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
- Phoenix (Arize)Stable
Open-source AI observability with embedding and RAG tracing
- Weave (W&B)Stable
Weights & Biases' LLM tracing and eval framework
- HeliconeStable
LLM gateway with logging, caching, and cost analytics
- OpenLLMetryEmerging
OpenTelemetry-based observability for LLMs
- PromptLayerStable
Prompt version control, A/B testing, and analytics platform
- BraintrustEmerging
End-to-end LLM evaluation and experimentation platform