Anthropic Releases Claude Opus 5.5 With Lower Costs and Improved Writing Behavior

Anthropic released Claude Opus 5.5 on September 22, 2026, positioning it as the first model in its Claude 5.5 family and a more efficient successor to Claude Opus 5. The company says the model reaches Claude Fable 5.1-level performance on most tasks while costing about 40% less to run than Opus 5, with early users also noting a more direct writing style that better follows requested tone and structure.