BlazorWasm_CannotAOT_InDebug test failure

[sbomer]

Build Information

Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1320821
Build error leg or test failing: Wasm.Build.Tests.Blazor.BuildPublishTests.BlazorWasm_CannotAOT_InDebug(config: Debug)
Pull request: #125190

Error Message

Replacing dotnet process output with messages from binlog
    Wasm.Build.Tests.Blazor.BuildPublishTests.BlazorWasm_CannotAOT_InDebug(config: Debug) [FAIL]
      Assert.Contains() Failure: Sub-string not found
      String:    "Property reassignment: $(MSBuildProjectEx"···
      Not found: "AOT is not supported in debug configurati"···
      Stack Trace:
        /_/src/mono/wasm/Wasm.Build.Tests/Blazor/BuildPublishTests.cs(148,0): at Wasm.Build.Tests.Blazor.BuildPublishTests.BlazorWasm_CannotAOT_InDebug(Configuration config)
           at System.Reflection.MethodBaseInvoker.InterpretedInvoke_Method(Object obj, IntPtr* args)
           at System.Reflection.MethodBaseInvoker.InvokeWithOneArg(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
      Output:
        
        ** -------- publish -------- **
        
        Binlog path: /root/helix/work/workitem/uploads/xharness-output/logs/blazorwasm_Debug_True_luwbcve3_g5k_鿀蜒枛遫䡫煉/BlazorBasicTestApp-publish.binlog
        [] Executing (Captured Output) - /root/helix/work/workitem/e/dotnet-latest/dotnet publish -bl:/root/helix/work/workitem/uploads/xharness-output/logs/blazorwasm_Debug_True_luwbcve3_g5k_鿀蜒枛遫䡫煉/BlazorBasicTestApp-publish.binlog -p:Configuration=Debug -nr:false -p:CompressionEnabled=false -p:WasmEnableHotReload=false   -  in pwd /root/helix/work/workitem/e/wbt artifacts/blazorwasm_Debug_True_luwbcve3_g5k_鿀蜒枛遫䡫煉/App
        	[DOTNET_ROOT] = /root/helix/work/workitem/e/dotnet-latest
        	[DOTNET_INSTALL_DIR] = /root/helix/work/workitem/e/dotnet-latest
        	[DOTNET_SKIP_FIRST_TIME_EXPERIENCE] = 1
        	[PATH] = /root/helix/work/workitem/e/dotnet-latest:/__w/1/s/artifacts/bin/geckodriver/geckodriver:/root/helix/work/correlation/dotnet-latest:/root/helix/work/correlation/xharness-cli:/root/helix/work/correlation/dotnet-cli:/root/helix/work/correlation/chrome-linux:/root/helix/work/correlation/chromedriver_linux64:/home/helixbot/.vsts-env/bin:/home/helixbot/.jsvu/bin:/home/helixbot/.vsts-env/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
        	[EM_WORKAROUND_PYTHON_BUG_34780] = 1
        	[NUGET_PACKAGES] = /root/helix/work/workitem/e/wbt artifacts/nuget/blazorwasm_Debug_True_luwbcve3_g5k_鿀蜒枛遫䡫煉
        	[TreatPreviousAsCurrent] = false
        []   Determining projects to restore...
        []   Restored /root/helix/work/workitem/e/wbt artifacts/blazorwasm_Debug_True_luwbcve3_g5k_鿀蜒枛遫䡫煉/App/BlazorBasicTestApp.csproj (in 1.66 sec).
        [] /root/helix/work/workitem/e/dotnet-latest/sdk/11.0.100-preview.3.26124.102/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.RuntimeIdentifierInference.targets(383,5): message NETSDK1057: You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy [/root/helix/work/workitem/e/wbt artifacts/blazorwasm_Debug_True_luwbcve3_g5k_鿀蜒枛遫䡫煉/App/BlazorBasicTestApp.csproj]
        []   BlazorBasicTestApp -> /root/helix/work/workitem/e/wbt artifacts/blazorwasm_Debug_True_luwbcve3_g5k_鿀蜒枛遫䡫煉/App/bin/Debug/net11.0/BlazorBasicTestApp.dll
        []   BlazorBasicTestApp (Blazor output) -> /root/helix/work/workitem/e/wbt artifacts/blazorwasm_Debug_True_luwbcve3_g5k_鿀蜒枛遫䡫煉/App/bin/Debug/net11.0/wwwroot
        []   ** MicrosoftNetCoreAppRuntimePackDir : '/root/helix/work/workitem/e/dotnet-latest/packs/Microsoft.NETCore.App.Runtime.Mono.browser-wasm/11.0.0-ci'
        []   Optimizing assemblies for size may change the behavior of the app. Be sure to test after publishing. See: https://aka.ms/dotnet-illink
        []   Optimizing assemblies for size. This process might take a while.
        Replacing dotnet process output with messages from binlog
    Wasm.Build.Tests.Blazor.BuildPublishTests.BlazorWasm_CannotAOT_InDebug(config: Debug) [FINISHED] Time: 54.9376157s
    Wasm.Build.Tests.Blazor.BuildPublishTests.DefaultTemplate_NoAOT_WithWorkload(config: Debug, testUnicode: False) [STARTING]

