenticationOptions
+                {
+                    Mode = authenticationMode,
+                },
                 Dashboard = new DashboardOptions
                 {
                     AllowAnonymousLocalhost = allowAnonymousLocalhost,

src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardLoginRateLimitTests.cs

@@ -0,0 +1,66 @@
+using System.Net;
+using System.Threading.RateLimiting;
+using Microsoft.AspNetCore.Http;
+using ZB.MOM.WW.MxGateway.Server.Configuration;
+using ZB.MOM.WW.MxGateway.Server.Dashboard;
+
+namespace ZB.MOM.WW.MxGateway.Tests.Gateway.Dashboard;
+
+/// <summary>
+/// SEC-11: the <c>POST /auth/login</c> fixed-window per-IP rate limiter. Exercised through the same
+/// partition factory the production policy registers, so the test pins the real permit limit and
+/// per-IP partitioning without standing up an HTTP server.
+/// </summary>
+public sealed class DashboardLoginRateLimitTests
+{
+    /// <summary>A burst beyond the permit limit from one IP has its excess attempts rejected (HTTP 429 in the pipeline).</summary>
+    [Fact]
+    public void LoginRateLimiter_BurstBeyondPermitLimit_RejectsExcessFromSameIp()
+    {
+        SecurityOptions security = new()
+        {
+            LoginRateLimitPermitLimit = 3,
+            LoginRateLimitWindowSeconds = 60,
+        };
+        using PartitionedRateLimiter<HttpContext> limiter =
+            DashboardEndpointRouteBuilderExtensions.CreateLoginRateLimiter(security);
+        HttpContext context = ContextWithIp("10.0.0.7");
+
+        for (int i = 0; i < 3; i++)
+        {
+            using RateLimitLease lease = limiter.AttemptAcquire(context);
+            Assert.True(lease.IsAcquired);
+        }
+
+        using RateLimitLease rejected = limiter.AttemptAcquire(context);
+        Assert.False(rejected.IsAcquired);
+    }
+
+    /// <summary>Distinct client IPs are partitioned independently — one IP's burst does not starve another.</summary>
+    [Fact]
+    public void LoginRateLimiter_DistinctIps_PartitionedIndependently()
+    {
+        SecurityOptions security = new()
+        {
+            LoginRateLimitPermitLimit = 1,
+            LoginRateLimitWindowSeconds = 60,
+        };
+        using PartitionedRateLimiter<HttpContext> limiter =
+            DashboardEndpointRouteBuilderExtensions.CreateLoginRateLimiter(security);
+
+        using RateLimitLease first = limiter.AttemptAcquire(ContextWithIp("10.0.0.1"));
+        using RateLimitLease exhaustedForFirst = limiter.AttemptAcquire(ContextWithIp("10.0.0.1"));
+        using RateLimitLease second = limiter.AttemptAcquire(ContextWithIp("10.0.0.2"));
+
+        Assert.True(first.IsAcquired);
+        Assert.False(exhaustedForFirst.IsAcquired);
+        Assert.True(second.IsAcquired);
+    }
+
+    private static HttpContext ContextWithIp(string ip)
+    {
+        DefaultHttpContext context = new();
+        context.Connection.RemoteIpAddress = IPAddress.Parse(ip);
+        return context;
+    }
+}

src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardSessionAdminServiceTests.cs

@@ -1,6 +1,8 @@
+using System.Collections.Concurrent;
 using System.Diagnostics.CodeAnalysis;
 using System.Security.Claims;
 using Microsoft.AspNetCore.Http;
+using ZB.MOM.WW.Audit;
 using ZB.MOM.WW.MxGateway.Contracts.Proto;
 using ZB.MOM.WW.MxGateway.Server.Dashboard;
 using ZB.MOM.WW.MxGateway.Server.Sessions;
@@ -198,14 +200,91 @@ public sealed class DashboardSessionAdminServiceTests
         Assert.False(string.IsNullOrWhiteSpace(result.Message));
     }
 
-    private static DashboardSessionAdminService CreateService(ISessionManager sessionManager)
+    /// <summary>
+    /// Verifies that a successful close writes a canonical <c>dashboard-close-session</c>
+    /// <see cref="AuditEvent"/> — actor, session-id target, and Success outcome — to the
+    /// audit store, not only the operational log (SEC-12).
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task CloseSessionAsync_AdminClose_WritesCanonicalAuditEvent()
+    {
+        FakeSessionManager sessionManager = new();
+        RecordingAuditWriter auditWriter = new();
+        DashboardSessionAdminService service = CreateService(sessionManager, auditWriter);
+
+        DashboardSessionAdminResult result = await service.CloseSessionAsync(
+            CreateUser(DashboardRoles.Admin),
+            "session-1",
+            CancellationToken.None);
+
+        Assert.True(result.Succeeded);
+        AuditEvent audit = Assert.Single(auditWriter.Events);
+        Assert.Equal(DashboardSessionAdminService.CloseSessionAction, audit.Action);
+        Assert.Equal(DashboardSessionAdminService.SessionAdminCategory, audit.Category);
+        Assert.Equal("session-1", audit.Target);
+        Assert.Equal("tester", audit.Actor);
+        Assert.Equal(AuditOutcome.Success, audit.Outcome);
+    }
+
+    /// <summary>
+    /// Verifies that a successful kill writes a canonical <c>dashboard-kill-worker</c>
+    /// <see cref="AuditEvent"/> to the audit store (SEC-12).
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task KillWorkerAsync_AdminKill_WritesCanonicalAuditEvent()
+    {
+        FakeSessionManager sessionManager = new();
+        RecordingAuditWriter auditWriter = new();
+        DashboardSessionAdminService service = CreateService(sessionManager, auditWriter);
+
+        DashboardSessionAdminResult result = await service.KillWorkerAsync(
+            CreateUser(DashboardRoles.Admin),
+            "session-1",
+            CancellationToken.None);
+
+        Assert.True(result.Succeeded);
+        AuditEvent audit = Assert.Single(auditWriter.Events);
+        Assert.Equal(DashboardSessionAdminService.KillWorkerAction, audit.Action);
+        Assert.Equal("session-1", audit.Target);
+        Assert.Equal(AuditOutcome.Success, audit.Outcome);
+    }
+
+    /// <summary>
+    /// Verifies that an unauthorized (viewer) close attempt still writes a <c>Denied</c>
+    /// audit row, so rejected destructive attempts are durably recorded (SEC-12).
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task CloseSessionAsync_ViewerDenied_WritesDeniedAuditEvent()
+    {
+        FakeSessionManager sessionManager = new();
+        RecordingAuditWriter auditWriter = new();
+        DashboardSessionAdminService service = CreateService(sessionManager, auditWriter);
+
+        DashboardSessionAdminResult result = await service.CloseSessionAsync(
+            CreateUser(DashboardRoles.Viewer),
+            "session-1",
+            CancellationToken.None);
+
+        Assert.False(result.Succeeded);
+        AuditEvent audit = Assert.Single(auditWriter.Events);
+        Assert.Equal(DashboardSessionAdminService.CloseSessionAction, audit.Action);
+        Assert.Equal(AuditOutcome.Denied, audit.Outcome);
+    }
+
+    private static DashboardSessionAdminService CreateService(
+        ISessionManager sessionManager,
+        IAuditWriter? auditWriter = null)
     {
         DefaultHttpContext httpContext = new();
         httpContext.Connection.RemoteIpAddress = System.Net.IPAddress.Loopback;
 
         return new DashboardSessionAdminService(
             sessionManager,
-            new HttpContextAccessor { HttpContext = httpContext });
+            new HttpContextAccessor { HttpContext = httpContext },
+            auditWriter ?? new RecordingAuditWriter());
     }
 
     private static ClaimsPrincipal CreateUser(string role)
@@ -219,6 +298,21 @@ public sealed class DashboardSessionAdminServiceTests
         return new ClaimsPrincipal(identity);
     }
 
+    private sealed class RecordingAuditWriter : IAuditWriter
+    {
+        private readonly ConcurrentQueue<AuditEvent> _events = new();
+
+        /// <summary>Gets the audit events written through this writer, in order.</summary>
+        public IReadOnlyList<AuditEvent> Events => _events.ToArray();
+
+        /// <inheritdoc />
+        public Task WriteAsync(AuditEvent evt, CancellationToken ct = default)
+        {
+            _events.Enqueue(evt);
+            return Task.CompletedTask;
+        }
+    }
+
     private sealed class FakeSessionManager : ISessionManager
     {
         /// <summary>Gets the number of times CloseSessionAsync was invoked.</summary>

src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardSnapshotServiceTests.cs

@@ -623,6 +623,27 @@ public sealed class DashboardSnapshotServiceTests
         {
             return Task.FromResult(false);
         }
+
+        /// <summary>Does nothing; the fake never changes scopes (added to IApiKeyAdminStore in Auth 0.1.3).</summary>
+        /// <param name="keyId">Key identifier.</param>
+        /// <param name="scopes">Replacement scope set.</param>
+        /// <param name="ct">Cancellation token.</param>
+        /// <returns><see langword="false"/>, always.</returns>
+        public Task<bool> SetScopesAsync(string keyId, IReadOnlySet<string> scopes, CancellationToken ct)
+        {
+            return Task.FromResult(false);
+        }
+
+        /// <summary>Does nothing; the fake never toggles key state (added to IApiKeyAdminStore in Auth 0.1.3).</summary>
+        /// <param name="keyId">Key identifier.</param>
+        /// <param name="enabled">Desired enabled state.</param>
+        /// <param name="whenUtc">Timestamp for the state change.</param>
+        /// <param name="ct">Cancellation token.</param>
+        /// <returns><see langword="false"/>, always.</returns>
+        public Task<bool> SetEnabledAsync(string keyId, bool enabled, DateTimeOffset whenUtc, CancellationToken ct)
+        {
+            return Task.FromResult(false);
+        }
     }
 
     private class CountingApiKeyAdminStore(params ApiKeyListItem[] records) : FakeApiKeyAdminStore

