Langfuse

Langfuse is the most widely adopted open-source LLM engineering platform (MIT license), covering tracing, prompt management, and evaluations in a single self-hostable stack. Its open-source posture and zero-license self-hosting cost give it a strong structural advantage in data-residency and compliance-sensitive enterprises, and its breadth of integrations (100+) and active GitHub community create real switching costs for teams already embedded. However, skeptics should note: the ClickHouse acquisition introduces genuine roadmap uncertainty at a critical growth moment; trace-logging benchmarks from a competitor place Langfuse's performance significantly behind newer rivals; agent-native gaps (no automatic issue clustering, manual multi-step causal analysis) are real and acknowledged; and the per-unit billing model can surprise finance teams when dense agent traces multiply costs far beyond raw request counts. The $2,499/month enterprise cloud tier is steep for what remains largely an open-source infrastructure product, and SSO is gated behind an additional $300/month add-on on the Pro plan.