Prototyping Toolkit

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Installing Codex in VS Code ​

A setup guide for non-experts. Accurate as of September 2026. If a screen looks different, check the official guide: https://developers.openai.com/codex/ide

This guide covers steps 1–4 of the TLDR, with more explanation. Using Claude Code instead? Follow "Installing Claude Code in VS Code" and skip this guide.

What You Are Setting Up ​

Codex is an AI coding assistant made by OpenAI. It runs inside VS Code as a chat panel next to your files. It can read your project, make changes, and run commands for you.

One thing to know from the start: Codex changes files in your project without asking first. It does ask before using the internet or touching anything outside your project folder. Because of this, you'll get in the habit of saving a starting point before each task, so you can always go back.

You don't need to know how to program to follow this guide.

Words You'll See ​

  • Extension: an add-on that gives VS Code new features. Codex is one.
  • Prompt: a message you send to Codex.
  • Chat: one conversation with Codex. You can start a fresh one at any time. Other guides may call this a session.
  • Permission mode: a setting that controls what Codex can do without asking.
  • Command: an instruction for your computer, usually typed in a terminal. Codex can run commands for you.
  • Command Palette: a search box at the top of VS Code for finding any command by name. Press Cmd + Shift + P on a Mac or Ctrl + Shift + P on Windows, type part of the command's name, choose it from the list, and press Enter.
  • Save point: a saved snapshot of your project (a "commit") that you can go back to.

Before You Start ​

You need:

  • VS Code, installed and up to date. On a Mac, go to Code → Check for Updates. On Windows, go to Help → Check for Updates.
  • A ChatGPT account. Codex is included with ChatGPT plans, including the free plan, which has lower limits. Each plan's allowance resets every five hours, and weekly limits may apply. Check your student access in Step 3 before buying a plan. Checking Your Costs and Limits explains the allowance.

Step 1: Set Up a Folder for Your Projects ​

Codex works on the files in whichever folder VS Code has open, and it won't answer until a folder is open. So start by making one place to keep your projects. Your project goes inside it later.

Put it in your home folder rather than Documents or Desktop, which are often synced by iCloud Drive or OneDrive. Syncing can interfere with your projects.

  • Mac: open Finder and press Cmd + Shift + H to go to your home folder, the one with a house icon and your name. Choose File → New Folder, and name it Projects.
  • Windows: open File Explorer, type %USERPROFILE% in the address bar, and press Enter to go to your home folder. Choose New → Folder, and name it Projects.

Already have a folder for your projects? Use that one instead. Whichever folder you use, the rest of these guides call it your Projects folder, whatever its name really is.

Step 2: Open Your Projects Folder in VS Code ​

  1. Open VS Code and choose File → Open Folder…
  2. Select your Projects folder and click Open (on Windows, Select Folder).
  3. If VS Code asks "Do you trust the authors of the files in this folder?", click Yes, I trust the authors. Codex doesn't work otherwise.

Codex can make folders and copy projects into them, but choosing which folder VS Code has open is the part it can't do for you, so it's always File → Open Folder…

Step 3: Choose and Install Your Agent ​

Check your student access ​

Check student access using your edu email before buying a plan. Follow Codex for Students to create or sign in to your ChatGPT account and verify your student status. OpenAI has offered verified university students in the United States and Canada Codex credits, which let you keep using Codex after you reach your plan's usage limits.

Install the extension ​

  1. Click Extensions, the four-squares icon in the left-hand bar. You can also press Cmd + Shift + X on a Mac or Ctrl + Shift + X on Windows.
  2. Search for Codex.
  3. Choose Codex – OpenAI's coding agent, published by OpenAI.
  4. Click Install.

You only do this once. The extension is then available in every VS Code window and project, and each chat works on the folder that's open.

Open its chat panel and sign in ​

  1. Look for the Codex icon in the sidebar on the right side of the window, and click it. If you don't see it, open the Command Palette, type Open Codex Sidebar, and press Enter.
  2. Choose to sign in with your ChatGPT account.
  3. Your browser opens. Log in to ChatGPT and approve the connection.
  4. Go back to VS Code. You should now see a prompt box in the Codex panel.

Starting a new chat. You sometimes need a fresh chat, for example after changing a setting. Click the new chat button at the top of the Codex panel, or press Cmd + N on a Mac or Ctrl + N on Windows while the Codex panel is selected.

Step 4: Ask Your Agent Where It Is ​

Send:

Which folder are you working in?

Check that it names the folder you opened in Step 2. If the send button is greyed out with "Please open a folder or workspace to continue", go back to Step 2.

About Permissions and Save Points ​

Below the prompt box is a permission mode control. Keep it on Ask for approval: Codex edits files and runs routine commands in your project folder on its own, and asks before using the internet or going outside your project folder. Avoid Full access, which lets Codex change any file on your computer and use the internet without asking. Setting Up Your Coding Assistant for Prototyping (TLDR step 10) explains the other settings.

After each task, Codex lists the files it changed. Read the summary, and look at any file you're unsure about.

When Codex does ask before acting:

  • Read Codex's explanation. If there isn't one, ask: "Explain that in plain language first."
  • Allow it if it matches what you asked for.
  • Deny it and ask why if it doesn't match what you asked for.
  • When in doubt, deny. Codex will explain or suggest another way.

Because Codex doesn't ask before changing your files, save a starting point before each task. Once your project is on your computer (TLDR step 6), send this before any change:

Save a checkpoint of my project with Git, so we can go back to this version if the next change goes wrong. Tell me in one sentence what you saved.

If a change goes wrong, you can ask Codex to go back to that save point.

Checkpoint ​

Before moving on, check that Codex is working.

  1. Start a new chat: click the new chat button at the top of the Codex panel.
  2. Send:

Which folder are you working in?

You should see: a short reply in the Codex panel that names your Projects folder.

If not: see Troubleshooting below.

Troubleshooting ​

The Codex icon is missing. Open the Command Palette, type Open Codex Sidebar, and press Enter. If nothing happens, open the Command Palette again and run Developer: Reload Window. Also check that the folder isn't in Restricted Mode: if VS Code asks whether you trust the authors of the folder, click Yes, I trust the authors.

I can't send a message: "Please open a folder or workspace to continue." Codex needs a folder open. Choose File → Open Folder… and open your Projects folder (Step 2).

The browser didn't open when I tried to sign in. Run Developer: Reload Window from the Command Palette, then try signing in again.

Windows: Codex asks to set something up first. Codex uses a protected area on Windows, called a sandbox, to run commands safely. If it asks to set this up, follow its prompts.

Codex doesn't respond. Check your internet connection, then start a new chat.

Typing codex in the terminal says "command not found". This is normal. The extension doesn't install the terminal version, and you don't need it.

Tips ​

  • Hide VS Code's built-in AI. VS Code has its own AI assistant, GitHub Copilot, whose icons sit near Codex's. If you find yourself clicking the wrong one, hide it: open VS Code settings with Cmd + , on a Mac or Ctrl + , on Windows, type @id:chat.disableAIFeatures in the search box, and check the box next to the setting that appears. This hides VS Code's own AI features only. It doesn't affect the Codex extension.
  • Check your usage. Type /status in the prompt box to see your account and usage. If you claimed student credits, your balance appears on your ChatGPT usage page.
  • Privacy. OpenAI may use your Codex chats to improve its models unless you turn this off in ChatGPT's Data controls settings.

Next ​

When this guide's checkpoint works, continue with Setting Up Git and GitHub CLI (TLDR steps 5–6).