langfuse vs FastChat

Common questions

What is the difference between langfuse and FastChat?

langfuse: Open source agent evals & observability: Trace, evaluate, and improve LLM applications with one open platform.. FastChat: An open platform for training, serving, and evaluating large language models. See the comparison table for live GitHub stats and shared categories.

When should I choose langfuse over FastChat?

Choose langfuse over FastChat when langfuse is primarily TypeScript; FastChat is Python; License: langfuse is Other, FastChat is Apache-2.0; Tags unique to langfuse: analytics, evaluation, llm-observability, monitoring; langfuse ships Docker support for self-hosted deployment; When you need a self-hosted solution for evaluating and monitoring large language model applications, as Langfuse supports local, VM, and Kubernetes environments.

When should I choose FastChat over langfuse?

Choose FastChat over langfuse when FastChat is primarily Python; langfuse is TypeScript; License: FastChat is Apache-2.0, langfuse is Other; Tags unique to FastChat: chatbot arena, llm-evaluation, multi-model serving, openai-compatible apis; Also covers Inference & Serving, LLM Frameworks, Model Training; When you need a platform that supports both training and evaluation of large language models, such as Vicuna, and you want to leverage human feedback for model evaluation.

When should I avoid langfuse?

If you are looking for a fully managed service without the need for self-hosting, as Langfuse requires setting up and maintaining the infrastructure yourself. When you need enterprise features that are not covered by the open-source version, as the ee folders are not open-source and may require additional licensing or services.

When should I avoid FastChat?

If you are looking for a platform that focuses solely on model training without serving or evaluation capabilities, FastChat offers a comprehensive suite that might be more than you need. If your project does not require human feedback for model evaluation, FastChat's integration with Chatbot Arena might be an unnecessary feature. If you are working with proprietary or closed-source models, FastChat's open-source nature and reliance on open-source models like Vicuna might not align with your project requirements.

Is langfuse or FastChat more popular on GitHub?

FastChat has more GitHub stars (39,536 vs 34,763). Stars measure visibility, not whether either tool fits your constraints.

Are langfuse and FastChat open source?

Yes - both are open-source projects on GitHub (langfuse: Other, FastChat: Apache-2.0).

Where can I find alternatives to langfuse or FastChat?

GraphCanon lists graph-backed alternatives at langfuse alternatives and FastChat alternatives (langfuse markdown twin, FastChat markdown twin), ranked by typed relationship edges rather than popularity votes.

Is there a machine-readable version of this comparison?

Yes. The markdown twin at this comparison mirrors this page for agents and LLM crawlers, with the same stats table and FAQ answers.

Which is better maintained, langfuse or FastChat?

langfuse: Very active. FastChat: Slowing. Compare maintenance labels, days since push, and release cadence in the trust section below - stars alone do not measure maintenance.

Where are the full trust reports for langfuse and FastChat?

GraphCanon publishes per-repo trust reports with dated maintenance, provenance, and scan summaries: langfuse trust report; FastChat trust report.