How to Debug AI Backend Systems

I want to tell you about the worst three days of my engineering career. It started with a Slack message from our support team: “Users are complaining that the AI is giving wrong answers.” That was it. There were no error codes, stack traces, or even reproducible steps. Just… the AI was wrong. I opened our logs and checked, the request received at 10:47 AM and the response was sent at 10:49 AM, and also the status was 200. Everything looked perfect. The system had done exactly what it was supposed to do, which was very simple. Accept a question, process it, and return an answer. Except at this time, the answer was completely wrong, and I had absolutely no idea why. I spent the next three days in debugging hell. I tried reproducing the issue locally, but of course, the AI gave different answers each time. I added more logging, but I was logging the wrong things. I stared at the database queries that returned the right data. I reviewed prompts that looked fine. I checked the API responses