Anthropic introduced Claude Opus 5.5 on 23 October as the first model in its Claude 5.5 family, saying it performs at the level of Claude Fable 5.1 on most work and costs 40% less to run than Opus 5. On Anthropic's published benchmark table the model scores 66.4% on Terminal-Bench 4.0 (Fable 5.1: 55.8%, Opus 5: 52.3%, GPT-6 Astra: 57.9%), 54.4% on FrontierCode v1.1 (Fable 5.1: 50.3%) and 57.8% on CursorBench 4.0 (Fable 5.1: 51.8%). Token prices are $4 per million input and $20 per million output, with cache reads at $0.20 per million, and Anthropic says output is generated more than 30% faster than on Opus 5. The model was tested before release by external evaluators including Frontier Design and METR, ships with biology and cyber safeguards tied to verification programmes, keeps the anti-distillation 'preserved thinking' control introduced with Fable 5.1, and is available on AWS, Google Cloud and Azure.
Our takeEvery headline number comes from Anthropic's own evaluation harness, and the post concedes that at this capability level benchmark margins no longer track real-world differences. The two strongest anecdotes - a 680,000-line migration in under a day, and load-time fixes on 39 of 40 pages - are single-tester reports with no repositories attached, so they cannot be reproduced. What is checkable is the system card's scenario suite and one compatibility change: preserved thinking blocks edits to prior context for API accounts created after 31 August, which teams should test before migrating.