xAI: grok-4-fast-reasoning API
A speed-optimized variant of Grok-4 designed for complex, multi-step logical problems. It utilizes a "reasoning-first" approach with visible thinking tokens, delivering near-frontier intelligence in science, finance, and coding at significantly lower latency.
- Context window: 2,097,152 tokens
- Max output: 30,000 tokens
- Input: text, image
- Output: text
- Reasoning: Supported
- Tool calling: Supported
- File input: Supported
- Released: 2025-08-27
- Knowledge cutoff: 2024-12-30
Frequently Asked Questions
What is the context window of grok-4-fast-reasoning?
grok-4-fast-reasoning supports a context window of up to 2,097,152 tokens.
Does grok-4-fast-reasoning support function calling?
Yes. grok-4-fast-reasoning supports tool / function calling.
Does grok-4-fast-reasoning support reasoning?
Yes. grok-4-fast-reasoning is a reasoning-capable model.
What is the knowledge cutoff of grok-4-fast-reasoning?
The knowledge cutoff of grok-4-fast-reasoning is 2024-12-30.