OpenAI Codex

What it does

Codex is OpenAI's coding agent. It takes on engineering work such as building features, refactoring or migrating code, and can run several agents in parallel using built-in worktrees and cloud environments. OpenAI presents it as one agent spread across several surfaces tied to a single ChatGPT account: the Codex app in ChatGPT, an extension for code editors and the Codex CLI in the terminal. According to its GitHub repository, the CLI runs locally on macOS, Linux and Windows and can be installed with a script, npm or Homebrew. Users sign in with their ChatGPT account or, with extra setup, an API key.

Pricing and plans

Codex is bundled with ChatGPT plans rather than sold separately. The Free plan gives limited Codex access, Go also has limited access, Plus offers expanded usage and Pro offers 5x or 20x the Plus allowance. For organisations, a Codex-only Business option has no fixed seat fee and is billed on usage, while Business with ChatGPT is billed per user, and Enterprise has custom pricing. Usage is counted in five-hour windows that depend on the model and on whether the task runs locally or in the cloud; Plus and Pro users can buy extra credits. The ChatGPT and Codex pricing pages we checked did not display amounts in plain text, so prices are not listed here; see OpenAI's site for current prices, which may vary by region and taxes.

Strengths and limits

Codex is a natural choice for teams already paying for ChatGPT, since the same account covers the app, the editor and the terminal. The CLI's repository is published under the Apache-2.0 licence; that licence covers the CLI code, while the service behind it requires a ChatGPT account or an API key, so the directory does not list Codex as a whole as open source. Usage caps vary by plan and model, and cloud tasks and code reviews are only available with certain models. Generated changes still need review and testing.