lm-sys/FastChat

Health v2 · maintenance only

Adoption not part of the score

39525 stars · 4781 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-29, confidence not recorded

FastChat is an open platform for training, serving, and evaluating large language model based chatbots, originally releasing the Vicuna model and powering Chatbot Arena. It provides a distributed multi-model serving system with a web UI and OpenAI-compatible RESTful APIs, plus training and evaluation code such as MT-Bench.

Use cases

• serve local LLMs behind an OpenAI-compatible API
• host a chatbot web UI for multiple models
• fine-tune chat models like Vicuna
• evaluate chatbots with MT-Bench
• run side-by-side LLM comparisons and collect human votes
• build an LLM leaderboard from human preference data

When to choose

• you need a distributed multi-model LLM serving system with OpenAI-compatible endpoints
• you want to train or fine-tune open chat models like Vicuna
• you need benchmarking and human evaluation tooling for chatbots

When to avoid

• you only need lightweight single-model inference without a serving platform
• you need the newest serving features, as development has slowed and newer stacks like vLLM may be better maintained
• you want a managed cloud service rather than self-hosted infrastructure

Facets

framework · maturity maintenance

llm-inference llm-training chatbot http-server api-framework machine-learning large-language-models artificial-intelligence chatbots python windows vicuna chatbot-arena openai-compatible-api model-serving llm-evaluation fine-tuning distributed-serving natural-language-processing linux macos docker gpu web-server

Member repositories

For agents

markdown · JSON · MCP: product_card(name="lm-sys/FastChat")