Your LLM traffic should land in the observability stack you already run. Here is how logging callbacks fan-out gateway events to Datadog, Langfuse, S3, and Slack without coupling your app to any of them.
Request logs are your debugger and your liability at once. Here is a practical policy for LLM logging — what to capture, what to redact, how long to keep it, and the four logging levels to choose from.
An average latency number hides the requests that ruin your UX. Here is how to measure LLM latency with percentiles, why p95/p99 matter more than the mean, and how to read tail latency on a gateway.
Head-to-head: NemoRouter vs Langfuse. A self-hostable observability + prompt + evals specialist vs a hosted LLM gateway that bundles observability, routing, and governance — every feature free on every tier. 4% PAYG, 0% on Tier 3 annual prepay. 2,000+ models behind one API key.
How to attribute LLM costs across multi-agent systems: virtual keys per agent role, per-run cost accumulation, budget enforcement, and the observability patterns that prevent surprise bills.