Fatal error during the build with System.Net.Http.HttpConnectionPool.ConnectAsync on the callstack

[jkotas]

Building managed test group 1: "D:\a\_work\1\s\\dotnet.cmd" msbuild D:\a\_work\1\s\src\tests\build.proj /t:CopyAllNativeTestProjectBinaries "/p:TargetArchitecture=x64" "/p:Configuration=Checked" "/p:LibrariesConfiguration=Debug" "/p:TasksConfiguration=Checked" "/p:TargetOS=windows" "/p:ToolsOS=" "/p:PackageOS=" "/p:RuntimeFlavor=coreclr" "/p:RuntimeVariant=" "/p:CLRTestBuildAllTargets=" "/p:UseCodeFlowEnforcement=" "/p:__TestGroupToBuild=1" "/p:__SkipRestorePackages=1" /nodeReuse:false /maxcpucount "/p:UseMonoRuntime=false" /bl:D:\a\_work\1\s\artifacts\/log/Checked/InnerManagedTestBuild.1.binlog "/p:DevTeamProvisioning=-"
  D:\a\_work\1\s\.dotnet
 Fatal error.
  Internal CLR error. (0x80131506)
     at System.Runtime.CompilerServices.AsyncMethodBuilderCore.Start[[System.Net.Http.HttpConnectionPool+<ConnectToTcpHostAsync>d__54, System.Net.Http, Version=11.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]](<ConnectToTcpHostAsync>d__54 ByRef)
     at System.Runtime.CompilerServices.AsyncValueTaskMethodBuilder`1[[System.__Canon, System.Private.CoreLib, Version=11.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].Start[[System.Net.Http.HttpConnectionPool+<ConnectToTcpHostAsync>d__54, System.Net.Http, Version=11.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]](<ConnectToTcpHostAsync>d__54 ByRef)
     at System.Net.Http.HttpConnectionPool.ConnectToTcpHostAsync(System.String, Int32, System.Net.Http.HttpRequestMessage, Boolean, System.Threading.CancellationToken)
     at System.Net.Http.HttpConnectionPool+<ConnectAsync>d__53.MoveNext()
     at System.Runtime.CompilerServices.AsyncMethodBuilderCore.Start[[System.Net.Http.HttpConnectionPool+<ConnectAsync>d__53, System.Net.Http, Version=11.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]](<ConnectAsync>d__53 ByRef)
     at System.Runtime.CompilerServices.AsyncValueTaskMethodBuilder`1[[System.ValueTuple`4[[System.__Canon, System.Private.CoreLib, Version=11.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=11.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=11.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=11.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]], System.Private.CoreLib, Version=11.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].Start[[System.Net.Http.HttpConnectionPool+<ConnectAsync>d__53, System.Net.Http, Version=11.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]](<ConnectAsync>d__53 ByRef)
     at System.Net.Http.HttpConnectionPool.ConnectAsync(System.Net.Http.HttpRequestMessage, Boolean, System.Threading.CancellationToken)
     at System.Net.Http.HttpConnectionPool+<CreateHttp11ConnectionAsync>d__81.MoveNext()
     at System.Runtime.CompilerServices.AsyncMethodBuilderCore.Start[[System.Net.Http.HttpConnectionPool+<CreateHttp11ConnectionAsync>d__81, System.Net.Http, Version=11.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]](<CreateHttp11ConnectionAsync>d__81 ByRef)
     at System.Runtime.CompilerServices.AsyncValueTaskMethodBuilder`1[[System.__Canon, System.Private.CoreLib, Version=11.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].Start[[System.Net.Http.HttpConnectionPool+<CreateHttp11ConnectionAsync>d__81, System.Net.Http, Version=11.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]](<CreateHttp11ConnectionAsync>d__81 ByRef)
     at System.Net.Http.HttpConnectionPool.CreateHttp11ConnectionAsync(System.Net.Http.HttpRequestMessage, Boolean, System.Threading.CancellationToken)
     at System.Net.Http.HttpConnectionPool+<InjectNewHttp11ConnectionAsync>d__80.MoveNext()
     at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1+AsyncStateMachineBox`1[[System.Threading.Tasks.VoidTaskResult, System.Private.CoreLib, Version=11.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.Net.Http.HttpConnectionPool+<InjectNewHttp11ConnectionAsync>d__80, System.Net.Http, Version=11.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]].ExecutionContextCallback(System.Object)
     at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(System.Threading.Thread, System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object)
     at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1+AsyncStateMachineBox`1[[System.Threading.Tasks.VoidTaskResult, System.Private.CoreLib, Version=11.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.Net.Http.HttpConnectionPool+<InjectNewHttp11ConnectionAsync>d__80, System.Net.Http, Version=11.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]].MoveNext(System.Threading.Thread)
     at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1+AsyncStateMachineBox`1[[System.Threading.Tasks.VoidTaskResult, System.Private.CoreLib, Version=11.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.Net.Http.HttpConnectionPool+<InjectNewHttp11ConnectionAsync>d__80, System.Net.Http, Version=11.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]].ExecuteFromThreadPool(System.Threading.Thread)
     at System.Threading.ThreadPoolWorkQueue.Dispatch()

Build Information

Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1326390&view=logs&j=36023878-3ad4-5624-c1ed-575c64898e0b
Build error leg or test failing: Build / coreclr Pri0 Runtime Tests Run windows x64 checked / Copy native test components to test output folder
Pull request: #125307

Error Message

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

{
  "ErrorMessage": ["Fatal error","System.Net.Http.HttpConnectionPool.ConnectAsync"],
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1326390
Error message validated: [Fatal error]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 3/9/2026 5:12:28 PM UTC

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1326390
Error message validated: [Fatal error System.Net.Http.HttpConnectionPool.ConnectAsync]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 3/9/2026 5:13:18 PM UTC

Report

Build	Repository	Step Name	Console log	Pull Request
1436990	dotnet/runtime	Run Trimming Tests	Log	#128638

Build	Repository	Test	Pull Request
1454131	dotnet/runtime	System.Net.Http.Functional.Tests.WorkItemExecution	#128777

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
1	1	2

[dotnet-policy-service]

Tagging subscribers to this area: @karelz, @dotnet/ncl
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[jkotas]

This looks very similar to #123464

[wfurt]

Any idea what may cause 0x80131506 @jkotas? I briefly looked at the relevant code and I don't see anything obviously wrong there at the networking layer.

[jkotas]

We need to get a crash dump to figure out what's going on. Unfortunately, we do not collect crash dumps during builds.

cc @steveisok Another build crash that we are not able to diagnose.

[ManickaP]

Not actionable ATM, we need a dump to investigate.