Claude Sonnet 4.6 is Anthropic's latest Sonnet-class model released in February 2026, delivering frontier performance across coding, agents, and professional work at the Sonnet price point. It features a 1M-token context window with extended thinking and 64K max output tokens, and introduces the effort parameter for fine-tuning the balance between speed, cost, and reasoning depth. The model excels at iterative development, complex codebase navigation, polished document creation, and confident computer use for web QA and workflow automation.