[🐛] iOS Build Failure After Adding Crashlytics - ERR_UNHANDLED_REJECTION

[patterueldev]

Issue

After successfully setting up a new React Native app and running it on iOS simulator, I followed the Firebase integration steps:

1. Installed @react-native-firebase/app
2. Updated Podfile to use frameworks as per documentation
3. Ran pod install and successfully ran the app
4. Installed @react-native-firebase/crashlytics
5. Ran pod install again
6. Attempted to run the app on iOS simulator

The build fails with xcodebuild error code 65. The error message is:

info 💡 Tip: Make sure that you have set up your development environment correctly, by running npx react-native doctor. To read more about doctor command visit: https://github.com/react-native-community/cli/blob/main/packages/cli-doctor/README.md#doctor 

node:internal/process/promises:330
      new UnhandledPromiseRejection(reason);
      ^

UnhandledPromiseRejection: This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). The promise rejected with the reason "Error: Failed to build ios project. "xcodebuild" exited with error code '65'. To debug build logs further, consider building your app with Xcode.app, by opening 'FirebaseDemo841.xcworkspace'.".
    at throwUnhandledRejectionsMode (node:internal/process/promises:330:7)
    at processPromiseRejections (node:internal/process/promises:413:17)
    at process.processTicksAndRejections (node:internal/process/task_queues:104:32) {
  code: 'ERR_UNHANDLED_REJECTION'
}

Node.js v25.2.1

I have not yet configured Firebase credentials (GoogleService-Info.plist) as the documentation suggests it should work without them initially. The app builds and runs fine before adding Crashlytics.

I've created a minimal reproduction repository: https://github.com/patterueldev/FirebaseDemo841/tree/firebase-integration

---

Project Files

Javascript

Click To Expand

package.json:

{
  "name": "FirebaseDemo841",
  "version": "0.0.1",
  "private": true,
  "scripts": {
    "android": "react-native run-android",
    "ios": "react-native run-ios",
    "lint": "eslint .",
    "start": "react-native start",
    "test": "jest"
  },
  "dependencies": {
    "@react-native-firebase/app": "^23.8.6",
    "@react-native-firebase/crashlytics": "^23.8.6",
    "@react-native/new-app-screen": "0.84.1",
    "react": "19.2.3",
    "react-native": "0.84.1",
    "react-native-safe-area-context": "^5.5.2"
  },
  "devDependencies": {
    "@babel/core": "^7.25.2",
    "@babel/preset-env": "^7.25.3",
    "@babel/runtime": "^7.25.0",
    "@react-native-community/cli": "20.1.0",
    "@react-native-community/cli-platform-android": "20.1.0",
    "@react-native-community/cli-platform-ios": "20.1.0",
    "@react-native/babel-preset": "0.84.1",
    "@react-native/eslint-config": "0.84.1",
    "@react-native/metro-config": "0.84.1",
    "@react-native/typescript-config": "0.84.1",
    "@types/jest": "^29.5.13",
    "@types/react": "^19.2.0",
    "@types/react-test-renderer": "^19.1.0",
    "eslint": "^8.19.0",
    "jest": "^29.6.3",
    "prettier": "2.8.8",
    "react-test-renderer": "19.2.3",
    "typescript": "^5.8.3"
  },
  "engines": {
    "node": ">= 22.11.0"
  }
}

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:

# Resolve react_native_pods.rb with node to allow for hoisting
require Pod::Executable.execute_command('node', ['-p',
  'require.resolve(
    "react-native/scripts/react_native_pods.rb",
    {paths: [process.argv[1]]},
  )', __dir__]).strip

platform :ios, min_ios_version_supported
prepare_react_native_project!

linkage = ENV['USE_FRAMEWORKS']
if linkage != nil
  Pod::UI.puts "Configuring Pod with #{linkage}ally linked Frameworks".green
  use_frameworks! :linkage => linkage.to_sym
else
  use_frameworks! :linkage => :static
  $RNFirebaseAsStaticFramework = true
end

target 'FirebaseDemo841' do
  config = use_native_modules!

