BadImageFormatException crash after tests complete with --coverage on .NET 10 + NUnit

Start by reproducing the failure with the .NET 10 project described in global.json using dotnet test --coverage --coverage-output-format cobertura, then compare it with dotnet test without coverage. Trace the Microsoft Testing Platform and CodeCoverage cleanup path, including the dotnet-coverage collect entry point. Done means coverage is generated, cleanup completes without BadImageFormatException, and the process exits with code 0.

Description

When running tests with --coverage flag using Microsoft Testing Platform (MTP) on .NET 10 with NUnit, tests pass successfully and the coverage file is generated, but the process crashes during async cleanup with BadImageFormatException: Index not found.

Environment

• OS: Ubuntu Linux (GitHub Actions runner) and macOS ARM64
• .NET SDK: 10.0.101
• Test Framework: NUnit 4.4.0
• Test Adapter: NUnit3TestAdapter 6.1.0
• MTP Packages:
  • Microsoft.Testing.Platform.MSBuild 2.0.2
  • Microsoft.Testing.Extensions.Telemetry 2.0.2
  • Microsoft.Testing.Extensions.CodeCoverage 18.3.1 and 18.3.2 (both crash)

Reproduction

1. Create a .NET 10 test project with NUnit and MTP enabled
2. Configure global.json with "test": { "runner": "Microsoft.Testing.Platform" }
3. Run: dotnet test --coverage --coverage-output-format cobertura

Expected Behavior

Tests complete and process exits with code 0.

Actual Behavior

Tests pass (762 passed in our case), coverage file IS generated, but then:

NUnit Adapter 6.1.0.0: Test execution complete

Error output: Unhandled exception. System.BadImageFormatException: Index not found. (0x80131124)
   at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.AsyncStateMachineBox`1.MoveNext(Thread threadPoolThread)
   at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.AsyncStateMachineBox`1.MoveNext()
   at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction(IAsyncStateMachineBox box, Boolean allowInlining)
--- End of stack trace from previous location ---
   at System.Threading.Tasks.Task.<>c.<ThrowAsync>b__124_1(Object state)
   at System.Threading.ThreadPoolWorkQueue.Dispatch()
   at System.Threading.PortableThreadPool.WorkerThread.WorkerThreadStart()
   at System.Threading.Thread.StartCallback()

In process file artifacts produced:
  - /path/to/TestResults/<guid>.cobertura.xml

Test run summary: Failed!
  error: 1
  total: 764
  failed: 0
  succeeded: 762
  skipped: 2

Exit code: 134 (SIGABRT)

Workaround

Running without --coverage flag works fine:

dotnet test  # Works, exit code 0
dotnet test --coverage  # Crashes with exit code 134

Notes

• The crash occurs AFTER tests complete and coverage file is written
• The exception is in async cleanup/finalization phase
• Tested with both CodeCoverage 18.3.1 and 18.3.2 - same crash
• dotnet-coverage collect CLI tool also shows "Profiler was not initialized"