Guides OpenAI published jan 16, 2026

Code From Your Phone With OpenAI’s Codex

intermediate

The Rundown

This guide teaches you how to set up OpenAI Codex in Cursor, run Codex in the cloud from your phone, and configure Codex to review your code automatically. You’ll produce a Codex-ready project setup and a workflow for local coding, cloud tasks, and pull request reviews.

Who This Is Useful For

Developers who want AI coding help but find terminal-based tools intimidating.
ChatGPT Plus or Pro subscribers who have not tried Codex yet.
Anyone curious about AI coding agents.

What You Will Build

You’ll install Codex, connect it to a project, and create an AGENTS.md file that tells Codex about your project. You’ll also explore slash commands and set up automated code reviews.

A Codex IDE setup in Cursor or another supported editor.
An AGENTS.md project configuration file.
A cloud Codex workflow connected to GitHub.
Automatic Codex reviews for new pull requests.

What You Need

A ChatGPT Plus account.
Cursor or another supported code editor, such as VS Code or Windsurf.
A GitHub account, optional for cloud workflows and pull requests.
An existing project, or a PRD or spec sheet if you are starting from scratch.

Going Further

After setup, you can run Codex tasks from chatgpt.com/codex, create pull requests from Codex’s work, customize project-specific virtual environments, and use cloud-based Codex calls to preserve your 5-hour local limit.

Cloud-based Codex calls from the web or other connectors do not count against your 5-hour local limit, so you can code locally in Cursor and use the cloud agent for pull requests and reviews.

Codex CLI runs in your terminal.
Codex Cloud runs in your browser at chatgpt.com/codex.
Codex IDE Extension runs in your IDE as a chat window.

For this guide, use the Cursor extension because it keeps your agent chat separate from your terminal. If you use VS Code or Windsurf, you can follow along as well.

Go to https://developers.openai.com/codex/quickstart/ and select your IDE, then follow the brief download instructions.

Open a project in Cursor. Press CMD+Shift+P, search for Codex, and select New Codex Agent.

You should see a Codex agent window open.

Ask the agent to create an AGENTS.md file from your project files.

Prompt

Create an AGENTS.md file based on the project files.

If you’re starting from scratch, give Codex your PRD or spec sheet instead.

After it creates AGENTS.md, ask it to initialize git and write a commit if you have not done that yet.

Click the slash button to see available commands.

The most important commands are:

/review — Quick code review of your changes.
/status — Shows context limit percentage and your 5-hour usage limit.
/mcp — Shows connected MCP servers.
/context — Toggles auto-context from recent files.

Use the official documentation for the full list of slash commands.

Go to https://chatgpt.com/codex/settings/connectors and connect your GitHub account.

This lets Codex access your repositories and create pull requests from its work. Tasks run in isolated cloud sandboxes, so your local machine stays free.

To access Codex from anywhere, go to chatgpt.com/codex, select a repository and branch, and give it a prompt. Codex will run the code in a virtual environment.

You can edit your project-specific virtual environments so Codex can use your API keys or browse the web.

Codex can automatically review every pull request in the cloud.

Go to https://chatgpt.com/codex/settings/code-review.
Enable automatic code reviews on new PRs.
Flip Auto code review to “Review my PRs” for your repo.

Now whenever you open a pull request, Codex will automatically review it.

Cloud-based Codex calls from the web or other connectors do not count against your 5-hour local limit. Use this workflow to save tokens:

Code locally using Codex in Cursor.
When you finish a feature, ask Codex to commit the changes to a new branch and submit a new pull request.
The cloud agent automatically reviews your PR. You can follow along in the GitHub app or website.

Prompt

Commit these changes to a new branch and submit a new pull request.

This guide

Rundown University Pro

$49 billed monthly

Every on-demand course
Certifications on completion
Exclusive bonus perk drops
24/7 support

Go Pro for $49

Guides and live sessions stay free for everyone. Cancel anytime.

More guides like this

Build a Website Hands-Free With Claude Voice Claude · Beginner Turn Any Idea Into an AI-Powered Site With Lovable Lovable · Beginner Build Interactive Lead Magnets With Canva Code Canva · Beginner Deploy a Mini-SaaS in 10 Minutes With ChatGPT Sites ChatGPT · Beginner

View all guides

Billy Howell is a Virginia-based entrepreneur and AI educator who used AI-driven marketing systems to generate millions of impressions for startups and small businesses. As he scaled his marketing business, he also grew audiences on YouTube and Twitter by teaching people how to build apps with AI. In 2025, Billy joined The Rundown University to create hands-on video content that helps professionals implement practical, revenue-generating AI workflows in their businesses.

Connect with Billy

LinkedIn X Website

$49 billed monthly · cancel anytime

Go Pro

Code From Your Phone With OpenAI’s Codex

The Rundown

Who This Is Useful For

What You Will Build

What You Need

Going Further

Choose your Codex version

Set up Codex in your project

Explore slash commands

Use Codex from anywhere

Set up automatic code reviews

Use the token-saving workflow

The Rundown

Who This Is Useful For

What You Will Build

What You Need

Going Further

Every workflow on Rundown University, free for 7 days