src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/HubTokenServiceTests.cs

@@ -115,4 +115,63 @@ public sealed class HubTokenServiceTests
 
         Assert.Null(service.Validate("this-is-not-a-protected-payload"));
     }
+
+    /// <summary>
+    /// Issue/validate round-trip: a freshly minted token (default <see cref="HubTokenService.TokenLifetime"/>)
+    /// validates and reconstructs the caller's identity and roles.
+    /// </summary>
+    [Fact]
+    public void IssueThenValidate_FreshToken_RoundTripsIdentityAndRoles()
+    {
+        HubTokenService service = new(new EphemeralDataProtectionProvider());
+        ClaimsIdentity identity = new(
+            [
+                new Claim(ClaimTypes.Name, "bob"),
+                new Claim(ClaimTypes.NameIdentifier, "bob-id"),
+                new Claim(ClaimTypes.Role, DashboardRoles.Viewer),
+                new Claim(ClaimTypes.Role, DashboardRoles.Admin),
+            ],
+            authenticationType: "test",
+            nameType: ClaimTypes.Name,
+            roleType: ClaimTypes.Role);
+
+        string token = service.Issue(new ClaimsPrincipal(identity));
+        ClaimsPrincipal? result = service.Validate(token);
+
+        Assert.NotNull(result);
+        Assert.Equal("bob", result.Identity?.Name);
+        Assert.True(result.IsInRole(DashboardRoles.Viewer));
+        Assert.True(result.IsInRole(DashboardRoles.Admin));
+    }
+
+    /// <summary>
+    /// The default token lifetime is the short (5-minute) window mandated by SEC-05, not the
+    /// former 30-minute window. Pins the value so a regression that widens the exposure window
+    /// of an irrevocable, query-string-carried token is caught in CI.
+    /// </summary>
+    [Fact]
+    public void TokenLifetime_IsFiveMinutes()
+    {
+        Assert.Equal(TimeSpan.FromMinutes(5), HubTokenService.TokenLifetime);
+    }
+
+    /// <summary>
+    /// A token whose lifetime has elapsed is rejected by <see cref="HubTokenService.Validate"/>.
+    /// Uses the internal lifetime-issuing seam with a negative lifetime so the token is already
+    /// expired at mint time — deterministic, no wall-clock delay.
+    /// </summary>
+    [Fact]
+    public void Validate_ExpiredToken_ReturnsNull()
+    {
+        HubTokenService service = new(new EphemeralDataProtectionProvider());
+        ClaimsIdentity identity = new(
+            [new Claim(ClaimTypes.Name, "carol")],
+            authenticationType: "test");
+
+        string expiredToken = service.Issue(
+            new ClaimsPrincipal(identity),
+            TimeSpan.FromMinutes(-1));
+
+        Assert.Null(service.Validate(expiredToken));
+    }
 }

src/ZB.MOM.WW.MxGateway.Tests/Gateway/GatewayTlsBootstrapTests.cs

@@ -9,6 +9,10 @@ using ZB.MOM.WW.MxGateway.Server;
 
 namespace ZB.MOM.WW.MxGateway.Tests.Gateway;
 
+// Sets process-global Kestrel/TLS environment variables that GatewayApplication.Build reads;
+// serialized against all other collections so a parallel host-building test cannot inherit them
+// mid-run and race on the generated-certificate file. See GlobalEnvironmentCollection.
+[Collection(TestSupport.GlobalEnvironmentCollection.Name)]
 public sealed class GatewayTlsBootstrapTests
 {
     /// <summary>

src/ZB.MOM.WW.MxGateway.Tests/Gateway/Grpc/MxAccessGrpcRequestValidatorTests.cs

@@ -0,0 +1,45 @@
+using Grpc.Core;
+using ZB.MOM.WW.MxGateway.Contracts.Proto;
+using ZB.MOM.WW.MxGateway.Server.Grpc;
+
+namespace ZB.MOM.WW.MxGateway.Tests.Gateway.Grpc;
+
+public sealed class MxAccessGrpcRequestValidatorTests
+{
+    private static MxCommandRequest DrainRequest(uint maxEvents) => new()
+    {
+        SessionId = "session-1",
+        Command = new MxCommand
+        {
+            Kind = MxCommandKind.DrainEvents,
+            DrainEvents = new DrainEventsCommand { MaxEvents = maxEvents },
+        },
+    };
+
+    /// <summary>
+    /// Verifies a DrainEvents request within the per-request ceiling passes validation, including the
+    /// <c>max_events = 0</c> "worker default cap" sentinel (IPC-04).
+    /// </summary>
+    [Theory]
+    [InlineData(0u)]
+    [InlineData(1u)]
+    [InlineData(10_000u)]
+    public void ValidateInvoke_AllowsDrainEvents_WithinCeiling(uint maxEvents)
+    {
+        MxAccessGrpcRequestValidator validator = new();
+        validator.ValidateInvoke(DrainRequest(maxEvents));
+    }
+
+    /// <summary>
+    /// Verifies a DrainEvents request above the per-request ceiling is rejected with InvalidArgument
+    /// so one accepted request cannot pack an unbounded reply frame (IPC-04).
+    /// </summary>
+    [Fact]
+    public void ValidateInvoke_RejectsDrainEvents_AboveCeiling()
+    {
+        MxAccessGrpcRequestValidator validator = new();
+        RpcException exception = Assert.Throws<RpcException>(() => validator.ValidateInvoke(DrainRequest(10_001)));
+        Assert.Equal(StatusCode.InvalidArgument, exception.StatusCode);
+        Assert.Contains("max_events", exception.Status.Detail, StringComparison.Ordinal);
+    }
+}

src/ZB.MOM.WW.MxGateway.Tests/Gateway/Workers/WorkerClientTests.cs

@@ -56,6 +56,52 @@ public sealed class WorkerClientTests
         Assert.Equal(MxCommandKind.Ping, reply.Reply.Kind);
     }
 
+    /// <summary>
+    /// Verifies that a command whose serialized envelope exceeds the negotiated worker-frame maximum
+    /// fails only that command with <see cref="WorkerClientErrorCode.CommandTooLarge"/> at the enqueue
+    /// boundary, leaving the client ready for subsequent commands (IPC-03). Without the pre-check the
+    /// oversized frame would reach the write loop and fault the whole session.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task InvokeAsync_WhenCommandExceedsFrameMax_FailsOnlyThatCommandAndStaysReady()
+    {
+        await using PipePair pipePair = await PipePair.CreateAsync();
+        await using WorkerClient client = CreateClient(pipePair, maxMessageBytes: 4096);
+        await CompleteHandshakeAsync(client, pipePair);
+
+        WorkerCommand oversized = new()
+        {
+            Command = new MxCommand
+            {
+                Kind = MxCommandKind.Write,
+                Write = new WriteCommand
+                {
+                    ServerHandle = 1,
+                    ItemHandle = 2,
+                    Value = new MxValue { StringValue = new string('x', 8192) },
+                },
+            },
+        };
+
+        WorkerClientException exception = await Assert.ThrowsAsync<WorkerClientException>(
+            async () => await client.InvokeAsync(oversized, TestTimeout, CancellationToken.None));
+        Assert.Equal(WorkerClientErrorCode.CommandTooLarge, exception.ErrorCode);
+        Assert.Equal(WorkerClientState.Ready, client.State);
+
+        // A subsequent normally-sized command still round-trips: the session was not faulted.
+        Task<WorkerCommandReply> nextInvoke = client.InvokeAsync(
+            CreateCommand(MxCommandKind.Ping),
+            TestTimeout,
+            CancellationToken.None);
+        WorkerEnvelope commandEnvelope = await pipePair.WorkerReader.ReadAsync().AsTask().WaitAsync(TestTimeout);
+        await pipePair.WorkerWriter.WriteAsync(
+            CreateCommandReplyEnvelope(commandEnvelope.CorrelationId, MxCommandKind.Ping));
+        WorkerCommandReply reply = await nextInvoke.WaitAsync(TestTimeout);
+        Assert.Equal(MxCommandKind.Ping, reply.Reply.Kind);
+        Assert.Equal(WorkerClientState.Ready, client.State);
+    }
+
     /// <summary>Verifies that InvokeAsync ignores late replies and keeps the client ready.</summary>
     /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
@@ -172,6 +218,51 @@ public sealed class WorkerClientTests
         Assert.Equal(WorkerClientState.Faulted, client.State);
     }
 
+    /// <summary>
+    /// Verifies that a command reply arriving on the pipe after events is dispatched promptly even
+    /// when the event channel is full and has no consumer — event enqueue is decoupled from the read
+    /// loop, so a blocked event writer cannot delay a reply (GWC-04). The event full-mode timeout is
+    /// set far above the command timeout: without the decoupling the read loop would block behind the
+    /// full event channel and the in-flight InvokeAsync would hit CommandTimeout.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task ReadLoop_WhenEventChannelFull_DispatchesCommandReplyWithoutBlocking()
+    {
+        await using PipePair pipePair = await PipePair.CreateAsync();
+        await using WorkerClient client = CreateClient(
+            pipePair,
+            new WorkerClientOptions
+            {
+                EventChannelCapacity = 1,
+                // Much larger than TestTimeout: the read loop must not block for this long behind the
+                // full event channel while a reply waits.
+                EventChannelFullModeTimeout = TimeSpan.FromSeconds(30),
+                HeartbeatGrace = TimeSpan.FromSeconds(60),
+                HeartbeatCheckInterval = TimeSpan.FromSeconds(60),
+            });
+        await CompleteHandshakeAsync(client, pipePair);
+
+        // No StreamEvents consumer is attached, so the capacity-1 event channel fills and the event
+        // writer blocks on the second event's timed WriteAsync.
+        await pipePair.WorkerWriter.WriteAsync(
+            CreateEventEnvelope(sequence: 11, MxEventFamily.OnDataChange));
+        await pipePair.WorkerWriter.WriteAsync(
+            CreateEventEnvelope(sequence: 12, MxEventFamily.OnDataChange));
+
+        Task<WorkerCommandReply> invokeTask = client.InvokeAsync(
+            CreateCommand(MxCommandKind.Ping),
+            TestTimeout,
+            CancellationToken.None);
+        WorkerEnvelope commandEnvelope = await pipePair.WorkerReader.ReadAsync().AsTask().WaitAsync(TestTimeout);
+        await pipePair.WorkerWriter.WriteAsync(
+            CreateCommandReplyEnvelope(commandEnvelope.CorrelationId, MxCommandKind.Ping));
+
+        WorkerCommandReply reply = await invokeTask.WaitAsync(TestTimeout);
+        Assert.Equal(MxCommandKind.Ping, reply.Reply.Kind);
+        Assert.Equal(WorkerClientState.Ready, client.State);
+    }
+
     /// <summary>
     /// Verifies that when the client faults it kills the owned worker process.
     /// The assertion waits on <see cref="FakeWorkerProcess.WaitForExitAsync"/>, which
@@ -564,9 +655,13 @@ public sealed class WorkerClientTests
         WorkerClientOptions? options = null,
         GatewayMetrics? metrics = null,
         WorkerProcessHandle? processHandle = null,
-        TimeProvider? timeProvider = null)
+        TimeProvider? timeProvider = null,
+        int maxMessageBytes = WorkerFrameProtocolOptions.DefaultMaxMessageBytes)
     {
-        WorkerFrameProtocolOptions frameOptions = new(SessionId);
+        WorkerFrameProtocolOptions frameOptions = new(
+            SessionId,
+            GatewayContractInfo.WorkerProtocolVersion,
+            maxMessageBytes);
         WorkerClientConnection connection = new(
             SessionId,
             Nonce,

src/ZB.MOM.WW.MxGateway.Tests/Metrics/GatewayMetricsTests.cs

@@ -157,6 +157,56 @@ public sealed class GatewayMetricsTests
         Assert.Equal(2, capturedMode);
     }
 