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

  post_install do |installer|
    react_native_post_install(
      installer,
      config[:reactNativePath],
      :mac_catalyst_enabled => false,
      # :ccache_enabled => true
    )
  end
end

AppDelegate.m:

// AppDelegate.swift (since it's Swift, not Objective-C)
import UIKit
import React
import React_RCTAppDelegate
import ReactAppDependencyProvider

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
  var window: UIWindow?

  var reactNativeDelegate: ReactNativeDelegate?
  var reactNativeFactory: RCTReactNativeFactory?

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

    reactNativeDelegate = delegate
    reactNativeFactory = factory

    window = UIWindow(frame: UIScreen.main.bounds)

    factory.startReactNative(
      withModuleName: "FirebaseDemo841",
      in: window,
      launchOptions: launchOptions
    )

    return true
  }
}

class ReactNativeDelegate: RCTDefaultReactNativeFactoryDelegate {
  override func sourceURL(for bridge: RCTBridge) -> URL? {
    self.bundleURL()
  }

  override func bundleURL() -> URL? {
#if DEBUG
    RCTBundleURLProvider.sharedSettings().jsBundleURL(forBundleRoot: "index")
#else
    Bundle.main.url(forResource: "main", withExtension: "jsbundle")
#endif
  }
}

---

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 {
    ext {
        buildToolsVersion = "36.0.0"
        minSdkVersion = 24
        compileSdkVersion = 36
        targetSdkVersion = 36
        ndkVersion = "27.1.12297006"
        kotlinVersion = "2.1.20"
    }
    repositories {
        google()
        mavenCentral()
    }
    dependencies {
        classpath("com.android.tools.build:gradle")
        classpath("com.facebook.react:react-native-gradle-plugin")
        classpath("org.jetbrains.kotlin:kotlin-gradle-plugin")
    }
}

apply plugin: "com.facebook.react.rootproject"

android/app/build.gradle:

apply plugin: "com.android.application"
apply plugin: "org.jetbrains.kotlin.android"
apply plugin: "com.facebook.react"

/**
 * This is the configuration block to customize your React Native Android app.
 * By default you don't need to apply any configuration, just uncomment the lines you need.
 */
react {
    /* Folders */
    //   The root of your project, i.e. where "package.json" lives. Default is '../..'
    // root = file("../../")
    //   The folder where the react-native NPM package is. Default is ../../node_modules/react-native
    // reactNativeDir = file("../../node_modules/react-native")
    //   The folder where the react-native Codegen package is. Default is ../../node_modules/@react-native/codegen
    // codegenDir = file("../../node_modules/@react-native/codegen")
    //   The cli.js file which is the React Native CLI entrypoint. Default is ../../node_modules/react-native/cli.js
    // cliFile = file("../../node_modules/react-native/cli.js")

    /* Variants */
    //   The list of variants to that are debuggable. For those we're going to
    //   skip the bundling of the JS bundle and the assets. Default is "debug", "debugOptimized".
    //   If you add flavors like lite, prod, etc. you'll have to list your debuggableVariants.
    // debuggableVariants = ["liteDebug", "liteDebugOptimized", "prodDebugOptimized"]

    /* Bundling */
    //   A list containing the node command and its flags. Default is just 'node'.
    // nodeExecutableAndArgs = ["node"]
    //
    //   The command to run when bundling. By default is 'bundle'
    // bundleCommand = "ram-bundle"
    //
    //   The path to the CLI configuration file. Default is empty.
    // bundleConfig = file(../rn-cli.config.js)
    //
    //   The entry file for bundle generation. Default is 'index.android.js' or 'index.js'
    // entryFile = file("../js/MyApplication.android.js")
    //
    //   A list of extra flags to pass to the 'bundle' commands.
    //   See https://github.com/react-native-community/cli/blob/main/docs/commands.md#bundle
    // extraPackagerArgs = []

    /* Hermes Commands */
    //   The hermes compiler command to run. Default is 'hermesc'
    // hermesCommand = "$rootDir/my-custom-hermesc/bin/hermesc"
    //
    //   The list of flags to pass to the Hermes compiler. By default is "-O", "-output-source-map"
    // hermesFlags = ["-O", "-output-source-map"]

    /* Autolinking */
    autolinkLibrariesWithApp()
}

/**
 * Set this to true to Run Proguard on Release builds to minify the Java bytecode.
 */
def enableProguardInReleaseBuilds = false

