Firebase Auth - GetAuth / InitialiseAuth... Import only crashes the native environment.

[cdevlin278]

Operating System

Windows 11 / MAC OS 15

Environment (if applicable)

Expo SDK 53 - Expo SDK 52

Firebase SDK Version

^11.0.0 - 11.10.0

Firebase SDK Product(s)

Auth

Project Tooling

Project Tooling
Firebase SDK: firebase@11.10.0
React Native: via Expo SDK 53 (React Native 0.73)
JavaScript Engine: Hermes (default enabled in Expo 53)
Platform: iOS & Android (Expo Dev Client and EAS Build)
Bundler: Metro (default from Expo)
Metro config patch:
config.resolver.unstable_enablePackageExports = false
config.resolver.sourceExts.push('cjs')
Expo CLI: 6.x
Node.js: 20.x
Firebase Auth Persistence Attempted:
initializeAuth() with customAsyncStoragePersistence (fails)
getAuth() fallback (no crash, but no persistence)

Detailed Problem Description

When using initializeAuth() from the modular Firebase Auth SDK (firebase@^11.0.0) in a React Native project via Expo SDK 53 (with Hermes enabled by default), the application crashes at runtime on native platforms (iOS and Android) with the following error:

@firebase/auth: Auth (11.10.0): INTERNAL ASSERTION FAILED: Expected a class definition
Error: INTERNAL ASSERTION FAILED: Expected a class definition, js engine: hermes

Error: INTERNAL ASSERTION FAILED: Expected a class definition, js engine: hermes
This happens even when:

initializeAuth() is wrapped in a Platform.OS !== "web" conditional

initializeAuth() is lazy-loaded using import("firebase/auth")

The Metro bundler is patched using:

config.resolver.unstable_enablePackageExports = false;
config.resolver.sourceExts.push("cjs");

Using a dev client or EAS build (not just Expo Go)

Firebase is downgraded to v10.11.0 (same crash)

In contrast, using getAuth(app) alone does not crash, but results in non-persistent authentication state on native platforms.

This issue blocks any use of native persistent auth in Firebase Auth when using Expo SDK 53 and Hermes.
Replacing initializeAuth() with getAuth() only avoids the crash at the cost of degraded functionality.
The same code worked prior to Expo SDK 53 (e.g. SDK 52 + JSC).
No issue occurs in Expo Web or when switching the JS engine to JSC in app.json, but only in custom clients — Expo Go still uses Hermes.

**KEY ISSUE -

THE CJS and Enable package exports = false fix.. this seems to fix development but does not fix a native build that would be placed for example on the store.**

When importing firebase auth on a native build.. that has been bundled for the store, there will be an immediate crash. This bug has been here for a long time and even rolling back Firebase versions, Sdk Versions etc.. induces the same bug.

Steps and code to reproduce issue

Steps to Reproduce
Create a new Expo project with SDK 53 and Hermes enabled (default):

npx create-expo-app firebase-crash-test
cd firebase-crash-test
npx expo install firebase
Set up firebaseConfig.ts with the following code:

asyncStoragePersistence.ts
Wrap AsyncStorage into the shape getReactNativePersistence expects:

// asyncStoragePersistence.ts
import AsyncStorage from '@react-native-async-storage/async-storage';
import { getReactNativePersistence } from 'firebase/auth/react-native';

export const customAsyncStoragePersistence = getReactNativePersistence(AsyncStorage);

// OR EXPO SECURE STORE
import * as SecureStore from 'expo-secure-store';
import { getReactNativePersistence } from 'firebase/auth/react-native';

const secureStoreWrapper = {
getItem: SecureStore.getItemAsync,
setItem: SecureStore.setItemAsync,
removeItem: SecureStore.deleteItemAsync,
};

export const customAsyncStoragePersistence =
getReactNativePersistence(secureStoreWrapper);

import { initializeApp, getApps, getApp, FirebaseOptions, FirebaseApp } from 'firebase/app';
import {
initializeAuth,
FirebaseAuth,
} from 'firebase/auth/react-native';
import { customAsyncStoragePersistence } from './asyncStoragePersistence';

const firebaseConfig: FirebaseOptions = {
apiKey: "YOUR_API_KEY",
authDomain: "YOUR_AUTH_DOMAIN",
projectId: "YOUR_PROJECT_ID",
storageBucket: "YOUR_STORAGE_BUCKET",
messagingSenderId: "YOUR_MESSAGING_SENDER_ID",
appId: "YOUR_APP_ID",
};

