OpenAI Codex CLI: Lightweight coding agent that runs in your terminal

Lightweight coding agent that runs in your terminal

npm i -g @openai/codex

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Table of Contents

• Experimental Technology Disclaimer
• Quickstart
• Why Codex?
• Security Model & Permissions
  • Platform sandboxing details
• System Requirements
• CLI Reference
• Memory & Project Docs
• Non‑interactive / CI mode
• Recipes
• Installation
• Configuration
• FAQ
• Funding Opportunity
• Contributing
  • Development workflow
  • Writing high‑impact code changes
  • Opening a pull request
  • Review process
  • Community values
  • Getting help
  • Contributor License Agreement (CLA)
    • Quick fixes
  • Releasing codex
• Security & Responsible AI
• License

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Codex CLI is an experimental project under active development. It is not yet stable, may contain bugs, incomplete features, or undergo breaking changes. We’re building it in the open with the community and welcome:

• Bug reports
• Feature requests
• Pull requests
• Good vibes

Help us improve by filing issues or submitting PRs (see the section below for how to contribute)!

Install globally:

Next, set your OpenAI API key as an environment variable:

Note: This command sets the key only for your current terminal session. To make it permanent, add the export line to your shell's configuration file (e.g., ~/.zshrc).

Run interactively:

Or, run with a prompt as input (and optionally in Full Auto mode):

That’s it – Codex will scaffold a file, run it inside a sandbox, install any missing dependencies, and show you the live result. Approve the changes and they’ll be committed to your working directory.

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Codex CLI is built for developers who already live in the terminal and want ChatGPT‑level reasoning plus the power to actually run code, manipulate files, and iterate – all under version control. In short, it’s chat‑driven development that understands and executes your repo.

• Zero setup — bring your OpenAI API key and it just works!
• Full auto-approval, while safe + secure by running network-disabled and directory-sandboxed
• Multimodal — pass in screenshots or diagrams to implement features ✨

And it's fully open-source so you can see and contribute to how it develops!

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Codex lets you decide how much autonomy the agent receives and auto-approval policy via the --approval-mode flag (or the interactive onboarding prompt):

Mode What the agent may do without asking Still requires approval

Suggest (default)	• Read any file in the repo	• All file writes/patches • All shell/Bash commands
Auto Edit	• Read and apply‑patch writes to files	• All shell/Bash commands
Full Auto	• Read/write files • Execute shell commands	–

In Full Auto every command is run network‑disabled and confined to the current working directory (plus temporary files) for defense‑in‑depth. Codex will also show a warning/confirmation if you start in auto‑edit or full‑auto while the directory is not tracked by Git, so you always have a safety net.

Coming soon: you’ll be able to whitelist specific commands to auto‑execute with the network enabled, once we’re confident in additional safeguards.

The hardening mechanism Codex uses depends on your OS:

• macOS 12+ – commands are wrapped with Apple Seatbelt (sandbox-exec).

  • Everything is placed in a read‑only jail except for a small set of writable roots ($PWD, $TMPDIR, ~/.codex, etc.).
  • Outbound network is fully blocked by default – even if a child process tries to curl somewhere it will fail.

• Linux – we recommend using Docker for sandboxing, where Codex launches itself inside a minimal container image and mounts your repo read/write at the same path. A custom iptables/ipset firewall script denies all egress except the OpenAI API. This gives you deterministic, reproducible runs without needing root on the host. You can read more in run_in_container.sh

Both approaches are transparent to everyday usage – you still run codex from your repo root and approve/reject steps as usual.

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Requirement Details

Operating systems	macOS 12+, Ubuntu 20.04+/Debian 10+, or Windows 11 via WSL2
Node.js	22 or newer (LTS recommended)
Git (optional, recommended)	2.23+ for built‑in PR helpers
RAM	4‑GB minimum (8‑GB recommended)

Never run sudo npm install -g; fix npm permissions instead.

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Command Purpose Example

codex	Interactive REPL	codex
codex "…"	Initial prompt for interactive REPL	codex "fix lint errors"
codex -q "…"	Non‑interactive "quiet mode"	codex -q --json "explain utils.ts"
codex completion <bash|zsh|fish>	Print shell completion script	codex completion bash

Key flags: --model/-m, --approval-mode/-a, and --quiet/-q.

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Codex merges Markdown instructions in this order:

1. ~/.codex/instructions.md – personal global guidance
2. codex.md at repo root – shared project notes
3. codex.md in cwd – sub‑package specifics

Disable with --no-project-doc or CODEX_DISABLE_PROJECT_DOC=1.

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Run Codex head‑less in pipelines. Example GitHub Action step:

Set CODEX_QUIET_MODE=1 to silence interactive UI noise.

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Below are a few bite‑size examples you can copy‑paste. Replace the text in quotes with your own task. See the prompting guide for more tips and usage patterns.

✨ What you type What happens

1	codex "Refactor the Dashboard component to React Hooks"	Codex rewrites the class component, runs npm test, and shows the diff.
2	codex "Generate SQL migrations for adding a users table"	Infers your ORM, creates migration files, and runs them in a sandboxed DB.
3	codex "Write unit tests for utils/date.ts"	Generates tests, executes them, and iterates until they pass.
4	codex "Bulk‑rename *.jpeg → *.jpg with git mv"	Safely renames files and updates imports/usages.
5	codex "Explain what this regex does: ^(?=.*[A-Z]).{8,}$"	Outputs a step‑by‑step human explanation.
6	codex "Carefully review this repo, and propose 3 high impact well-scoped PRs"	Suggests impactful PRs in the current codebase.
7	codex "Look for vulnerabilities and create a security review report"	Finds and explains security bugs.

