Codex is OpenAI’s coding agent, and it is offered in several places that share one ChatGPT sign-in. According to OpenAI, you can use it in ChatGPT (the desktop app and the web), in your editor through the Codex IDE extension, in the terminal through the Codex CLI, and in the cloud. The CLI is open source under the Apache-2.0 license and runs locally on your computer.
OpenAI positions Codex as a command center for agentic coding: built-in worktrees and cloud environments let agents work in parallel across projects, Skills teach it your team’s standards and workflows, and you can schedule it to pick up routine background work such as issue triage, alert monitoring, and CI/CD. It is aimed at end-to-end tasks such as building features, refactors, and migrations rather than line-by-line suggestions.
On cost, the CLI’s README says Codex is included with the Plus, Pro, Business, Edu, and Enterprise ChatGPT plans, and you can sign in with your ChatGPT account (the recommended route) or use an OpenAI API key. The trade-off is that it is built around OpenAI’s models and plans, so if you want to switch model providers freely, an open agent such as Cline may suit you better.
Verdict: a natural pick if you already pay for ChatGPT and want one agent across the terminal, the editor, and the cloud. If you prefer Anthropic’s approach, compare it with Claude Code, and see our best AI coding tools guide for the wider field.
Sources: OpenAI’s Codex page and the Codex CLI repository, checked on September 20, 2026.
