Mono WASM test failure with "MONO_WASM: Unhandled error: TypeError: Failed to fetch"

[jakobbotsch]

Build Information

Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1396034
Build error leg or test failing: WasmTestOnChrome-MONO-ST-System.Buffers.Tests.WorkItemExecution
Pull request: #127336

Error Message

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

{
  "ErrorMessage": "MONO_WASM: Unhandled error: TypeError: Failed to fetch",
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1396034
Error message validated: [MONO_WASM: Unhandled error: TypeError: Failed to fetch]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 4/25/2026 12:25:00 PM UTC

Report

Build	Definition	Test	Pull Request
1402754	dotnet/runtime	WasmTestOnChrome-MONO-ST-System.Collections.Tests.WorkItemExecution	#127561
1400931	dotnet/runtime	WasmTestOnChrome-MONO-ST-System.Linq.Tests.WorkItemExecution	#126769
1400864	dotnet/runtime	WasmTestOnChrome-MONO-ST-System.Xml.Linq.Axes.Tests.WorkItemExecution	#123920
1400776	dotnet/runtime	WasmTestOnChrome-MONO-ST-Microsoft.Bcl.AsyncInterfaces.Tests.WorkItemExecution
1396628	dotnet/runtime	WasmTestOnChrome-MONO-ST-Microsoft.XmlSerializer.Generator.Tests.WorkItemExecution	#127428
1396624	dotnet/runtime	WasmTestOnChrome-MONO-ST-System.Text.RegularExpressions.Unit.Tests.WorkItemExecution	#127429
2960038	dotnet-runtime	WasmTestOnChrome-MONO-ST-System.Data.DataSetExtensions.Tests.WorkItemExecution
1396034	dotnet/runtime	WasmTestOnChrome-MONO-ST-System.Buffers.Tests.WorkItemExecution	#127336

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
1	8	8

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