FastChat

Overview

FastChat is an open-source Python framework for training, serving, and evaluating large language models. It provides infrastructure for model deployment and includes Vicuna (a fine-tuned LLM) and Chatbot Arena (a benchmark for comparing model outputs). Built for researchers and developers who need end-to-end LLM workflows beyond inference alone.

Best for

Best for
Researchers and ML engineers building custom LLM applications who need training, serving, and evaluation in one framework.

Use cases

• Fine-tuning and training custom language models
• Serving multiple LLMs in production with a unified API
• Benchmarking and comparing model performance across variants

Notes

FastChat is an open-source Python framework for training, serving, and evaluating large language models. It provides infrastructure for model deployment and includes Vicuna (a fine-tuned LLM) and Chatbot Arena (a benchmark for comparing model outputs). Built for researchers and developers who need end-to-end LLM workflows beyond inference alone.

39,479 stars on GitHub. Last updated 2026-05-01. Licensed Apache-2.0.

Use cases

• Fine-tuning and training custom language models
• Serving multiple LLMs in production with a unified API
• Benchmarking and comparing model performance across variants

Pros

• Complete pipeline from training through evaluation, not just inference
• Includes Chatbot Arena for human-in-the-loop model comparison
• Active community project with 39k+ stars and ongoing maintenance

Cons

• Requires Python expertise and infrastructure setup for training workflows
• Primarily research-focused, less polished than commercial LLM platforms
• Evaluation tools depend on external judge models, adding latency and cost

Indexed from awesome-llm and enriched against its public facts.