Improve gateway reliability and dashboard docs

src/MxGateway.Tests/Gateway/Dashboard/DashboardSnapshotServiceTests.cs

@@ -42,8 +42,15 @@ public sealed class DashboardSnapshotServiceTests
             DateTimeOffset.Parse("2026-04-26T10:01:00Z"));
         faultedSession.AttachWorkerClient(new FakeWorkerClient("session-faulted", 1202, WorkerClientState.Faulted));
         faultedSession.MarkFaulted("worker pipe disconnected");
+        GatewaySession closedSession = CreateSession(
+            "session-closed",
+            "client-three",
+            DateTimeOffset.Parse("2026-04-26T09:59:00Z"));
+        closedSession.AttachWorkerClient(new FakeWorkerClient("session-closed", 1203, WorkerClientState.Closed));
+        closedSession.TransitionTo(SessionState.Closed);
         registry.TryAdd(activeSession);
         registry.TryAdd(faultedSession);
+        registry.TryAdd(closedSession);
         using GatewayMetrics metrics = new();
         metrics.SessionOpened();
         metrics.SessionOpened();
@@ -55,10 +62,15 @@ public sealed class DashboardSnapshotServiceTests
 
         DashboardSnapshot snapshot = service.GetSnapshot();
 
-        Assert.Equal(2, snapshot.Sessions.Count);
+        Assert.Equal(3, snapshot.Sessions.Count);
         Assert.Equal("session-faulted", snapshot.Sessions[0].SessionId);
         Assert.Equal(SessionState.Faulted, snapshot.Sessions[0].State);
+        DashboardSessionSummary activeSummary = Assert.Single(
+            snapshot.Sessions,
+            session => session.SessionId == "session-active");
+        Assert.Equal(1, activeSummary.EventsReceived);
         Assert.Equal(2, snapshot.Workers.Count);
+        Assert.DoesNotContain(snapshot.Workers, worker => worker.SessionId == "session-closed");
         Assert.Contains(snapshot.Metrics, metric => metric.Name == "mxgateway.commands.started" && metric.Value == 1);
         Assert.Contains(
             snapshot.Metrics,

src/MxGateway.Tests/Gateway/Sessions/SessionManagerTests.cs

@@ -32,6 +32,35 @@ public sealed class SessionManagerTests
         Assert.Equal(1, metrics.GetSnapshot().SessionsOpened);
     }
 
+    [Fact]
+    public async Task OpenSessionAsync_GeneratesClientCorrelationIdFromClientNameAndSessionId()
+    {
+        SessionOpenRequest request = CreateOpenRequest() with
+        {
+            ClientSessionName = "rust-load-client",
+            ClientCorrelationId = "caller-provided-correlation",
+        };
+        SessionManager manager = CreateManager(new FakeSessionWorkerClientFactory(new FakeWorkerClient()));
+
+        GatewaySession session = await manager.OpenSessionAsync(request, "client-1", CancellationToken.None);
+
+        Assert.Equal($"rust-load-client-{session.SessionId}", session.ClientCorrelationId);
+    }
+
+    [Fact]
+    public async Task OpenSessionAsync_WhenClientSessionNameMissing_UsesClientCorrelationPrefix()
+    {
+        SessionOpenRequest request = CreateOpenRequest() with
+        {
+            ClientSessionName = "",
+        };
+        SessionManager manager = CreateManager(new FakeSessionWorkerClientFactory(new FakeWorkerClient()));
+
+        GatewaySession session = await manager.OpenSessionAsync(request, "client-1", CancellationToken.None);
+
+        Assert.Equal($"client-{session.SessionId}", session.ClientCorrelationId);
+    }
+
     [Fact]
     public async Task InvokeAsync_WhenSessionReady_ForwardsCommandToWorker()
     {
@@ -111,7 +140,7 @@ public sealed class SessionManagerTests
     }
 
     [Fact]
-    public async Task CloseSessionAsync_WhenCalledTwice_IsIdempotent()
+    public async Task CloseSessionAsync_RemovesClosedSession()
     {
         FakeWorkerClient workerClient = new();
         using GatewayMetrics metrics = new();
@@ -119,12 +148,12 @@ public sealed class SessionManagerTests
         GatewaySession session = await manager.OpenSessionAsync(CreateOpenRequest(), "client-1", CancellationToken.None);
 
         SessionCloseResult firstClose = await manager.CloseSessionAsync(session.SessionId, CancellationToken.None);
-        SessionCloseResult secondClose = await manager.CloseSessionAsync(session.SessionId, CancellationToken.None);
+        SessionManagerException secondClose = await Assert.ThrowsAsync<SessionManagerException>(
+            async () => await manager.CloseSessionAsync(session.SessionId, CancellationToken.None));
 