** -------- publish -------- **

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

{
  "ErrorMessage": "BlazorWasm_CannotAOT_InDebug",
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1320821
Error message validated: [BlazorWasm_CannotAOT_InDebug]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 3/5/2026 10:17:47 PM UTC

Report

Build	Definition	Test	Pull Request
1323909	dotnet/runtime	WBT-Workloads-MONO-ST-Wasm.Build.Tests.Blazor.BuildPublishTests.WorkItemExecution	#124923
1320821	dotnet/runtime	Wasm.Build.Tests.Blazor.BuildPublishTests.DefaultTemplate_NoAOT_WithWorkload	#125190

Summary

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

[lewing]

Analysis: Same root cause as #125233 — truncated binlog from OOM

What happens

1. The BlazorWasm_CannotAOT_InDebug test runs dotnet publish with RunAOTCompilation=true + Configuration=Debug
2. The test expects the build to fail with error "AOT is not supported in debug configuration" (emitted by _WasmAotCompileApp target in WasmApp.Common.targets)
3. However, the dotnet publish process is terminated before reaching that target (likely OOM on the Helix machine — a core dump core.1000.2656 was also found in the work item artifacts)
4. Since the process was terminated mid-write, the binlog is truncated (only 2 nodes, 0ms duration)
5. The WBT test harness detects no "Build succeeded"/"Build failed" in stdout, falls back to parsing the binlog via BinaryLog.ReadBuild()
6. The truncated binlog reader manages to extract "Property reassignment: $(MSBuildProjectEx..." before hitting EndOfStreamException
7. Test asserts the output contains "AOT is not supported in debug configuration" — it does not — FAIL

Evidence from Helix

• Helix job: 5c8ef215-ef71-43dc-b4d3-b71924dd3185
• Work item: WBT-Workloads-MONO-ST-Wasm.Build.Tests.Blazor.BuildPublishTests
• Binlog: blazorwasm_Debug_True_luwbcve3_g5k_*/BlazorBasicTestApp-publish.binlog — only 2 nodes, throws EndOfStreamException: Unable to read beyond the end of the stream
• Core dump: core.1000.2656 present in artifacts, confirming process crash
• Console log: Shows "Replacing dotnet process output with messages from binlog" then failure assertion on "Property reassignment..." not containing the expected error

Same root cause as #125233

Both tests fail because the dotnet publish process is terminated (OOM) during the build, before reaching the _WasmAotCompileApp target that emits the expected validation error. The binlog is truncated, and the fallback binlog parser produces garbage output that does not contain the expected error string.

The difference in observed error text is cosmetic:

• BlazorWasm AOT not requiring trimming #125233: binlog hits EOF immediately, output is "Error when reading the fil..."
• BlazorWasm_CannotAOT_InDebug test failure #125244: binlog has a few readable nodes before EOF, output is "Property reassignment: $(MSBuildProjectEx..."

Both are transient OOM-related failures, not test logic bugs.