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/Probes/MxAccessComProbe.cs

@@ -0,0 +1,102 @@
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.TestSupport.Probes;
+
+/// <summary>
+///     Confirms MXAccess COM server registration by resolving the
+///     <c>LMXProxy.LMXProxyServer</c> ProgID to its CLSID, then checking that the CLSID's
+///     32-bit <c>InprocServer32</c> entry points at a file that exists on disk.
+/// </summary>
+/// <remarks>
+///     A common failure mode on partial installs: ProgID is registered but the CLSID
+///     InprocServer32 DLL is missing (previous install uninstalled but registry orphan remains).
+///     This probe surfaces that case with an actionable message instead of the
+///     <c>0x80040154 REGDB_E_CLASSNOTREG</c> you'd see from a late COM activation failure.
+/// </remarks>
+public static class MxAccessComProbe
+{
+    public const string ProgId = "LMXProxy.LMXProxyServer";
+    public const string VersionedProgId = "LMXProxy.LMXProxyServer.1";
+
+    public static PrerequisiteCheck Check()
+    {
+        if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+        {
+            return new PrerequisiteCheck("com:LMXProxy", PrerequisiteCategory.MxAccessCom,
+                PrerequisiteStatus.Skip, "COM registration probes only run on Windows.");
+        }
+        return CheckWindows();
+    }
+
+    [SupportedOSPlatform("windows")]
+    private static PrerequisiteCheck CheckWindows()
+    {
+        try
+        {
+            var (clsid, dll) = RegistryProbe.ResolveProgIdToInproc(ProgId);
+            if (clsid is null)
+            {
+                return new PrerequisiteCheck("com:LMXProxy", PrerequisiteCategory.MxAccessCom,
+                    PrerequisiteStatus.Fail,
+                    $"ProgID {ProgId} not registered — MXAccess COM server isn't installed. " +
+                    $"Install System Platform's MXAccess component and re-run.");
+            }
+
+            if (string.IsNullOrWhiteSpace(dll))
+            {
+                return new PrerequisiteCheck("com:LMXProxy", PrerequisiteCategory.MxAccessCom,
+                    PrerequisiteStatus.Fail,
+                    $"ProgID {ProgId} → CLSID {clsid} but InprocServer32 is empty. " +
+                    $"Registry is orphaned; re-register with: regsvr32 /s LmxProxy.dll (from an elevated cmd in the Framework bin dir).");
+            }
+
+            // Resolve the recorded path — sometimes registered as a bare filename that the COM
+            // runtime resolves via the current process's DLL-search path. Accept either an
+            // absolute path that exists, or a bare filename whose resolution we can't verify
+            // without loading it (treat as Pass-with-note).
+            if (Path.IsPathRooted(dll))
+            {
+                if (!File.Exists(dll))
+                {
+                    return new PrerequisiteCheck("com:LMXProxy", PrerequisiteCategory.MxAccessCom,
+                        PrerequisiteStatus.Fail,
+                        $"ProgID {ProgId} → CLSID {clsid} → InprocServer32 {dll}, but the file is missing. " +
+                        $"Re-install the Framework or restore from backup.");
+                }
+                return new PrerequisiteCheck("com:LMXProxy", PrerequisiteCategory.MxAccessCom,
+                    PrerequisiteStatus.Pass,
+                    $"ProgID {ProgId} → {dll} (file exists).");
+            }
+
+            return new PrerequisiteCheck("com:LMXProxy", PrerequisiteCategory.MxAccessCom,
+                PrerequisiteStatus.Pass,
+                $"ProgID {ProgId} → {dll} (bare filename — relies on PATH resolution at COM activation time).");
+        }
+        catch (Exception ex)
+        {
+            return new PrerequisiteCheck("com:LMXProxy", PrerequisiteCategory.MxAccessCom,
+                PrerequisiteStatus.Warn,
+                $"Probe failed: {ex.GetType().Name}: {ex.Message}");
+        }
+    }
+
+    /// <summary>
+    ///     Warn when running as a 64-bit process — MXAccess COM activation will fail with
+    ///     <c>0x80040154</c> regardless of registration state. The production drivers run net48
+    ///     x86; xunit hosts run 64-bit by default so this often surfaces first.
+    /// </summary>
+    public static PrerequisiteCheck CheckProcessBitness()
+    {
+        if (Environment.Is64BitProcess)
+        {
+            return new PrerequisiteCheck("env:ProcessBitness", PrerequisiteCategory.Environment,
+                PrerequisiteStatus.Warn,
+                "Test host is 64-bit. Direct MXAccess COM activation would fail with REGDB_E_CLASSNOTREG (0x80040154); " +
+                "the production driver workaround is to run Galaxy.Host as a 32-bit process. Tests that only " +
+                "talk to the Host service over the named pipe aren't affected.");
+        }
+        return new PrerequisiteCheck("env:ProcessBitness", PrerequisiteCategory.Environment,
+            PrerequisiteStatus.Pass, "Test host is 32-bit.");
+    }
+}