After analyzing over 50 real production agent traces from developers building with LangChain, AutoGen, and custom agents, I found out that most agent failures are silent. No error thrown. No obvious log. Its just the wrong output being delivered confidently.

Here are the five most common patterns:

1) Hallucinated retry

The agent claims a retry succeeded but no retry tool call exists in the trace. The payment failed, but the agent said it retried successfully, also there's zero observable evidence of any retry happening.

2) Date misinterpretation

The tool schedules deliver for June 18th, but the agent confirms June 19th to the user. One day off and its delivered with full confidence.

3) Unverifiable runtime assertion

The agent says "retry logic prevented further retries" but no retry mechanism step exists anywhere in the trace. The agent is making claims about its own internal behavior with no observable evidence.

4) Status contradiction

The tool returns status: cancelled. The agent says "your order is on its way." Direct contradiction, zero error thrown out.

5) Missing mandatory tool call

The agent claims to have booked a flight without ever calling a booking tool. It found the flight, but skipped the booking step, and confirmed it to the user anyway.

All five of these produce a confident, well-formatted response to the user. None of them throw an error. Standard logging won't catch them as well.

I built a free tool that detects these patterns automatically, paste any agent trace and get root cause diagnosis and specific fixes instantly.

No API key needed: [https://6jovkucbyygcamzbeksa67.streamlit.app]

What silent failures have you hit in production? Drop them in the comments.