If you already pay for ChatGPT, this is the shortest path in the whole course. One naming thing first, because it trips people up. Codex is not a separate download any more. It lives inside the ChatGPT desktop app.
One application, three ways to use it. Chat is the conversation you already know. Work is the toggle above the composer. Codex is the coding surface that sees the folder you open. Same account, same window, different job.
Download it for your system and open it. On Windows it ships as a Microsoft Store package, so there is a documented one line option from PowerShell as well. Then open the app and sign in with your ChatGPT account.
Two sign in routes, and they do not bill the same. Continue to sign in uses your ChatGPT plan's included usage. Sign in another way takes an API key and charges API pricing, per token, separately. Pick deliberately.
Make an empty folder called pick-test on your Desktop first. Then choose where to work: start a chat, create a project, or open a folder. Choose open a folder and pick that one. The folder you open is the context it gets.
Three prompts, one at a time. Explain this folder without changing anything. Create a file. Then change it and show the change first. These three are identical in all five paths, so two tools get judged on the same work.
Open pick-test in Finder or File Explorer. hello dot t x t is there, on your own disk, outside the app. That is the whole point of the exercise. The agent touched a real file, and you can see it without asking the agent.
This surface has documented voice. Start new voice chat, or set a hotkey in settings. Your configuration lives in the dot codex folder, shared with the terminal version, which is why moving to the next session costs almost nothing.
You have a coding agent in a window you already had open, billing against a plan you already pay for. Next session is the same product in a terminal, on the same account, which is one install command away from here.
If you already pay for ChatGPT, this is the shortest path in the whole course. You install one app you may already want anyway, sign in with the account you already have, point it at a folder, and you have a coding agent. No terminal.
One naming thing first, because it trips people up. Codex is not a separate download any more. It lives inside the ChatGPT desktop app. You install ChatGPT and you switch into the Codex surface. Same three prompts as every other path in this course.
OpenAI describes the desktop app as a "command center for complex work," where you "run projects in parallel, work with files, use your computer, and keep long-running work moving from one desktop workspace." (learn.chatgpt.com/docs/app)
Suits you if: you already have a ChatGPT subscription, you want a graphical window, and you would like the chat you already use and the coding agent in the same application. Not for you if you want the agent inside a script, or if you specifically want the terminal workflow the rest of this academy assumes. That is Path D.
What you will use
Mac and Windows: the documented download page is chatgpt.com/download. Download the build for your operating system and open it. Linux: follow the Linux installation guide.
On Windows the app is distributed as a Microsoft Store package, so there is also a documented one-line option from PowerShell:
winget install --id 9PLM9XGG6VKS -s msstore
Source: learn.chatgpt.com/docs/windows/windows-app
Caution: the only download domain you should use for this is chatgpt.com, or the Microsoft Store package above. Every install link in this academy points at claude.ai, chatgpt.com, or x.ai. A "ChatGPT desktop" installer on any other domain is somebody else's software wearing a logo.
Do this now: install it and open it once. Do not sign in yet if you are not sure which account you want to use; sort that out first, because the agent's usage bills against whichever account you pick.
"Open the app, then sign in with your ChatGPT account."
The documented sign-in steps for the desktop app: "On the signed-out screen, select Continue to sign in, then complete the browser flow." If you would rather pay per use from a developer account instead of using your subscription, the documented alternative is: "On the signed-out screen, select Sign in another way, enter your key, then select Continue."
Source: learn.chatgpt.com/docs/auth
Caution: those two choices bill differently. Signing in with ChatGPT uses your plan's included usage. An API key is billed on API pricing, separately, per token (learn.chatgpt.com/docs/pricing). Pick deliberately.
To sign out later, open the profile menu and "Select Log out to clear the current credentials."
Make an empty folder called pick-test on your Desktop in Finder or File Explorer first.
Then, in the app, after signing in you "choose where to work" by one of three routes: "Start a chat, create a project, or open a folder." The app "can use the files and context in the location you choose." Choose open a folder and pick pick-test.
On Windows there is a documented shortcut for the same thing: click Add new project or press Ctrl+O.
To get into the coding surface rather than ordinary chat, "use the toggle above the composer to select Chat or Work," and in Codex you begin with New chat. For a one-off question that needs no project, "point to New chat and select the Quick chat icon on its right."
Caution: the folder you open is the context the agent gets. Start with one empty folder you would not miss. Not Documents. Not your whole Desktop.
Windows users, one more documented detail: the agent "runs natively on Windows using PowerShell" by default, and you can switch it to WSL2 in Settings, but "the change doesn't take effect until you restart." The docs also recommend "storing projects on your Windows filesystem" rather than working directly from WSL paths.
Send these three, one at a time. They are identical in all five paths of this course, so you can run this one and, say, the Claude Code desktop one, and compare the same work rather than two different demos.
Prompt 1
Explain what is in this folder in plain English. Do not change anything.
Prompt 2
Create a file named hello.txt in this folder. The file should contain the sentence: I am set up.
Prompt 3
Add a second line to hello.txt that says: I can change files too. Show me the change before you save it.
Then open pick-test in Finder or File Explorer. hello.txt is there. That is the whole point of the exercise: the agent touched a real file on a real disk, and you can see it outside the app.
This surface has it, and it is documented. ChatGPT Voice lets you "talk through ideas and coordinate tasks in Chat, Work, and Codex."
How to start it: in a new conversation, select Start new voice chat. In an existing task, select Start voice chat. You can also "set a shortcut in Settings > Voice > Voice chat hotkey."
Availability, per the same page: "ChatGPT Plus, Pro, Business, Edu, and Enterprise plans."
Know which one you want, because the docs draw the line clearly: "Use ChatGPT Voice for a live conversation with ChatGPT. Use voice dictation when you only want to turn speech into prompt text before sending it."
Source: learn.chatgpt.com/docs/features/voice
Caution: a live voice conversation is a microphone that is on. Think about the room before you start one on a client call day.
Your project files stay in the folder you opened. Codex's own configuration is shared with the CLI, which is the useful part if you ever move to Path D:
~/.codex/config.toml, on every platform.codex/config.toml inside the repository, loaded only for trusted projects~/.codex/auth.json, or your operating system's credential store, depending on your settingsSources: learn.chatgpt.com/docs/config-file/config-basic and learn.chatgpt.com/docs/auth
Honest answer: OpenAI's app documentation does not publish a consumer update or uninstall procedure, and this academy does not invent steps that are not on an official page.
What that means in practice. On Windows the app is a Microsoft Store package, so it updates and removes the way Store apps do on your machine. On macOS, remove it the way you remove any other application. If you want to clear the credentials and configuration as well, that is the ~/.codex folder from Step 6, and codex logout is the documented way to clear stored credentials if you also have the CLI installed (learn.chatgpt.com/docs/auth).
If a newer page appears with an official uninstall procedure, follow that instead of this paragraph.
Switch to the Codex CLI when:
They are the same product on the same account. The sign-in, the config file, and the ~/.codex folder carry straight over, so moving to Path D costs you one install command and nothing else.
The app is installed and signed in, the Codex surface is open on your pick-test folder, all three prompts have been sent, and hello.txt exists on your Desktop with two lines in it that you did not type.
Template included: Members get a one-page Codex desktop card: the download routes for Mac and Windows, the sign-in choices and what each one bills, the open-a-folder path, the three comparison prompts, and the voice chat steps. Find it in your member dashboard under Templates.
Short on time? Agentic Quarks will implement this end to end, wired into your stack, and hand you the keys.
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