Codex
Delegate well-scoped tasks, control the sandbox, and review what comes back.
Start: What Codex is and where things liveAbout Codex
Codex is OpenAI's coding agent. It runs in your terminal as the Codex CLI, in IDE extensions, in the ChatGPT desktop app and in Codex Cloud. It reads your project, edits files and runs commands inside a sandbox, and asks for approval when it needs more access. It can also review pull requests on GitHub. You sign in with ChatGPT, or use an API key for automation.
Best for: Developers who want to hand well-scoped tasks to an agent, locally or in the cloud, and review what comes back.
Good for
- Taking on a clearly described task in your project
- Following project instructions you write once in AGENTS.md
- Reviewing your changes with /review before you commit
- Running in scripts and CI with codex exec
Where people slip
- Turning off the sandbox with --yolo. It removes both the sandbox and approvals
- Picking a "don't ask again" option for a command you haven't read
- Setting CODEX_API_KEY for a whole CI job instead of the one step that needs it
- Committing changes you haven't checked with /diff or /review
What is AGENTS.md in Codex?
A file of project instructions Codex reads before it works. Run /init to create a draft. Codex reads a global file, then files from the project root down to your folder, so closer files win. The default size limit is 32 KiB.
How does the Codex sandbox work?
In a Git project the default is Auto. Codex can edit files in your workspace and asks before editing outside it or running commands that need the network. Network is off by default. Use /permissions to see and change what it may do.
How do I get Codex to review a pull request?
Comment @codex review on the pull request in GitHub. It flags only P0 and P1 issues. Put review rules under a Code Review Rules heading in the closest AGENTS.md.
Is --full-auto still supported?
No. Use --sandbox workspace-write when codex exec needs to edit files. By default codex exec runs read-only.
Checked against Codex's own docs on 2026-11-06.
Basics
Know what Codex is, start it in the right folder, and make one small change you've reviewed.
New to Codex? Start here. Already use it? Skip to the next milestone.
0 of 2 lessons completeDelegate with clear instructions
Write AGENTS.md files and task briefs that Codex can finish and you can check.
0 of 3 lessons completeControl the sandbox and review locally
Pick the right permissions, answer approval prompts on purpose, and review changes before you commit.
0 of 2 lessons complete