OpenAI Launches Codex, an Agentic Coding Tool for Developers

OpenAI has unveiled Codex, an advanced coding tool designed to assist developers in automating routine programming tasks. Available as a research preview, Codex enables experienced developers to delegate repetitive or straightforward coding work to an AI agent that generates production-ready code. The tool, accessible via the ChatGPT web app sidebar, allows users to input prompts and choose between "code" to generate code or "ask" for advice and answers.
Codex operates within a containerized environment that mirrors the user's development setup, ensuring accurate task execution. Developers can enhance Codex's effectiveness by including an "AGENTS.md" file, providing context or style guidelines for the AI to follow. Built on codex-1, a fine-tuned version of OpenAI's o3 reasoning model, Codex is trained to analyze and generate code while iterating through tests.
OpenAI addresses common concerns about AI-generated code, emphasizing Codex's transparency and the importance of manual review before integration. While Codex is now available to ChatGPT Pro, Enterprise, and Team users, Plus and Edu access will follow. Currently, users have generous access at no additional cost, though rate limits and pricing changes are expected in the future.

Published: 5/17/2025