Grok 4 Fast (Reasoning)
Redirected. Grok 4 Fast (Reasoning) is shut down on 2 platforms, with no shutdown date announced. xAI names Grok 4.1 Fast (Reasoning) as the replacement.
- Next shutdown
- None setNo date on 2 platforms
- Arena Text
- 1,405#73 of 128 · Arena
- Arena WebDev
- 1,159#68 of 69 · Arena
- Context window
- 2Mtokens
- Released
- Sep 19, 2025xAI
Dates on every platform
| Platform | Model ID and status | Deprecated | Shuts down | Replacement |
|---|---|---|---|---|
| Azure AI FoundryMicrosoft: Model retirement schedule - Microsoft Foundry (opens in a new tab) · checked Oct 14, 2026 | grok-4-fast-reasoning:1Shut down | – | Shut down | Grok 4.1 Fast (Reasoning) |
| xAI APIxAI: Grok Model Retirement on May 15, 2026 (opens in a new tab) · checked Oct 14, 2026 | grok-4-fast-reasoningShut down | – | Shut down | Grok 4.3 |
Requests to retired deployments return 410 Gone.
Since the retirement, requests to grok-4-fast-reasoning are served by grok-4.3 with low reasoning effort and billed at grok-4.3 rates.
Since May 15, 2026, requests to grok-4-fast-reasoning on xAI API are answered by Grok 4.3, with no error. Behavior and price follow the newer model.
What breaks when you move off Grok 4 Fast (Reasoning)
- Pricing
- Defaults
- Parameters
- Availability
Intelligence
| Benchmark | Publisher | Score | Rank | Published |
|---|---|---|---|---|
| Arena Text | Arena | 1,405 ± 3 | #73 of 128 | Oct 8, 2026 |
| Arena WebDev | Arena | 1,159 ± 14 | #68 of 69 | Oct 8, 2026 |
Arena (arena.ai), https://arena.ai/leaderboard
Change history
RedirectSix Grok models retired on the xAI API and redirected to Grok 4.3xAI API3 breaks
xAI retired grok-4-1-fast-reasoning, grok-4-1-fast-non-reasoning, grok-4-fast-reasoning, grok-4-fast-non-reasoning, grok-4-0709 and grok-3. The slugs still resolve: requests are served by grok-4.3 instead of returning an error.
- Platform
- xAI API
- Models
- Grok 4.1 Fast (Reasoning), Grok 4.1 Fast (Non-Reasoning), Grok 4 Fast (Reasoning), Grok 4 Fast (Non-Reasoning), Grok 4, Grok 3
- Replacement
- Grok 4.3
- PricingRequests to the retired slugs are billed at grok-4.3 rates, not the rates of the original model.
- DefaultsReasoning slugs are served with low reasoning effort and non-reasoning slugs with none; set medium or high explicitly for deeper reasoning.
- Parametersgrok-4.20 and newer models silently ignore logprobs and top_logprobs.
Source: xAI, Grok Model Retirement on May 15, 2026 (opens in a new tab); xAI, Models (opens in a new tab)
ShutdownGrok 3, Grok 3 mini and Grok 4 Fast retired on Azure AI FoundryAzure AI Foundry1 break
Microsoft retired grok-3, grok-3-mini, grok-4-fast-reasoning and grok-4-fast-non-reasoning. It lists grok-4 and the Grok 4.1 Fast models as replacements.
- Platform
- Azure AI Foundry
- AvailabilityInference requests to retired deployments return 410 Gone.
Source: Microsoft, Model retirement schedule - Microsoft Foundry (opens in a new tab); Microsoft, Microsoft Foundry Models lifecycle and support policy (opens in a new tab)