--- title: "FastChat vs rhesis" type: "comparison" canonical_url: "https://www.graphcanon.com/compare/lm-sys-fastchat-vs-rhesis-ai-rhesis" tools: ["lm-sys-fastchat", "rhesis-ai-rhesis"] --- # FastChat vs rhesis *GraphCanon updated Jul 11, 2026* ## Verdict Pick FastChat when license: FastChat is Apache-2.0, rhesis is Other; pick rhesis when license: rhesis is Other, FastChat is Apache-2.0. [FastChat](https://github.com/lm-sys/FastChat) reports 39k GitHub stars, 4.8k forks, and 1.0k open issues, last pushed May 1, 2026. [rhesis](https://www.rhesis.ai/) has 379 stars, 27 forks, and 119 open issues, last pushed Jul 10, 2026. Figures are from public GitHub metadata via [FastChat's repository](https://github.com/lm-sys/FastChat) and [rhesis's repository](https://github.com/rhesis-ai/rhesis). | | [FastChat](/tools/lm-sys-fastchat.md) | [rhesis](/tools/rhesis-ai-rhesis.md) | | --- | --- | --- | | Tagline | An open platform for training, serving, and evaluating large language models | The testing platform for AI teams. Bring engineers, PMs, and domain experts together to generate tests, simulate (adversarial) conversations, and trace every failure to its root cause. | | Stars | 39,490 | 379 | | Forks | 4,788 | 27 | | Open issues | 1,027 | 119 | | Language | Python | Python | | Adopt for | FastChat is a comprehensive open platform for managing large language models (LLMs) that includes capabilities for training, serving, evaluating, and comparing chatbot models via web UIs and RESTful APIs. It powers ChatB | - | | Persona | - | - | | Runtime | - | - | | License | Apache-2.0 | Other | | Categories | LLM Frameworks, Model Training, Inference & Serving, Evaluation & Observability | LLM Frameworks, Evaluation & Observability | ## Trust and health _Sourced signals - not a safety guarantee. No winner column._ | | [FastChat](/tools/lm-sys-fastchat.md) | [rhesis](/tools/rhesis-ai-rhesis.md) | | --- | --- | --- | | Maintenance | Steady (60%) | Very active (96%) | | Days since push | 71d | 0d | | Open issues (now) | 1.0k | 119 | | Full report | [trust report](/tools/lm-sys-fastchat/trust.md) | [trust report](/tools/rhesis-ai-rhesis/trust.md) | ## Decision facts: FastChat - **Adopt for:** FastChat is a comprehensive open platform for managing large language models (LLMs) that includes capabilities for training, serving, evaluating, and comparing chatbot models via web UIs and RESTful APIs. It powers ChatB ## Choose when ### Choose FastChat if… - License: FastChat is Apache-2.0, rhesis is Other. - Tags unique to FastChat: evaluation system, large-language-models, chatbots, distributed serving. - Also covers Model Training, Inference & Serving. - - You are looking to train and evaluate state-of-the-art models such as Vicuna or MT-Bench. ### Choose rhesis if… - License: rhesis is Other, FastChat is Apache-2.0. - Tags unique to rhesis: llmops, quality-assessment, generative-ai, responsible-ai. - More recently updated (last pushed Jul 10, 2026). ## When NOT to use FastChat - - You require a proprietary or closed-source framework; FastChat is open-source under Apache-2.0 license and its use might be unsuitable for environments requiring proprietary solutions. - - Your chatbot evaluation needs do not align with the types of data used in FastChat's datasets (e.g., human votes, MT-Bench evaluations). - - You prefer a more user-friendly setup without the need to clone a repository and manually install dependencies; FastChat requires installation from source with additional steps for Rust and CMake on - + Mac. ## When NOT to use rhesis - LLM Frameworks: Avoid a framework for a single prompt-and-retrieve call; the abstraction can cost more than it saves. - Evaluation & Observability: Defer heavyweight eval infra only until you have real traffic - never skip it once users depend on answers. ## Common questions ### What is the difference between FastChat and rhesis? FastChat: An open platform for training, serving, and evaluating large language models. rhesis: The testing platform for AI teams. Bring engineers, PMs, and domain experts together to generate tests, simulate (adversarial) conversations, and trace every failure to its root cause.. See the comparison table for live GitHub stats and shared categories. ### When should I choose FastChat over rhesis? Choose FastChat over rhesis when License: FastChat is Apache-2.0, rhesis is Other; Tags unique to FastChat: evaluation system, large-language-models, chatbots, distributed serving; Also covers Model Training, Inference & Serving; - You are looking to train and evaluate state-of-the-art models such as Vicuna or MT-Bench. ### When should I choose rhesis over FastChat? Choose rhesis over FastChat when License: rhesis is Other, FastChat is Apache-2.0; Tags unique to rhesis: llmops, quality-assessment, generative-ai, responsible-ai; More recently updated (last pushed Jul 10, 2026). ### When should I avoid FastChat? - You require a proprietary or closed-source framework; FastChat is open-source under Apache-2.0 license and its use might be unsuitable for environments requiring proprietary solutions. - Your chatbot evaluation needs do not align with the types of data used in FastChat's datasets (e.g., human votes, MT-Bench evaluations). - You prefer a more user-friendly setup without the need to clone a repository and manually install dependencies; FastChat requires installation from source with additional steps for Rust and CMake on + Mac. ### When should I avoid rhesis? LLM Frameworks: Avoid a framework for a single prompt-and-retrieve call; the abstraction can cost more than it saves. Evaluation & Observability: Defer heavyweight eval infra only until you have real traffic - never skip it once users depend on answers. ### Is FastChat or rhesis more popular on GitHub? FastChat has more GitHub stars (39,490 vs 379). Stars measure visibility, not whether either tool fits your constraints. ### Are FastChat and rhesis open source? Yes - both are open-source projects on GitHub (FastChat: Apache-2.0, rhesis: Other). ### Where can I find alternatives to FastChat or rhesis? GraphCanon lists graph-backed alternatives at [FastChat alternatives](/tools/lm-sys-fastchat/alternatives) and [rhesis alternatives](/tools/rhesis-ai-rhesis/alternatives) ([FastChat markdown twin](/tools/lm-sys-fastchat/alternatives.md), [rhesis markdown twin](/tools/rhesis-ai-rhesis/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/lm-sys-fastchat-vs-rhesis-ai-rhesis.md) mirrors this page for agents and LLM crawlers, with the same stats table and FAQ answers. ### Which is better maintained, FastChat or rhesis? FastChat: Steady. rhesis: Very active. 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 FastChat and rhesis? GraphCanon publishes per-repo trust reports with dated maintenance, provenance, and scan summaries: [FastChat trust report](/tools/lm-sys-fastchat/trust); [rhesis trust report](/tools/rhesis-ai-rhesis/trust). --- **Machine-readable endpoints** - JSON: [`/api/graphcanon/graph?tool=lm-sys-fastchat`](/api/graphcanon/graph?tool=lm-sys-fastchat) - 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/_