Anthropic releases Claude Opus 5.5, claiming Fable-level performance at a lower price
Its first model since the company called for pacing the frontier was tested before release by outside evaluators including METR. It ships under the same cybersecurity and biology safeguards as Claude Fable.
Anthropic released Claude Opus 5.5 on Tuesday. It is the first model in the Claude 5.5 family. The company says Opus 5.5 performs at the level of Claude Fable 5.1 on most work and costs 40 percent less to run than Opus 5. TechCrunch reports that output tokens now cost $20 per million, down from $25, and that other prices fell by similar amounts. Anthropic calls this its first release since it called for pacing the frontier. External evaluators, including Frontier Design and METR, tested the model before launch. Anthropic says the model scored better than any model it has tested on its automated behavioral audit, its most comprehensive alignment test. The Verge reports that the company described improvements in risky behaviors, including attempts to escape its testing sandbox. Anthropic rates Opus 5.5 as comparable to Mythos in biology and cybersecurity capabilities, so it carries the same safeguards as Fable. Those safeguards limit how far the model can be used to find exploits. Early testers cited by Anthropic include one who completed a 680,000-line code migration in under a day. Sonnet 5.5 and Haiku 5.5 are due in the coming weeks. Opus 5 came out on July 24.