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The Cortex desktop app carries Cortex Chat and Cortex Code in a single window. It draws its own title bar with a switcher between Chat and Code and its own window controls, and it is the only client that can run a Code session on your own machine. This page covers what the installer does on each platform, the first launch and signing in, what the app adds over a browser tab, how to start a Code session on This PC, notifications, and how the app updates itself.
Cortex does not publish a public download page yet, so there is no installer link here. See Ways to run Cortex for the full picture.

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Install

Open the downloaded disk image and drag Cortex to your Applications folder, then open it. The build is notarised, so you do not have to override any security warning.

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First launch

1

Read the welcome screen

The first launch shows a welcome screen, once. It names your platform (Cortex for Mac, Cortex for Windows or Cortex for Linux) above the line Chat and Code — on this machine. and the body Sign in for Cortex models and cloud runtimes, or continue on This PC with your own provider keys.
2

Choose Get started or Continue without an account

Get started takes you to the sign-in screen. Continue without an account skips sign-in and lets you work on This PC with your own provider keys.
3

Sign in

On the Sign in screen, under Continue to Cortex, pick Continue with Google, Continue with GitHub, Continue with Apple or Continue with SSO, or type an Email address and Password. The email and password form stays inside the app window.
4

Finish in your browser, if you chose a button

Each of the four buttons opens your system browser. When you are done there, a Cortex page says Finish signing in in the Cortex app and hands you back. If the app does not come forward by itself, select Open Cortex, then close the browser window.
To work without a Cortex account, open Settings → Providers and either point the app at a model server running on this machine or paste a provider key. On the desktop app that key is kept in your operating system’s own credential store, not in the app.

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What the desktop app adds over the browser

The theme, the notification inbox, an optional remote-host address and whether you have seen the welcome screen are preferences of this device, not account settings, so they do not follow you to another machine.

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Run a Code session on This PC

1

Switch to Code and start a session

Use the switcher in the title bar, then start a new session and choose This PC.
2

Pick a folder

The system’s folder picker opens. There is no workspace-name field: the folder’s name identifies the repository. If you cancel the picker, no session is created.
3

Work

Once the session has some history, the composer shows chips for the runtime, This PC, the repository, the branch and the worktree. Each action asks for Allow, Always or Deny, and the session runs in Ask, Plan or Agent mode, with Agent as the default.
If nothing on this machine is attached yet, the session says so: This session runs on This PC, and no host is connected. Pair one from the Host pane and the composer comes back. Cortex never silently moves a This PC session into the cloud. If the place you chose is unavailable, the session tells you instead of relocating. To use a machine you reach over the network, go to Code → Connect a server and follow the connection form. To attach to a machine that is already running Cortex Code, open Code → Settings and enter that host’s address; only the address is needed. The host status is shown as one of Cloud only, Connecting, Connected, Disconnected, Cloud session running, Permission blocked or Failed wake. To let Code see your repositories, open Code → Settings → Integrations and select Connect GitHub. The installation page opens in your system browser. There is no personal-access-token field to fill in.

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Notifications

Chat and Code share one notification inbox, and the desktop app also raises your operating system’s own notifications when the window is not focused. You are notified when a scheduled task produces something, when you are mentioned, when a Code run finishes, when a Code run is waiting on a permission, when a bot needs an answer, and when a computer fails to wake. Open the in-app centre from the command palette (Notifications), where the empty state reads Nothing new. The Notifications page under Code shows the same items, with the empty state Nothing needs you and Runs that finish or fail while you are elsewhere will land here. Mark-as-read is offered only while something is unread.

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Updates

The app checks for an update when it starts and then every four hours, and downloads it quietly in the background. While it downloads you may see Downloading Cortex… with a percentage. When a build is ready a toast says Cortex {version} is ready to install. with Restart now and Later. Choosing Later installs the update the next time you quit. The app never moves you to an older version, and it keeps checking the channel the build you installed came from, so there is no channel picker inside the app. Mac builds are notarised and Windows builds are code-signed, and Windows verifies the signature of an update before installing it. In a browser tab the update banner never appears, because there is nothing there to install.