[firebase-auth] Blocking function timeout returns UNKNOWN error code (code 47) instead of a dedicated timeout code

[Ortes]

Description

When a Firebase Auth blocking function (e.g. beforeUserCreated) times out, the Android SDK throws an error with code UNKNOWN (error code 47) instead of a dedicated, meaningful error code.

This makes it impossible for developers to programmatically distinguish between a genuine internal error and a blocking function timeout, leading to hours of debugging.

Steps to Reproduce

1. Set up a beforeUserCreated blocking function that takes longer than the allowed timeout.
2. Call createUserWithEmailAndPassword (or any auth method guarded by the blocking function) from an Android app.
3. Observe the exception: it surfaces as UNKNOWN / error code 47 with a generic message like "An internal error has occurred."

Expected Behavior

A dedicated error code (e.g. BLOCKING_FUNCTION_TIMEOUT or similar) should be returned so that developers can handle this case explicitly.

Actual Behavior

The error is surfaced as UNKNOWN (error code 47):

Error code: 47
Message: An internal error has occurred.

From Flutter/FlutterFire (where this was originally reported):

[firebase_auth/unknown] An internal error has occurred. [ Error code:47
FirebaseAuthException
Firebase Auth error code: unknown
Firebase Auth error message: An internal error has occurred. [ Error code:47

Context

This was reported on the FlutterFire repository: firebase/flutterfire#18022

The FlutterFire maintainer confirmed that error codes and messages are passed through as-is from the native Android SDK, and recommended opening this issue upstream to request a dedicated error code for blocking function timeouts.

A dedicated error code would benefit all Firebase Auth consumers on Android (native and cross-platform via FlutterFire, React Native Firebase, etc.).

Platform

• Android (Firebase Auth Android SDK)
• Also surfaced via FlutterFire (Flutter wrapper)

[lehcar09]

Hi @Ortes, thank you for reaching out. I tried reproducing the issue, however, I can't seem to reproduce the error.

Here's the code for beforeUserCreated I used

exports.beforeUserCreated = beforeUserCreated((event) => {
  const user = event.data;
  const suffix = "@example.com";

  if (user.email.toLowerCase().endsWith(suffix.toLowerCase())) {
    throw new HttpsError("invalid-argument", "Unauthorized email");
  }
});

And here's the response I got for triggering the error:

createUserWithEmail:failure
com.google.firebase.FirebaseException: An internal error has occurred. [ BLOCKING_FUNCTION_ERROR_RESPONSE:HTTP Cloud Function returned an error: {"error":{"message":"Unauthorized email","status":"INVALID_ARGUMENT"}} ]

Am I missing anything? By any chance can you share a runnable MCVE to help us investigate the issue? Thanks!

[Ortes]

Hi thanks for the reply, can you try with an await that last 30s in the beforeUserCreated function?

[lehcar09]

Hi @Ortes, I added the timeout for 30s, and still getting the error message.

Can you share the Firebase SDK version you're using? I'm using the Firebase version 34.10.0.