We’re introducing Claude Opus 5.5, the first model in our new Claude 5.5 family.

By Claude · September 23, 2026 · Curated by George's Blog

We’re introducing Claude Opus 5.5, the first model in our new Claude 5.5 family. It performs at the level of Claude Fable 5.1 for most tasks, and costs 40% less to run than Opus 5.

Opus 5.5 is our first model since we called for pacing the frontier. As with previous models, it was tested by external evaluators before release, including METR and Frontier Design. On our most comprehensive alignment test, it achieves the strongest score to date.

It outperforms both Opus 5 and Fable 5.1 on nearly every benchmark we report, leading on agentic coding and real-world knowledge work.

It’s also more efficient. Opus 5.5 uses fewer tokens per task at a lower price per token, and generates output more than 30% faster than Opus 5.

Opus 5.5 communicates more naturally, addressing some of the most common feedback we heard on Opus 5. It puts the most important information up front and follows the writing rules you give it.

Claude Opus 5.5 is available today. We're also raising five-hour limits on Pro, Max, and Team plans, so there’s more room to explore what it can do.