Why does my preview say "No URL"?
The preview is a browser, so it needs an address to load, and it does not have one yet. The message reads in full: "No URL. Start a dev server in this quadrant, or set a manual URL via the quadrant ⚙ → Preview URL." Do one of those two things and the page appears. The most common fix is to start your project's dev server, because codus reads the address straight from it.
A dev server is the small program that runs your app while you build it, usually with a command like npm run dev. When it starts, it prints a local address such as http://localhost:5173. codus watches for that line and fills the preview in for you.
The quickest fix: start the dev server
Every quadrant has a set of small helper terminals for exactly this. One of them, dev, is where your dev server runs.
- In the quadrant header, click the terminal dot (the small terminal icon with a caret). It reads Show aux terminals on hover.
- A row of panes opens: npm run dev, npm run workers, and freehand.
- In the npm run dev pane, click ▶ start.
- Wait for it to print its address. codus picks it up and the preview loads on its own. The dot turns green once something is running.
To stop it later, click ◼ stop in the same pane.
You do not have to use these terminals. If your agent starts the dev server, or you run it in your own terminal, codus still reads the address the same way.
If your project does not use npm run dev
The dev terminal runs npm run dev by default, but many projects start a different way. You set the real command once, per folder:
- Click the quadrant settings icon (the tools icon at the end of the button row).
- Click Start commands to open it. The hint reads dev / workers / free.
- In the dev command chain box, type your start command, one command per line. They are joined with
&&when they run. - Click out of the box to save. It is saved for this folder, not just this slot.
If you leave a box empty, codus falls back to the default: npm run dev for dev, npm run workers for workers, and for free there is no default, so you must type a command there.
If there is no dev server to start
Some pages are just a web address, not a local project. You can point the preview at any address by hand:
- Open the quadrant settings icon.
- Find Preview URL (folder).
- Type or paste the address and press return.
This is pinned to the folder. The hint tells you which state you are in: whether it is a manual address you set, an address codus auto-detected from the dev terminal, or nothing yet. To go back to the auto-detected address, clear the box.
How do I know it worked?
The "No URL" message disappears and your page loads. The address bar, which showed the grey placeholder "no URL — start a dev server or set one in ⚙", now shows the real address.
Common problems
The dev server is running but the preview still says "No URL". codus reads the address from the dev server's printed line, so give it a moment after the server starts. If it never appears, copy the address the server printed (something like http://localhost:3000) and paste it into Preview URL (folder) by hand.
The Preview URL box is greyed out. No folder is pinned to this quadrant yet. Pin a folder first, then the box becomes editable. The placeholder changes from "pin a folder first" to "no URL detected — start a dev server, or paste one".
It loaded the wrong page. You may have an old manual address pinned. Open Preview URL (folder) and clear it to fall back to the auto-detected one, or type the address you actually want.