--- title: "langfuse vs FastChat" type: "comparison" canonical_url: "https://www.graphcanon.com/compare/langfuse-langfuse-vs-lm-sys-fastchat" tools: ["langfuse-langfuse", "lm-sys-fastchat"] --- # langfuse vs FastChat *GraphCanon updated Sep 20, 2026* ## Verdict Pick langfuse if langfuse is an open-source platform for evaluating and monitoring large language model applications, offering self-hosting options for local, VM, and Kubernetes environments; pick FastChat if fastChat is an open-source platform for training, serving, and evaluating large language models, including Vicuna, and supports Chatbot Arena, a platform for LLM evaluations with human feedback. [langfuse](https://langfuse.com) reports 35k GitHub stars, 3.8k forks, and 906 open issues, last pushed Sep 18, 2026. [FastChat](https://github.com/lm-sys/FastChat) has 40k stars, 4.8k forks, and 1.0k open issues, last pushed May 1, 2026. Figures are from public GitHub metadata via [langfuse's repository](https://github.com/langfuse/langfuse) and [FastChat's repository](https://github.com/lm-sys/FastChat). | | [langfuse](/tools/langfuse-langfuse.md) | [FastChat](/tools/lm-sys-fastchat.md) | | --- | --- | --- | | Tagline | Open source agent evals & observability: Trace, evaluate, and improve LLM applications with one open platform. | An open platform for training, serving, and evaluating large language models | | Stars | 34,763 | 39,536 | | Forks | 3,793 | 4,774 | | Open issues | 906 | 1,043 | | Language | TypeScript | Python | | Adopt for | Langfuse is an open-source platform for evaluating and monitoring large language model applications, offering self-hosting options for local, VM, and Kubernetes environments. | FastChat is an open-source platform for training, serving, and evaluating large language models, including Vicuna, and supports Chatbot Arena, a platform for LLM evaluations with human feedback. | | Persona | - | - | | Runtime | - | - | | License | Other | Apache-2.0 | | Categories | Evaluation & Observability | Evaluation & Observability, Inference & Serving, LLM Frameworks, Model Training | ## Trust and health _Sourced signals - not a safety guarantee. No winner column._ | | [langfuse](/tools/langfuse-langfuse.md) | [FastChat](/tools/lm-sys-fastchat.md) | | --- | --- | --- | | Maintenance | Very active (96%) | Slowing (36%) | | Days since push | 0d | 140d | | Open issues (now) | 906 | 1.0k | | Stars delta | +2.5k (30d) | +19 (30d) | | Open issues delta | +197 (30d) | +5 (30d) | | Full report | [trust report](/tools/langfuse-langfuse/trust.md) | [trust report](/tools/lm-sys-fastchat/trust.md) | ## Decision facts: langfuse - **Adopt for:** Langfuse is an open-source platform for evaluating and monitoring large language model applications, offering self-hosting options for local, VM, and Kubernetes environments. ## Decision facts: FastChat - **Adopt for:** FastChat is an open-source platform for training, serving, and evaluating large language models, including Vicuna, and supports Chatbot Arena, a platform for LLM evaluations with human feedback. ## Choose when ### Choose langfuse if… - 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. ### Choose FastChat if… - 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 NOT to use 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 NOT to use 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. ## 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](/tools/langfuse-langfuse/alternatives) and [FastChat alternatives](/tools/lm-sys-fastchat/alternatives) ([langfuse markdown twin](/tools/langfuse-langfuse/alternatives.md), [FastChat markdown twin](/tools/lm-sys-fastchat/alternatives.md)), 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](/compare/langfuse-langfuse-vs-lm-sys-fastchat.md) 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](/tools/langfuse-langfuse/trust); [FastChat trust report](/tools/lm-sys-fastchat/trust). --- **Machine-readable endpoints** - JSON: [`/api/graphcanon/graph?tool=langfuse-langfuse`](/api/graphcanon/graph?tool=langfuse-langfuse) - LLM index: [/llms.txt](/llms.txt) - Full corpus: [/llms-full.txt](/llms-full.txt) _GraphCanon - The knowledge graph for AI development. https://www.graphcanon.com/_