OpenAI Codex

OpenAI Codex is OpenAI's agent for software engineering. It reads a codebase, plans changes, writes and runs code, executes tests and opens pull requests, working either locally on a developer's machine or in an isolated cloud sandbox. It runs on OpenAI's frontier coding models; the developer documentation lists the GPT 6 Sol and Luna models as the newest options, with GPT 5.5 scheduled to retire on October 14, 2026. Codex is available in several surfaces that share one ChatGPT sign in: a CLI for the terminal, an IDE extension, the ChatGPT desktop apps for macOS and Windows, ChatGPT on the web, Codex cloud for delegating tasks that run in the background, a GitHub integration that reviews pull requests, and Slack. OpenAI positions the ChatGPT app as a command center for agentic coding, where multiple agents can run in parallel, tasks can be scheduled and reviews requested. It is aimed at professional developers and engineering teams who want to hand off bounded tasks such as bug fixes, refactors and test writing. There is no standalone Codex price. Access is included with ChatGPT plans: Free and Go include limited access, Plus at $20 per month includes standard access, and Pro, from $100 per month, includes the highest task allowances. Usage is metered in five hour windows and varies by model. Plus and Pro subscribers can buy additional credits when they reach a limit, and developers can instead authenticate with an API key and pay standard usage rates. As of September 10, 2026, OpenAI has paused new sign ups and upgrades to the $200 Pro 20X tier; the $100 Pro tier remains open.