Claude Mythos 5.1

Mythos-class model, vetted-partner access only.

Knowledge cutoff Jun 2026. Adaptive thinking is always on. $0.60/$1.20 per M; cache reads $0.06/M. Access is restricted to vetted organizations.

Make your first request

{
  "model": "claude-mythos-5.1",
  "messages": [
    {
      "role": "user",
      "content": "Hello, world."
    }
  ]
}