Langfuse
Open-source LLM engineering platform — traces, evals, prompts
Verdict
Best open-source observability suite. Traces every LLM call with token costs, latency, and full prompt/response. Self-hostable on Docker. Prompt management UI is excellent.
Other Observability & Evals
- Arize AIStable
ML and LLM observability platform with drift detection and evaluation
- BraintrustExperimental
End-to-end LLM evaluation and experimentation platform
- HeliconeStable
LLM gateway with logging, caching, and cost analytics
- OpenLLMetryExperimental
OpenTelemetry-based observability for LLMs
- Phoenix (Arize)Stable
Open-source AI observability with embedding and RAG tracing
- PromptLayerStable
Prompt version control, A/B testing, and analytics platform