GPT-5 Codex

OpenAI's code-specialized model built on the GPT-5 foundation with a 400k token context window, released in September 2025.

Strengths

Optimized for software engineering and programming tasks, handling large codebases and complex technical contexts with its extended context window.

Best for

Code generation, debugging, refactoring, and understanding large repository structures.

Limitations

Narrower focus on code-specific tasks compared to general-purpose reasoning models like GPT-5 Pro; use GPT-5 Pro for tasks requiring broad reasoning beyond programming.