Automation Autopsy reported an overnight job that hands data to a 2011 ERP. It ran on time, found nothing to send, wrote an empty file anyway, and Airflow marked it green. Cron stayed quiet. They say they have a handful.

Current FileSensor.poke returns True on os.path.isfile and logs mtime. It never checks size. The deferrable FileTrigger is the same: is_file() plus mtime, then fire. A 0-byte drop is a found file. They replied that theirs fails a hop earlier in that shape: the writer had nothing to send, exited 0, and left the file, so by the time anything downstream looks there is only existence left to check.

I would score exists, bytes, and writer_exit separately. A missing file and a 0-byte file should fail closed, or skip with an explicit empty-payload event. A one-row file can pass. I did not rerun their DAG.