[ci-scan] Test failure: System.Threading.Tasks.Tests.TaskContinueWithTests.RunContinueWithStressTestsNoState #136268

Description

TaskContinueWithTests.RunContinueWithStressTestsNoState failed with OutOfMemoryException while collecting canceled-task exceptions in a Windows x86 CoreCLR CI run.

Reproduction Steps

Run the existing System.Threading.Tasks.Tests.TaskContinueWithTests.RunContinueWithStressTestsNoState test in the configuration from the linked build. A local reproduction has not been established.

Expected behavior

The continuation stress test completes without exhausting memory.

Actual behavior

Task.WaitAll failed with OutOfMemoryException. The reported stack starts in StringBuilder.ToString and includes Task.AddExceptionsForCompletedTask. The complete failure excerpt is below.

Regression?

Unknown. The failing CoreLib and task-test source files are not changed by the associated PR; no PR-specific code fix has been identified.

Known Workarounds

None verified. No tests have been disabled.

Configuration

• Target framework: net11.0-windows.
• Runtime configuration: CoreCLR Release.
• Process architecture: x86.
• Helix queue: Windows.Server2025.Amd64.Open.
• CI merge commit: 8f99bc69fbd3400ef93c60d45f943c2326403803.
• PR head: 4661e533bf2fd5e88182d0b9194648c12870f813.

Other information

The failure is recorded in the Helix console log. This issue tracks only the task-continuation OOM.

Build Information

Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1644344
Build error leg or test failing: net11.0-windows-Release-x86-coreclr_release-Windows.Server2025.Amd64.Open-System.Threading.Tasks.Tests.TaskContinueWithTests.RunContinueWithStressTestsNoState
Pull request: #136221

Error Details

System.Threading.Tasks.Tests.TaskContinueWithTests.RunContinueWithStressTestsNoState [FAIL]
  System.OutOfMemoryException : Exception of type 'System.OutOfMemoryException' was thrown.
  Stack Trace:
    /_/src/libraries/System.Private.CoreLib/src/System/Text/StringBuilder.cs(324,0): at System.Text.StringBuilder.ToString()
    /_/src/libraries/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs(5328,0): at System.Threading.Tasks.Task.AddExceptionsForCompletedTask(List`1& exceptions, Task t)
    /_/src/libraries/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs(5233,0): at System.Threading.Tasks.Task.WaitAllCore(ReadOnlySpan`1 tasks, Int32 millisecondsTimeout, CancellationToken cancellationToken)
    /_/src/libraries/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs(4903,0): at System.Threading.Tasks.Task.WaitAll(Task[] tasks)
    /_/src/libraries/System.Runtime/tests/System.Threading.Tasks.Tests/Task/TaskContinueWithTests.cs(1380,0): at System.Threading.Tasks.Tests.TaskContinueWithTests.ContinueWithTortureTest(Int32 numCanceled, Int32 numLeftover, Int32 completeAfter, Int32 cancelAfter)
    /_/src/libraries/System.Runtime/tests/System.Threading.Tasks.Tests/Task/TaskContinueWithTests.cs(71,0): at System.Threading.Tasks.Tests.TaskContinueWithTests.RunContinueWithStressTestsNoState()
    /_/src/coreclr/System.Private.CoreLib/src/System/Reflection/IntrinsicInvokeHelper.cs(432,0): at System.Reflection.IntrinsicInvokeHelper.Static_Void_0(IntPtr fn, Object _, IntPtr* __, RuntimeType ___)
    /_/src/coreclr/System.Private.CoreLib/src/System/Reflection/MethodBaseInvoker.CoreCLR.cs(30,0): at System.Reflection.MethodBaseInvoker.InvokeWithSharedThunk(Object obj, IntPtr* args)
    /_/src/libraries/System.Private.CoreLib/src/System/Reflection/RuntimeMethodInfo.cs(134,0): at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)

Error Message

{
  "ErrorMessage": [
    "System.Threading.Tasks.Tests.TaskContinueWithTests.RunContinueWithStressTestsNoState [FAIL]",
    "System.OutOfMemoryException : Exception of type 'System.OutOfMemoryException' was thrown.",
    "at System.Threading.Tasks.Tests.TaskContinueWithTests.RunContinueWithStressTestsNoState()"
  ],
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1644344
Error message validated: [System.Threading.Tasks.Tests.TaskContinueWithTests.RunContinueWithStressTestsNoState [FAIL] System.OutOfMemoryException : Exception of type 'System.OutOfMemoryException' was thrown. at System.Threading.Tasks.Tests.TaskContinueWithTests.RunContinueWithStressTestsNoState()]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 10/22/2026 3:01:53 AM UTC

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Summary