Changes from previous version
Optimized inference versus Grok 4 with a much larger context window for long documents and agent traces.
Release Summary
Cost-efficient Grok 4 generation model with a 2M-token context window and faster responses for high-volume chat and tool use.
Timeline
September 19, 2025
Grok 4 Fast released
xAI releases Grok 4 Fast with 2M context for API and consumer surfaces.