Claude Opus 4.8
AnthropicReleased May 28. Adaptive reasoning + max-effort mode; now #2 on the AA Intelligence Index v4.0 behind Fable 5.
- Intelligence Index v4.0: 61.4
- Adaptive reasoning mode
- Coding + agentic upgrade over 4.7
- Long-running work consistency
- Released 2026-05-28