OpenAI Codex

OpenAI Codex is a second-generation coding agent, built on codex‑1, a variant of the o3 reasoning model and launched in research preview on May 16, 2025 . It operates within sandboxed cloud environments linked to your repository, capable of interpreting natural-language instructions, writing new features, fixing bugs, running test suites, and submitting pull requests—all autonomously and in parallel . Developers can monitor progress in real time and interact via the ChatGPT sidebar using simple prompts like “Code” or “Ask” . Codex emphasizes traceability, security, and consistency: each task is executed in isolated sandboxes without internet access and relies on whitelisted dependencies . It provides logs and test results for auditability, aligning output with preferred coding styles and patterns . Internally adopted by companies like Cisco, Temporal, Superhuman, and Kodiak for refactoring, test coverage improvement, and autonomous coding workflows .