xAI releases Grok 4 Fast. It uses the same architecture as Grok 4 but incorporates efficiency improvements from training data and reinforcement learning. It supports a 2 million token context window and unified weights handle both chain-of-thought reasoning and direct responses, controlled by prompts.

Also, it’s cheap! 47x cheaper than Grok 4. I think it’s cheaper compared to the average, with a price of 0.20$ per input million tokens and 0.50$ per output million tokens. These prices refer to requests under 128k.