+    /// <summary>
+    /// Verifies that <see cref="GatewayMetrics.HeartbeatFailed"/> increments
+    /// <c>mxgateway.heartbeats.failed</c> without emitting a <c>session_id</c> tag: the tag is
+    /// unbounded cardinality (every session mints a new exporter time series), so per-session
+    /// attribution is deliberately kept out of the exported counter (SEC-20).
+    /// </summary>
+    [Fact]
+    public void HeartbeatFailed_IncrementsCounterWithoutSessionIdTag()
+    {
+        using GatewayMetrics metrics = new();
+        using MeterListener listener = new();
+
+        long capturedValue = 0;
+        bool sawSessionIdTag = false;
+
+        listener.InstrumentPublished = (instrument, meterListener) =>
+        {
+            if (ReferenceEquals(instrument.Meter, metrics.Meter)
+                && instrument.Name == "mxgateway.heartbeats.failed")
+            {
+                meterListener.EnableMeasurementEvents(instrument);
+            }
+        };
+        listener.SetMeasurementEventCallback<long>(
+            (instrument, measurement, tags, _) =>
+            {
+                if (!ReferenceEquals(instrument.Meter, metrics.Meter)
+                    || instrument.Name != "mxgateway.heartbeats.failed")
+                {
+                    return;
+                }
+
+                capturedValue += measurement;
+                foreach (KeyValuePair<string, object?> tag in tags)
+                {
+                    if (tag.Key == "session_id")
+                    {
+                        sawSessionIdTag = true;
+                    }
+                }
+            });
+        listener.Start();
+
+        metrics.HeartbeatFailed("session-1");
+
+        Assert.Equal(1, capturedValue);
+        Assert.False(sawSessionIdTag);
+        Assert.Equal(1, metrics.GetSnapshot().HeartbeatFailures);
+    }
+
     /// <summary>Verifies that removing session events only affects that session.</summary>
     [Fact]
     public void RemoveSessionEvents_RemovesOnlyThatSession()

src/ZB.MOM.WW.MxGateway.Tests/ProjectStructure/GatewayTreeHygieneTests.cs

@@ -0,0 +1,54 @@
+namespace ZB.MOM.WW.MxGateway.Tests.ProjectStructure;
+
+/// <summary>
+/// Repo-hygiene guards over the source tree. See SEC-01: a Windows-absolute default path that
+/// resolves relative to the launch working directory silently materializes a SQLite credential
+/// store inside the tree. This test fails if any such <c>*.db</c> file appears under <c>src/</c>.
+/// </summary>
+public sealed class GatewayTreeHygieneTests
+{
+    /// <summary>Verifies no SQLite database files are committed/materialized under the source tree (build output excluded).</summary>
+    [Fact]
+    public void SourceTree_ContainsNoSqliteDatabaseFiles()
+    {
+        DirectoryInfo sourceRoot = FindSourceRoot();
+
+        string[] databaseFiles = Directory
+            .EnumerateFiles(sourceRoot.FullName, "*.db", SearchOption.AllDirectories)
+            .Where(path => !IsBuildOutput(path))
+            .ToArray();
+
+        Assert.True(
+            databaseFiles.Length == 0,
+            "Unexpected *.db file(s) found under the source tree (build output excluded): "
+            + string.Join(", ", databaseFiles)
+            + ". A SQLite DB in the tree usually means a Windows-absolute default path resolved "
+            + "relative to the working directory; see SEC-01.");
+    }
+
+    // Build output (bin/obj) is regenerated by test/compile runs and is gitignored, so exclude it.
+    private static bool IsBuildOutput(string path)
+    {
+        string normalized = path.Replace('\\', '/');
+        return normalized.Contains("/bin/", StringComparison.Ordinal)
+            || normalized.Contains("/obj/", StringComparison.Ordinal);
+    }
+
+    // The directory holding ZB.MOM.WW.MxGateway.slnx is the src/ root of the working tree.
+    private static DirectoryInfo FindSourceRoot()
+    {
+        DirectoryInfo? current = new(AppContext.BaseDirectory);
+
+        while (current is not null)
+        {
+            if (File.Exists(Path.Combine(current.FullName, "ZB.MOM.WW.MxGateway.slnx")))
+            {
+                return current;
+            }
+
+            current = current.Parent;
+        }
+
+        throw new DirectoryNotFoundException("Could not locate src/ZB.MOM.WW.MxGateway.slnx from the test output directory.");
+    }
+}

src/ZB.MOM.WW.MxGateway.Tests/Security/Authentication/ApiKeyAdminCliRunnerTests.cs

@@ -52,6 +52,40 @@ public sealed class ApiKeyAdminCliRunnerTests : IDisposable
         Assert.Contains(auditRecords, record => record.EventType == "create-key" && record.KeyId == "operator01");
     }
 
+    /// <summary>
+    /// Verifies that a key created with an already-past <c>--expires</c> is rejected by the verifier
+    /// — the CLI expiry wiring reaches the store and the library enforces it end-to-end (SEC-10).
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task CreateKeyAsync_WithPastExpiry_KeyIsRejectedByVerifier()
+    {
+        await using ServiceProvider services = BuildServices(CreateTempDatabasePath());
+        ApiKeyAdminCliRunner runner = services.GetRequiredService<ApiKeyAdminCliRunner>();
+        StringWriter output = new();
+
+        await runner.RunAsync(
+            new ApiKeyAdminCommand(
+                Kind: ApiKeyAdminCommandKind.CreateKey,
+                Json: true,
+                SqlitePath: null,
+                Pepper: null,
+                KeyId: "operator01",
+                DisplayName: "Operator",
+                Scopes: new HashSet<string>(StringComparer.Ordinal) { "session:open" },
+                Constraints: ApiKeyConstraints.Empty,
+                ExpiresUtc: DateTimeOffset.UtcNow - TimeSpan.FromMinutes(1)),
+            output,
+            CancellationToken.None);
+
+        string apiKey = ReadApiKey(output.ToString());
+
+        IApiKeyVerifier verifier = services.GetRequiredService<IApiKeyVerifier>();
+        ApiKeyVerification verification = await verifier.VerifyAsync($"Bearer {apiKey}", CancellationToken.None);
+
+        Assert.False(verification.Succeeded);
+    }
+
     /// <summary>Verifies that ListKeysAsync does not print the raw secret.</summary>
     /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]

src/ZB.MOM.WW.MxGateway.Tests/Security/Authentication/ApiKeyAdminCommandLineParserTests.cs

@@ -52,6 +52,61 @@ public sealed class ApiKeyAdminCommandLineParserTests
         Assert.Contains("events:read", result.Command.Scopes);
     }
 
+    /// <summary>A create-key command without --expires leaves the key non-expiring (opt-in, SEC-10).</summary>
+    [Fact]
+    public void Parse_CreateKeyCommand_WithoutExpires_HasNoExpiry()
+    {
+        ApiKeyAdminParseResult result = ApiKeyAdminCommandLineParser.Parse(
+            ["apikey", "create-key", "--key-id", "operator01", "--display-name", "Operator", "--scopes", "session:open"]);
+
+        Assert.NotNull(result.Command);
+        Assert.Null(result.Command.ExpiresUtc);
+    }
+
+    /// <summary>An absolute ISO-8601 --expires value is parsed to that exact UTC instant (SEC-10).</summary>
+    [Fact]
+    public void Parse_CreateKeyCommand_WithAbsoluteExpires_ParsesInstant()
+    {
+        ApiKeyAdminParseResult result = ApiKeyAdminCommandLineParser.Parse(
+            ["apikey", "create-key", "--key-id", "operator01", "--display-name", "Operator", "--scopes", "session:open",
+             "--expires", "2030-01-02T03:04:05Z"]);
+
+        Assert.NotNull(result.Command);
+        Assert.Equal(
+            new DateTimeOffset(2030, 1, 2, 3, 4, 5, TimeSpan.Zero),
+            result.Command.ExpiresUtc);
+    }
+
+    /// <summary>A relative "&lt;N&gt;d" --expires value resolves to a future UTC instant (SEC-10).</summary>
+    [Fact]
+    public void Parse_CreateKeyCommand_WithRelativeExpires_ResolvesToFuture()
+    {
+        DateTimeOffset before = DateTimeOffset.UtcNow;
+        ApiKeyAdminParseResult result = ApiKeyAdminCommandLineParser.Parse(
+            ["apikey", "create-key", "--key-id", "operator01", "--display-name", "Operator", "--scopes", "session:open",
+             "--expires", "30d"]);
+
+        Assert.NotNull(result.Command);
+        Assert.NotNull(result.Command.ExpiresUtc);
+        Assert.InRange(
+            result.Command.ExpiresUtc!.Value,
+            before + TimeSpan.FromDays(30) - TimeSpan.FromMinutes(1),
+            DateTimeOffset.UtcNow + TimeSpan.FromDays(30) + TimeSpan.FromMinutes(1));
+    }
+
+    /// <summary>An unparseable --expires value fails at parse time (SEC-10).</summary>
+    [Fact]
+    public void Parse_CreateKeyCommand_WithInvalidExpires_Fails()
+    {
+        ApiKeyAdminParseResult result = ApiKeyAdminCommandLineParser.Parse(
+            ["apikey", "create-key", "--key-id", "operator01", "--display-name", "Operator", "--scopes", "session:open",
+             "--expires", "not-a-date"]);
+
+        Assert.Null(result.Command);
+        Assert.NotNull(result.Error);
+        Assert.Contains("--expires", result.Error, StringComparison.Ordinal);
+    }
+
     /// <summary>
     ///     A create-key command with a non-canonical scope
     ///     string (e.g. CLAUDE.md's stale <c>invoke</c> instead of <c>invoke:read</c>)

src/ZB.MOM.WW.MxGateway.Tests/Security/Authentication/CachingApiKeyVerifierTests.cs

