Test Failure: System.Net.WebSockets.Client.Tests.CancelTest_SharedHandler_Loopback.ConnectAsync_Cancel_ThrowsCancellationException

[JulieLeeMSFT]

Build Information

Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1500785
Build error leg or test failing: System.Net.WebSockets.Client.Tests.CancelTest_SharedHandler_Loopback.ConnectAsync_Cancel_ThrowsCancellationException

Error Message

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

{
  "ErrorPattern": "System\\.Net\\.WebSockets\\.Client\\.Tests\\.CancelTest_\\w+Loopback\\.ConnectAsync_Cancel_ThrowsCancellationException[^\\n]*\\[FAIL\\]",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1500785
Error message validated: [System.Net.WebSockets.Client.Tests.CancelTest_SharedHandler_Loopback.ConnectAsync_Cancel_ThrowsCancellationException(useSsl: False) [FAIL]]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 7/9/2026 10:27:44 PM UTC

Report

Build	Repository	Test	Pull Request
1500785	dotnet/runtime	System.Net.WebSockets.Client.Tests.CancelTest_SharedHandler_Loopback.ConnectAsync_Cancel_ThrowsCancellationException

Summary

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

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1500785
Error message validated: [System\.Net\.WebSockets\.Client\.Tests\.CancelTest_\w+Loopback\.ConnectAsync_Cancel_ThrowsCancellationException[^\n]*\[FAIL\]]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 7/27/2026 3:30:50 AM UTC

Report

Build	Repository	Test	Pull Request
1500785	dotnet/runtime	System.Net.WebSockets.Client.Tests.CancelTest_SharedHandler_Loopback.ConnectAsync_Cancel_ThrowsCancellationException

Summary

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

Report

Build	Repository	Test	Pull Request
1534779	dotnet/runtime	System.Net.WebSockets.Client.Tests.CancelTest_Invoker_Http2Loopback.CloseAsync_Cancel_Success	#131538
1533564	dotnet/runtime	System.Net.WebSockets.Client.Tests.CancelTest_HttpClient_Http2Loopback.CloseAsync_Cancel_Success	#131538
1531754	dotnet/runtime	System.Net.WebSockets.Client.Tests.CancelTest_Invoker_Http2Loopback.CloseAsync_Cancel_Success	#131538
1527384	dotnet/runtime	System.Net.WebSockets.Client.Tests.CancelTest_HttpClient_Loopback.ConnectAsync_Cancel_ThrowsCancellationException	#131401
1500785	dotnet/runtime	System.Net.WebSockets.Client.Tests.CancelTest_SharedHandler_Loopback.ConnectAsync_Cancel_ThrowsCancellationException

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
0	4	5

[dotnet-policy-service]

Tagging subscribers to this area: @karelz, @dotnet/ncl
See info in area-owners.md if you want to be subscribed.

[lewing]

Broadened the matcher from a fixed ErrorMessage on CancelTest_SharedHandler_Loopback to an ErrorPattern covering every CancelTest_*Loopback fixture, since the same test method is now failing the same way under other fixtures.

{
  "ErrorPattern": "System\\.Net\\.WebSockets\\.Client\\.Tests\\.CancelTest_\\w+Loopback\\.ConnectAsync_Cancel_ThrowsCancellationException[^\\n]*\\[FAIL\\]",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

The pattern matches SharedHandler_Loopback, HttpClient_Loopback, Invoker_Loopback and the *_Http2Loopback variants, and does not match *_External fixtures or other test methods on the same classes.

Recent occurrences

Latest hit is on dotnet/runtime#131401, build 1527384 — CancelTest_HttpClient_Loopback.ConnectAsync_Cancel_ThrowsCancellationException(useSsl: False) on net11.0-windows-Debug-x86-coreclr_checked-Windows.10.Amd64.Open:

System.TimeoutException : The operation has timed out.
   at System.Threading.Tasks.TaskTimeoutExtensions.WhenAllOrAnyFailed(Task[] tasks, Int32 millisecondsTimeout)
   at System.Net.WebSockets.Client.Tests.LoopbackWebSocketServer.HttpRunner.RunAsync(...)
      in src/libraries/System.Net.WebSockets.Client/tests/LoopbackServer/LoopbackWebSocketServer.Http.cs:line 32

That PR only touches src/coreclr/jit/lclvars.cpp inside a #if ... || defined(TARGET_WASM) guard, so it is a no-op for a Windows x86 leg and cannot be the cause.

Failure history from the AzDO test-history API (7-day retention window, refs/pull/*):

Fixture	Runs	Failures	Dates
CancelTest_HttpClient_Loopback	8962	2	2026-07-24 (1524298), 2026-07-27 (1527384)
CancelTest_SharedHandler_Loopback	8962	0	—
CancelTest_Invoker_Loopback	8962	0	—

So roughly a 0.02% hit rate, matching what Build Analysis reports. The two HttpClient_Loopback hits are on unrelated PRs (#131177 and #131401), which is consistent with infrastructure/timing flakiness rather than a product regression. The original SharedHandler_Loopback hit that opened this issue was on 2026-07-09 and has not recurred since.

Note

This comment and the issue body update were generated by GitHub Copilot on behalf of @lewing.