Merge branch 'worktree-agent-aae48b78656e5a4e0' into arch-review-remediation

# Conflicts:
#	src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Repositories/SiteExternalSystemRepository.cs

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Actors/DeploymentManagerActor.cs

@@ -16,6 +16,7 @@ using ZB.MOM.WW.ScadaBridge.SiteEventLogging;
 using ZB.MOM.WW.ScadaBridge.SiteRuntime.Deployment;
 using ZB.MOM.WW.ScadaBridge.SiteRuntime.Messages;
 using ZB.MOM.WW.ScadaBridge.SiteRuntime.Persistence;
+using ZB.MOM.WW.ScadaBridge.SiteRuntime.Repositories;
 using ZB.MOM.WW.ScadaBridge.SiteRuntime.Scripts;
 using ZB.MOM.WW.ScadaBridge.SiteRuntime.Streaming;
 
@@ -40,6 +41,14 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
     // DeployInstanceCommand is validated before any actor/persistence work.
     private readonly DeployCompileValidator _deployCompileValidator;
     private readonly SharedScriptLibrary _sharedScriptLibrary;
+    /// <summary>
+    /// WP2.6a: the shared cache backing <c>SiteExternalSystemRepository</c> reads.
+    /// Invalidated wholesale after <see cref="HandleDeployArtifacts"/> applies
+    /// external-system changes so a script's next call re-reads fresh definitions/method
+    /// lists instead of serving a stale cached snapshot. Null in tests that do not wire
+    /// external-system caching — the invalidation call is then simply skipped.
+    /// </summary>
+    private readonly ExternalSystemDefinitionCache? _externalSystemCache;
     private readonly SiteStreamManager? _streamManager;
     private readonly SiteRuntimeOptions _options;
     private readonly ILogger<DeploymentManagerActor> _logger;
@@ -157,6 +166,12 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
     /// deployed configuration at startup; defaults to 5 seconds when null.</param>
     /// <param name="configLoader">Optional override for loading all deployed configurations
     /// at startup; defaults to reading from <paramref name="storage"/>. Primarily for tests.</param>
+    /// <param name="externalSystemCache">
+    /// WP2.6a: the shared <see cref="ExternalSystemDefinitionCache"/> backing
+    /// <c>SiteExternalSystemRepository</c> reads, invalidated after this actor applies
+    /// external-system changes. Optional/null in tests that do not exercise external-system
+    /// caching.
+    /// </param>
     public DeploymentManagerActor(
         SiteStorageService storage,
         ScriptCompilationService compilationService,
@@ -170,12 +185,14 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
         ILoggerFactory? loggerFactory = null,
         IDeploymentConfigFetcher? configFetcher = null,
         TimeSpan? startupLoadRetryInterval = null,
-        Func<Task<List<DeployedInstance>>>? configLoader = null)
+        Func<Task<List<DeployedInstance>>>? configLoader = null,
+        ExternalSystemDefinitionCache? externalSystemCache = null)
     {
         _storage = storage;
         _compilationService = compilationService;
         _deployCompileValidator = new DeployCompileValidator(compilationService);
         _sharedScriptLibrary = sharedScriptLibrary;
+        _externalSystemCache = externalSystemCache;
         _streamManager = streamManager;
         _options = options;
         _dclManager = dclManager;
@@ -1914,6 +1931,11 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
 
                     await _storage.DeleteExternalSystemsExceptAsync(
                         command.ExternalSystems.Select(es => es.Name).ToList());
+
+                    // WP2.6a: drop the shared read cache so the next script call sees
+                    // the freshly-applied definitions/method lists instead of a stale
+                    // snapshot loaded before this deploy.
+                    _externalSystemCache?.InvalidateAll();
                 }
 
                 // Store database connection definitions