Claude Opus 5.5 (Azure Anthropic)

Claude Opus 5.5 is the inaugural model in Anthropic's Claude 5.5 family, released on September 22, 2026, and positioned as a major step up from Opus 5. Anthropic describes it as performing at the level of Claude Fable 5.1 on most work while costing 40% less to run than Opus 5. Early testers reported large jumps on complex assignments, including one who completed a 680,000-line code migration in less than a day and another who used several Claude models to build a product from a single prompt, where Opus 5.5 produced graphics and polish that outscored the alternatives.

In agentic coding evaluations, Opus 5.5 reached 66.4% on Terminal-Bench 4.0, a benchmark Anthropic uses to measure real-world software engineering capability. The model also proved effective at profiling and refactoring, succeeding in 39 of 40 attempts to cut load times across every page of a web app without altering the application's behavior. Opus 5.5 was reviewed before launch by external evaluators including Frontier Design and METR, and on Anthropic's automated behavioral audit it achieved the strongest alignment scores of any model tested to date, making it a natural fit for enterprises on Azure that need advanced reasoning and long-horizon coding agents through LLM Gateway.