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.

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).

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

Configuration

Package name

android/app/build.gradle

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

Package name matches the Firebase Android app configuration.

SHA-1 fingerprint

• Debug SHA-1 generated via:

./gradlew signingReport

• Added in:

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

google-services.json

• Downloaded again after adding SHA-1

• Placed at:

android/app/google-services.json

• Package name inside JSON matches the app.

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"
}

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);

AndroidManifest (queries section)

What I already tried

• Added SHA-1 fingerprint

• Re-downloaded google-services.json

• Ran flutter clean

• Rebuilt project

• Tested on emulator and physical device

Problem

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

ConnectionResult{statusCode=DEVELOPER_ERROR}

Sometimes Google Sign-In fails or behaves inconsistently.

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?