The two coverage passes shared fixed paths (coverage/lcov.info →
lcov.parallel.info → merge → rm -f), so a concurrent flutter test
--coverage — a second push gate, or a `make test` during a push — raced
and deleted this run's intermediate mid-merge, crashing merge_lcov with
FileNotFoundError.
Each pass now writes to a per-run mktemp dir via --coverage-path; the
merge runs from there and only the final result lands in coverage/lcov.info
via an atomic rename within coverage/. No shared intermediates, so
concurrent runs can't corrupt each other.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
jpmschweitzerandClaude Opus 4.8
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