FastChat vs. Grok

Overview

FastChat is the open platform for training, serving, and evaluating LLM chatbots developed and maintained by LMSYS.

FastChat is an open-source library for training, serving, and evaluating LLM chat systems from LMSYS. It includes training and evaluation code, a model serving system, a Web GUI, and a finetuning pipeline, and is the de facto system for Vicuna as well as FastChat-T5. FastChat also includes the Chatbot Arena for benchmarking LLMs.

Initial release: 2023-04-28

Reference

https://github.com/lm-sys/FastChat

Further Reading

• https://chat.lmsys.org/
• https://lmsys.org/projects/

Overview

Grok is the proprietary model family available through xAI's products and API. Grok 4.5 is the current generation, focused on coding, agentic tasks, reasoning, and knowledge work.

xAI introduced Grok in November 2023 and released the weights for Grok-1 under Apache 2.0 in March 2024. Later generations are proprietary and available through Grok, X, and the xAI API. Grok 4.5, released in July 2026, is xAI's current flagship model for software engineering, tool-driven agents, complex reasoning, and professional knowledge work.

Initial release: 2023-11-05

Current generation: Grok 4.5

Reference

https://x.ai/news/grok-4-5

Further Reading

• https://github.com/xai-org/grok-1/tree/main
• https://x.ai/news/grok-4-5