Real-world case: Firebase, Google Sign-In, MLKit (mobile_scanner) & CocoaPods
This post documents a real production-level dependency conflict on iOS in a large Flutter project. The goal is to explain why these issues happen, how to diagnose them correctly, and how to apply a single, stable fix — not temporary hacks.
Technical Context
Stack involved:
- Flutter (large-scale app, many plugins)
- Firebase (firebase_core, firebase_messaging, firebase_auth)
- Google Sign-In
- MLKit via mobile_scanner
- CocoaPods (iOS)
Main symptom:
CocoaPods could not find compatible versions for pod “GoogleUtilities/*”
Seen as:
- GoogleUtilities/UserDefaults
- GoogleUtilities/Environment
- mixed constraints: ~> 7.x, < 8.0, ~> 8.0
Why this happens (the real reason)
This is not a Flutter issue.
This is not a CocoaPods bug.
It is a structural incompatibility inside the Google iOS ecosystem.
- Firebase
- Firebase 10.x → GoogleUtilities 7.x
- Firebase 11.x → GoogleUtilities 8.x
- Google Sign-In
- GoogleSignIn 8.x → GoogleUtilities 8.x (via AppCheck)
- MLKit (mobile_scanner)
- mobile_scanner ≤ 5.x
→ MLKitCommon 11.x
→ GoogleUtilities < 8.0
💥 Result:
- Firebase 10.x requires 7.x
- GoogleSignIn 8.x requires 8.x
- MLKit blocks < 8.0
➡️ There is no version combination that can satisfy all three.
CocoaPods correctly refuses to resolve this graph.
The common mistake (and why it fails)
Forcing Firebase in Podfile:
$FirebaseSDKVersion = ‘10.25.0’
This may:
- temporarily “fix” Firebase
- but immediately breaks Google Sign-In
- and still conflicts with MLKit
This is an anti-pattern in modern Flutter projects.
The correct solution (one stable fix)
Core rule
👉 All Google dependencies must be aligned on the same major generation (8.x)
That means:
- Firebase 11.x
- GoogleSignIn 8.x
- MLKit compatible with GoogleUtilities 8.x
Final working fix (tested and stable)
1️⃣ pubspec.yaml
dependencies:
firebase_core: ^3.15.2
firebase_messaging: ^15.2.10
firebase_auth: ^5.7.0
google_sign_in: ^6.3.0
mobile_scanner: ^7.1.4
⚠️ Important: mobile_scanner 7.x is mandatory.
Older versions explicitly block GoogleUtilities < 8.0.
2️⃣ ios/Podfile
Remove any Firebase pinning.
Correct:
platform :ios, ‘15.0’
ENV[‘COCOAPODS_DISABLE_STATS’] = ‘true’
❌ Incorrect:
$FirebaseSDKVersion = ‘10.25.0’
3️⃣ Clean rebuild (strict order)
cd <project-root>
flutter clean
rm -rf .dart_tool pubspec.lock
flutter pub get
ls ios/Flutter/Generated.xcconfig # must exist
cd ios
rm -rf Pods Podfile.lock .symlinks Runner.xcworkspace
pod repo update
pod install –repo-update
4️⃣ Xcode
Open only:
ios/Runner.xcworkspace
Never open Runner.xcodeproj.
Why this fix works
- Eliminates all 7.x vs 8.x conflicts
- Avoids forcing CocoaPods
- Follows Google’s official dependency direction
- Future-proof against SDK upgrades
- Prevents subtle runtime crashes (AppCheck, Messaging, Sign-In)
Key lessons (for large Flutter projects)
- Never mix Google dependency generations
- Podfile pinning is a last resort, not a solution
- In Flutter, dependency issues are solved in pubspec.yaml, not CocoaPods
- mobile_scanner is a critical dependency on iOS
- If you see GoogleUtilities/* errors → you have a version alignment problem
Conclusion
If your Flutter iOS project uses Firebase, Google Sign-In, and MLKit:
- version alignment is mandatory
- temporary workarounds will fail again
- the only stable solution is a coherent, modern Google stack
Save this post as an advanced troubleshooting reference — it can save days of debugging next time.