Claude Opus 5.5

Claude Opus 5.5 is the first model released as part of the new Claude 5.5 family. It performs at the level of Claude Fable 5.1 on most tasks, but at 40% lower cost to run. Opus 5.5 is the strongest model in the suite to date after undergoing external evaluation by experts in alignment and safety. The model is notable for its improved performance in complex work, such as migrating large codebases with surprising speed and accuracy.

It also excels at finding and fixing software inefficiencies, creating high-quality games, and generating clear, natural language output. Opus 5.5 has been designed with enhanced safety features, such as reduced likelihood of taking harmful actions, and is being made available to approved organizations for biology and cybersecurity research.

The model costs less compute to serve than its predecessor and is available at a lower price point. Notable improvements include 40% reduced output costs and 30% faster generation times.