OpenAI: GPT-5 Codex

GPT-5 Codex is a specialized version of GPT-5, meticulously optimized for software engineering and coding workflows. This powerful AI is designed for both interactive development sessions and the long, independent execution of complex engineering tasks. It supports building projects from scratch, feature development, debugging, large-scale refactoring, and comprehensive code review. Compared to the base GPT-5, Codex is more steerable, adheres closely to developer instructions, and consistently produces cleaner, higher-quality code outputs. Developers can adjust reasoning effort with the `reasoning.effort` parameter for optimal performance. Codex seamlessly integrates into various developer environments, including CLI, IDE extensions, GitHub, and cloud tasks. It dynamically adapts its reasoning effort, providing fast responses for small tasks while sustaining extended multi-hour runs for large projects. The model is expertly trained to perform structured code reviews, identifying critical flaws by reasoning over dependencies and validating behavior against tests. It also supports multimodal inputs, such as images or screenshots for UI development, and integrates tool use for search, dependency installation, and environment setup. With a 400K token context window and 128K max output, it's ideal for agentic coding applications. Access this PRO tier model for $1.25/10.00 per 1M tokens (input/output). Capabilities include JSON mode, functions, long context, vision, code generation, structured output, and streaming. Note: It does not support image generation.