grok-4-fast-reasoning

grok-4-fast-reasoning (xAI) was retired on May 15, 2026; calls are now answered by grok-4.3 (low reasoning effort) instead of failing.

Provider

xAI

Shutdown

May 15, 2026, calls now go to grok-4.3 (low reasoning effort)

Announced

—

Replace with

grok-4.3

Also written as

xai/grok-4-fast-reasoning

• xAI 'retired' this slug but requests are auto-redirected (not rejected): calls succeed, served by grok-4.3 (low reasoning effort) and billed at its price. Flag as retired-with-redirect, not as a hard failure.
• Effective 12:00 PM PT on 2026-05-15.

Source: https://docs.x.ai/developers/migration/may-15-retirement · report a wrong date