**[BUG]: Critical Native Deadlock on Auth.CreateUserWithEmailAndPasswordAsync when user already exists (RAM Spike / Freeze)**

[mehmetbelen]

Description

The application (Unity Editor) completely freezes and enters a deadlock state when calling Auth.CreateUserWithEmailAndPasswordAsync() with an email address that is already registered. RAM usage rapidly spikes up to [max ram usage approx. 2.5 GB]. This suggests a thread synchronization/mutex deadlock within the Firebase Native SDK layer when attempting to return an error to the C# environment.

Reproducing the issue

1. Ensure a user with administrator privileges is currently signed in.
2. Call the Auth.CreateUserWithEmailAndPasswordAsync() method.
3. Use an email address in the parameters that is already present in your Firebase Authentication console.

Firebase Unity SDK Version

12.10.1

Unity editor version

6000.1.7f1

Installation Method

.unitypackage

Problematic Firebase Component(s)

Authentication

Other Firebase Component(s) in use

Authentication, Firestore

Additional SDKs you are using

This bug persists even after trying aggressive asynchronous isolation techniques such as Task.Run() and task.GetAwaiter().GetResult() to bypass the SynchronizationContext deadlock. The high RAM usage during the freeze strongly suggests the issue lies in a native thread lock within the SDK's internal C++ wrapper, preventing resource cleanup and halting the main thread.

Targeted Platform(s)

Android

Unity editor platform

Windows

Scripting Runtime

IL2CPP

Release Distribution Type

Pre-built SDK from https://firebase.google.com/download/unity

Relevant Log Output

This bug persists even after trying aggressive asynchronous isolation techniques such as **Task.Run()** and **task.GetAwaiter().GetResult()** to bypass the `SynchronizationContext` deadlock. The high RAM usage during the freeze strongly suggests the issue lies in a **native thread lock** within the SDK's internal C++ wrapper, preventing resource cleanup and halting the main thread.

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[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.

[niccolo-hare]

Hi @mehmetbelen, I hope you're doing well. I tried following along using my own test app with the latest SDK version available, but I didn't encounter any issues. What I did was record the session using Unity's built-in Profiler while reproducing the behavior based on your guide, and at most I could only see a spike of 2MB in terms of memory usage.

I'm thinking it might be the difference in SDK versions we used. Could you try updating your SDK(s) to the latest version available (v13.3.0 atm), and see if that helps resolve the issue? It's likely there may already be a fix or optimization for the deadlock you encountered included on a newer version that might be able to mitigate this behavior.

It's also possible that other plugins/components might also be affecting RAM usage. You could try testing with our quickstart application for Firebase Auth as well, to help isolate the issue to just our official SDKs.

[google-oss-bot]

Hey @mehmetbelen. We need more information to resolve this issue but there hasn't been an update in 5 weekdays. I'm marking the issue as stale and if there are no new updates in the next 5 days I will close it automatically.

If you have more information that will help us get to the bottom of this, just add a comment!