System.Net.WebSockets.Tests.WebSocketCloseTests fail with TaskCanceledException

[jkotas]

    System.Net.WebSockets.Tests.WebSocketCloseTests.ReceiveAsync_ValidCloseStatus_Success(closeStatus: PolicyViolation) [FAIL]
      System.Threading.Tasks.TaskCanceledException : A task was canceled.
      Stack Trace:
        /_/src/libraries/System.Net.WebSockets/src/System/Net/WebSockets/ManagedWebSocket.cs(610,0): at System.Net.WebSockets.ManagedWebSocket.SendFrameFallbackAsync(MessageOpcode opcode, Boolean endOfMessage, Boolean disableCompression, ReadOnlyMemory`1 payloadBuffer, Task lockTask, CancellationToken cancellationToken)
        /_/src/libraries/System.Net.WebSockets/src/System/Net/WebSockets/ManagedWebSocket.cs(487,0): at System.Net.WebSockets.ManagedWebSocket.SendFrameAsync(MessageOpcode opcode, Boolean endOfMessage, Boolean disableCompression, ReadOnlyMemory`1 payloadBuffer, CancellationToken cancellationToken)
        /_/src/libraries/System.Net.WebSockets/src/System/Net/WebSockets/ManagedWebSocket.cs(1579,0): at System.Net.WebSockets.ManagedWebSocket.SendCloseFrameAsync(WebSocketCloseStatus closeStatus, String closeStatusDescription, CancellationToken cancellationToken)
        /_/src/libraries/System.Net.WebSockets/src/System/Net/WebSockets/ManagedWebSocket.cs(420,0): at System.Net.WebSockets.ManagedWebSocket.CloseOutputAsyncCore(WebSocketCloseStatus closeStatus, String statusDescription, Boolean enterReceiveMutex, CancellationToken cancellationToken)
        /_/src/libraries/System.Net.WebSockets/src/System/Net/WebSockets/ManagedWebSocket.cs(411,0): at System.Net.WebSockets.ManagedWebSocket.CloseOutputAsync(WebSocketCloseStatus closeStatus, String statusDescription, CancellationToken cancellationToken)
        /_/src/libraries/System.Net.WebSockets/tests/WebSocketCloseTests.cs(73,0): at System.Net.WebSockets.Tests.WebSocketCloseTests.ReceiveAsync_ValidCloseStatus_Success(WebSocketCloseStatus closeStatus)
        --- End of stack trace from previous location ---

Build Information

Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1609152
Build error leg or test failing: System.Net.WebSockets.Tests.WebSocketCloseTests.ReceiveAsync_ValidCloseStatus_Success
Pull request: #134506

Error Message

DO NOT USE JSON BELOW IF THIS IS A BUILD BREAK otherwise build analysis will allow pull requests to merge that break the build worse. For a build break, do not use this issue form. Make a regular new issue.

Fill the error message using step by step known issues guidance.

{
  "ErrorMessage": ["System.Net.WebSockets.Tests.WebSocketCloseTests","TaskCanceledException"],
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1609152
Error message validated: [System.Net.WebSockets.Tests.WebSocketCloseTests TaskCanceledException]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 9/24/2026 4:33:50 AM UTC

Report

Build	Repository	Test	Pull Request
1609152	dotnet/runtime	System.Net.WebSockets.Tests.WebSocketCloseTests.ReceiveAsync_ValidCloseStatus_Success	#134506

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
0	1	1

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