From Stack Trace to Suggested Fix in 4 Seconds: Building a Self-Healing .NET API Gateway. (opens in new tab)

Last Tuesday my API gateway caught a NullReferenceException, streamed it to a dashboard in real-time, and pushed a draft code fix to the browser tab of the on-call engineer — before I finished reading the error myself. That sentence used to be vendor marketing. Now it's just my Program.cs. This is the architecture post-mortem. I built it on weekends. It runs in Docker. It cost me exactly $0 in LLM credits during development because Groq's free tier is generous and Ollama works as a swap-in. T...