Claude Opus 5.5

Anthropic's flagship model for complex reasoning, long-context analysis, and agentic work, with a 1 million token context window.

Strengths

Handles multi-step code changes in large codebases, extended reasoning chains, and long-horizon autonomous tasks with high accuracy.

Best for

Complex software development, refactoring large systems, sustained reasoning over extended inputs, and agentic workflows requiring multiple steps.

Limitations

Superseded by Claude Fable 5 for the most demanding reasoning tasks; use Fable tier models when maximum reasoning capability is required.