fix(communication): resolve Communication-002/003 — gRPC reconnect stream cleanup and subscription map safety

tests/ScadaLink.Communication.Tests/Grpc/DebugStreamBridgeActorTests.cs

@@ -159,6 +159,34 @@ public class DebugStreamBridgeActorTests : TestKit
         Assert.Equal("corr-1", ctx.MockGrpcClient.SubscribeCalls[1].CorrelationId);
     }
 
+    [Fact]
+    public void On_GrpcError_Unsubscribes_Old_Stream_Before_Reconnect()
+    {
+        // Communication-002 regression: a reconnect must unsubscribe the previous
+        // stream so the old node does not keep a zombie relay actor / subscription.
+        var ctx = CreateBridgeActor();
+        ctx.CommProbe.ExpectMsg<SiteEnvelope>();
+
+        var snapshot = new DebugViewSnapshot(
+            InstanceName,
+            new List<AttributeValueChanged>(),
+            new List<AlarmStateChanged>(),
+            DateTimeOffset.UtcNow);
+
+        ctx.BridgeActor.Tell(snapshot);
+        AwaitCondition(() => ctx.MockGrpcClient.SubscribeCalls.Count == 1, TimeSpan.FromSeconds(3));
+
+        // Simulate gRPC error → reconnect
+        ctx.MockGrpcClient.SubscribeCalls[0].OnError(new Exception("Stream broken"));
+
+        // Should resubscribe...
+        AwaitCondition(() => ctx.MockGrpcClient.SubscribeCalls.Count == 2, TimeSpan.FromSeconds(5));
+
+        // ...and must have unsubscribed the prior correlation ID so the old node's
+        // relay actor is released rather than left zombie.
+        Assert.Contains("corr-1", ctx.MockGrpcClient.UnsubscribedCorrelationIds);
+    }
+
     [Fact]
     public void After_MaxRetries_Terminates()
     {

tests/ScadaLink.Communication.Tests/Grpc/SiteStreamGrpcClientTests.cs

@@ -176,4 +176,49 @@ public class SiteStreamGrpcClientTests
         Assert.True(cts1.IsCancellationRequested);
         Assert.True(cts2.IsCancellationRequested);
     }
+
+    // --- Communication-003 regression tests ---
+
+    [Fact]
+    public void RegisterSubscription_ReusedCorrelationId_CancelsAndDisposesPriorCts()
+    {
+        // Two SubscribeAsync calls briefly sharing a correlation ID (reconnect race).
+        // Inserting the second must cancel + dispose the first so it does not leak.
+        var client = SiteStreamGrpcClient.CreateForTesting();
+
+        var first = new CancellationTokenSource();
+        var second = new CancellationTokenSource();
+
+        client.RegisterSubscription("corr-shared", first);
+        client.RegisterSubscription("corr-shared", second);
+
+        Assert.True(first.IsCancellationRequested);
+        // Disposed CTS throws ObjectDisposedException when its token is touched.
+        Assert.Throws<ObjectDisposedException>(() => _ = first.Token);
+
+        // The second (live) CTS must remain intact.
+        Assert.False(second.IsCancellationRequested);
+    }
+
+    [Fact]
+    public void RemoveSubscription_OnlyRemovesOwnCts_NotAReplacement()
+    {
+        // First call's finally must NOT remove the second call's live entry.
+        var client = SiteStreamGrpcClient.CreateForTesting();
+
+        var first = new CancellationTokenSource();
+        var second = new CancellationTokenSource();
+
+        client.RegisterSubscription("corr-shared", first);
+        // A racing second SubscribeAsync replaces the entry.
+        client.RegisterSubscription("corr-shared", second);
+
+        // The first call's finally runs and tries to remove its (already-replaced) entry.
+        client.RemoveSubscription("corr-shared", first);
+
+        // The live (second) subscription must still be cancellable via Unsubscribe.
+        Assert.False(second.IsCancellationRequested);
+        client.Unsubscribe("corr-shared");
+        Assert.True(second.IsCancellationRequested);
+    }
 }