[firebase_auth][windows]: SetLogLevel(kLogLevelVerbose) causes 60s cold Firebase.initializeApp stall

[slarimore02]

Is there an existing issue for this?

• I have searched the existing issues.

Which plugins are affected?

Auth

Which platforms are affected?

Windows

Description

On Windows, firebase_auth calls this unconditionally in the native plugin constructor:

FirebaseAuthPlugin::FirebaseAuthPlugin() {
  firebase::SetLogLevel(firebase::kLogLevelVerbose);
}

In my app this turns a cold Firebase.initializeApp from sub-second into ~60 seconds.
A/B result:
With the firebase_auth constructor line restored:

    App::Create exit ms=30009
    Auth::GetAuth exit ms=10002
    current_user exit ms=20018 valid=true
    GetPluginConstantsForFirebaseApp exit ms=30026
    Firebase.initializeApp returned after 60667ms

With only this line disabled:
// firebase::SetLogLevel(firebase::kLogLevelVerbose);

and with firebase_auth registration/constants otherwise restored normally:

App::Create exit ms=3
Auth::GetAuth exit ms=2
current_user exit ms=2 valid=true
GetPluginConstantsForFirebaseApp exit ms=5
Firebase.initializeApp returned after 733ms

Suspected cause:
SetLogLevel(kLogLevelVerbose) enables Firebase C++ LogDebug(...) calls. On Windows, the Firebase C++ stdio logger writes through OutputDebugString(...). The slowdown pattern matches roughly one blocking debug-output write per Firebase debug log.

Expected behavior:
firebase_auth should not globally force verbose Firebase C++ SDK logging for every Windows app.

Possible fix:
Remove or gate:

firebase::SetLogLevel(firebase::kLogLevelVerbose);

behind an explicit diagnostic/debug opt-in.

Reproducing the issue

1. Create or use a Flutter Windows app with:

firebase_core: 4.11.0
firebase_auth: 6.5.4

2. Ensure the Windows app has a cached signed-in Firebase Auth session.

3. Add temporary timing logs around the Windows native Firebase.initializeApp path:

   • firebase_core/windows/firebase_core_plugin.cpp: time firebase::App::Create(...)
   • firebase_auth/windows/firebase_auth_plugin.cpp: time Auth::GetAuth(...), auth->current_user(), and GetPluginConstantsForFirebaseApp(...)

4. Run the app on Windows with the stock firebase_auth Windows plugin code:

FirebaseAuthPlugin::FirebaseAuthPlugin() {
  firebase::SetLogLevel(firebase::kLogLevelVerbose);
}

5. Observe that cold Firebase.initializeApp blocks for about 60 seconds. In my run:

App::Create exit ms=30009
Auth::GetAuth exit ms=10002
current_user exit ms=20018 valid=true
GetPluginConstantsForFirebaseApp exit ms=30026
Firebase.initializeApp returned after 60667ms

6. Comment out only this line in firebase_auth/windows/firebase_auth_plugin.cpp:

// firebase::SetLogLevel(firebase::kLogLevelVerbose);

7. Rebuild and run the same app state again.

8. Observe that cold Firebase.initializeApp returns in under a second. In my run:

App::Create exit ms=3
Auth::GetAuth exit ms=2
current_user exit ms=2 valid=true
GetPluginConstantsForFirebaseApp exit ms=5
Firebase.initializeApp returned after 733ms

The only behavioral difference between the slow and fast run was whether the firebase_auth Windows plugin constructor called firebase::SetLogLevel(firebase::kLogLevelVerbose);.

Firebase Core version

4.11.0

Flutter Version

3.44.1

Relevant Log Output

Flutter dependencies

Expand Flutter dependencies snippet

Replace this line with the contents of your `flutter pub deps -- --style=compact`.

Additional context and comments

No response

[SelaseKay]

cc @Lyokone