Run a second copy of any Electron app.
A second Claude, a second Slack, a second Discord, each with its own login, settings, and Dock icon. The original app stays untouched and keeps updating itself.
Three lines, no Gatekeeper warnings.
brew tap bnimit/tap brew trust bnimit/tap brew install --cask duplex
brew trust is a one-time step Homebrew asks for on third-party taps. Prefer a direct download? Grab the notarized zip from the latest release. Requires macOS 13 or later.
A login for every copy
Each instance keeps its profile, cookies, and settings in an isolated data folder. Two accounts, zero collisions.
The original stays untouched
Each instance is a copy-on-write clone of the app with its own identity. The original is never modified, keeps updating itself, and instances follow its updates.
Logins that actually work
macOS sees every instance as a separate app, so the original opens from the Dock while instances run, and Duplex's link routing sends OAuth callbacks to the instance you are signing in to.
Small and inspectable
Native Swift, zero dependencies, notarized by Apple. The source is public on GitHub under a source-available license.