Trial
Langfuse is the most widely used open-source LLM observability platform: tracing, prompt management, cost tracking, datasets and trace-based evaluation (LLM-as-judge on production traces, scores API, annotation queues).
- MIT-licensed core including evals, playground and experiments; only enterprise features (SCIM, audit logs) are commercial. Fully self-hostable - note the infrastructure footprint (Postgres + ClickHouse).
- Acquired by ClickHouse in January 2026 with an explicit open-source and self-hosting commitment.
- Observability-first: the natural fit when tracing and monitoring come first and evals run on top of production traces - for CI-first evaluation see Opik or Deepeval.