The hook double-forked the rebuild subprocess and returned before the
subprocess wrote .planning/graphs/.rebuild.lock. Callers (notably the
feat-3347 test cleanup) waited for the lock to disappear before
rm -rf'ing the tmpdir, but an absent lock was ambiguous: it could mean
"subprocess finished and trapped lock removal" OR "subprocess hasn't
started yet." Under ubuntu CI load the second case won, cleanup raced
ahead, and rmSync walked into .planning/graphs while the subprocess
was still creating files — surfacing as
ENOTEMPTY: directory not empty, rmdir '/tmp/gsd-3347-*/.planning/graphs'
on the "dispatches on: git commit -m fix" test.
Spawn the rebuild as a regular backgrounded job, capture $!, and write
the lock file synchronously in the parent before exit. Lock-presence
is now a reliable in-flight signal; the rebuild script's existing
trap-on-EXIT rm still owns cleanup.
Validated: holodeck (ubuntu docker) 11224 pass / 0 fail.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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