The diff-lines error-boundary test mocked './syntax-diff' with a factory
that THREW. vitest hoists the factory and registers its module promise in
the mocker registry; a throwing factory leaves rejected promises there,
and under CI load one escapes as "Vitest caught 1 unhandled error during
the test run" attributed to whichever sibling file the worker is running
(user-message-edit.test.tsx in run 32803716726) — an intermittent js-tests
red on green code.
Rework: the factory now resolves to a component that throws the fetch
error during render — the same way React surfaces a rejected lazy payload
— so no rejected promise ever sits in the registry.
Guard proof (sabotage A/B): with the local syntax-diff ErrorBoundary
removed from diff-lines.tsx, the reworked test still fails (workspace
fallback renders), so the #93479 regression pin is intact. Full ui
project: 596 files / 5729 tests green, no unhandled errors in 3 full-run
repetitions.
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