The same interop launch flake that produced exit 127 with an empty log has a
second face: a non-zero exit after the engine banner and not one line more.
test_fleet_growth went that way once in six full-suite runs and passed alone
every time.
The line between a flake and a failure is output, not the exit code and not
the banner - every test says something before it stops, its own FAIL
verdict, a SCRIPT ERROR, an engine complaint. A log holding nothing but the
banner is a run that did not happen, so it is retried and, if it stays
silent, reported as NOSTART rather than as a test that failed. A
deterministic silent crash still fails all three attempts.
The check reads grep's output rather than its exit status: `grep -q -v` does
not agree across implementations - ugrep, which is what `grep` resolves to
on the WSL box, reports success for an empty file and failure for a file
full of matching lines.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
88b53abf52
