[claude-opus-5-5]

September 23, 2026

• Anthropic released Claude Opus 5.5, which it says matches Claude Fable 5.1 on most tasks at about 40% lower cost to run than Opus 5; Sonnet 5.5 and Haiku 5.5 are expected in the coming weeks (The Decoder). · AI & Model Security

in Attack Chains That Run Themselves