// Initialize or reuse app instance
const app: FirebaseApp = !getApps().length
? initializeApp(firebaseConfig)
: getApp();

// Initialize Auth with React Native persistence
export const auth: FirebaseAuth = initializeAuth(app, {
persistence: customAsyncStoragePersistence,
});

// (Optional) export the raw app if you need other Firebase services
export { app };

Run the app on Android/iOS using a dev client or EAS build:

// App.tsx
import React, { useEffect, useState } from 'react';
import { auth } from './firebaseConfig';
import { onAuthStateChanged, signInAnonymously, User } from 'firebase/auth';
import { Text, View, Button } from 'react-native';

export default function App() {
const [user, setUser] = useState<User | null>(null);

useEffect(() => {
const unsubscribe = onAuthStateChanged(auth, (u) => {
setUser(u);
});
return unsubscribe;
}, []);

const signIn = () => {
signInAnonymously(auth).catch(console.error);
};

return (
<View style={{ flex: 1, alignItems: 'center', justifyContent: 'center' }}>
{user ? (
Welcome, {user.uid}
) : (
<>
Not signed in

</>
)}

);
}

npx expo run:android
The app crashes at runtime with this error:

@firebase/auth: Auth (11.7.1): INTERNAL ASSERTION FAILED: Expected a class definition
Error: INTERNAL ASSERTION FAILED: Expected a class definition,

[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.

[karl-mccoubrey]

I am having this exact same issue.

It is fine on development, but on full build used for test flight or stores, I get this failure.

I have followed any suggested steps, which did initially fix the development build, but remains a failure on full build.

I will try your steps as well @cdevlin278 and get back to you.

Thank you.

[FrankCEL]

I’m experiencing the same crash:

• Dev build: works after CJS / unstable_enablePackageExports = false tweaks
• EAS / TestFlight / store build: still crashes on import

Env: Expo SDK 53 (Hermes), firebase 11.10.0, React Native 0.73, iOS & Android

initializeAuth with async/secure-store persistence ->
@firebase/auth: INTERNAL ASSERTION FAILED: Expected a class definition

Rolling back Firebase or Expo versions doesn’t help.

[karl-mccoubrey]

Hi @cdevlin278

Still no luck on my end after exhaustive attempts.

This appears to be the same as @FrankCEL even with rollbacks.

At this point I am almost certain that it's nothing locally within projects and the fault is directly from firebase-js-sdk.

[mike-4040]

I guess my issue is related.

1. I can't import getReactNativePersistence() from 'firebase/auth/react-native'

// Cannot find module 'firebase/auth/react-native' or its corresponding type declarations.ts(2307)
import { getReactNativePersistence } from 'firebase/auth/react-native';

2. Resolved the issue importing from 'firebase/auth, but have to ignore ts error

import {
  // @ts-expect-error - the function exists but is not typed in the Firebase SDK
  getReactNativePersistence,
  initializeAuth,
} from 'firebase/auth';

And it works just fine.

[cdevlin278]

I guess my issue is related.

1. I can't import getReactNativePersistence() from 'firebase/auth/react-native'

// Cannot find module 'firebase/auth/react-native' or its corresponding type declarations.ts(2307)
import { getReactNativePersistence } from 'firebase/auth/react-native';
2. Resolved the issue importing from 'firebase/auth, but have to ignore ts error

import {
// @ts-expect-error - the function exists but is not typed in the Firebase SDK
getReactNativePersistence,
initializeAuth,
} from 'firebase/auth';
And it works just fine.

but when you do a full build and release, for example on test flight? Does it not crash?

In our system, it's legacy and it's using regular JS not typescript.

I've attached screenshots below. Even just simple code and const auth = initializeAuth with the react native persistence absolutely crashes the app.

[mike-4040]

but when you do a full build and release, for example on test flight? Does it not crash?

Idn, just upgraded to expo 53 yesterday night, and make it run locally.

npx expo run:ios --device

the local build works fine and persistence works in local simulator.