WebPreview

Preview web apps from an Agent sandbox by turning localhost links into external Buda preview URLs.

WebPreview lets you see a web app that is running inside an Agent sandbox. You can ask the Agent in natural language to start the app, wait for a localhost preview link, and open it using your Local Browser.

When to use WebPreview

Use WebPreview when the Agent builds or edits a website, demo, game, dashboard, or frontend project and you want to see it running in a browser.

You can ask in plain language:

Start the dev server and give me the preview link.

Please use /buda-web-preview to check the process and give me a working preview link.

Open the page in your Local Browser and check whether it works.

Basic flow

Ask the Agent to run the web app or start a preview.
Wait until the Agent outputs a localhost link, for example:

http://localhost:3000

Click that link in the Buda page, or open your Local Browser (do not use CloudBrowser) and enter the link in the address bar.
Buda converts the localhost link into an external preview URL, usually a URL ending in *.budaapps.com.
Wait for that *.budaapps.com URL to open in the browser.

The same works for other ports. For example, if you type this in your Local Browser:

http://localhost:4000

Buda requests a preview URL for port 4000 and opens the externally reachable page.

If the preview does not load

If the preview page is blank, stuck, or shows an error, ask the Agent to check whether the app is running and to return a fresh link.

Good prompts:

Please check whether the preview service is running and give me the preview link.

Please use /buda-web-preview to check the process and give me a preview link.

The preview did not load. Please check the dev server on port 3000 and give me a working link.

If your Local Browser shows the WakeUp button, you can click it. Buda will send a restart/check request to the Agent and refresh the preview after the service comes back.

Q&A

I opened a `*.budaapps.com` URL and it says `Unauthorized`. What should I do?

Go back to your Local Browser and enter the original localhost URL again, for example:

http://localhost:3000

Buda will request a fresh signed preview URL and open it again.

The preview shows `Gateway Error`. What should I do?

The app process may not be running, or it may be running on a different port. Ask the Agent:

Please use /buda-web-preview to check the process and give me a preview link.

You can also click WakeUp in your Local Browser to trigger the same recovery flow. You can open the buda-web-preview skill page to view the details of this system-managed skill.

Do I need to know the command to start the app?

Usually no. Tell the Agent what you want in natural language, such as:

Please start this project and show me the web preview.

The Agent should inspect the project, start the correct server, and output the preview link.

WebPreview

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