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From npm (Recommended) Build from source

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Codex looks for config files in ~/.codex/.

You can also define custom instructions:

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OpenAI released a model called Codex in 2021 - is this related?

In 2021, OpenAI released Codex, an AI system designed to generate code from natural language prompts. That original Codex model was deprecated as of March 2023 and is separate from the CLI tool.

How do I stop Codex from touching my repo?

Codex always runs in a sandbox first. If a proposed command or file change looks suspicious you can simply answer n when prompted and nothing happens to your working tree.

Does it work on Windows?

Not directly. It requires Windows Subsystem for Linux (WSL2) – Codex has been tested on macOS and Linux with Node ≥ 22.

Which models are supported?

Any model available with Responses API. The default is o4-mini, but pass --model gpt-4o or set model: gpt-4o in your config file to override.

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We’re excited to launch a $1 million initiative supporting open source projects that use Codex CLI and other OpenAI models.

• Grants are awarded in $25,000 API credit increments.
• Applications are reviewed on a rolling basis.

Interested? Apply here.

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This project is under active development and the code will likely change pretty significantly. We'll update this message once that's complete!

More broadly we welcome contributions – whether you are opening your very first pull request or you’re a seasoned maintainer. At the same time we care about reliability and long‑term maintainability, so the bar for merging code is intentionally high. The guidelines below spell out what “high‑quality” means in practice and should make the whole process transparent and friendly.

• Create a topic branch from main – e.g. feat/interactive-prompt.

• Keep your changes focused. Multiple unrelated fixes should be opened as separate PRs.

• Use npm run test:watch during development for super‑fast feedback.

• We use Vitest for unit tests, ESLint + Prettier for style, and TypeScript for type‑checking.

• Before pushing, run the full test/type/lint suite:

  npm test && npm run lint && npm run typecheck

• If you have not yet signed the Contributor License Agreement (CLA), add a PR comment containing the exact text

  I have read the CLA Document and I hereby sign the CLA

  The CLA‑Assistant bot will turn the PR status green once all authors have signed.

1. Start with an issue. Open a new one or comment on an existing discussion so we can agree on the solution before code is written.
2. Add or update tests. Every new feature or bug‑fix should come with test coverage that fails before your change and passes afterwards. 100 % coverage is not required, but aim for meaningful assertions.
3. Document behaviour. If your change affects user‑facing behaviour, update the README, inline help (codex --help), or relevant example projects.
4. Keep commits atomic. Each commit should compile and the tests should pass. This makes reviews and potential rollbacks easier.

• Fill in the PR template (or include similar information) – What? Why? How?
• Run all checks locally (npm test && npm run lint && npm run typecheck). CI failures that could have been caught locally slow down the process.
• Make sure your branch is up‑to‑date with main and that you have resolved merge conflicts.
• Mark the PR as Ready for review only when you believe it is in a merge‑able state.

1. One maintainer will be assigned as a primary reviewer.
2. We may ask for changes – please do not take this personally. We value the work, we just also value consistency and long‑term maintainability.
3. When there is consensus that the PR meets the bar, a maintainer will squash‑and‑merge.

• Be kind and inclusive. Treat others with respect; we follow the Contributor Covenant.
• Assume good intent. Written communication is hard – err on the side of generosity.
• Teach & learn. If you spot something confusing, open an issue or PR with improvements.

If you run into problems setting up the project, would like feedback on an idea, or just want to say hi – please open a Discussion or jump into the relevant issue. We are happy to help.

Together we can make Codex CLI an incredible tool. Happy hacking! 🚀

All contributors must accept the CLA. The process is lightweight:

1. Open your pull request.

2. Paste the following comment (or reply recheck if you’ve signed before):

   I have read the CLA Document and I hereby sign the CLA

3. The CLA‑Assistant bot records your signature in the repo and marks the status check as passed.

No special Git commands, email attachments, or commit footers required.

Scenario Command

Amend last commit	git commit --amend -s --no-edit && git push -f
GitHub UI only	Edit the commit message in the PR → add Signed-off-by: Your Name <[email protected]>

The DCO check blocks merges until every commit in the PR carries the footer (with squash this is just the one).

To publish a new version of the CLI, run the release scripts defined in codex-cli/package.json:

1. Open the codex-cli directory
2. Make sure you're on a branch like git checkout -b bump-version
3. Bump the version and CLI_VERSION to current datetime: npm run release:version
4. Commit the version bump (with DCO sign-off):
   git add codex-cli/src/utils/session.ts codex-cli/package.json git commit -s -m "chore(release): codex-cli v$(node -p \"require('./codex-cli/package.json').version\")"
5. Copy README, build, and publish to npm: npm run release
6. Push to branch: git push origin HEAD

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Have you discovered a vulnerability or have concerns about model output? Please e‑mail [email protected] and we will respond promptly.

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This repository is licensed under the Apache-2.0 License.