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xAI model product
Grok 4 Fast Reasoning
Grok 4 Fast Reasoning is an xAI LLM and a high-speed variant of Grok-4 optimized for faster inference and reasoning through thinking tokens.
Updated Sep 8, 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 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.
Sort by
Arena | Category | Rank | Rating / score | Votes | Observations | Result date |
|---|
| Arenatext | Categoryindustry legal and government | Rank78 | Rating / score1,429.76 | Votes1,139 | ObservationsN/A | Result date |
| Arenatext factuality | Categorycreative writing | Rank78 | Rating / score1,399.32 | Votes771 | ObservationsN/A | Result date |
| Arenatext style control | Categoryjapanese | Rank78 | Rating / score1,369.93 | Votes207 | ObservationsN/A | Result date |
| Arenatext | Categoryjapanese | Rank80 | Rating / score1,358.75 | Votes207 | ObservationsN/A | Result date |
| Arenatext | Categoryfrench | Rank82 | Rating / score1,430.20 | Votes284 | ObservationsN/A | Result date |
| Arenatext style control | Categoryfrench | Rank82 | Rating / score1,439.87 | Votes284 | ObservationsN/A | Result date |
| Arenatext | Categorykorean | Rank83 | Rating / score1,358.38 | Votes359 | ObservationsN/A | Result date |
| Arenatext factuality | Categoryindustry life and physical and social science | Rank83 | Rating / score1,440.75 | Votes929 | ObservationsN/A | Result date |
| Arenatext factuality | Categoryindustry writing and literature and language | Rank83 | Rating / score1,400.85 | Votes1,396 | ObservationsN/A | Result date |
| Arenatext factuality | Categorylonger query | Rank83 | Rating / score1,430.54 | Votes1,611 | ObservationsN/A | Result date |
| Arenatext factuality | Categorymulti turn | Rank83 | Rating / score1,424.81 | Votes1,019 | ObservationsN/A | Result date |
| Arenatext factuality | Categoryhard prompts english | Rank84 | Rating / score1,451.58 | Votes1,497 | ObservationsN/A | Result date |
| Arenatext factuality | Categoryindustry entertainment and sports and media | Rank86 | Rating / score1,384.67 | Votes1,080 | ObservationsN/A | Result date |
| Arenatext style control | Categorykorean | Rank86 | Rating / score1,356.52 | Votes359 | ObservationsN/A | Result date |
| Arenatext factuality | Categoryinstruction following | Rank87 | Rating / score1,408.85 | Votes1,809 | ObservationsN/A | Result date |
| Arenatext style control | Categoryindustry legal and government | Rank87 | Rating / score1,427.74 | Votes1,139 | ObservationsN/A | Result date |
| Arenatext | Categorylonger query | Rank89 | Rating / score1,411.51 | Votes4,415 | ObservationsN/A | Result date |
| Arenatext factuality | Categoryindustry business and management and financial operations | Rank89 | Rating / score1,419.72 | Votes1,203 | ObservationsN/A | Result date |
| Arenatext | Categoryindustry life and physical and social science | Rank90 | Rating / score1,426.50 | Votes2,916 | ObservationsN/A | Result date |
| Arenatext style control | Categoryindustry medicine and healthcare | Rank90 | Rating / score1,435.29 | Votes848 | ObservationsN/A | Result date |
| Arenatext | Categoryindustry medicine and healthcare | Rank91 | Rating / score1,420.56 | Votes848 | ObservationsN/A | Result date |
| Arenatext factuality | Categoryenglish | Rank91 | Rating / score1,427.19 | Votes3,759 | ObservationsN/A | Result date |
| Arenatext style control | Categoryindustry life and physical and social science | Rank91 | Rating / score1,435.44 | Votes2,916 | ObservationsN/A | Result date |
| Arenatext | Categorycreative writing | Rank92 | Rating / score1,374.85 | Votes2,440 | ObservationsN/A | Result date |
| Arenatext factuality | Categorycoding | Rank92 | Rating / score1,455.61 | Votes1,362 | ObservationsN/A | Result date |
| Arenatext style control | Categorycreative writing | Rank93 | Rating / score1,381.04 | Votes2,440 | ObservationsN/A | Result date |
| Arenatext style control | Categoryspanish | Rank93 | Rating / score1,405.17 | Votes591 | ObservationsN/A | Result date |
| Arenatext | Categorypolish | Rank94 | Rating / score1,380.32 | Votes725 | ObservationsN/A | Result date |
| Arenatext | Categoryspanish | Rank94 | Rating / score1,403.38 | Votes591 | ObservationsN/A | Result date |
| Arenatext style control | Categorychinese | Rank94 | Rating / score1,444.55 | Votes1,094 | ObservationsN/A | Result date |
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
Sort by
Provider | Provider model ID | Region | Input / 1M | Output / 1M | Context | Updated |
|---|
| ProviderJiekou.AI | Provider model IDgrok-4-fast-reasoning | Regionglobal | Input / 1M$0.18 | Output / 1M$0.45 | Context2M | Updated |
| ProviderHelicone | Provider model IDgrok-4-fast-reasoning | Regionglobal | Input / 1M$0.20 | Output / 1M$0.50 | Context2M | Updated |
| Provider302.AI | Provider model IDgrok-4-fast-reasoning | Regionglobal | Input / 1M$0.20 | Output / 1M$0.50 | Context2M | Updated |
| ProviderPoe | Provider model IDxai/grok-4-fast-reasoning | Regionglobal | Input / 1M$0.20 | Output / 1M$0.50 | Context2M | Updated |
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 Runtime Performance
Provider-specific output speed and catalog latency for Grok-4 Fast Reasoning. Runtime does not affect the capability score.
Sort by
Provider | Output Speed | Catalog Latency | Max Input | Max Output | Updated |
|---|
| ProviderxAI | Output Speed90.00 tok/s | Catalog LatencyN/A | Max Input2M | Max Output30K | Updated |
Output Speed is generated output tokens received per second. Catalog latency is reported separately from observed provider TTFT.
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 Versions
Available versions of this model. The score column identifies the version used in the overall ranking.
Sort by
Version | Released | LLMBoard | Parameters | Context | Max output | Open weights | License |
|---|
| VersionGrok-4 Fast Reasoning | Released | LLMBoardN/A | ParametersN/A | Context2M | Max output30K | Open weightsNo | LicenseProprietary |
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What is Grok 4 Fast Reasoning?
Key information about Grok 4 Fast Reasoning and its available data.
Grok 4 Fast Reasoning is an LLM from xAI. It is a high-speed variant of Grok-4 optimized for faster inference while maintaining reasoning capabilities through thinking tokens.
Data as of 2026-09-08.
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.