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@@ -48,3 +48,21 @@ Join our community of developers creating universal apps.
 
 - [Expo on GitHub](https://github.com/expo/expo): View our open source platform and contribute.
 - [Discord community](https://chat.expo.dev): Chat with Expo users and ask questions.
+
+## Google Auth Setup
+
+This app uses Google ID tokens from Expo Auth Session and sends them to backend endpoint `/signin/google`.
+
+Set these values in Expo config under `expo.extra` in `app.json` (or override with environment variables):
+
+- `GOOGLE_IOS_CLIENT_ID` or `EXPO_PUBLIC_GOOGLE_IOS_CLIENT_ID`
+- `GOOGLE_ANDROID_CLIENT_ID` or `EXPO_PUBLIC_GOOGLE_ANDROID_CLIENT_ID`
+- `GOOGLE_WEB_CLIENT_ID` or `EXPO_PUBLIC_GOOGLE_WEB_CLIENT_ID` (used for Expo Go / web-based auth session)
+
+Notes:
+
+- Use OAuth client IDs from Google Cloud Console.
+- Ensure IDs match this app:
+  - Android package: `sh.lajo.buddyforparents`
+  - iOS bundle ID: `sh.lajo.buddyforparents`
+- The frontend sends `idToken` to backend, and backend handles both existing-user sign-in and automatic account creation.