AL
Jamba 1.5 Large
AI21 Labs
xAI model product
Grok 4 Fast Reasoning
Pushing the Frontier of Cost-Efficient Intelligence.
Updated Aug 12, 2026. Default version: Grok-4 Fast Reasoning
LLMBoard scoreN/ANot scored
CoverageN/ANot scored
Context window2MTokens
Official input priceN/AOfficial price unavailable
Grok 4 Fast Reasoning Specifications
Technical details for the model's default version.
- Version
- Grok-4 Fast Reasoning
- Released
- Aug 28, 2025
- Knowledge cutoff
- Unknown
- Parameters
- N/A
- Context window
- 2M
- Max output
- 30K
- Inputs
- image, text
- Outputs
- text
- Open weights
- No
- License
- Proprietary
Grok 4 Fast Reasoning Capability Profile
This profile uses the model's current scored version. Arena ratings and prices are shown separately.
No capability profile
No version of this model currently has enough benchmark coverage for a score.
Grok 4 Fast Reasoning Benchmark Results
Benchmark scores for the scored version.
No benchmark results
No benchmark result is linked to the scored version.
Grok 4 Fast Reasoning Arena Results
Preference and agent-evaluation results for the default version.
| webdev | overall | 110 | 1161.5 | 733 | N/A | |
| text factuality | overall | 116 | 1415.8 | 10,844 | N/A | |
| text style control | overall | 132 | 1403.6 | 18,805 | N/A | |
| text | overall | 134 | 1397.7 | 18,805 | N/A |
Grok 4 Fast Reasoning Runtime Performance
Provider-specific output speed and catalog latency for Grok-4 Fast Reasoning. Runtime does not affect the capability score.
| xAI | 37.956 tok/s | 1.268 s | 2M | 30K |
Output Speed is generated output tokens received per second. Catalog latency is reported separately from observed provider TTFT.
Grok 4 Fast Reasoning Pricing
Official vendor API pricing appears first, followed by individual provider offers.
- Official API
- N/A
- Official provider
- N/A
- Lowest third-party
- From $0.18 input, $0.45 output per 1M via Jiekou.AI
- Tracked offerings
- 4
| Jiekou.AI | grok-4-fast-reasoning | global | $0.18 | $0.45 | 2M | |
| Helicone | grok-4-fast-reasoning | global | $0.20 | $0.50 | 2M | |
| Poe | xai/grok-4-fast-reasoning | global | $0.20 | $0.50 | 2M | |
| 302.AI | grok-4-fast-reasoning | global | $0.20 | $0.50 | 2M |
Official prices use only the vendor's configured official Provider and positive standard USD PAYG rates. Third-party offers remain explicitly labeled.
Grok 4 Fast Reasoning Versions
Available versions of this model. The score column identifies the version used in the overall ranking.
| Grok-4 Fast Reasoning | N/A | N/A | 2M | 30K | No | Proprietary |
What is Grok 4 Fast Reasoning?
Key information about Grok 4 Fast Reasoning and its available data.
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.
Data as of 2026-08-11.
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FAQ
Common questions about Grok 4 Fast Reasoning.
When was Grok 4 Fast Reasoning released?
Grok 4 Fast Reasoning's default version was released on Aug 28, 2025.
How much does Grok 4 Fast Reasoning cost?
No official standard PAYG price is currently available for Grok 4 Fast Reasoning. The lowest tracked third-party offer starts at $0.18 input and $0.45 output via Jiekou.AI.
Who created Grok 4 Fast Reasoning?
Grok 4 Fast Reasoning was created by xAI.
What is the context window for Grok 4 Fast Reasoning?
The default version has a 2M token context window.
Is Grok 4 Fast Reasoning open weight?
No. The default version is not marked as having publicly available weights.
How many API providers offer Grok 4 Fast Reasoning?
4 provider offerings are linked to the default version.
What models should I compare Grok 4 Fast Reasoning with?
No nearby ranked alternatives are currently available.