@@ -0,0 +1,201 @@
+using Microsoft.Extensions.Caching.Memory;
+using Microsoft.Extensions.Time.Testing;
+using ZB.MOM.WW.Auth.Abstractions.ApiKeys;
+using ZB.MOM.WW.MxGateway.Server.Security.Authentication;
+
+using LibApiKeyIdentity = ZB.MOM.WW.Auth.Abstractions.ApiKeys.ApiKeyIdentity;
+
+namespace ZB.MOM.WW.MxGateway.Tests.Security.Authentication;
+
+/// <summary>
+/// SEC-08 hot-path decorators. Covers both mechanisms: <see cref="CachingApiKeyVerifier"/>
+/// (read/verification coalescing plus revoke/rotate invalidation) and
+/// <see cref="CoalescingMarkApiKeyStore"/> (the <c>last_used</c> write coalescing that keeps the
+/// per-RPC database write off the throughput ceiling).
+/// </summary>
+public sealed class CachingApiKeyVerifierTests
+{
+    private const string Header = "Bearer mxgw_operator01_super-secret";
+
+    /// <summary>A cache hit within the TTL returns the cached result and never calls the inner verifier.</summary>
+    [Fact]
+    public async Task VerifyAsync_RepeatedWithinTtl_CallsInnerOnce()
+    {
+        FakeVerifier inner = new(Success("operator01"));
+        using MemoryCache cache = NewCache();
+        CachingApiKeyVerifier verifier = new(inner, cache, TimeSpan.FromSeconds(15));
+
+        ApiKeyVerification first = await verifier.VerifyAsync(Header, CancellationToken.None);
+        ApiKeyVerification second = await verifier.VerifyAsync(Header, CancellationToken.None);
+
+        Assert.True(first.Succeeded);
+        Assert.True(second.Succeeded);
+        Assert.Equal(1, inner.CallCount);
+    }
+
+    /// <summary>Different presented secrets are cached under distinct keys (no cross-secret aliasing).</summary>
+    [Fact]
+    public async Task VerifyAsync_DifferentTokens_NotAliased()
+    {
+        FakeVerifier inner = new(Success("operator01"));
+        using MemoryCache cache = NewCache();
+        CachingApiKeyVerifier verifier = new(inner, cache, TimeSpan.FromSeconds(15));
+
+        await verifier.VerifyAsync("Bearer mxgw_operator01_secret-a", CancellationToken.None);
+        await verifier.VerifyAsync("Bearer mxgw_operator01_secret-b", CancellationToken.None);
+
+        Assert.Equal(2, inner.CallCount);
+    }
+
+    /// <summary>Failed verifications are never cached; every attempt reaches the inner verifier.</summary>
+    [Fact]
+    public async Task VerifyAsync_FailedVerification_NotCached()
+    {
+        FakeVerifier inner = new(Failure(ApiKeyFailure.SecretMismatch));
+        using MemoryCache cache = NewCache();
+        CachingApiKeyVerifier verifier = new(inner, cache, TimeSpan.FromSeconds(15));
+
+        await verifier.VerifyAsync(Header, CancellationToken.None);
+        await verifier.VerifyAsync(Header, CancellationToken.None);
+
+        Assert.Equal(2, inner.CallCount);
+    }
+
+    /// <summary>A TTL of zero disables caching: the inner verifier is called on every request.</summary>
+    [Fact]
+    public async Task VerifyAsync_ZeroTtl_DisablesCache()
+    {
+        FakeVerifier inner = new(Success("operator01"));
+        using MemoryCache cache = NewCache();
+        CachingApiKeyVerifier verifier = new(inner, cache, TimeSpan.Zero);
+
+        await verifier.VerifyAsync(Header, CancellationToken.None);
+        await verifier.VerifyAsync(Header, CancellationToken.None);
+
+        Assert.Equal(2, inner.CallCount);
+    }
+
+    /// <summary>Invalidating a key id (revoke/rotate) drops its cached verification, forcing a re-verify.</summary>
+    [Fact]
+    public async Task Invalidate_DropsCachedEntry_ForcesReverify()
+    {
+        FakeVerifier inner = new(Success("operator01"));
+        using MemoryCache cache = NewCache();
+        CachingApiKeyVerifier verifier = new(inner, cache, TimeSpan.FromSeconds(30));
+
+        await verifier.VerifyAsync(Header, CancellationToken.None);
+        Assert.Equal(1, inner.CallCount);
+
+        ((IApiKeyCacheInvalidator)verifier).Invalidate("operator01");
+
+        await verifier.VerifyAsync(Header, CancellationToken.None);
+        Assert.Equal(2, inner.CallCount);
+    }
+
+    /// <summary>
+    /// The store decorator coalesces repeated <c>MarkUsed</c> writes for the same key inside the
+    /// window down to a single forwarded write — the ≤1/min guarantee for <c>last_used_utc</c>.
+    /// </summary>
+    [Fact]
+    public async Task CoalescingStore_RepeatedMarksWithinWindow_ForwardsOnce()
+    {
+        FakeStore inner = new();
+        FakeTimeProvider clock = new(DateTimeOffset.UtcNow);
+        CoalescingMarkApiKeyStore store = new(inner, TimeSpan.FromMinutes(1), clock);
+
+        // Ten rapid authenticated calls in the same minute.
+        for (int i = 0; i < 10; i++)
+        {
+            await store.MarkUsedAsync("operator01", clock.GetUtcNow(), CancellationToken.None);
+            clock.Advance(TimeSpan.FromSeconds(5));
+        }
+
+        Assert.Equal(1, inner.MarkUsedCount);
+    }
+
+    /// <summary>After the window elapses the next mark is forwarded again (staleness is bounded, not frozen).</summary>
+    [Fact]
+    public async Task CoalescingStore_AfterWindow_ForwardsAgain()
+    {
+        FakeStore inner = new();
+        FakeTimeProvider clock = new(DateTimeOffset.UtcNow);
+        CoalescingMarkApiKeyStore store = new(inner, TimeSpan.FromMinutes(1), clock);
+
+        await store.MarkUsedAsync("operator01", clock.GetUtcNow(), CancellationToken.None);
+        clock.Advance(TimeSpan.FromSeconds(61));
+        await store.MarkUsedAsync("operator01", clock.GetUtcNow(), CancellationToken.None);
+
+        Assert.Equal(2, inner.MarkUsedCount);
+    }
+
+    /// <summary>Distinct keys are coalesced independently.</summary>
+    [Fact]
+    public async Task CoalescingStore_DistinctKeys_TrackedSeparately()
+    {
+        FakeStore inner = new();
+        FakeTimeProvider clock = new(DateTimeOffset.UtcNow);
+        CoalescingMarkApiKeyStore store = new(inner, TimeSpan.FromMinutes(1), clock);
+
+        await store.MarkUsedAsync("key-a", clock.GetUtcNow(), CancellationToken.None);
+        await store.MarkUsedAsync("key-b", clock.GetUtcNow(), CancellationToken.None);
+        await store.MarkUsedAsync("key-a", clock.GetUtcNow(), CancellationToken.None);
+
+        Assert.Equal(2, inner.MarkUsedCount);
+    }
+
+    /// <summary>A zero window disables coalescing: every mark is forwarded.</summary>
+    [Fact]
+    public async Task CoalescingStore_ZeroWindow_ForwardsEveryMark()
+    {
+        FakeStore inner = new();
+        FakeTimeProvider clock = new(DateTimeOffset.UtcNow);
+        CoalescingMarkApiKeyStore store = new(inner, TimeSpan.Zero, clock);
+
+        await store.MarkUsedAsync("operator01", clock.GetUtcNow(), CancellationToken.None);
+        await store.MarkUsedAsync("operator01", clock.GetUtcNow(), CancellationToken.None);
+
+        Assert.Equal(2, inner.MarkUsedCount);
+    }
+
+    private static MemoryCache NewCache() => new(new MemoryCacheOptions());
+
+    private static ApiKeyVerification Success(string keyId) => new(
+        Succeeded: true,
+        Identity: new LibApiKeyIdentity(
+            KeyId: keyId,
+            DisplayName: "Operator Key",
+            Scopes: new HashSet<string>(StringComparer.Ordinal),
+            Constraints: null),
+        Failure: null);
+
+    private static ApiKeyVerification Failure(ApiKeyFailure failure) =>
+        new(Succeeded: false, Identity: null, Failure: failure);
+
+    private sealed class FakeVerifier(ApiKeyVerification result) : IApiKeyVerifier
+    {
+        public int CallCount { get; private set; }
+
+        public Task<ApiKeyVerification> VerifyAsync(string authorizationHeader, CancellationToken ct)
+        {
+            CallCount++;
+            return Task.FromResult(result);
+        }
+    }
+
+    private sealed class FakeStore : IApiKeyStore
+    {
+        public int MarkUsedCount { get; private set; }
+
+        public Task<ApiKeyRecord?> FindByKeyIdAsync(string keyId, CancellationToken ct)
+            => Task.FromResult<ApiKeyRecord?>(null);
+
+        public Task<ApiKeyRecord?> FindActiveByKeyIdAsync(string keyId, CancellationToken ct)
+            => Task.FromResult<ApiKeyRecord?>(null);
+
+        public Task MarkUsedAsync(string keyId, DateTimeOffset whenUtc, CancellationToken ct)
+        {
+            MarkUsedCount++;
+            return Task.CompletedTask;
+        }
+    }
+}

src/ZB.MOM.WW.MxGateway.Tests/Security/Authorization/GatewayGrpcAuthorizationInterceptorTests.cs

