Grok 4 Fast Reasoning

API ID grok-4-fast-reasoning

grok-4-fast-reasoning was an xAI model.

Status: Retired
Released: —
Shutdown: May 15, 2026
Replacement: Grok 4.3grok-4.3

grok-4-fast-reasoning stopped serving on May 15, 2026. Requests to it are now redirected to grok-4.3 and billed at its price.

How to migrate to Grok 4.3

Benchmarks

Scores as each source published them

No comparison. Pick a model to see the difference on each benchmark.

Arena

Arena	Grok 4 Fast Reasoning	Rank	Date	Source
Text By category Math 1411 rank 144 Creative writing 1384 rank 137 Instruction following 1389 rank 161 Hard prompts 1414 rank 171 Long prompts 1413 rank 152 Multi-turn 1405 rank 154 Expert 1422 rank 154	1405 ±5	154 of 415 18,272 votes	Oct 13, 2026	source
Text: Coding	1439 ±9	168 of 410 3,941 votes	Oct 13, 2026	source
WebDev	1159 ±27	141 of 142 742 votes	Oct 13, 2026	source
Search	1161 ±5	34 of 42 43,083 votes	Oct 13, 2026	source

Rated as grok-4-fast-search. Ratings come from people voting between two anonymous answers; Text and Search are style-controlled, as on arena.ai. Data: Arena (arena.ai), CC BY 4.0.

On cloud platforms

All platform dates

Platform	Platform ID	State	Shutdown	Time left	Replacement	Source
Microsoft Foundryversion 1	grok-4-fast-reasoning	Retired on May 1, 2026	May 1, 2026		Grok 4.1 Fast Reasoninggrok-4-1-fast-reasoning	source

Microsoft Foundry (version 1) retired this model 14 days before xAI's own API.

Read daily from each platform's own pages. The shutdown date and countdown on this page use xAI's own date.

Price history

USD per 1M tokens, standard tier

No price history yet.

Prices

USD per 1M tokens, every type and band, by tier

No published prices.

Changelog

Changes we detected on xAI's pages

Oct 5, 2026
Retired
grok-4-fast-reasoning has been retired
Info

Last checked Oct 15, 2026, 2:00 am ET · Sources: xAI pricing, xAI notices, xAI release notes