Flutter Google Sign-In: DEVELOPER_ERROR / Unknown calling package name 'com.google.android.gms' on app startup

I am getting a Google Play Services error in my Flutter app after adding Google Sign-In (Firebase Authentication).
The error appears immediately when the app starts, even before triggering the sign-in flow.

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Error (shortened logcat)

E/GoogleApiManager: Failed to get service from broker. E/GoogleApiManager: java.lang.SecurityException: Unknown calling package name 'com.google.android.gms' W/GoogleApiManager: ConnectionResult{statusCode=DEVELOPER_ERROR}

The stack trace originates from Google Play Services (com.google.android.gms).

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Environment

Flutter: 3.x (stable)

Android Studio: latest stable

Device: Android Emulator / Physical device (both tested)

Android version: Android 13–14

firebase_core: latest

firebase_auth: latest

google_sign_in: latest

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Configuration

Package name

android/app/build.gradle

android { defaultConfig { applicationId = "com.example.app" } }

Package name matches the Firebase Android app configuration.

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SHA-1 fingerprint

Debug SHA-1 generated via: ./gradlew signingReport Added in:

Firebase Console → Project Settings → Android App → SHA certificate fingerprints

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google-services.json

Downloaded again after adding SHA-1

Placed at:

android/app/google-services.json Package name inside JSON matches the app.

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Gradle plugins

android/app/build.gradle

plugins { id "com.android.application" id "com.google.gms.google-services" id "kotlin-android" id "dev.flutter.flutter-gradle-plugin" }

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Google Sign-In code

final GoogleSignInAccount? googleUser = await GoogleSignIn().signIn(); final GoogleSignInAuthentication googleAuth = await googleUser!.authentication; final credential = GoogleAuthProvider.credential( accessToken: googleAuth.accessToken, idToken: googleAuth.idToken, ); await FirebaseAuth.instance.signInWithCredential(credential);

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AndroidManifest (queries section)

<queries> <package android:name="com.google.android.gms" /> <package android:name="com.android.vending" /> </queries>

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What I already tried

Added SHA-1 fingerprint

Re-downloaded google-services.json

Ran flutter clean

Rebuilt project

Tested on emulator and physical device

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Problem

The app runs, but the following error appears on every startup:

ConnectionResult{statusCode=DEVELOPER_ERROR}

Sometimes Google Sign-In fails or behaves inconsistently.

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Question

What typically causes:

Unknown calling package name 'com.google.android.gms'

together with:

ConnectionResult{statusCode=DEVELOPER_ERROR}

in a Flutter + Firebase Google Sign-In setup?

Could this be related to:

OAuth client configuration

missing Web client ID

Google Play Services environment issues

or another configuration step I might be missing?