/**
 * The preferred build flavor of JavaScriptCore (JSC)
 *
 * For example, to use the international variant, you can use:
 * `def jscFlavor = io.github.react-native-community:jsc-android-intl:2026004.+`
 *
 * The international variant includes ICU i18n library and necessary data
 * allowing to use e.g. `Date.toLocaleString` and `String.localeCompare` that
 * give correct results when using with locales other than en-US. Note that
 * this variant is about 6MiB larger per architecture than default.
 */
def jscFlavor = 'io.github.react-native-community:jsc-android:2026004.+'

android {
    ndkVersion rootProject.ext.ndkVersion
    buildToolsVersion rootProject.ext.buildToolsVersion
    compileSdk rootProject.ext.compileSdkVersion

    namespace "com.firebasedemo841"
    defaultConfig {
        applicationId "com.firebasedemo841"
        minSdkVersion rootProject.ext.minSdkVersion
        targetSdkVersion rootProject.ext.targetSdkVersion
        versionCode 1
        versionName "1.0"
    }
    signingConfigs {
        debug {
            storeFile file('debug.keystore')
            storePassword 'android'
            keyAlias 'androiddebugkey'
            keyPassword 'android'
        }
    }
    buildTypes {
        debug {
            signingConfig signingConfigs.debug
        }
        release {
            // Caution! In production, you need to generate your own keystore file.
            // see https://reactnative.dev/docs/signed-apk-android.
            signingConfig signingConfigs.debug
            minifyEnabled enableProguardInReleaseBuilds
            proguardFiles getDefaultProguardFile("proguard-android.txt"), "proguard-rules.pro"
        }
    }
}

dependencies {
    // The version of react-native is set by the React Native Gradle Plugin
    implementation("com.facebook.react:react-android")

    if (hermesEnabled.toBoolean()) {
        implementation("com.facebook.react:hermes-android")
    } else {
        implementation jscFlavor
    }
}

android/settings.gradle:

pluginManagement { includeBuild("../node_modules/@react-native/gradle-plugin") }
plugins { id("com.facebook.react.settings") }
extensions.configure(com.facebook.react.ReactSettingsExtension){ ex -> ex.autolinkLibrariesFromCommand() }
rootProject.name = 'FirebaseDemo841'
include ':app'
includeBuild('../node_modules/@react-native/gradle-plugin')

MainApplication.java:

// MainApplication.kt (since it's Kotlin)
package com.firebasedemo841

import android.app.Application
import com.facebook.react.PackageList
import com.facebook.react.ReactApplication
import com.facebook.react.ReactHost
import com.facebook.react.ReactNativeApplicationEntryPoint.loadReactNative
import com.facebook.react.defaults.DefaultReactHost.getDefaultReactHost

class MainApplication : Application(), ReactApplication {

  override val reactHost: ReactHost by lazy {
    getDefaultReactHost(
      context = applicationContext,
      packageList =
        PackageList(this).packages.apply {
          // Packages that cannot be autolinked yet can be added manually here, for example:
          // add(MyReactNativePackage())
        },
    )
  }

  override fun onCreate() {
    super.onCreate()
    loadReactNative(this)
  }
}

AndroidManifest.xml:

<manifest xmlns:android="http://schemas.android.com/apk/res/android">

    <uses-permission android:name="android.permission.INTERNET" />

    <application
      android:name=".MainApplication"
      android:label="@string/app_name"
      android:icon="@mipmap/ic_launcher"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:allowBackup="false"
      android:theme="@style/AppTheme"
      android:usesCleartextTraffic="${usesCleartextTraffic}"
      android:supportsRtl="true">
      <activity
        android:name=".MainActivity"
        android:label="@string/app_name"
        android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|screenSize|smallestScreenSize|uiMode"
        android:launchMode="singleTask"
        android:windowSoftInputMode="adjustResize"
        android:exported="true">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
      </activity>
    </application>
</manifest>

