# grok-4-fast-reasoning

Calls to the model grok-4-fast-reasoning on Azure AI Foundry stopped working on May 1, 2026.

On May 1, 2026, Azure AI Foundry retired model grok-4-fast-reasoning. Calls targeting model grok-4-fast-reasoning fail since that date.

## What to use instead

Migrate to grok-4-1-fast-reasoning, which stops working on May 19, 2027. No permanent replacement is named yet.

- API: Azure AI Foundry (*.services.ai.azure.com)
- Model: grok-4-fast-reasoning
- Released: December 18, 2025 (models.dev)
- Kind: Model retirement
- Takes effect: May 1, 2026
- Calls after that day: fail
- Calls it hits: `model grok-4-fast-reasoning`
- Source: [Deprecations page](https://learn.microsoft.com/en-us/azure/foundry/openai/concepts/model-retirement-schedule)
- Verified: November 6, 2026, against Azure AI Foundry's own pages
- Page: https://www.okapi.bot/models/azure-ai-foundry/grok-4-fast-reasoning/

## Azure AI Foundry's words

> Model: grok-4-fast-reasoning; Version: 1; Lifecycle: Retired; Retirement date: 2026-05-01; Replacement: grok-4-1-fast-reasoning

Okapi finds the calls this change hits in your repo and opens the pull request with the fix: https://github.com/apps/okapi-agent