The demo ran 50 times without a failure. Then we shipped it.
Three days into production, the agent started returning confident nonsense. Not errors. Not crashes. It finished its task, wrote a result, logged success. The result was wrong. Nobody caught it for six hours.
The agent's job was to pull structured data from a third-party endpoint, summarize it, and route a decision. In testing, that endpoint always returned a list with at least one item. On day three, it returned an empty list. Valid JSON, zero items. The agent had never seen this input. It did not stop. It summarized the absence of data as if it meant something, filled in plausible context, and routed confidently.
Confident autocomplete on an empty input. That is the production failure mode demos never surface.
Why the demo hid it