---

Environment

Click To Expand

react-native info output:

info Fetching system and libraries information...
System:
  OS: macOS 26.3
  CPU: (12) arm64 Apple M2 Pro
  Memory: 129.70 MB / 16.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 25.2.1
    path: /Users/pat/.nvm/versions/node/v25.2.1/bin/node
  Yarn:
    version: 1.22.22
    path: /Users/pat/.nvm/versions/node/v25.2.1/bin/yarn
  npm:
    version: 11.6.2
    path: /Users/pat/.nvm/versions/node/v25.2.1/bin/npm
  Watchman:
    version: 2026.01.12.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.16.2
    path: /Users/pat/.rbenv/shims/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 25.2
      - iOS 26.2
      - macOS 26.2
      - tvOS 26.2
      - visionOS 26.2
      - watchOS 26.2
  Android SDK:
    API Levels:
      - "23"
      - "26"
      - "27"
      - "28"
      - "30"
      - "31"
      - "32"
      - "33"
      - "34"
      - "35"
      - "36"
    Build Tools:
      - 28.0.3
      - 30.0.3
      - 33.0.1
      - 34.0.0
      - 35.0.0
      - 36.0.0
    System Images:
      - android-34 | Google APIs ARM 64 v8a
      - android-36.1 | Google APIs ARM 64 v8a
      - android-36 | Google Play ARM 64 v8a
      - android-VanillaIceCream | Google Play ARM 64 v8a
    Android NDK: Not Found
IDEs:
  Android Studio: 2025.3 AI-253.30387.90.2532.14935130
  Xcode:
    version: 26.2/17C52
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.12
    path: /usr/bin/javac
  Ruby:
    version: 3.3.6
    path: /Users/pat/.rbenv/shims/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 20.1.0
    wanted: 20.1.0
  react:
    installed: 19.2.3
    wanted: 19.2.3
  react-native:
    installed: 0.84.1
    wanted: 0.84.1
  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 version you're using that has this issue:
  • 23.8.6
• Firebase module(s) you're using that has the issue:
  • Crashlytics
• Are you using TypeScript?
  • Y & 5.8.3

---

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

[patterueldev]

This is an addressable thing, but it requires you to be an experienced one to understand it. The real issue appears when you run the project in an Xcode app, and it turns out the issue is related to the Modular libraries.

If we take my sample project, the fix applied:

# remove the `linkage` part that was added by default and replace with just  the use_frameworks line from the document

# replace
linkage = ENV['USE_FRAMEWORKS']
if linkage != nil
  Pod::UI.puts "Configuring Pod with #{linkage}ally linked Frameworks".green
  use_frameworks! :linkage => linkage.to_sym
end

# with
use_frameworks! :linkage => :static
$RNFirebaseAsStaticFramework = true

Then, inside the post_install line, insert the build setting to allow the non-modular includes:

  post_install do |installer|
    react_native_post_install( # ...

    # Allow non-modular headers in framework modules
    installer.pods_project.targets.each do |target|
      target.build_configurations.each do |config|
        config.build_settings['CLANG_ALLOW_NON_MODULAR_INCLUDES_IN_FRAMEWORK_MODULES'] = 'YES'
      end
    end
  end

Do a pod install or npx pod-install ios, then rebuild the app.
It's probably a Firebase thing and not really a React Native Firebase thing, but I don't know because setting up through Expo actually works more straightforward than here.

At the end, I just want some documentation improvements for these kinds of cases, so that we know what needs to be done to solve the issue if we encounter this in the future (or by new people)

[MichaelVerdon]

Hi there, I can certainly look at updating docs for this. Thank you for submitting the ticket

[mikehardy]

This is just a sub-case of this issue I bet, where pre-built react-native core is now default on react-native 0.84+ and is not statically linked, causing problems for all modules that expect use_frameworks! to be in place and work:

• [🐛] compile errors with react-native pre-compiled iOS distribution default on RN 0.84 - workaround - disable pre-compiled react-native or use Podfile preinstall hook #8883

Pre-built react-native core violates that use_frameworks assumption. For RN CLI, this comment has the Podfile fix that works:

#8883 (comment)

For Expo, this demonstrator shows how to add expo-build-properties module and use forceStaticLinking for the RNFB packages: https://github.com/mikehardy/rnfbdemo/blob/99644c9ab1812ca56a667c84d30d61a05af20d71/make-expo-demo.sh#L105-L111

Without testing carefully I can't assert 100% this is a duplicate but I'm pretty sure it is

The documentation in this area is definitely lacking as it is still an area of active work where I'm discovering new compile error modes and fixing them literally daily, e.g.

• fix(ios): fix objective-c / swift interop in the non-use_frameworks! case for pre-built rncore #8925

We're definitely trying, and we'll get there 😅