Claude Code currently utilizes Claude Opus 4 as its underlying language model, which represents Anthropic’s most advanced and capable model in the Claude 4 family. This is not a limitation but rather a deliberate choice to provide developers with the highest quality coding assistance available. While Claude 3 offered different model variants (Haiku, Sonnet, and Opus) with varying capabilities and performance characteristics, Claude Code specifically leverages the Opus tier to ensure it can handle complex coding tasks, understand large codebases, and maintain coherent context across extended development sessions.
The integration with Claude Opus 4 means that Claude Code benefits from the model’s enhanced reasoning capabilities, improved code understanding, and better performance on technical tasks compared to earlier model versions. For developers with Max plans, Claude Code automatically manages model selection and may switch between Opus 4 and Sonnet 4 based on usage patterns to optimize both performance and rate limit management. Pro plan subscribers have access to Sonnet 4 through Claude Code but cannot use Opus 4, which may limit the tool’s effectiveness for highly complex coding tasks or very large codebases.
This model-specific approach ensures that Claude Code delivers consistent, high-quality results rather than offering multiple model options that might confuse users or provide inconsistent experiences. The focus on using the most capable available model reflects Anthropic’s commitment to making Claude Code a professional-grade development tool rather than a general-purpose AI assistant. For users who require different model characteristics for specific use cases, they can still access other Claude models through the regular web interface or API, while using Claude Code for intensive development work that benefits from the advanced capabilities of Opus 4.