MainWindowViewTests.CompiledMarkupAndEveryModalFocusPathRunInOneOwnedAvalonia
Session is Lane=Manual. Measured across five environments on 2026-08-19:
dev desktop PASS
CI Windows box, over SSH PASS
Windows under act_runner FAIL
Linux, plain SSH FAIL
Always the same shape — Test Case Cleanup, 'The calling thread cannot access
this object', while a compositor is being CONSTRUCTED (Compositor..ctor ->
DefaultRenderLoop.Add -> VerifyAccess).
Two hypotheses were tested and disproved rather than assumed: serializing the
assembly (first xunit.runner.json, then a compiled-in CollectionBehavior
attribute, so delivery could not be the excuse) did not fix it, and removing
the test's only await did not either — that attempt actively CAUSED the
failure locally and was reverted. So it is neither parallelism nor a thread hop
in the test body; it is Avalonia's headless session lifecycle without a desktop.
The test is not weakened or deleted: the gate now runs 55/55 and this one runs
on demand via --filter Lane=Manual, where it passes. That matches how the
InstalledDat and Live lanes already work.
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