@@ -327,7 +327,7 @@ public sealed class GatewayGrpcAuthorizationInterceptorTests
 
         RpcException exception = await Assert.ThrowsAsync<RpcException>(
             () => interceptor.ServerStreamingServerHandler(
-                new StreamAlarmsRequest(),
+                new QueryActiveAlarmsRequest(),
                 new RecordingServerStreamWriter<ActiveAlarmSnapshot>(),
                 ContextWithAuthorization("Bearer mxgw_operator01_secret"),
                 (_, _, _) => Task.CompletedTask));
@@ -347,7 +347,7 @@ public sealed class GatewayGrpcAuthorizationInterceptorTests
         RecordingServerStreamWriter<ActiveAlarmSnapshot> streamWriter = new();
 
         await interceptor.ServerStreamingServerHandler(
-            new StreamAlarmsRequest(),
+            new QueryActiveAlarmsRequest(),
             streamWriter,
             ContextWithAuthorization("Bearer mxgw_operator01_secret"),
             async (_, writer, _) =>
@@ -358,6 +358,102 @@ public sealed class GatewayGrpcAuthorizationInterceptorTests
         Assert.Single(streamWriter.Messages);
     }
 
+    /// <summary>
+    /// SEC-11: once a peer has exceeded the failure limit, the interceptor short-circuits with
+    /// <see cref="StatusCode.ResourceExhausted"/> BEFORE calling the verifier, so an online guessing
+    /// loop stops spending a store read per attempt. A verifier that always fails is used; after the
+    /// limit is reached the verifier is no longer invoked.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task UnaryServerHandler_ExceedsFailureLimit_ShortCircuitsBeforeVerify()
+    {
+        CountingFailureVerifier verifier = new(Failure(ApiKeyFailure.SecretMismatch));
+        ApiKeyFailureLimiter limiter = new(
+            limit: 3,
+            window: TimeSpan.FromMinutes(1),
+            maxPeers: 16,
+            clock: TimeProvider.System);
+        GatewayGrpcAuthorizationInterceptor interceptor = CreateInterceptor(
+            verifier,
+            new GatewayRequestIdentityAccessor(),
+            failureLimiter: limiter);
+
+        // The first three attempts reach the verifier and fail (recording a failure each time).
+        for (int attempt = 0; attempt < 3; attempt++)
+        {
+            RpcException failure = await Assert.ThrowsAsync<RpcException>(
+                () => interceptor.UnaryServerHandler(
+                    new OpenSessionRequest(),
+                    ContextWithAuthorization("Bearer mxgw_operator01_bad-secret"),
+                    (_, _) => Task.FromResult(new OpenSessionReply())));
+            Assert.Equal(StatusCode.Unauthenticated, failure.StatusCode);
+        }
+
+        Assert.Equal(3, verifier.CallCount);
+
+        // The fourth attempt is short-circuited: ResourceExhausted, and the verifier is NOT called.
+        RpcException throttled = await Assert.ThrowsAsync<RpcException>(
+            () => interceptor.UnaryServerHandler(
+                new OpenSessionRequest(),
+                ContextWithAuthorization("Bearer mxgw_operator01_bad-secret"),
+                (_, _) => Task.FromResult(new OpenSessionReply())));
+
+        Assert.Equal(StatusCode.ResourceExhausted, throttled.StatusCode);
+        Assert.Equal(3, verifier.CallCount);
+    }
+
+    /// <summary>
+    /// SEC-11: a successful verification resets the peer's failure counter, so accumulated failures
+    /// from a fat-fingered secret do not lock out a client that subsequently authenticates.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task UnaryServerHandler_SuccessResetsFailureCounter()
+    {
+        ApiKeyFailureLimiter limiter = new(
+            limit: 3,
+            window: TimeSpan.FromMinutes(1),
+            maxPeers: 16,
+            clock: TimeProvider.System);
+
+        // Two failures against the same key id, then a success (which resets), then two more
+        // failures — without the reset the fifth attempt would be blocked at the limit of 3.
+        GatewayGrpcAuthorizationInterceptor failing = CreateInterceptor(
+            new FakeApiKeyVerifier(Failure(ApiKeyFailure.SecretMismatch)),
+            new GatewayRequestIdentityAccessor(),
+            failureLimiter: limiter);
+        GatewayGrpcAuthorizationInterceptor succeeding = CreateInterceptor(
+            new FakeApiKeyVerifier(SuccessWithScopes(GatewayScopes.SessionOpen)),
+            new GatewayRequestIdentityAccessor(),
+            failureLimiter: limiter);
+
+        for (int i = 0; i < 2; i++)
+        {
+            await Assert.ThrowsAsync<RpcException>(
+                () => failing.UnaryServerHandler(
+                    new OpenSessionRequest(),
+                    ContextWithAuthorization("Bearer mxgw_operator01_bad"),
+                    (_, _) => Task.FromResult(new OpenSessionReply())));
+        }
+
+        await succeeding.UnaryServerHandler(
+            new OpenSessionRequest(),
+            ContextWithAuthorization("Bearer mxgw_operator01_good"),
+            (_, _) => Task.FromResult(new OpenSessionReply { SessionId = "s" }));
+
+        // Post-reset: two more failures still map to Unauthenticated (not ResourceExhausted).
+        for (int i = 0; i < 2; i++)
+        {
+            RpcException ex = await Assert.ThrowsAsync<RpcException>(
+                () => failing.UnaryServerHandler(
+                    new OpenSessionRequest(),
+                    ContextWithAuthorization("Bearer mxgw_operator01_bad"),
+                    (_, _) => Task.FromResult(new OpenSessionReply())));
+            Assert.Equal(StatusCode.Unauthenticated, ex.StatusCode);
+        }
+    }
+
     private static MxAccessGatewayService CreateService(
         ISessionManager sessionManager,
         IGatewayRequestIdentityAccessor identityAccessor)
@@ -377,7 +473,8 @@ public sealed class GatewayGrpcAuthorizationInterceptorTests
     private static GatewayGrpcAuthorizationInterceptor CreateInterceptor(
         IApiKeyVerifier apiKeyVerifier,
         IGatewayRequestIdentityAccessor identityAccessor,
-        AuthenticationMode authenticationMode = AuthenticationMode.ApiKey)
+        AuthenticationMode authenticationMode = AuthenticationMode.ApiKey,
+        ApiKeyFailureLimiter? failureLimiter = null)
     {
         return new GatewayGrpcAuthorizationInterceptor(
             apiKeyVerifier,
@@ -389,7 +486,12 @@ public sealed class GatewayGrpcAuthorizationInterceptorTests
                 {
                     Mode = authenticationMode
                 }
-            }));
+            }),
+            failureLimiter ?? new ApiKeyFailureLimiter(
+                limit: 1000,
+                window: TimeSpan.FromMinutes(1),
+                maxPeers: 1000,
+                clock: TimeProvider.System));
     }
 
     private static ApiKeyVerification SuccessWithScopes(params string[] scopes)
@@ -531,6 +633,22 @@ public sealed class GatewayGrpcAuthorizationInterceptorTests
         }
     }
 
+    private sealed class CountingFailureVerifier(ApiKeyVerification result) : IApiKeyVerifier
+    {
+        /// <summary>Gets the number of times the verifier was invoked.</summary>
+        public int CallCount { get; private set; }
+
+        /// <summary>Returns the configured result and counts the invocation.</summary>
+        /// <param name="authorizationHeader">The authorization header to verify.</param>
+        /// <param name="ct">Cancellation token.</param>
+        /// <returns>The configured verification result.</returns>
+        public Task<ApiKeyVerification> VerifyAsync(string authorizationHeader, CancellationToken ct)
+        {
+            CallCount++;
+            return Task.FromResult(result);
+        }
+    }
+
     private sealed class FakeApiKeyVerifier(ApiKeyVerification result) : IApiKeyVerifier
     {
         /// <summary>Gets whether the verifier was called.</summary>

src/ZB.MOM.WW.MxGateway.Tests/TestSupport/GlobalEnvironmentCollection.cs

@@ -0,0 +1,18 @@
+namespace ZB.MOM.WW.MxGateway.Tests.TestSupport;
+
+/// <summary>
+/// xUnit collection for tests that mutate <em>process-global</em> state (environment variables
+/// read by <c>GatewayApplication.Build</c>, e.g. <c>Kestrel__Endpoints__…</c> and
+/// <c>MxGateway__Tls__SelfSignedCertPath</c>). <c>DisableParallelization</c> keeps such a test from
+/// running concurrently with any other collection: otherwise a parallel host-building test inherits
+/// the mutated variables mid-run and the two race on the same generated-certificate file (on Windows,
+/// "the process cannot access the file … because it is being used by another process"). Membership is
+/// deliberately narrow — only add classes that set/clear real environment variables, not ones that
+/// pass configuration through <c>Build([...])</c> command-line args.
+/// </summary>
+[CollectionDefinition(Name, DisableParallelization = true)]
+public sealed class GlobalEnvironmentCollection
+{
+    /// <summary>The collection name applied via <c>[Collection(GlobalEnvironmentCollection.Name)]</c>.</summary>
+    public const string Name = "GlobalEnvironmentMutation";
+}

