GPT-5-Codex

GPT-5-Codex is a version of GPT-5 that OpenAI has further optimized for agentic coding inside its Codex environment. According to OpenAI's release notes, the model was trained with a focus on real-world software engineering work, aiming to be equally capable during quick, interactive sessions and when independently powering through long, complex tasks. Its code review capability is positioned to catch critical bugs before they ship, making the model useful not only for generating code but also for acting as an automated reviewer across pull requests.

Because GPT-5-Codex is designed to handle extended, multi-step developer work, it fits naturally into the surfaces where engineers already write code: the terminal, IDE, web, and phone. OpenAI describes it as the default model across the Codex experience, with a Responses API surface available to developers using an API key in addition to ChatGPT subscribers. Third-party coverage highlights repository-scale context handling, more style-aware generation, and tighter integration with CLI and IDE workflows, pointing to a model that is meant to stay useful as projects grow rather than just assist with isolated snippets.