# 2.x -> 3.0.0

Version 3.x of the Customer.io Flutter SDK introduces Firebase wrapper support for FCM users that improves Firebase compatibility and simplifies push notification setup.

## What changed?[](#what-changed)

Version 3.x introduces a Firebase wrapper that improves compatibility with Firebase Cloud Messaging (FCM).

## What needs to change?[](#what-needs-to-change)

You need to add the `CioFirebaseWrapper` import to your Swift files that use `CioMessagingPushFCM`.

Add the Firebase wrapper import to your `AppDelegate.swift` file:

```swift
import UIKit
import Flutter
import CioMessagingPushFCM
import CioFirebaseWrapper  // Add this import for FCM users
import FirebaseMessaging
import FirebaseCore

@main
class AppDelegateWithCioIntegration: CioAppDelegateWrapper<AppDelegate> {}
```

## Troubleshooting[](#troubleshooting)

If you see build errors related to Firebase after upgrading:

1.  **Clean your build**: Run `cd ios && pod install && cd ..` then rebuild
2.  **Check imports**: Ensure you’ve added `import CioFirebaseWrapper` to all files that import `CioMessagingPushFCM`