Claude Opus 5

Previous Opus generation, still available.

Knowledge cutoff May 2026. Legacy model: Opus 5.5 is the current Opus release. Default effort is high.

Make your first request

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