[ci-scan] Wasm.Build.Tests ManagedToNativeGenerator task host node crash

[kotlarmilos]

Build Information

Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1491378
Build error leg or test failing: runtime / Build / browser-wasm linux Release — Helix work item WBT-NoWebcil-MONO-ST-Wasm.Build.Tests.PInvokeTableGeneratorTests (queue Ubuntu.2604.Amd64.Open)
Failing test (symptom): Wasm.Build.Tests.PInvokeTableGeneratorTests.UnmanagedStructAndMethodIn_SameAssembly_WithoutDisableRuntimeMarshallingAttribute_NotConsideredBlittable(config: Release, aot: False)
Pull request (first observed): #125437

Error Message

{
  "ErrorMessage": "error MSB4027: The \"ManagedToNativeGenerator\" task generated invalid items from the \"FileWrites\" output parameter. This object is no longer valid because the MetadataLoadContext that created it has been disposed.",
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Failure details:

The WASM not_blittable build inside PInvokeTableGeneratorTests is expected to fail with the diagnostic
error : Parameter types of pinvoke callback method '...' needs to be blittable. Instead, the
ManagedToNativeGenerator MSBuild task host crashed and the build failed early with:

WasmApp.Common.targets(787,5): error MSB4217: Task host node exited prematurely. Diagnostic information may be found in files in the temporary files directory named MSBuild_*.failure.txt.
WasmApp.Common.targets(796,7): error MSB4027: The "ManagedToNativeGenerator" task generated invalid items from the "FileWrites" output parameter. This object is no longer valid because the MetadataLoadContext that created it has been disposed.

Because the expected pinvoke-blittable diagnostic never printed, the test's Assert.Matches failed downstream:

Wasm.Build.Tests.PInvokeTableGeneratorTests.UnmanagedStructAndMethodIn_SameAssembly_WithoutDisableRuntimeMarshallingAttribute_NotConsideredBlittable(config: Release, aot: False) [FAIL]
  Assert.Matches() Failure: Pattern not found in value
  Regex: "error.*Parameter.*types.*pinvoke.*.*blittable"
  Value: "[]   Determining projects to restore...\n[]   Rest"...
  /_/src/mono/wasm/Wasm.Build.Tests/PInvokeTableGeneratorTests.cs(32,0)

The Assert.Matches Pattern not found message and the WorkItemExecution ... BadExit entry that Build
Analysis lists separately are both symptoms of the same root cause: the ManagedToNativeGenerator
task-host crash (MSB4217 + MSB4027 MetadataLoadContext ... has been disposed). Tracking the root
cause is more reusable than the downstream assertion text.

This is an infrastructure/flaky MSBuild task-host crash (Build Analysis reports a ~0.24% failure rate) and
is unrelated to the change in PR #125437 (Apple-mobile NativeAOT library tests).

Affected legs:

• runtime / Build / browser-wasm linux Release → Helix WBT-NoWebcil-MONO-ST-Wasm.Build.Tests.PInvokeTableGeneratorTests

Console Log:

• console.352ebce7.log (runId 41125472), work item WBT-NoWebcil-MONO-ST-Wasm.Build.Tests.PInvokeTableGeneratorTests

First build in window:

• Build 1491378 (PR [mobile] Enable NativeAOT library tests on Apple mobile platforms #125437, head SHA e34e28f)

Recommended action:
File as a Known Build Error so Build Analysis correlates future occurrences of the ManagedToNativeGenerator
task-host crash. Consider setting BuildRetry: true if this flake recurs frequently, since the crash is
transient and a rebuild typically produces the expected diagnostic.

Note

This issue was drafted with GitHub Copilot assistance and reviewed by the submitting developer.

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1491378
Error message validated: [error MSB4027: The "ManagedToNativeGenerator" task generated invalid items from the "FileWrites" output parameter. This object is no longer valid because the MetadataLoadContext that created it has been disposed.]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 7/2/2026 4:17:46 PM UTC

Report

Build	Repository	Test	Pull Request
1588168	dotnet/runtime	Wasm.Build.Tests.PInvokeTableGeneratorTests.UnmanagedStructAndMethodIn_SameAssembly_WithoutDisableRuntimeMarshallingAttribute_NotConsideredBlittable(config: Release, aot: False)	#133461
1586814	dotnet/runtime	Wasm.Build.Tests.PInvokeTableGeneratorTests.UnmanagedStructAndMethodIn_SameAssembly_WithoutDisableRuntimeMarshallingAttribute_NotConsideredBlittable(config: Release, aot: False)
1553903	dotnet/runtime	WBT-NoWorkload-CLR-ST-Wasm.Build.Tests.PInvokeTableGeneratorTests.WorkItemExecution	#132315

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
2	2	3

[lewing]

Have we ever seen another instance of this failure? It is a crash in the task host that doesn't have an obvious cause, we can harden the exception handling and possibly diagnose it better but I have not seen any other instances.

[dotnet-policy-service]

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
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