[Known Build Error] System.Threading.Tasks.TaskCanceledException

## Build Information
Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1547946
Build error leg or test failing: Microsoft.CodeAnalysis.LanguageServer.UnitTests.HandlerTests.NonMutatingHandlerExceptionNFWIsReported(mutatingLspWorkspace: False)
Pull request: https://github.com/dotnet/roslyn/pull/84725

## Error Message

Fill the error message using [step by step known issues guidance](https://github.com/dotnet/arcade/blob/main/Documentation/Build%20Analysis/KnownIssueJsonStepByStep.md).

```json
{
"ErrorMessage": "System.Threading.Tasks.TaskCanceledException",
"BuildRetry": true,
"ExcludeConsoleLog": false
}
```

### Known issue validation
**Build: :mag_right:** https://dev.azure.com/dnceng-public/public/_build/results?buildId=1547946
**Error message validated:** `[System.Threading.Tasks.TaskCanceledException`]
**Result validation:** :white_check_mark: Known issue matched with the provided build.
**Validation performed at:** 8/11/2026 10:11:33 AM UTC

### Report
|Build|Repository|Step Name|Console log|Pull Request|
|---|---|---|---|---|
|[1569675](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1569675)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1569675/logs/340)||
|[1569572](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1569572)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1569572/logs/214)|dotnet/roslyn#85051|
|[1569553](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1569553)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1569553/logs/258)|dotnet/roslyn#85013|
|[1569536](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1569536)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1569536/logs/209)|dotnet/roslyn#85055|
|[1569520](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1569520)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1569520/logs/214)|dotnet/roslyn#85061|
|[1568797](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1568797)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1568797/logs/398)||
|[1568853](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1568853)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1568853/logs/393)||
|[1568781](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1568781)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1568781/logs/398)||
|[1569453](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1569453)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1569453/logs/340)||
|[1568799](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1568799)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1568799/logs/398)||
|[1569347](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1569347)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1569347/logs/258)|dotnet/roslyn#84655|
|[1569307](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1569307)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1569307/logs/214)|dotnet/roslyn#85053|
|[1569285](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1569285)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1569285/logs/340)||
|[1569025](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1569025)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1569025/logs/258)|dotnet/roslyn#85052|
|[1569021](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1569021)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1569021/logs/214)|dotnet/roslyn#85037|
|[1568997](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1568997)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1568997/logs/340)||
|[1568897](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1568897)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1568897/logs/258)|dotnet/roslyn#85015|
|[1568895](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1568895)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1568895/logs/214)|dotnet/roslyn#85050|
|[1567702](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567702)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1567702/logs/267)|dotnet/roslyn#85038|
|[1567751](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567751)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1567751/logs/223)|dotnet/roslyn#85030|
|[1567757](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567757)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1567757/logs/232)|dotnet/roslyn#85040|
|[1568528](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1568528)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1568528/logs/258)|dotnet/roslyn#85027|
|[1567866](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567866)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1567866/logs/253)|dotnet/roslyn#85042|
|[1567627](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567627)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1567627/logs/369)||
|[1567600](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567600)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1567600/logs/387)||
|[1567843](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567843)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1567843/logs/258)|dotnet/roslyn#84701|
|[1567537](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567537)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1567537/logs/304)|dotnet/roslyn#85035|
|[1567256](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567256)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1567256/logs/222)|dotnet/roslyn#85031|
|[1567657](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567657)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1567657/logs/259)|dotnet/roslyn#85039|
|[1567633](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567633)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1567633/logs/258)|dotnet/roslyn#85034|
|[1567558](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567558)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1567558/logs/214)|dotnet/roslyn#85037|
|[1567495](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567495)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1567495/logs/213)|dotnet/roslyn#85033|
|[1567331](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567331)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1567331/logs/395)|dotnet/roslyn#85029|
|[1567320](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567320)|dotnet/roslyn|Post-job: Cache Roslyn Outputs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1567320/logs/39)|dotnet/roslyn#84701|
|[1567259](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567259)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1567259/logs/213)|dotnet/roslyn#85032|
|[1567220](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567220)|dotnet/roslyn|Monitor Helix Jobs|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1567220/logs/257)|dotnet/roslyn#85028|

