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Browser Preview

As you build your app with CatDoes, a live browser preview appears in a panel alongside your conversation. Every change the agent makes — new screens, design tweaks, feature additions — is reflected in the preview automatically.

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Auto-Refresh

The preview refreshes automatically when:
  • The agent finishes writing or modifying code files
  • A codebase scan completes
  • The agent explicitly reloads the preview after installing packages or making structural changes
You can also manually refresh the preview at any time using the Refresh preview button in the bottom-left corner of the preview. The first time you open a project, the preview can take a few minutes to start while everything gets installed. If it doesn’t load, click Try again.

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Screen Sizes

Use the size picker at the top of the preview to see how your project looks on different screens — like an iPhone, a Pixel, an iPad, a laptop, or a desktop monitor. Choose Responsive to have the preview fill the whole panel. Mobile apps open on an iPhone-sized screen by default, and websites open in responsive mode.

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Projects with More Than One App

If your project has more than one app — for example, a website and a mobile app — a second dropdown appears next to the size picker. Use it to switch which app you’re previewing.

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Soft Reload

A soft reload refreshes the preview without restarting anything. It’s a quick way to reconnect and see recent changes. When to use it: Sometimes the agent disconnects from the preview and you can’t see the latest changes. A soft reload reconnects it and brings everything up to date. How to soft reload:
  • In the browser preview — click the Refresh preview button in the bottom-left corner of the preview.
  • In Expo Go — hold three fingers on the screen to open the reload menu.
  • Ask the agent — tell the agent to soft reload. For example:
    “Soft reload the preview”

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Hard Reload

A hard reload fully restarts the development server. It clears cached data and gives your project a fresh start. When to use it: If something isn’t working and you can’t figure out why — the page looks stuck, a change isn’t showing up, or the app is behaving strangely — a hard reload often fixes it. These are usually cache-related problems that go away with a restart. How to hard reload: Ask the agent to hard reload for you. For example:
“Hard reload”
A hard reload can take up to 2 minutes.
If you’ve been trying to fix an issue and nothing seems to work, try a hard reload before spending more time debugging. It clears out cached data and restarts fresh — many mysterious problems turn out to be a simple cache issue.

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Runtime Errors

If your app encounters a runtime error during preview, CatDoes captures it and makes it available to the agent. The agent can inspect these errors and attempt to fix them automatically as part of its workflow. For more on how the agent monitors and responds to errors, see CatDoes Watch.

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Share a Screenshot of the Preview

Want to show the agent exactly what you’re seeing? Click Attach preview screenshot in the bottom-left corner of the preview. A screenshot of the preview is added to your message, so you can point out what to change or what looks wrong.

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Mobile Preview with Expo Go

Beyond the browser preview, you can test your app on a physical mobile device using Expo Go.
  1. Click Preview on mobile in the bottom-left corner of the preview.
  2. The first time, CatDoes shows a QR code to download Expo Go. Pick iOS or Android, scan the code, and install the app. Then check I downloaded and already have Expo Go and click Continue.
  3. Open your phone’s camera, point it at the QR code, and tap the notification to open your app in Expo Go.
This lets you test touch interactions, native features, and real-world performance directly on your phone. Using CatDoes on your phone? Open the Preview tab and tap Open in Expo Go to run your app live on the same device. For websites, tap Open in browser instead. Some features, like certain native libraries, can’t run in the browser preview at all. When that happens, the preview tells you and offers to open your app in Expo Go instead.
Expo Go is only for mobile apps. For websites, the QR code simply opens your site in your phone’s browser.
The browser preview renders your app in a web view, which may look or behave slightly differently from the native mobile experience. Use the Expo Go preview on a physical device to verify native-specific behavior.
Use the QR code to share your in-progress app with teammates or stakeholders for quick feedback — no install required, just the Expo Go app.