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When the agent changes how your app looks or works, it tests the change itself. It opens your app, clicks or taps through what it just built, checks that it works, and fixes what it finds before it finishes. This is on for every Web app and Mobile app project. There’s nothing to set up. Native iOS apps get their own version, covered below.

Real recording: the agent adds tasks, completes one, and checks the Done tab in its live view

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When the Agent Tests

The agent tests after any change to your app’s screens or behavior. Code that compiles isn’t enough. It checks that the app actually does what you asked before it tells you it’s done.
Want a specific flow checked? Say so in your prompt, for example: “Sign up with a new account and make sure the welcome screen shows.”

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Watch It Live

While the agent tests, its browser appears right in your preview with an Agent is testing your app badge. When it’s done, your normal preview comes back.
  • Web app: the agent’s browser fills the preview frame. The preview toolbar hides until the agent is done.
  • Mobile app: the agent’s browser shows inside the phone frame. If you have iOS (beta) selected in the preview, the agent tests on the iOS simulator instead.
While the agent is testing, the preview picker stays where it is: “The agent is testing here. You can switch when it’s done.” You can click and scroll in the live view. It’s the same page the agent is using, so your clicks land there too.
You see the live view in projects you own.

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In the iPhone App

In the Vibecode iPhone app, your preview stays on screen and usable while the agent works on a web or mobile app, instead of switching to a loading screen. On web app projects, you’ll also see the agent testing in the preview, with the same badge.

In the iPhone app: the agent tests in your preview, then Vibecode tells you the app is ready

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What the Agent Can’t Check

For mobile apps, the agent tells you where it tested. The web version in the phone frame can’t confirm native-only features such as the camera, haptics, push notifications, purchases, secure storage, native tab bars and pickers, or the keyboard moving your layout. The agent lists these as not verified, so check them on your phone.

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Native iOS Apps

Native Swift projects get agent testing too. The agent builds your app, opens it in the cloud iOS Simulator, and taps through the flow it changed. At the end of each turn, Vibecode checks the build. If it fails, the agent is sent back to fix it automatically. See Native iOS Apps for how the simulator preview works.
Testing is part of the agent’s turn, so it uses credits like the rest of the turn. See Plans and Credits.

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Next Steps

Creating Your First App

Write a prompt and generate your app

Native iOS Apps

Build and preview native Swift apps