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

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);
+    }
 }