Claude Code is powered by three distinct models—Opus, Sonnet, and Haiku— each optimized for a specific role within the development lifecycle. Claude Opus is the "deep thinker" and primary architect, used for complex reasoning, high-level system design, and surgical bug fixes in large codebases. Claude Sonnet serves as the versatile "balanced builder," providing a high-speed middle ground for daily tasks like implementing feature logic, writing boilerplate, and managing state across multiple files. Claude Haiku is the "fast-response specialist," designed for near-instant execution of lightweight tasks, such as generating rapid UI prototypes, drafting commit messages, or acting as parallel sub-agents to scan logs and run quick checks.
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