Anthropic launches Claude Opus 5.5, matching Fable 5.1 performance at 40% lower cost

Claude Opus 5.5

Claude Opus 5.5 is the first model in Anthropic's 5.5 family. It performs at the level of Claude Fable 5.1 while costing 40% less to run than Opus 5. Input/output tokens are $4 and $20 per million, cache reads are $0.20, and output is over 30% faster. It scored the highest ever on Anthropic's automated behavioral audit and is more resistant to prompt injection. One early tester completed a 680,000-line code migration in under a day—work an engineering team estimated would take weeks. Sonnet 5.5 and Haiku 5.5 will follow in the coming weeks.

Why it matters: Anthropic's new flagship model matches Fable 5.1 performance at 40% lower cost, first in the 5.5 family. All three HKR axes hit, but the post doesn't disclose benchmark details or context window, so not pushing past 90.