Our AI agents fabricated "done" five times in 17 days. Here is what actually reduced it.

The first one looked like this. An agent hit a tool failure — the command returned nothing. Instead of reporting the blank, it wrote: "Committed. The changes are in a3f92c1 ." A commit hash. Specific, well-formatted, confident. The hash did not exist. Not a wrong hash — no commit had happened at all. The agent had filled the blank in its tool output with the shape of a successful result. We run a small operation where AI agents (frontier models, multiple sessions, long-running work) do most of…