Product / UX / Telemetry & observability

Langfuse

Open-source LLM engineering platform providing tracing, prompt management, evaluations, cost tracking, and datasets. Self-hostable or cloud-hosted. The leading open source LLM observability platform with broad integrations (OpenTelemetry, LangChain, OpenAI SDK, LiteLLM). YC W23, 27.7K GitHub stars.

Active 2026; acquired by ClickHouse Mar 2026; MIT core

Openness

4 high confidence

4.0

license: MIT(core:tracing/integrations/API/data-model/exports/evals/playground/SSO)
commercial: enterprise-security(SCIM,audit-logs,data-retention)
source: public

https://github.com/langfuse/langfuse recorded 2026-06-04
flagship phase-C verification source
https://langfuse.com/blog/2025-06-04-open-sourcing-langfuse-product recorded 2026-06-04
flagship phase-C verification source
https://clickhouse.com/blog/clickhouse-acquires-langfuse-open-source-llm-observability recorded 2026-06-04
flagship phase-C verification source

Adoption

3 high confidence

3.0

Described as the most widely adopted open source LLM engineering platform; acquired by ClickHouse Mar 2026. No precise verified download/active-user count, rated 3 on reported traction.

https://github.com/langfuse/langfuse recorded 2026-06-04
flagship phase-C verification source
https://clickhouse.com/blog/clickhouse-acquires-langfuse-open-source-llm-observability recorded 2026-06-04
flagship phase-C verification source

Capability

4 high confidence

4.0

End-to-end tracing, prompt management, evals (incl. LLM-as-judge), datasets, annotation queues, playground; OpenTelemetry + LangChain/OpenAI/LiteLLM integrations. Rated on feature matrix.

https://github.com/langfuse/langfuse recorded 2026-06-04
flagship phase-C verification source
https://langfuse.com/docs/observability/overview recorded 2026-06-04
flagship phase-C verification source

Unchanged since 2026-06-24 (last edited, not re-checked)