GSTACK_FREE_JOBS overrides the computed shard count (the free runner's
analogue of the paid runner's EVALS_JOBS). On Vercel sandboxes, PID 1
installs a seccomp filter whose supervisor spuriously fails access(2) for
busy processes — measured: 200/200 git-init probes fail 'Cannot access work
tree: Permission denied' while the suite runs at 6 shards, 0/200 idle;
statx succeeds while access fails on the same path in the same process.
One serial mega-shard maximizes per-process pressure and fails too; 2
shards is the measured sweet spot.
GSTACK_FREE_RETRY_FLAKY=1 (default OFF — dev boxes should see flakes)
re-runs attributed failures once, serially, capped at 5 files; a clean
retry downgrades to a loud FLAKY-PASS naming the offenders, a repeat
failure stays red, timeouts and unattributed failures never retry.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
