The problem
The Codex desktop app signs in to one ChatGPT account at a time. If you have a personal plan and a work or Business plan, switching means signing out and back in, and you can't run a task on one account while you work in the other.
You can't just open Codex twice, either. macOS brings the existing window forward, and Codex keeps its sign-in in one shared place, so even a second copy would end up on the same account.
How to run a second Codex with Duplex
- Install Duplex 1.2.2 or later (instructions below). Earlier versions don't support Codex.
- Click "New Instance…" and pick
Codex.appfrom your Applications folder. - Name it, for example "Codex Work". Keep the original icon, or pick a badge so you can tell the two apart in the Dock.
- Launch it. It opens signed out. Sign in with your second ChatGPT account.
Your original Codex stays on your first account and "Codex Work" stays on the second. Both open from the Dock and run at the same time, and signing out of one never signs out the other.
What you should know
- Settings are separate. Each Codex instance gets its own Codex settings folder, so its sign-in,
config.toml, MCP servers, and plugins are its own. Set up anything you need again in the instance. - The terminal follows the instance. A
codexcommand run from the instance's built-in terminal uses the instance's account and settings. - Updates follow the original. Update Codex as usual. The instance rebuilds itself from the new version the next time it launches.
- Download Codex from OpenAI. Duplex needs the regular Codex app in your Applications folder.
Get Duplex
Your first instance is free, forever. A $9 one-time license unlocks unlimited instances on up to 2 Macs. Requires macOS 13 or later.
brew tap bnimit/tap brew trust bnimit/tap brew install --cask duplex
Questions
Can I use two ChatGPT accounts in Codex on one Mac?
Yes. Use the Codex desktop app for one account and a Duplex instance of Codex for the other. Both can be open at the same time, each signed in to its own ChatGPT account.
Does signing out of one Codex sign out the other?
No. Each Duplex instance of Codex keeps its sign-in in its own folder, separate from the original app.
Do my MCP servers and settings carry over?
No. A Codex instance starts with its own settings, so add the MCP servers, plugins, and configuration you want in that instance.
Does a second copy take up double the disk space?
No. Duplex makes a copy-on-write clone, which shares its disk blocks with the original. Finder shows the full app size, but a Claude instance costs about 6 MB of real disk.
Does Duplex change the original app?
No. The original is never modified and keeps updating itself. Each instance follows its updates automatically the next time you launch it.
Is Duplex free?
Your first instance is free, forever, which is all you need for a second account. A $9 one-time license unlocks unlimited instances on up to 2 Macs. There is no subscription.
Is it safe?
Duplex is native Swift, notarized by Apple, and collects no analytics. The source is public on GitHub, so you can read exactly what it does.