Developer Wires Sentry Monitoring Into LLM Pipeline After Silent CPU and Data Bugs

A developer building TextStack, an open-source .NET-based technical book reader, discovered that its LLM routing pipeline was producing zero alerts despite serious failures, including a 390% CPU spike and a 156 GB data leak. The core problem was that observability tooling was misconfigured, sending all telemetry spans to a closed socket in production, making monitoring effectively nonexistent. To fix the underlying issue, four pull requests were merged adding Sentry integration across the API and background Worker, route-decision logging, throttled alerts for expensive misdirected tasks, and a circuit breaker to prevent dead providers from stalling startup. The updated router now records not just which provider handled a request but why it was chosen, distinguishing deliberate routing from silent fallback to defaults. Additional fixes addressed a data-scrubbing gap that exposed SQL queries in logs and a race condition causing real users to lose their reading progress.