[🐛] getIdToken() returns token with new UID when using modular API

[anastasiia-nahaiska]

Issue

When using the modular API from @react-native-firebase/auth, calling getIdToken(currentUser, true) occasionally returns a valid ID token associated with a new Firebase UID.

This behavior does not occur when using the older namespaced API (firebase.auth().currentUser.getIdToken(true)), which correctly returns a fresh token for the existing user.

This is critical for apps that sync user data with a backend based on UID.

Code sample

With modular API (causes unexpected new UID):

public async refreshToken() {
  const auth = getAuth()

  if (auth.currentUser) {
    const idToken = await getIdToken(auth.currentUser, true) // returns token with new UID 

    return idToken
  }
}

With namespaced API (works as expected):

public async refreshToken() {
  const auth = getAuth()

  if (auth.currentUser) {
    const idToken = await auth.currentUser.getIdToken(true) // returns token with existing UID 

    return idToken
  }
}

---

Project Files

Javascript

Click To Expand

package.json:

{
  "dependencies": {
    "@react-native-firebase/app": "22.4.0",
    "@react-native-firebase/auth": "22.4.0",
    "react-native": "0.80.1"
  }
}

firebase.json for react-native-firebase v6:

# N/A

iOS

Click To Expand

ios/Podfile:

• I'm not using Pods
• I'm using Pods and my Podfile looks like:

...

  config = use_native_modules!
  use_frameworks! :linkage => :static
  
  $RNFirebaseAsStaticFramework = true

  use_react_native!(
    :path => config[:reactNativePath],
    # An absolute path to your application root.
    :app_path => "#{Pod::Config.instance.installation_root}/.."
  )

...

AppDelegate.m:

import Firebase

...

  func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication
      .LaunchOptionsKey: Any]? = nil
  ) -> Bool {
    FirebaseApp.configure()
    
    let delegate = ReactNativeDelegate()
...

---

Android

Click To Expand

Have you converted to AndroidX?

• my application is an AndroidX application?
• I am using android/gradle.settings jetifier=true for Android compatibility?
• I am using the NPM package jetifier for react-native compatibility?

android/build.gradle:

buildscript {
  dependencies {
    ...
    classpath 'com.google.gms:google-services:4.4.3'
  }
}

android/app/build.gradle:

apply plugin: 'com.google.gms.google-services' 

android/settings.gradle:

// N/A

MainApplication.java:

// N/A

AndroidManifest.xml:

<!-- N/A -->

---

Environment

Click To Expand

react-native info output:

 System:
  OS: macOS 14.5
  CPU: (8) arm64 Apple M3
  Memory: 89.20 MB / 16.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 20.9.0
    path: /var/folders/nr/kt8fqryx0ndch1jk3_wdswqc0000gp/T/yarn--1754037765131-0.4040609396968249/node
  Yarn:
    version: 1.22.22
    path: /var/folders/nr/kt8fqryx0ndch1jk3_wdswqc0000gp/T/yarn--1754037765131-0.4040609396968249/yarn
  npm:
    version: 10.1.0
    path: /usr/local/bin/npm
  Watchman:
    version: 2025.06.30.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.16.2
    path: /Users/anastasiianahaiska/.rbenv/shims/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 24.2
      - iOS 18.2
      - macOS 15.2
      - tvOS 18.2
      - visionOS 2.2
      - watchOS 11.2
  Android SDK: Not Found
IDEs:
  Android Studio: 2024.3 AI-243.24978.46.2431.13208083
  Xcode:
    version: 16.2/16C5032a
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.14
    path: /usr/bin/javac
  Ruby:
    version: 3.4.2
    path: /Users/anastasiianahaiska/.rbenv/shims/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 19.0.0
    wanted: 19.0.0
  react:
    installed: 19.1.0
    wanted: 19.1.0
  react-native:
    installed: 0.80.1
    wanted: 0.80.1
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: true
  newArchEnabled: true

• Platform that you're experiencing the issue on:
  • iOS
  • Android
  • iOS but have not tested behavior on Android
  • Android but have not tested behavior on iOS
  • Both
• @react-native-firebase/auth version you're using that has this issue:
  • 22.4.0
• Firebase module(s) you're using that has the issue:
  • e.g. Instance ID
• Are you using TypeScript?
  • Y 5.8.3

---

• 👉 Check out React Native Firebase and Invertase on Twitter for updates on the library.

[mikehardy]

I'm not sure how that could happen since the modular API is literally calling the namespaced API internally immediately and they both follow the same path to native after a quick deprecation warning check

react-native-firebase/packages/auth/lib/modular/index.js

Lines 418 to 420 in fe4550f

	export async function getIdToken(user, forceRefresh) {
	return user.getIdToken.call(user, forceRefresh, MODULAR_DEPRECATION_ARG);
	}

Could this be a sample-size issue in testing methodology rending a false-negative for the namespaced API? Stated differently: If the modular API has this problem the namespaced API likely also has the problem and might show it with more test iterations. And that would indicate the problem is more general and not an API style problem. That knowledge would affect how to approach reproducing it which is important.

Approximately how many test iterations do you have to do to show it in modular API currently? What is your test setup in details - which mobile device type and version are you using to reproduce this?

[MichaelVerdon]

I have been unable to replicate the behaviour in a setup where I compare the result of the modular call and name-spaced where the UID was consistent after each call, I tested this with anonymous sign in. What platform are you experiencing this on?

I suspect there is a configuration issue on your end.