Phase 3 PR 37 — End-to-end live-stack Galaxy smoke test. Closes the code side of LMX follow-up #5; once OtOpcUaGalaxyHost is installed + started on the dev box, the suite exercises the full topology GalaxyProxyDriver in-process → named-pipe IPC → running OtOpcUaGalaxyHost Windows service → MxAccessGalaxyBackend → live MXAccess runtime → real deployed Galaxy objects. Never spawns the Host process itself — connects to the already-running service per project_galaxy_host_service.md, which is the only way to exercise the production COM-apartment + service-account + pipe-ACL configuration.

LiveStackConfig resolves the pipe name + per-install shared secret from two sources in order: OTOPCUA_GALAXY_PIPE + OTOPCUA_GALAXY_SECRET env vars first (for CI / benchwork overrides), then the service's per-process Environment registry values under HKLM\SYSTEM\CurrentControlSet\Services\OtOpcUaGalaxyHost (what Install-Services.ps1 writes at install time). Registry read requires the test host to run elevated on most boxes — the skip message says so explicitly so operators see the right remediation. Hard-coded secrets are deliberately avoided: the installer generates 32 fresh random bytes per install, a committed secret would diverge from production the moment the service is re-installed.
LiveStackFixture is an IAsyncLifetime that (1) runs AvevaPrerequisites.CheckAllAsync with CheckGalaxyHostPipe=true + CheckHistorian=false — produces a structured PrerequisiteReport whose SkipReason is the exact operator-facing 'here's what you need to fix' text, (2) resolves LiveStackConfig and surfaces a clear skip when the secret isn't discoverable, (3) instantiates GalaxyProxyDriver + calls InitializeAsync (the IPC handshake), capturing a skip with the exception detail + common-cause hints (secret mismatch, SID not in pipe ACL, Host's backend couldn't connect to ZB) rather than letting a NullRef cascade through every subsequent test. SkipIfUnavailable() translates the captured SkipReason into Assert.Skip at the top of every fact so tests read as cleanly-skipped with a visible reason, not silently-passed or crashed.
LiveStackSmokeTests (5 facts, Collection=LiveStack, Category=LiveGalaxy): Fixture_initialized_successfully (cheapest possible end-to-end assertion — if this passes, the IPC handshake worked); Driver_reports_Healthy_after_IPC_handshake (DriverHealth.State post-connect); DiscoverAsync_returns_at_least_one_variable_from_live_galaxy (captures every Variable() call from DiscoverAsync via CapturingAddressSpaceBuilder and asserts > 0 — zero here usually means the Host couldn't read ZB, the skip message names OTOPCUA_GALAXY_ZB_CONN to check); GetHostStatuses_reports_at_least_one_platform (IHostConnectivityProbe surface — zero means the probe loop hasn't fired or no Platform is deployed locally); Can_read_a_discovered_variable_from_live_galaxy (reads the first discovered attribute's full reference, asserts status != BadInternalError — Galaxy's Uncertain-quality-until-first-Engine-scan is intentionally NOT treated as failure since it depends on runtime state that varies across test runs). Read-only by design; writes need an agreed scratch tag to avoid mutating a process-critical attribute — deferred to a follow-up PR that reuses this fixture.
CapturingAddressSpaceBuilder is a minimal IAddressSpaceBuilder that flattens every Variable() call into a list so tests can inspect what discovery produced without booting the full OPC UA node-manager stack; alarm annotation + property calls are no-ops. Scoped private to the test class.
Galaxy.Proxy.Tests csproj gains a ProjectReference to Driver.Galaxy.TestSupport (PR 36) for AvevaPrerequisites. The NU1702 warning about the Host project being net48-referenced-by-net10 is pre-existing from the HostSubprocessParityTests — Proxy.Tests only needs the Host EXE path for that parity scenario, not type surface.
Test run on THIS machine (OtOpcUaGalaxyHost not yet installed): Skipped! Failed 0, Passed 0, Skipped 5 — each skip message includes the full prerequisites report pointing at the missing service. Once the service is installed + started (scripts\install\Install-Services.ps1), the 5 facts will execute against live Galaxy. Proxy.Tests Unit: 17 pass / 0 fail (unchanged — new tests are Category=LiveGalaxy, separate suite). Full Proxy build clean. Memory already captures the 'live tests run via already-running service, don't spawn' convention (project_galaxy_host_service.md).
lmx-followups.md #5 updated: status is 'IN PROGRESS' across PRs 36 + 37 with the explicit remaining work (install + start services, subscribe-and-receive, write round-trip).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/v2/lmx-followups.md

@@ -77,18 +77,36 @@ drive a full OPC UA session with username/password, then read an
 `IHostConnectivityProbe`-style "whoami" node to verify the role surfaced).
 That needs a test-only address-space node and is a separate PR.
 
-## 5. Full Galaxy live-service smoke test against the merged v2 stack
+## 5. Full Galaxy live-service smoke test against the merged v2 stack — **IN PROGRESS (PRs 36 + 37)**
 
-**Status**: Individual pieces have live smoke tests (PR 5 MXAccess, PR 13
-probe manager, PR 14 alarm tracker), but the full loop — OPC UA client →
-`OtOpcUaServer` → `GalaxyProxyDriver` (in-process) → named-pipe to
-Galaxy.Host subprocess → live MXAccess runtime → real Galaxy objects — has
-no single end-to-end smoke test.
+PR 36 shipped the prerequisites helper (`AvevaPrerequisites`) that probes
+every dependency a live smoke test needs and produces actionable skip
+messages.
 
-**To do**:
-- Test that spawns the full topology, discovers a deployed Galaxy object,
-  subscribes to one of its attributes, writes a value back, and asserts the
-  write round-tripped through MXAccess. Skip when ArchestrA isn't running.
+PR 37 shipped the live-stack smoke test project structure:
+`tests/Driver.Galaxy.Proxy.Tests/LiveStack/` with `LiveStackFixture` (connects
+to the *already-running* `OtOpcUaGalaxyHost` Windows service via named pipe;
+never spawns the Host process) and `LiveStackSmokeTests` covering:
+
+- Fixture initializes successfully (IPC handshake succeeds end-to-end).
+- Driver reports `DriverState.Healthy` post-handshake.
+- `DiscoverAsync` returns at least one variable from the live Galaxy.
+- `GetHostStatuses` reports at least one Platform/AppEngine host.
+- `ReadAsync` on a discovered variable round-trips through
+  Proxy → Host pipe → MXAccess → back without a BadInternalError.
+
+Shared secret + pipe name resolve from `OTOPCUA_GALAXY_SECRET` /
+`OTOPCUA_GALAXY_PIPE` env vars, falling back to reading the service's
+registry-stored Environment values (requires elevated test host).
+
+**Remaining**:
+- Install + run the `OtOpcUaGalaxyHost` + `OtOpcUa` services on the dev box
+  (`scripts/install/Install-Services.ps1`) so the skip-on-unready tests
+  actually execute and the smoke PR lands green.
+- Subscribe-and-receive-data-change fact (needs a known tag that actually
+  ticks; deferred until operators confirm a scratch tag exists).
+- Write-and-roundtrip fact (needs a test-only UDA or agreed scratch tag
+  so we can't accidentally mutate a process-critical value).
 
 ## 6. Second driver instance on the same server — **DONE (PR 32)**