wasm lanes fail with log error: Error message: Could not load file or assembly '/System.Private.CoreLib.dll'. The module was expected to contain an assembly manifest. (0x80131018)

[danmoseley]

Build Information

Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1371487
Build error leg or test failing: WasmTestOnChrome-CLR-ST-Invariant.Tests.WorkItemExecution
Pull request: #126657

Error Message

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

{
  "ErrorMessage": "log error: Error message: Could not load file or assembly '/System.Private.CoreLib.dll'. The module was expected to contain an assembly manifest. (0x80131018)",
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

ChromeDriver was started successfully on port 46709.
[04:23:22] info: Running in: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) HeadlessChrome/146.0.0.0 Safari/537.36
[04:23:22] info: Running at: http://127.0.0.1:40169/index.html?arg=--run&arg=WasmTestRunner.dll&arg=Common.Tests.dll&arg=-notrait&arg=category%3dIgnoreForCI&arg=-notrait&arg=category%3dOuterLoop&arg=-notrait&arg=category%3dfailing&arg=-verbosity&arg=Info
[04:23:22] info: could not load /runArgs.json: 404. Ignoring
[04:23:22] info: Incoming arguments: --run WasmTestRunner.dll Common.Tests.dll -notrait category=IgnoreForCI -notrait category=OuterLoop -notrait category=failing -verbosity Info
[04:23:22] info: Application arguments: --run WasmTestRunner.dll Common.Tests.dll -notrait category=IgnoreForCI -notrait category=OuterLoop -notrait category=failing -verbosity Info
[04:23:23] info: log error: Failed to load System.Private.CoreLib.dll (error code 0x80131018)
[04:23:23] info: log error: Path: /System.Private.CoreLib.dll
[04:23:23] info: log error: Error message: Could not load file or assembly '/System.Private.CoreLib.dll'. The module was expected to contain an assembly manifest. (0x80131018)
[04:23:23] info: coreclr_initialize failed - Error: 0x80131018
[04:23:23] info: WASM EXIT -1
[04:23:23] info: Waiting to flush log messages with a timeout of 120 secs ..
[04:23:23] info: DOTNET: Aborting startup, reason: Error: Failed to initialize CoreCLR
[04:23:23] fail: Application has finished with exit code -1 but 0 was expected
[04:23:23] info: Closing 1 browser tabs before setting the main tab to config page and quitting.

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1371487
Error message validated: [log error: Error message: Could not load file or assembly '/System.Private.CoreLib.dll'. The module was expected to contain an assembly manifest. (0x80131018)]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 4/9/2026 3:36:07 PM UTC

Report

Build	Definition	Test	Pull Request
1370009	dotnet/runtime	Wasm.Build.Tests.DebugLevelTests.PublishWithExplicitValue	#126308

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
0	0	1

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/area-infrastructure-libraries
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[danmoseley]

@vitek-karas

[dotnet-policy-service]

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
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[vitek-karas]

This was very likely caused by #126388 . The CI in that PR already reported these failures, but they were ignored via override.
@davidwrighton could you please look into this? It cases a LOT of failures on PRs - for example https://github.com/dotnet/runtime/pull/125966/checks?check_run_id=70586795175 - reports more than 1500 failures.

[akoeplinger]

It's probably not that PR, we see a similar issue about missing corelib in mono wasm legs: #126675

[radekdoulik]

This should be fixed with #126709 which landed yesterday.