initializeAuth() crashes on Expo SDK 53 + Hermes with "INTERNAL ASSERTION FAILED: Expected a class definition"

[aaronrk1997]

Operating System

MACOS 15.0.1

Environment (if applicable)

Expo SDK 53 (React Native 0.73 / Hermes enabled by default)

Firebase SDK Version

11.7.1

Firebase SDK Product(s)

Auth

Project Tooling

• Firebase SDK: firebase@11.7.1
• 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

🧨 Detailed Problem Description

When using initializeAuth() from the modular Firebase Auth SDK (firebase@11.7.1) 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 (11.7.1): INTERNAL ASSERTION FAILED: Expected a class definition
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.

---

🔍 Additional Notes

• 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.

Steps and code to reproduce issue

Steps to Reproduce

1. 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

2. Set up firebaseConfig.ts with the following code:

   // firebaseConfig.ts
   import { initializeApp, getApps, getApp } from "firebase/app";
   import { getAuth } from "firebase/auth";
   import { Platform } from "react-native";
   
   const firebaseConfig = {
     apiKey: "demo",
     authDomain: "demo.firebaseapp.com",
     projectId: "demo",
     storageBucket: "demo.appspot.com",
     messagingSenderId: "123",
     appId: "123:web:demo",
   };
   
   const app = getApps().length ? getApp() : initializeApp(firebaseConfig);
   let auth = getAuth(app);
   
   if (Platform.OS !== "web") {
     import("firebase/auth")
       .then(({ initializeAuth }) => {
         try {
           initializeAuth(app, {
             persistence: require("./asyncStoragePersistence").customAsyncStoragePersistence,
           });
         } catch (e: any) {
           if (e.code !== "auth/already-initialized") throw e;
         }
       })
       .catch((err) => {
         console.error("Firebase native auth init error:", err);
       });
   }
   
   export { app, auth };

3. Create a dummy asyncStoragePersistence.ts file:

   // asyncStoragePersistence.ts
   import { getReactNativePersistence } from "firebase/auth/react-native";
   import AsyncStorage from "@react-native-async-storage/async-storage";
   
   export const customAsyncStoragePersistence = getReactNativePersistence(AsyncStorage);

4. Use auth anywhere in your app (e.g., in App.tsx).

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

   npx expo run:android

---

Result

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, js engine: hermes

[google-oss-bot]

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