src/ZB.MOM.WW.MxGateway.Tests/TestSupport/TestHostEnvironmentInitializer.cs

@@ -0,0 +1,51 @@
+using System.Runtime.CompilerServices;
+
+namespace ZB.MOM.WW.MxGateway.Tests.TestSupport;
+
+/// <summary>
+/// Defaults the host environment to Development and isolates the test process's on-disk
+/// gateway paths, for the whole test assembly.
+/// </summary>
+/// <remarks>
+/// Many tests build the full gateway host through <c>GatewayApplication.Build</c> against the dev
+/// <c>appsettings.json</c> (which ships <c>Ldap:Transport=None</c> and other dev-only defaults).
+/// An unset environment resolves to Production, where the SEC-04/06 production guards fail startup
+/// by design — so those host-building tests would trip the guards. Setting the environment to
+/// Development once, before any test runs, keeps that suite exercising app wiring rather than
+/// production-config validation. Tests that specifically assert production behavior construct
+/// <c>GatewayOptionsValidator</c> with its <c>isProduction</c> constructor (no host environment) and
+/// are unaffected; a test that needs Production can still pass <c>--environment=Production</c>, which
+/// overrides this default.
+/// <para>
+/// The self-signed-cert path is also defaulted to a per-process temp file. Otherwise every
+/// full-host test that triggers HTTPS-cert generation writes the shared
+/// <c>CommonApplicationData/MxGateway/certs/gateway-selfsigned.pfx</c> default — parallel xUnit
+/// test classes then collide on that path's temp file (Windows: "the process cannot access the
+/// file ... because it is being used by another process"), and on a shared CI/dev box the suite
+/// also fights the deployed gateway service for the same file. Pointing at a per-process path
+/// isolates the suite: the first host-building test generates the cert, the rest load it.
+/// </para>
+/// </remarks>
+internal static class TestHostEnvironmentInitializer
+{
+    [ModuleInitializer]
+    internal static void SetDevelopmentEnvironmentDefault()
+    {
+        if (string.IsNullOrEmpty(Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT")))
+        {
+            Environment.SetEnvironmentVariable("ASPNETCORE_ENVIRONMENT", "Development");
+        }
+
+        if (string.IsNullOrEmpty(Environment.GetEnvironmentVariable("MxGateway__Tls__SelfSignedCertPath")))
+        {
+            // ProcessId keeps the path stable within this test process (so a valid cert
+            // generated by the first host-building test is reused by the rest) yet unique
+            // across processes (so concurrent test runs / the deployed service never share it).
+            string certPath = Path.Combine(
+                Path.GetTempPath(),
+                $"mxgw-tests-{Environment.ProcessId}",
+                "gateway-selfsigned.pfx");
+            Environment.SetEnvironmentVariable("MxGateway__Tls__SelfSignedCertPath", certPath);
+        }
+    }
+}

src/ZB.MOM.WW.MxGateway.Worker.Tests/Ipc/WorkerFrameProtocolTests.cs

@@ -1,5 +1,7 @@
+using System;
 using System.IO;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 using ZB.MOM.WW.MxGateway.Contracts;
 using ZB.MOM.WW.MxGateway.Contracts.Proto;
@@ -305,6 +307,101 @@ public sealed class WorkerFrameProtocolTests
             Nonce);
     }
 
+    /// <summary>
+    /// Verifies that under concurrent writers every frame receives a distinct, gap-free sequence in
+    /// strictly increasing on-wire order — the sequence is stamped by the writer at write time, so the
+    /// wire order and the stamped sequence always agree (WRK-04).
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task WriteAsync_UnderConcurrentCalls_StampsGapFreeMonotonicSequence()
+    {
+        const int frameCount = 50;
+        WorkerFrameProtocolOptions options = CreateOptions();
+        using MemoryStream stream = new();
+        WorkerFrameWriter writer = new(stream, options);
+
+        await Task.WhenAll(
+            Enumerable.Range(0, frameCount).Select(_ => writer.WriteAsync(CreateEventEnvelope())));
+
+        stream.Position = 0;
+        WorkerFrameReader reader = new(stream, options);
+        ulong[] sequences = new ulong[frameCount];
+        for (int index = 0; index < frameCount; index++)
+        {
+            sequences[index] = (await reader.ReadAsync()).Sequence;
+        }
+
+        // On-wire order is strictly increasing 1..frameCount with no gaps or duplicates.
+        Assert.Equal(Enumerable.Range(1, frameCount).Select(value => (ulong)value), sequences);
+    }
+
+    /// <summary>
+    /// Verifies that when a control frame and an event frame are both queued behind an in-progress
+    /// write, the draining lock-holder writes the control frame first even though the event was queued
+    /// earlier (WRK-07).
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task WriteAsync_WhenControlAndEventQueuedTogether_WritesControlFirst()
+    {
+        WorkerFrameProtocolOptions options = CreateOptions();
+        using GatedWriteStream stream = new();
+        WorkerFrameWriter writer = new(stream, options);
+
+        // First write occupies the writer and blocks inside the stream, holding the write lock.
+        Task firstWrite = writer.WriteAsync(CreateGatewayHelloEnvelope(), WorkerFrameWritePriority.Control);
+        await AwaitWithTimeoutAsync(stream.FirstWriteStarted);
+
+        // Queue an event first, then a control frame, while the writer is blocked. Both wait for the lock.
+        Task eventWrite = writer.WriteAsync(CreateEventEnvelope(), WorkerFrameWritePriority.Event);
+        Task controlWrite = writer.WriteAsync(CreateGatewayHelloEnvelope(), WorkerFrameWritePriority.Control);
+        await Task.Delay(50);
+
+        stream.ReleaseFirstWrite();
+        await AwaitWithTimeoutAsync(Task.WhenAll(firstWrite, eventWrite, controlWrite));
+
+        stream.Position = 0;
+        WorkerFrameReader reader = new(stream, options);
+        WorkerEnvelope frame1 = await reader.ReadAsync();
+        WorkerEnvelope frame2 = await reader.ReadAsync();
+        WorkerEnvelope frame3 = await reader.ReadAsync();
+
+        Assert.Equal(WorkerEnvelope.BodyOneofCase.GatewayHello, frame1.BodyCase);
+        // The control frame jumped ahead of the earlier-queued event.
+        Assert.Equal(WorkerEnvelope.BodyOneofCase.GatewayHello, frame2.BodyCase);
+        Assert.Equal(WorkerEnvelope.BodyOneofCase.WorkerEvent, frame3.BodyCase);
+    }
+
+    /// <summary>Verifies a zero negotiated frame maximum keeps the constructor default (IPC-02).</summary>
+    [Fact]
+    public void AdoptNegotiatedMaxMessageBytes_WithZero_KeepsDefault()
+    {
+        WorkerFrameProtocolOptions options = CreateOptions();
+        int original = options.MaxMessageBytes;
+        options.AdoptNegotiatedMaxMessageBytes(0);
+        Assert.Equal(original, options.MaxMessageBytes);
+    }
+
+    /// <summary>Verifies an in-range negotiated frame maximum is adopted (IPC-02).</summary>
+    [Fact]
+    public void AdoptNegotiatedMaxMessageBytes_WithInRangeValue_Adopts()
+    {
+        WorkerFrameProtocolOptions options = CreateOptions();
+        options.AdoptNegotiatedMaxMessageBytes(4 * 1024 * 1024);
+        Assert.Equal(4 * 1024 * 1024, options.MaxMessageBytes);
+    }
+
+    /// <summary>Verifies a negotiated frame maximum above the worker ceiling is rejected (IPC-02).</summary>
+    [Fact]
+    public void AdoptNegotiatedMaxMessageBytes_AboveCeiling_Throws()
+    {
+        WorkerFrameProtocolOptions options = CreateOptions();
+        WorkerFrameProtocolException exception = Assert.Throws<WorkerFrameProtocolException>(
+            () => options.AdoptNegotiatedMaxMessageBytes((uint)WorkerFrameProtocolOptions.MaxNegotiableFrameBytes + 1));
+        Assert.Equal(WorkerFrameProtocolErrorCode.InvalidConfiguration, exception.ErrorCode);
+    }
+
     private static WorkerEnvelope CreateGatewayHelloEnvelope(ulong sequence = 1)
     {
         return new WorkerEnvelope
@@ -321,4 +418,63 @@ public sealed class WorkerFrameProtocolTests
         };
     }
 
+    // net48 has no Task.WaitAsync(TimeSpan); fail the test rather than hang if the writer misbehaves.
+    private static async Task AwaitWithTimeoutAsync(Task task)
+    {
+        Task completed = await Task.WhenAny(task, Task.Delay(TimeSpan.FromSeconds(5)));
+        if (completed != task)
+        {
+            throw new TimeoutException("Timed out waiting for the frame writer.");
+        }
+
+        await task;
+    }
+
+    private static WorkerEnvelope CreateEventEnvelope()
+    {
+        return new WorkerEnvelope
+        {
+            ProtocolVersion = GatewayContractInfo.WorkerProtocolVersion,
+            SessionId = SessionId,
+            WorkerEvent = new WorkerEvent
+            {
+                Event = new MxEvent { SessionId = SessionId },
+            },
+        };
+    }
+
+    // A MemoryStream whose first WriteAsync blocks until released, so a test can queue additional frames
+    // behind an in-progress write and observe the writer's priority ordering.
+    private sealed class GatedWriteStream : MemoryStream
+    {
+        private readonly SemaphoreSlim _release = new SemaphoreSlim(0);
+        private readonly TaskCompletionSource<bool> _firstWriteStarted =
+            new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
+        private int _writeCount;
+
+        public Task FirstWriteStarted => _firstWriteStarted.Task;
+
+        public void ReleaseFirstWrite() => _release.Release();
+
+        public override async Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            if (Interlocked.Increment(ref _writeCount) == 1)
+            {
+                _firstWriteStarted.TrySetResult(true);
+                await _release.WaitAsync(cancellationToken);
+            }
+
+            await base.WriteAsync(buffer, offset, count, cancellationToken);
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+                _release.Dispose();
+            }
+
+            base.Dispose(disposing);
+        }
+    }
 }

src/ZB.MOM.WW.MxGateway.Worker.Tests/Ipc/WorkerPipeSessionTests.cs

@@ -449,6 +449,44 @@ public sealed class WorkerPipeSessionTests
         await SendShutdownAndWaitAsync(pipePair, runTask, cancellation.Token);
     }
 
