Anthropic releases Opus 5.5, says it beats larger Fable model

Anthropic released Opus 5.5 on September 22, 2026, calling it the strongest-performing model it had tested to date. The company said Opus 5.5 outpaces its larger Fable model in many benchmarks, with Sonnet 5.5 and Haiku 5.5 to follow in the coming weeks.