Improve shutdown cleanup and CTS disposal

ScreencastService: Unsubscribe page close handler and cancel the frame pump immediately to avoid a circular dependency between the pump and page disposal; leave full cleanup to StopAsync/DisposeAsync.

Browser: Mark connection as closed earlier, unregister signal handlers, and dispose the transport to terminate the WebSocket receive loop before waiting on the browser process. Use a dedicated 5s CancellationTokenSource when waiting for process exit and kill the process if it doesn't exit in time.

NetworkManager: Ensure the linked CancellationTokenSource is disposed when waiter tasks complete (success, timeout, or cancellation) to avoid CTS leaks in WaitForRequest/WaitForResponse.

Author: TorreyBetts

src/Motus.Runner/Services/ScreencastService.cs

@@ -46,7 +46,14 @@ await _page.StartScreencastAsync(
 
     private void OnPageClose(object? sender, EventArgs e)
     {
-        _ = StopAsync();
+        // Unsubscribe immediately and cancel the frame pump.
+        // Full cleanup (awaiting _pumpTask, StopScreencastAsync) happens in
+        // StopAsync/DisposeAsync to avoid a circular dependency where the pump
+        // blocks on a CDP channel that is only completed after page disposal.
+        if (sender is InternalPage page)
+            page.Close -= OnPageClose;
+
+        _pumpCts?.Cancel();
     }
 
     public async Task HighlightElementAsync(string? objectId, CancellationToken ct = default)

src/Motus/Browser/Browser.cs

@@ -75,6 +75,10 @@ public async Task CloseAsync()
         if (!_isConnected)
             return;
 
+        _isConnected = false;
+
+        UnregisterSignalHandlers();
+
         // Close all contexts first
         List<BrowserContext> contextsToClose;
         lock (_contexts)
@@ -100,19 +104,21 @@ await _registry.BrowserSession.SendAsync(
             // Expected: browser closes the WebSocket on shutdown
         }
 
+        // Dispose the transport to terminate the WebSocket receive loop
+        await _transport.DisposeAsync().ConfigureAwait(false);
+
         if (_process is not null && !_process.HasExited)
         {
+            using var exitCts = new CancellationTokenSource(TimeSpan.FromSeconds(5));
             try
             {
-                await _process.WaitForExitAsync(new CancellationTokenSource(TimeSpan.FromSeconds(5)).Token).ConfigureAwait(false);
+                await _process.WaitForExitAsync(exitCts.Token).ConfigureAwait(false);
             }
             catch (OperationCanceledException)
             {
                 _process.Kill(entireProcessTree: true);
             }
         }
-
-        _isConnected = false;
     }
 
     public async ValueTask DisposeAsync()

src/Motus/Network/NetworkManager.cs

@@ -113,6 +113,9 @@ internal Task<IRequest> WaitForRequestAsync(string urlPattern, TimeSpan timeout)
         cts.Token.Register(() => tcs.TrySetException(
             new TimeoutException($"WaitForRequest timed out after {timeout.TotalMilliseconds}ms.")));
 
+        // Dispose the linked CTS once the waiter completes (success, timeout, or cancellation)
+        tcs.Task.ContinueWith(_ => cts.Dispose(), TaskContinuationOptions.ExecuteSynchronously);
+
         return tcs.Task;
     }
 
@@ -127,6 +130,9 @@ internal Task<IResponse> WaitForResponseAsync(string urlPattern, TimeSpan timeou
         cts.Token.Register(() => tcs.TrySetException(
             new TimeoutException($"WaitForResponse timed out after {timeout.TotalMilliseconds}ms.")));
 
+        // Dispose the linked CTS once the waiter completes (success, timeout, or cancellation)
+        tcs.Task.ContinueWith(_ => cts.Dispose(), TaskContinuationOptions.ExecuteSynchronously);
+
         return tcs.Task;
     }