+    /// <summary>
+    ///     Verifies that a DrainEvents control command with <c>max_events = 0</c> is bounded by the
+    ///     worker rather than draining the entire queue into one reply frame: the session passes a
+    ///     capped, non-zero maximum to the runtime session (IPC-04).
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task RunAsync_DrainEventsWithZeroMaxEvents_BoundsTheDrain()
+    {
+        using CancellationTokenSource cancellation = new(TimeSpan.FromSeconds(5));
+        using PipePair pipePair = await PipePair.CreateAsync(cancellation.Token);
+        FakeRuntimeSession runtime = new() { SuppressDrainForBatchSize = 128 };
+        WorkerPipeSession session = CreatePipeSession(pipePair.WorkerStream, runtime);
+        runtime.EnqueueEvent(CreateWorkerEvent(sequence: 11));
+        Task runTask = session.RunAsync(cancellation.Token);
+        await CompleteGatewayHandshakeAsync(pipePair, cancellation.Token);
+
+        await pipePair.GatewayWriter
+            .WriteAsync(
+                CreateControlCommandEnvelope(
+                    "drain-cap-1",
+                    MxCommandKind.DrainEvents,
+                    command => command.DrainEvents = new DrainEventsCommand { MaxEvents = 0 }),
+                cancellation.Token);
+
+        await ReadUntilAsync(
+            pipePair.GatewayReader,
+            WorkerEnvelope.BodyOneofCase.WorkerCommandReply,
+            cancellation.Token);
+
+        // The client asked for "all" (0) but the worker must pass a bounded, non-zero cap so the reply
+        // frame cannot grow without limit.
+        Assert.NotNull(runtime.LastDrainMaxEvents);
+        Assert.NotEqual(0u, runtime.LastDrainMaxEvents!.Value);
+
+        await SendShutdownAndWaitAsync(pipePair, runTask, cancellation.Token);
+    }
+
     /// <summary>
     ///     Verifies that ShutdownWorker returns its OK reply BEFORE the graceful
     ///     shutdown runs and disposes the runtime session, and that the message

src/ZB.MOM.WW.MxGateway.Worker.Tests/TestSupport/FakeRuntimeSession.cs

@@ -125,6 +125,14 @@ internal sealed class FakeRuntimeSession : IWorkerRuntimeSession
     /// </summary>
     public uint? SuppressDrainForBatchSize { get; set; }
 
+    /// <summary>
+    ///     Records the <c>maxEvents</c> argument of the most recent non-suppressed
+    ///     <see cref="DrainEvents"/> call — i.e. the effective cap the session passed for an explicit
+    ///     DrainEvents control command. Lets a test assert the worker bounds the drain (IPC-04) rather
+    ///     than forwarding the client's raw <c>max_events = 0</c>.
+    /// </summary>
+    public uint? LastDrainMaxEvents { get; private set; }
+
     /// <inheritdoc />
     public IReadOnlyList<WorkerEvent> DrainEvents(uint maxEvents)
     {
@@ -133,6 +141,8 @@ internal sealed class FakeRuntimeSession : IWorkerRuntimeSession
             return Array.Empty<WorkerEvent>();
         }
 
+        LastDrainMaxEvents = maxEvents;
+
         lock (gate)
         {
             int drainCount = maxEvents == 0

src/ZB.MOM.WW.MxGateway.Worker/Ipc/WorkerFrameProtocolOptions.cs

@@ -10,6 +10,14 @@ public sealed class WorkerFrameProtocolOptions
     /// <summary>Default maximum message size in bytes (16 MB).</summary>
     public const int DefaultMaxMessageBytes = 16 * 1024 * 1024;
 
+    /// <summary>
+    /// Upper ceiling the worker will accept for a gateway-negotiated frame maximum
+    /// (<c>GatewayHello.max_frame_bytes</c>, IPC-02). Matches the gateway's own configuration ceiling
+    /// so a nonsensical negotiated value is rejected at the handshake rather than driving an absurd
+    /// per-frame allocation. 256 MiB.
+    /// </summary>
+    public const int MaxNegotiableFrameBytes = 256 * 1024 * 1024;
+
     /// <summary>Initializes a new instance of the WorkerFrameProtocolOptions class from WorkerOptions.</summary>
     /// <param name="options">Worker initialization options.</param>
     public WorkerFrameProtocolOptions(WorkerOptions options)
@@ -98,6 +106,36 @@ public sealed class WorkerFrameProtocolOptions
     /// <summary>Gets the nonce for startup validation.</summary>
     public string Nonce { get; }
 
-    /// <summary>Gets the maximum message size in bytes.</summary>
-    public int MaxMessageBytes { get; }
+    /// <summary>
+    /// Gets the maximum worker-frame message size in bytes. Initialized from the constructor and
+    /// then adopted once from the gateway-negotiated value during the startup handshake
+    /// (<c>GatewayHello.max_frame_bytes</c>, IPC-02) via <see cref="AdoptNegotiatedMaxMessageBytes"/>,
+    /// before the message loop starts. Not mutated afterwards, so the single-threaded handshake write
+    /// is safe for the reader/writer that share this instance.
+    /// </summary>
+    public int MaxMessageBytes { get; private set; }
+
+    /// <summary>
+    /// Adopts the gateway-negotiated frame maximum conveyed in <c>GatewayHello.max_frame_bytes</c>
+    /// (IPC-02). A value of 0 (an older gateway that never set the field) is ignored and the
+    /// constructor default is kept. A value above <see cref="MaxNegotiableFrameBytes"/> is rejected.
+    /// </summary>
+    /// <param name="negotiatedMaxFrameBytes">The gateway-negotiated maximum, or 0 for "keep default".</param>
+    internal void AdoptNegotiatedMaxMessageBytes(uint negotiatedMaxFrameBytes)
+    {
+        if (negotiatedMaxFrameBytes == 0)
+        {
+            return;
+        }
+
+        if (negotiatedMaxFrameBytes > MaxNegotiableFrameBytes)
+        {
+            throw new WorkerFrameProtocolException(
+                WorkerFrameProtocolErrorCode.InvalidConfiguration,
+                $"GatewayHello negotiated frame maximum {negotiatedMaxFrameBytes} exceeds the worker ceiling "
+                + $"of {MaxNegotiableFrameBytes} bytes.");
+        }
+
+        MaxMessageBytes = (int)negotiatedMaxFrameBytes;
+    }
 }

src/ZB.MOM.WW.MxGateway.Worker/Ipc/WorkerFrameWritePriority.cs

@@ -0,0 +1,17 @@
+namespace ZB.MOM.WW.MxGateway.Worker.Ipc;
+
+/// <summary>
+/// Relative scheduling priority for an outbound worker frame. The single writer task drains all
+/// pending <see cref="Control"/> frames before any <see cref="Event"/> frame, so a command reply,
+/// fault, heartbeat, or shutdown acknowledgement is not delayed behind a backlog of queued events
+/// (WRK-07). Priority only reorders the write; the frame sequence is stamped at actual write time,
+/// so the on-wire order and the envelope <c>Sequence</c> always agree (WRK-04).
+/// </summary>
+public enum WorkerFrameWritePriority
+{
+    /// <summary>Control-plane frame (hello, ready, command reply, heartbeat, fault, shutdown ack). Written ahead of events.</summary>
+    Control = 0,
+
+    /// <summary>Event frame. Written only when no control frame is pending.</summary>
+    Event = 1,
+}

src/ZB.MOM.WW.MxGateway.Worker/Ipc/WorkerFrameWriter.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
@@ -7,12 +8,40 @@ using ZB.MOM.WW.MxGateway.Contracts.Proto;
 
 namespace ZB.MOM.WW.MxGateway.Worker.Ipc;
 
-/// <summary>Writes worker frames to a stream with length-prefixed protobuf serialization.</summary>
+/// <summary>
+/// Writes worker frames to a stream with length-prefixed protobuf serialization. Callers enqueue a
+/// frame at a <see cref="WorkerFrameWritePriority"/> and then contend for a single write lock; whoever
+/// holds the lock drains every queued frame, control frames first, so a reply, fault, or heartbeat is
+/// never delayed behind an event backlog (WRK-07). The envelope <c>Sequence</c> is stamped by the
+/// draining lock-holder at the moment of writing, so the on-wire order and the stamped sequence always
+/// agree even under concurrent callers and priority reordering (WRK-04).
+/// </summary>
 public sealed class WorkerFrameWriter
 {
+    private sealed class PendingFrame
+    {
+        public PendingFrame(WorkerEnvelope envelope)
+        {
+            Envelope = envelope;
+            Completion = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
+        }
+
+        public WorkerEnvelope Envelope { get; }
+
+        public TaskCompletionSource<bool> Completion { get; }
+    }
+
     private readonly WorkerFrameProtocolOptions _options;
-    private readonly SemaphoreSlim _writeLock = new(1, 1);
+    private readonly SemaphoreSlim _writeLock = new SemaphoreSlim(1, 1);
     private readonly Stream _stream;
+    private readonly object _gate = new object();
+    private readonly Queue<PendingFrame> _controlFrames = new Queue<PendingFrame>();
+    private readonly Queue<PendingFrame> _eventFrames = new Queue<PendingFrame>();
+
+    // Only ever read/written by the current write-lock holder while draining, so no interlock is
+    // needed. Starts at 0 and is pre-incremented, so the first written frame carries sequence 1
+    // (matching the previous behaviour).
+    private ulong _nextSequence;
 
     /// <summary>Initializes a new instance of the WorkerFrameWriter class.</summary>
     /// <param name="stream">Stream to write frames to.</param>
@@ -25,12 +54,25 @@ public sealed class WorkerFrameWriter
         _options = options ?? throw new ArgumentNullException(nameof(options));
     }
 
-    /// <summary>Writes a worker envelope frame to the stream with length prefix.</summary>
+    /// <summary>Writes a control-priority worker envelope frame to the stream with length prefix.</summary>
     /// <param name="envelope">Worker envelope to write.</param>
     /// <param name="cancellationToken">Token to cancel the asynchronous operation.</param>
-    /// <returns>A task that represents the asynchronous operation.</returns>
+    /// <returns>A task that completes when the frame has been written and flushed.</returns>
+    public Task WriteAsync(
+        WorkerEnvelope envelope,
+        CancellationToken cancellationToken = default)
+    {
+        return WriteAsync(envelope, WorkerFrameWritePriority.Control, cancellationToken);
+    }
+
+    /// <summary>Queues a worker envelope frame for writing at the given priority and drains the queue.</summary>
+    /// <param name="envelope">Worker envelope to write.</param>
+    /// <param name="priority">Scheduling priority; control frames are written ahead of event frames.</param>
+    /// <param name="cancellationToken">Token to cancel waiting for the write lock.</param>
+    /// <returns>A task that completes when the frame has been written and flushed.</returns>
     public async Task WriteAsync(
         WorkerEnvelope envelope,
+        WorkerFrameWritePriority priority,
         CancellationToken cancellationToken = default)
     {
         if (envelope is null)
@@ -38,8 +80,120 @@ public sealed class WorkerFrameWriter
             throw new ArgumentNullException(nameof(envelope));
         }
 
