GPT-5.1-Codex is a specialized version of GPT-5.1 optimized for software engineering and coding workflows. It's designed for both interactive development sessions and long, independent execution of complex engineering tasks. The model supports building projects from scratch, feature development, debugging, large-scale refactoring, and code review. Compared to GPT-5.1, Codex is more steerable, closely follows developer instructions, and produces cleaner, higher-quality code. Codex integrates into developer environments like the CLI, IDE extensions, GitHub, and cloud tasks. It adapts its reasoning dynamically—providing quick answers for small tasks and sustaining long, multi-hour runs for large projects. The model is trained for structured code reviews, identifying critical flaws by reasoning over dependencies and validating behavior against tests. It also supports multimodal inputs like images or screenshots for UI development and integrates tools for search, dependency installation, and environment setup. Codex is specifically intended for agentic coding applications.