Langfuse
Open-source platform for tracing, evaluations, and prompt management. Self-hostable alternative to LangSmith with broad framework support. Acquired by ClickHouse in January 2026; OSS core continues with deeper ClickHouse-backed analytics.
Traceloop
Open-source LLM observability using OpenTelemetry standards. Automatic instrumentation for LangChain, OpenAI, and other frameworks with zero code changes.