Phase 3 PR 36 — AVEVA prerequisites test-support library. New tests/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.TestSupport multi-targeted class library (net10.0 + net48 so both the modern and the MXAccess-COM x86 test projects can consume it) that probes every piece of the AVEVA System Platform + OtOpcUa stack a live-Galaxy test depends on and returns a structured PrerequisiteReport. Closes the gap where live-smoke tests silently returned 'unreachable' without telling operators which specific piece failed.

AvevaPrerequisites.CheckAllAsync walks eight probe categories producing PrerequisiteCheck rows each with Name (e.g. 'service:aaBootstrap', 'sql:ZB', 'com:LMXProxy', 'registry:ArchestrA.Framework'), Category (AvevaCoreService / AvevaSoftService / AvevaInstall / MxAccessCom / GalaxyRepository / AvevaHistorian / OtOpcUaService / Environment), Status (Pass / Warn / Fail / Skip), and operator-facing Detail message. Report aggregates them: IsLivetestReady (no Fails anywhere) and IsAvevaSideReady (AVEVA-side categories pass, our v2 services can be absent while still considering the environment AVEVA-ready) so different test tiers can use the right threshold.
Individual probes: ServiceProbe.Check queries the Windows Service Control Manager via System.ServiceProcess.ServiceController — treats DemandStart+Stopped as Warn (NmxSvc is DemandStart by design; master pulls it up) but AutoStart+Stopped as Fail; not-installed is Fail for hard-required services, Warn for soft ones; non-Windows hosts get Skip; transitional states like StartPending get Warn with a 'try again' hint. RegistryProbe reads HKLM\SOFTWARE\WOW6432Node\ArchestrA\{Framework,Framework\Platform,MSIInstall} — Framework key presence + populated InstallPath/RootPath values mean System Platform installed; PfeConfigOptions in the Platform subkey (format 'PlatformId=N,EngineId=N,...') indicates a Platform has been deployed from the IDE (PlatformId=0 means never deployed — MXAccess will connect but every subscription will be Bad quality); RebootRequired='True' under MSIInstall surfaces as a loud warn since post-patch behavior is undefined. MxAccessComProbe resolves the LMXProxy.LMXProxyServer ProgID → CLSID → HKLM\SOFTWARE\Classes\WOW6432Node\CLSID\{guid}\InprocServer32, verifying the registered file exists on disk (catches the orphan-registry case where a previous uninstall left the ProgID registered but the DLL is gone — distinguishes it from the 'totally not installed' case by message); also emits a Warn when the test process is 64-bit (MXAccess COM activation fails with REGDB_E_CLASSNOTREG 0x80040154 regardless of registration, so seeing this warning tells operators why the activation would fail even on a fully-installed machine). SqlProbe tests Galaxy Repository via Microsoft.Data.SqlClient using the Windows-auth localhost connection string the repo code defaults to — distinguishes 'SQL Server unreachable' (connection fails) from 'ZB database does not exist' (SELECT DB_ID('ZB') returns null) because they have different remediation paths (sc.exe start MSSQLSERVER vs. restore from .cab backup); a secondary CheckDeployedObjectCountAsync query on 'gobject WHERE deployed_version > 0' warns when the count is zero because discovery smoke tests will return empty hierarchies. NamedPipeProbe opens a 2s NamedPipeClientStream against OtOpcUaGalaxyHost's pipe ('OtOpcUaGalaxy' per the installer default) — pipe accepting a connection proves the Host service is listening; disconnects immediately so we don't consume a session slot.
Service lists kept as internal static data so tests can inspect + override: CoreServices (aaBootstrap + aaGR + NmxSvc + MSSQLSERVER — hard fail if missing), SoftServices (aaLogger + aaUserValidator + aaGlobalDataCacheMonitorSvr — warn only; stack runs without them but diagnostics/auth are degraded), HistorianServices (aahClientAccessPoint + aahGateway — opt-in via Options.CheckHistorian, only matters for HistoryRead IPC paths), OtOpcUaServices (our OtOpcUaGalaxyHost hard-required for end-to-end live tests + OtOpcUa warn + GLAuth warn). Narrower entry points CheckRepositoryOnlyAsync and CheckGalaxyHostPipeOnlyAsync for tests that only care about specific subsystems — avoid paying the full probe cost on every GalaxyRepositoryLiveSmokeTests fact.
Multi-targeting mechanics: System.ServiceProcess.ServiceController + Microsoft.Win32.Registry are NuGet packages on net10 but in-box BCL references on net48; csproj conditions Package vs Reference by TargetFramework. Microsoft.Data.SqlClient v6 supports both frameworks so single PackageReference. Net48Polyfills.cs provides IsExternalInit shim (records/init-only setters) and SupportedOSPlatformAttribute stub so the same Probe sources compile on both frameworks without per-callsite preprocessor guards — lets Roslyn's platform-compatibility analyzer stay useful on net10 without breaking net48 builds.
Existing GalaxyRepositoryLiveSmokeTests updated to delegate its skip decision to AvevaPrerequisites.CheckRepositoryOnlyAsync (legacy ZbReachableAsync kept as a compatibility adapter so the in-test 'if (!await ZbReachableAsync()) return;' pattern keeps working while the surrounding fixtures gradually migrate to Assert.Skip-with-reason). Slnx file registers the new project.
Tests — AvevaPrerequisitesLiveTests (8 new Integration cases, Category=LiveGalaxy): the helper correctly reports Framework install (registry pass), aaBootstrap Running (service pass), aaGR Running (service pass), MxAccess COM registered (com pass), ZB database reachable (sql pass), deployed-object count > 0 (warn-upgraded-to-pass because this box has 49 objects deployed), the AVEVA side is ready even when our own services (OtOpcUaGalaxyHost) aren't installed yet (IsAvevaSideReady=true), and the helper emits rows for OtOpcUaGalaxyHost + OtOpcUa + GLAuth even when not installed (regression guard — nobody can accidentally ship a check that omits our own services). Full Galaxy.Host.Tests Category=LiveGalaxy suite: 13 pass (5 prior smoke + 8 new prerequisites). Full solution build clean, 0 errors.
What's NOT in this PR: end-to-end Galaxy stack smoke (Proxy → Host pipe → MXAccess → real Galaxy tag). That's the next PR — this one is the gate the end-to-end smoke will call first to produce actionable skip messages instead of silent returns.