         Assert.False(firstClose.AlreadyClosed);
-        Assert.True(secondClose.AlreadyClosed);
         Assert.Equal(SessionState.Closed, firstClose.FinalState);
-        Assert.Equal(SessionState.Closed, secondClose.FinalState);
+        Assert.Equal(SessionManagerErrorCode.SessionNotFound, secondClose.ErrorCode);
         Assert.Equal(1, workerClient.ShutdownCount);
         Assert.Equal(1, metrics.GetSnapshot().SessionsClosed);
         Assert.Equal(0, metrics.GetSnapshot().OpenSessions);

src/MxGateway.Tests/Gateway/Workers/WorkerClientTests.cs

@@ -2,6 +2,7 @@ using System.IO.Pipes;
 using Google.Protobuf.WellKnownTypes;
 using MxGateway.Contracts;
 using MxGateway.Contracts.Proto;
+using MxGateway.Server.Metrics;
 using MxGateway.Server.Workers;
 
 namespace MxGateway.Tests.Gateway.Workers;
@@ -152,6 +153,27 @@ public sealed class WorkerClientTests
         Assert.Equal(WorkerClientState.Faulted, client.State);
     }
 
+    [Fact]
+    public async Task ReadLoop_WhenPipeDisconnects_StopsRunningWorkerMetric()
+    {
+        await using PipePair pipePair = await PipePair.CreateAsync();
+        using GatewayMetrics metrics = new();
+        await using WorkerClient client = CreateClient(pipePair, metrics: metrics);
+        await CompleteHandshakeAsync(client, pipePair);
+
+        Assert.Equal(1, metrics.GetSnapshot().WorkersRunning);
+
+        await pipePair.DisposeWorkerSideAsync();
+
+        await WaitUntilAsync(
+            () => client.State == WorkerClientState.Faulted,
+            TestTimeout);
+
+        GatewayMetricsSnapshot snapshot = metrics.GetSnapshot();
+        Assert.Equal(0, snapshot.WorkersRunning);
+        Assert.Equal(1, snapshot.WorkerExits);
+    }
+
     [Fact]
     public async Task ReadLoop_WhenHeartbeatArrives_UpdatesLastHeartbeatAndWorkerProcess()
     {
@@ -193,7 +215,8 @@ public sealed class WorkerClientTests
 
     private static WorkerClient CreateClient(
         PipePair pipePair,
-        WorkerClientOptions? options = null)
+        WorkerClientOptions? options = null,
+        GatewayMetrics? metrics = null)
     {
         WorkerFrameProtocolOptions frameOptions = new(SessionId);
         WorkerClientConnection connection = new(
@@ -202,7 +225,7 @@ public sealed class WorkerClientTests
             pipePair.GatewayStream,
             frameOptions);
 
-        return new WorkerClient(connection, options);
+        return new WorkerClient(connection, options, metrics);
     }
 
     private static async Task CompleteHandshakeAsync(

src/MxGateway.Tests/Gateway/Workers/WorkerProcessLauncherTests.cs

@@ -43,7 +43,7 @@ public sealed class WorkerProcessLauncherTests
         Assert.DoesNotContain(Nonce, handle.CommandLine.ToString(), StringComparison.Ordinal);
         Assert.DoesNotContain(Nonce, string.Join(" ", handle.CommandLine.Arguments), StringComparison.Ordinal);
         Assert.False(pipeReservation.DisposeCalled);
-        Assert.Equal(1, metrics.GetSnapshot().WorkersRunning);
+        Assert.Equal(0, metrics.GetSnapshot().WorkersRunning);
     }
 
     [Fact]

src/MxGateway.Tests/Metrics/GatewayMetricsTests.cs

@@ -17,7 +17,8 @@ public sealed class GatewayMetricsTests
         metrics.CommandFailed("WriteSecured", "AuthorizationFailed", TimeSpan.FromMilliseconds(12));
         metrics.EventReceived("session-1", "OnDataChange");
         metrics.EventReceived("session-1", "OnDataChange");
-        metrics.SetEventQueueDepth(7);
+        metrics.SetWorkerEventQueueDepth(7);
+        metrics.SetGrpcEventStreamQueueDepth(3);
         metrics.QueueOverflow("session-events");
         metrics.Fault("CommandTimeout");
         metrics.WorkerKilled("CommandTimeout");
@@ -30,7 +31,8 @@ public sealed class GatewayMetricsTests
 
         Assert.Equal(0, snapshot.OpenSessions);
         Assert.Equal(0, snapshot.WorkersRunning);
-        Assert.Equal(7, snapshot.EventQueueDepth);
+        Assert.Equal(7, snapshot.WorkerEventQueueDepth);
+        Assert.Equal(3, snapshot.GrpcEventStreamQueueDepth);
         Assert.Equal(1, snapshot.SessionsOpened);
         Assert.Equal(1, snapshot.SessionsClosed);
         Assert.Equal(2, snapshot.CommandsStarted);
@@ -45,6 +47,7 @@ public sealed class GatewayMetricsTests
         Assert.Equal(1, snapshot.StreamDisconnects);
         Assert.Equal(1, snapshot.CommandFailuresByMethod["WriteSecured"]);
         Assert.Equal(2, snapshot.EventsByFamily["OnDataChange"]);
+        Assert.Equal(2, snapshot.EventsBySession["session-1"]);
     }
 
     [Fact]
@@ -53,7 +56,7 @@ public sealed class GatewayMetricsTests
         using GatewayMetrics metrics = new();
 
         ArgumentOutOfRangeException exception = Assert.Throws<ArgumentOutOfRangeException>(
-            () => metrics.SetEventQueueDepth(-1));
+            () => metrics.SetWorkerEventQueueDepth(-1));
 
         Assert.Equal("depth", exception.ParamName);
     }