GPT-5.1-Codex-Max

GPT-5.1-Codex-Max is OpenAI's expanded-capacity variant of GPT-5.1-Codex, optimized for software engineering tasks with a 400k token context window.

Strengths

Handles large codebases, long file sequences, and complex code generation tasks within a single request due to its extended context capacity.

Best for

Working with large repositories, multi-file refactoring, and code analysis that requires processing extensive context in one pass.

Limitations

Designed specifically for coding tasks; use GPT-5.1 or GPT-5.2 for general-purpose reasoning work that doesn't center on software engineering.