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

tests/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.TestSupport/PrerequisiteCheck.cs

@@ -0,0 +1,44 @@
+namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.TestSupport;
+
+/// <summary>One prerequisite probe's outcome. <see cref="AvevaPrerequisites"/> returns many of these.</summary>
+/// <param name="Name">Short diagnostic id — e.g. <c>service:aaBootstrap</c>, <c>sql:ZB</c>, <c>registry:ArchestrA.Framework</c>.</param>
+/// <param name="Category">Which subsystem the probe belongs to — lets callers filter (e.g. "Historian warns don't gate the core Galaxy smoke").</param>
+/// <param name="Status">Outcome.</param>
+/// <param name="Detail">One-line specific message an operator can act on — <c>"aaGR not installed — install the Galaxy Repository role from the System Platform setup"</c> beats <c>"failed"</c>.</param>
+public sealed record PrerequisiteCheck(
+    string Name,
+    PrerequisiteCategory Category,
+    PrerequisiteStatus Status,
+    string Detail);
+
+public enum PrerequisiteStatus
+{
+    /// <summary>Prerequisite is met; no action needed.</summary>
+    Pass,
+    /// <summary>Soft dependency missing — stack still runs but some feature (e.g. logging) is degraded.</summary>
+    Warn,
+    /// <summary>Hard dependency missing — live tests can't proceed; <see cref="PrerequisiteReport.SkipReason"/> surfaces this.</summary>
+    Fail,
+    /// <summary>Probe wasn't applicable in this environment (e.g. non-Windows host, Historian not installed).</summary>
+    Skip,
+}
+
+public enum PrerequisiteCategory
+{
+    /// <summary>Platform sanity — process bitness, OS platform, DCOM/RPCSS.</summary>
+    Environment,
+    /// <summary>Hard-required AVEVA Windows services (aaBootstrap, aaGR, NmxSvc).</summary>
+    AvevaCoreService,
+    /// <summary>Soft-required AVEVA Windows services (aaLogger, aaUserValidator) — warn only.</summary>
+    AvevaSoftService,
+    /// <summary>ArchestrA Framework install markers (registry + files).</summary>
+    AvevaInstall,
+    /// <summary>MXAccess COM server registration + file on disk.</summary>
+    MxAccessCom,
+    /// <summary>SQL Server reachability + ZB database presence + deployed-object count.</summary>
+    GalaxyRepository,
+    /// <summary>Historian services (optional — only required for HistoryRead IPC paths).</summary>
+    AvevaHistorian,
+    /// <summary>OtOpcUa-side services (OtOpcUa, OtOpcUaGalaxyHost) + third-party deps (GLAuth).</summary>
+    OtOpcUaService,
+}