{
  "$schema": "https://modeldeprecations.dev/api/v1/schema.json",
  "provider": "xai",
  "model": "grok-4-fast-reasoning",
  "name": "Grok 4 Fast Reasoning",
  "aliases": [],
  "description": "The September 2025 model that introduced the 2M context window to the xAI API and undercut every comparable frontier model on price, which is why it ended up in so many agent frameworks as the default. Retired 15 May 2026, one generation behind 4.1 Fast and shut down on the same day as it.",
  "shutdown_on": "2026-05-15",
  "status": "retired",
  "replacements": [
    {
      "provider": "xai",
      "model": "grok-4.3",
      "recommended": true,
      "note": "Maps to grok-4.3 with reasoning effort \"low\".",
      "external": false
    }
  ],
  "sources": [
    {
      "url": "https://docs.x.ai/developers/migration/may-15-retirement",
      "title": "Grok Model Retirement on May 15, 2026",
      "accessed": "2026-08-03"
    }
  ],
  "last_verified": "2026-08-03",
  "computed_status": "retired",
  "asOf": "2026-08-03"
}