Thread 1: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value

Description

Thread 1: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value

Steps to reproduce

yarn ios

React Native Version

0.83.1

Affected Platforms

Runtime - iOS

Output of npx @react-native-community/cli info

info Fetching system and libraries information...
System:
  OS: macOS 15.6
  CPU: (8) x64 Intel(R) Core(TM) i5-1038NG7 CPU @ 2.00GHz
  Memory: 1.01 GB / 16.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 20.19.4
    path: /usr/local/opt/node@20/bin/node
  Yarn:
    version: 4.9.1
    path: /usr/local/opt/node@20/bin/yarn
  npm:
    version: 10.8.2
    path: /usr/local/opt/node@20/bin/npm
  Watchman:
    version: 2025.09.01.00
    path: /usr/local/bin/watchman
Managers:
  CocoaPods:
    version: 1.16.2
    path: /Users/yousyoeun/.rbenv/shims/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 25.0
      - iOS 26.0
      - macOS 26.0
      - tvOS 26.0
      - visionOS 26.0
      - watchOS 26.0
  Android SDK: Not Found
IDEs:
  Android Studio: 2025.2 AI-252.27397.103.2522.14617522
  Xcode:
    version: 26.0.1/17A400
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.15
    path: /usr/bin/javac
  Ruby:
    version: 3.2.2
    path: /Users/yousyoeun/.rbenv/shims/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 20.0.0
    wanted: 20.0.0
  react:
    installed: 19.2.0
    wanted: 19.2.0
  react-native:
    installed: 0.83.1
    wanted: 0.83.1
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: true
  newArchEnabled: true

Stacktrace or Logs

Thread 1: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value

MANDATORY Reproducer

j

Screenshots and Videos

このレポートには、yarn ios 以外のソースファイル、テスト、または実行可能な再現手順が記載されていません。まず React Native 0.83.1 を使って iOS で再現し、完全なネイティブスタックトレースを取得してください。nil クラッシュを切り分け、回帰チェックで修正できれば完了ですが、そのチェックをどこに置くべきかは issue からは特定できません。