Claude Fable 5

Mythos-class capability, released with safeguards.

Knowledge cutoff Jan 2026. Adaptive thinking is always on. $0.40/$0.70 per M; cache reads $0.04/M.

Make your first request

{
  "model": "claude-fable-5",
  "messages": [
    {
      "role": "user",
      "content": "Hello, world."
    }
  ]
}