xAI: Grok 4 Fast
x-ai/grok-4-fast
Grok 4 Fast is xAI's latest multimodal model with SOTA cost-efficiency and a 2M token context window. It comes in two flavors: non-reasoning and reasoning. Read more about the model on xAI's news post(opens in new tab).
Reasoning can be enabled/disabled using the reasoning enabled parameter in the API. Learn more in our docs(opens in new tab)
Modalities
Context
2M
Weekly Tokens
66.4B
Released
Sep 19, 2025