Grok-4 Fast Reasoning: Benchmarks, Pricing & Context Window
Grok-4 Fast Reasoning is a language model from xAI, released in August 2025, with multimodal input, a 2M-token context window, and pricing from $0.200/M input and $0.500/M output.
Pushing the Frontier of Cost-Efficient Intelligence. Grok-4 Fast Reasoning is a high-speed variant of Grok-4 optimized for faster inference while maintaining strong reasoning capabilities through thinking tokens.
Grok-4 Fast Reasoning pricing
Providers
Grok-4 Fast Reasoning starts at $0.200 per million input tokens and $0.500 per million output tokens via xAI.
| Provider | Input $/M | Cached input $/M | Output $/M | Context in / out | TTFT p95 s | Output p5 c/s | Modalities in / out |
|---|---|---|---|---|---|---|---|
 xAI | $0.200 | — | $0.500 | 2.0M/30.0K | 2.97 | 14 | / |
Cached input is the discounted price for prompt tokens served from a provider cache. TTFT is time to first token. Output is characters per second; p5 is the sustained floor exceeded by 95% of observed requests.
Grok-4 Fast Reasoning context window
Input and output token limits for Grok-4 Fast Reasoning, plus how it ranks on long-context understanding.
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Grok-4 Fast Reasoning latency
Grok-4 Fast Reasoning time to first token, sustained output throughput, and failed-request rate from live model usage over the trailing 7 days.
Provider operational metrics
Time to first token, output throughput, and failed-request rate from live model usage
Grok-4 Fast Reasoning examples
Recent arena outputs from Grok-4 Fast Reasoning, picked from the highest-ranked matchups.
Grok-4 Fast Reasoning license
Grok-4 Fast Reasoning is a proprietary model available under its provider's product and API terms.
- License
- Proprietary
- Hosted access
Proprietary license - usage restrictions apply
Grok-4 Fast Reasoning resources
Official sources for Grok-4 Fast Reasoning: provider documentation.
FAQ
Common questions about Grok-4 Fast Reasoning.