serve-question answered POST /build-path with 200 and only then wrote the
flip file. The caller is a separate process, so the response could reach it
while the server was still preempted before the write landed: a poller that
trusted the 200 could look for the flip file and miss it.
Measured on a loaded machine, the old order lost that race 29 times out of
40; writing first and answering after loses it 0 times out of 40. This is
what made tests/serve-question.test.mjs fail intermittently in CI on the
Node 22 job while passing on Node 24.
AI-assisted change: diagnosed and implemented with Claude Code under
maintainer direction.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Abdul WahabandClaude Fable 5
f031eb0b9f