|Build|Repository|Test|Pull Request|
|---|---|---|---|
|[1595110](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1595110)|dotnet/roslyn|[Roslyn.VisualStudio.NewIntegrationTests.VisualBasic.BasicChangeSignatureDialog.VerifyAddParametersAcrossLanguages](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1595110&view=ms.vss-test-web.build-test-results-tab&runId=44038620&resultId=100804)|dotnet/roslyn#85286|
|[1581891](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1581891)|dotnet/roslyn|[Microsoft.CodeAnalysis.LanguageServer.UnitTests.MiscellaneousFiles.LspMiscellaneousFilesWorkspaceProviderTests.TestLspTransfersFromMiscellaneousFilesToHostWorkspaceAsync](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1581891&view=ms.vss-test-web.build-test-results-tab&runId=43644724&resultId=194081)||
|[1564362](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1564362)|dotnet/roslyn|[Roslyn.VisualStudio.NewIntegrationTests.VisualBasic.BasicChangeSignatureDialog.VerifyAddParametersAcrossLanguages](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1564362&view=ms.vss-test-web.build-test-results-tab&runId=43074484&resultId=100804)|dotnet/roslyn#85002|
|[1561921](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1561921)|dotnet/roslyn|[Microsoft.CodeAnalysis.LanguageServer.UnitTests.CodeLens.CSharpCodeLensTests.TestDoesNotCrashWhenSyntaxVersionsMismatch(mutatingLspWorkspace: False)](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1561921&view=ms.vss-test-web.build-test-results-tab&runId=43003862&resultId=248168)||
|[1561859](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1561859)|dotnet/roslyn|[Microsoft.CodeAnalysis.LanguageServer.UnitTests.Diagnostics.PullDiagnosticTests.TestStreamingWorkspaceDiagnostics(useVSDiagnostics: False, mutatingLspWorkspace: False)](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1561859&view=ms.vss-test-web.build-test-results-tab&runId=43002124&resultId=217482)||
|[1560154](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1560154)|dotnet/roslyn|[Microsoft.CodeAnalysis.LanguageServer.ProcessHost.UnitTests.DaemonServerLifecycleTests.OneEditorKilled_OnlyThatClientTornDown](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1560154&view=ms.vss-test-web.build-test-results-tab&runId=42950706&resultId=114646)|dotnet/roslyn#84944|
|[1558460](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1558460)|dotnet/roslyn|[Microsoft.CodeAnalysis.LanguageServer.UnitTests.RequestOrdering.RequestOrderingTests.FailingMutableTaskShutsDownQueue](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1558460&view=ms.vss-test-web.build-test-results-tab&runId=42896012&resultId=120311)|dotnet/roslyn#84944|
|[1558242](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1558242)|dotnet/roslyn|[Microsoft.CodeAnalysis.LanguageServer.UnitTests.Workspaces.LspWorkspaceManagerTests.TestLspUsesWorkspaceInstanceOnChangesAsync(mutatingLspWorkspace: True)](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1558242&view=ms.vss-test-web.build-test-results-tab&runId=42886580&resultId=249591)|dotnet/roslyn#84951|
|[1557933](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1557933)|dotnet/roslyn|[Microsoft.CodeAnalysis.LanguageServer.UnitTests.FileBasedPrograms.FileBasedProgramsWorkspaceTests.TestDiagnosticsRequestedAfterDocumentClosed](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1557933&view=ms.vss-test-web.build-test-results-tab&runId=42881478&resultId=115821)|dotnet/roslyn#84944|
|[1557281](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1557281)|dotnet/roslyn|[Microsoft.CodeAnalysis.LanguageServer.UnitTests.Definitions.GoToDefinitionTests.TestGotoDefinitionAsync_NoResultsOnNamespace(mutatingLspWorkspace: False)](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1557281&view=ms.vss-test-web.build-test-results-tab&runId=42863398&resultId=248471)|dotnet/roslyn#84935|
|[1557098](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1557098)|dotnet/roslyn|[Roslyn.VisualStudio.NewIntegrationTests.VisualBasic.BasicChangeSignatureDialog.VerifyAddParametersAcrossLanguages](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1557098&view=ms.vss-test-web.build-test-results-tab&runId=42858444&resultId=100804)||
|[1557003](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1557003)|dotnet/roslyn|[Microsoft.CodeAnalysis.LanguageServer.UnitTests.Symbols.DocumentSymbolsTests.TestGetDocumentSymbolsAsync_Hierarchical_GenericMethod(mutatingLspWorkspace: False)](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1557003&view=ms.vss-test-web.build-test-results-tab&runId=42855454&resultId=249427)|dotnet/roslyn#84929|
|[1557055](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1557055)|dotnet/roslyn|[Microsoft.CodeAnalysis.LanguageServer.UnitTests.OnAutoInsert.RawStringOnAutoInsertTests.OnAutoInsert_RawString_DoNotGrowEmptyInsideFourQuotes(mutatingLspWorkspace: False)](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1557055&view=ms.vss-test-web.build-test-results-tab&runId=42856032&resultId=249116)||
|[1556280](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1556280)|dotnet/roslyn|[Microsoft.CodeAnalysis.LanguageServer.UnitTests.ProtocolConversionsTests.ProjectToProjectContext_MiscellaneousFilesWorkspace(mutatingLspWorkspace: False)](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1556280&view=ms.vss-test-web.build-test-results-tab&runId=42832060&resultId=249198)||
|[1555163](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1555163)|dotnet/roslyn|[Roslyn.VisualStudio.NewIntegrationTests.VisualBasic.BasicChangeSignatureDialog.VerifyAddParametersAcrossLanguages](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1555163&view=ms.vss-test-web.build-test-results-tab&runId=42805874&resultId=100374)|dotnet/roslyn#84910|
|[1554941](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1554941)|dotnet/roslyn|[Roslyn.VisualStudio.NewIntegrationTests.VisualBasic.BasicChangeSignatureDialog.VerifyAddParametersAcrossLanguages](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1554941&view=ms.vss-test-web.build-test-results-tab&runId=42798208&resultId=100804)|dotnet/roslyn#84903|
#### Summary
|24-Hour Hit Count|7-Day Hit Count|1-Month Count|
|---|---|---|
|0|1|52|

Start with the failing Microsoft.CodeAnalysis.LanguageServer.UnitTests.HandlerTests.NonMutatingHandlerExceptionNFWIsReported test and the linked Azure DevOps build logs. Read the known-issue guidance and compare the reported TaskCanceledException with the referenced pull requests and repeated failures. Done means the failure's ownership and remediation are established, with validation showing the known-issue handling is correct.

Written by the indexing model from the issue text.