+        PendingFrame frame = new PendingFrame(envelope);
+        lock (_gate)
+        {
+            if (priority == WorkerFrameWritePriority.Event)
+            {
+                _eventFrames.Enqueue(frame);
+            }
+            else
+            {
+                _controlFrames.Enqueue(frame);
+            }
+        }
+
+        // Contend for the single writer: whoever wins drains every currently-queued frame in priority
+        // order, so this frame is written by this call or by a concurrent caller that got the lock
+        // first. Either way it completes via its own TaskCompletionSource.
+        await _writeLock.WaitAsync(cancellationToken).ConfigureAwait(false);
+        try
+        {
+            await DrainQueuedFramesAsync().ConfigureAwait(false);
+        }
+        finally
+        {
+            _writeLock.Release();
+        }
+
+        await frame.Completion.Task.ConfigureAwait(false);
+    }
+
+    // Runs only under _writeLock. Drains control frames before event frames, stamping and writing each.
+    // The stream write itself is not cancellable: a frame is written atomically or fails, never left
+    // half-written on the pipe because a caller gave up waiting.
+    private async Task DrainQueuedFramesAsync()
+    {
+        while (true)
+        {
+            PendingFrame? frame = DequeueNext();
+            if (frame is null)
+            {
+                return;
+            }
+
+            try
+            {
+                await WriteFrameAsync(frame.Envelope).ConfigureAwait(false);
+                frame.Completion.TrySetResult(true);
+            }
+            catch (WorkerFrameProtocolException exception) when (IsPerFrameRejection(exception))
+            {
+                // Validation, empty-payload, and oversized-frame errors are specific to this frame and
+                // do not damage the stream; fail only this frame and keep draining the rest.
+                frame.Completion.TrySetException(exception);
+            }
+            catch (Exception exception)
+            {
+                // A stream write/flush failure means the pipe is broken; fail this frame and every frame
+                // still queued so no caller awaits forever, then stop draining.
+                frame.Completion.TrySetException(exception);
+                FailAllQueued(exception);
+                return;
+            }
+        }
+    }
+
+    private static bool IsPerFrameRejection(WorkerFrameProtocolException exception)
+    {
+        return exception.ErrorCode is WorkerFrameProtocolErrorCode.InvalidEnvelope
+            or WorkerFrameProtocolErrorCode.MessageTooLarge
+            or WorkerFrameProtocolErrorCode.ProtocolVersionMismatch
+            or WorkerFrameProtocolErrorCode.SessionMismatch;
+    }
+
+    private PendingFrame? DequeueNext()
+    {
+        lock (_gate)
+        {
+            if (_controlFrames.Count > 0)
+            {
+                return _controlFrames.Dequeue();
+            }
+
+            if (_eventFrames.Count > 0)
+            {
+                return _eventFrames.Dequeue();
+            }
+
+            return null;
+        }
+    }
+
+    private void FailAllQueued(Exception exception)
+    {
+        lock (_gate)
+        {
+            while (_controlFrames.Count > 0)
+            {
+                _controlFrames.Dequeue().Completion.TrySetException(exception);
+            }
+
+            while (_eventFrames.Count > 0)
+            {
+                _eventFrames.Dequeue().Completion.TrySetException(exception);
+            }
+        }
+    }
+
+    private async Task WriteFrameAsync(WorkerEnvelope envelope)
+    {
         WorkerEnvelopeValidator.Validate(envelope, _options);
 
+        // Stamp the sequence at the actual point of writing, under the write lock, so the wire order
+        // and the stamped sequence agree regardless of caller concurrency or priority (WRK-04).
+        envelope.Sequence = unchecked(++_nextSequence);
+
         int payloadLength = envelope.CalculateSize();
         if (payloadLength == 0)
         {
@@ -55,26 +209,16 @@ public sealed class WorkerFrameWriter
                 $"Worker envelope payload length {payloadLength} exceeds the configured maximum of {_options.MaxMessageBytes} bytes.");
         }
 
-        // Serialize once into a single buffer that carries the 4-byte
-        // length prefix followed by the payload, then issue one stream write.
-        // This avoids a second serialization pass (envelope.ToByteArray()
-        // would re-run CalculateSize internally), a separate prefix array,
-        // and a separate prefix write.
+        // Serialize once into a single buffer that carries the 4-byte length prefix followed by the
+        // payload, then issue one stream write. This avoids a second serialization pass, a separate
+        // prefix array, and a separate prefix write.
         int frameLength = sizeof(uint) + payloadLength;
         byte[] frame = new byte[frameLength];
         WriteUInt32LittleEndian(frame, (uint)payloadLength);
         envelope.WriteTo(new Span<byte>(frame, sizeof(uint), payloadLength));
 
-        await _writeLock.WaitAsync(cancellationToken).ConfigureAwait(false);
-        try
-        {
-            await _stream.WriteAsync(frame, 0, frameLength, cancellationToken).ConfigureAwait(false);
-            await _stream.FlushAsync(cancellationToken).ConfigureAwait(false);
-        }
-        finally
-        {
-            _writeLock.Release();
-        }
+        await _stream.WriteAsync(frame, 0, frameLength, CancellationToken.None).ConfigureAwait(false);
+        await _stream.FlushAsync(CancellationToken.None).ConfigureAwait(false);
     }
 
     private static void WriteUInt32LittleEndian(

src/ZB.MOM.WW.MxGateway.Worker/Ipc/WorkerPipeSession.cs

@@ -18,6 +18,13 @@ public sealed class WorkerPipeSession
     private static readonly TimeSpan BackgroundTaskStopTimeout = TimeSpan.FromSeconds(1);
     private const uint EventDrainBatchSize = 128;
 
+    // Hard cap on how many events a single DrainEvents diagnostic reply may carry. DrainEvents is a
+    // non-streaming control command, so an unbounded drain (including the max_events = 0 "as many as
+    // available" request) could pack the whole queue into one session-killing reply frame (IPC-04).
+    // The gateway request validator rejects requests above its public ceiling; this worker-side cap is
+    // the backstop and defines the effective per-reply maximum. Kept in step with that public ceiling.
+    private const uint MaxDrainEventsPerReply = 10_000;
+
     private readonly WorkerFrameProtocolOptions _options;
     private readonly Func<int> _processIdProvider;
     private readonly Func<IWorkerRuntimeSession> _runtimeSessionFactory;
@@ -28,7 +35,6 @@ public sealed class WorkerPipeSession
     private readonly object _commandTaskGate = new();
     private readonly HashSet<Task> _activeCommandTasks = new();
     private IWorkerRuntimeSession? _runtimeSession;
-    private long _nextSequence;
 
     // Mutated from the message loop, command tasks, the heartbeat loop and the
     // shutdown path; volatile so cross-thread reads observe the latest state
@@ -225,6 +231,12 @@ public sealed class WorkerPipeSession
                 WorkerFrameProtocolErrorCode.NonceMismatch,
                 "GatewayHello nonce does not match the worker launch nonce.");
         }
+
+        // Adopt the gateway-negotiated frame maximum so both ends frame to the same limit instead of
+        // matched compile-time defaults (IPC-02). Applied here, before the message loop, so every
+        // post-handshake frame is validated against the negotiated value; the reader and writer share
+        // this options instance. The hello frame itself was small and already read under the default.
+        _options.AdoptNegotiatedMaxMessageBytes(gatewayHello.MaxFrameBytes);
     }
 
     private Task WriteWorkerHelloAsync(CancellationToken cancellationToken)
@@ -361,8 +373,11 @@ public sealed class WorkerPipeSession
 
             foreach (WorkerEvent workerEvent in events)
             {
+                // Events are the low-priority frame class: the writer holds them behind any pending
+                // control frame (reply, fault, heartbeat, shutdown ack) so those are not delayed
+                // behind an event backlog (WRK-07).
                 await _writer
-                    .WriteAsync(CreateEnvelope(workerEvent), cancellationToken)
+                    .WriteAsync(CreateEnvelope(workerEvent), WorkerFrameWritePriority.Event, cancellationToken)
                     .ConfigureAwait(false);
             }
         }
@@ -527,7 +542,12 @@ public sealed class WorkerPipeSession
         IWorkerRuntimeSession? runtimeSession = _runtimeSession;
         if (runtimeSession is not null)
         {
-            uint maxEvents = command.DrainEvents?.MaxEvents ?? 0;
+            // Bound the diagnostic drain so max_events = 0 ("as many as available") or an over-large
+            // request cannot pack the whole queue into one session-killing reply frame (IPC-04).
+            uint requested = command.DrainEvents?.MaxEvents ?? 0;
+            uint maxEvents = requested == 0 || requested > MaxDrainEventsPerReply
+                ? MaxDrainEventsPerReply
+                : requested;
             foreach (WorkerEvent workerEvent in runtimeSession.DrainEvents(maxEvents))
             {
                 if (workerEvent.Event is not null)
@@ -1004,19 +1024,16 @@ public sealed class WorkerPipeSession
 
     private WorkerEnvelope CreateBaseEnvelope()
     {
+        // Sequence is deliberately left unset here: the frame writer stamps it at the actual point of
+        // writing, under its single drain task, so the on-wire order and the stamped sequence agree
+        // even under concurrent producers and priority reordering (WRK-04).
         return new WorkerEnvelope
         {
             ProtocolVersion = _options.ProtocolVersion,
             SessionId = _options.SessionId,
-            Sequence = NextSequence(),
         };
     }
 
-    private ulong NextSequence()
-    {
-        return unchecked((ulong)Interlocked.Increment(ref _nextSequence));
-    }
-
     private async Task<WorkerReady> InitializeMxAccessAsync(CancellationToken cancellationToken)
     {
         // RunAsync constructs the runtime session via _runtimeSessionFactory()