Langfuse

Langfuse is an open source platform purpose built for teams developing LLM applications. It gives you observability into your language model calls, letting you trace requests through prompts, completions, and tool usage. You get a timeline view of each interaction, including token usage and latency, making debugging and optimization straightforward.

Langfuse supports Python, JavaScript/TypeScript, and REST APIs, integrating directly with frameworks like LangChain, LlamaIndex, and OpenAI SDK. Features include prompt versioning, dataset creation for evaluations, and cost tracking per model. The platform can be self-hosted via Docker or used on their managed cloud. It also offers role based access control for team collaboration.

This tool is ideal for ML engineers and product teams who need to monitor and improve LLM behavior in production. Langfuse is released under the MIT license, with an optional enterprise tier for advanced security and compliance needs. It has gained traction in the open source community for its practical approach to LLM debugging.