TypeError: Cannot read property 'OS' of undefined in Libraries/Settings/Settings.js due to circular dependency on startup

Description

When launching React Native applications with specific initialization/module loading sequences (such as during the boot of Expo host apps), the app crashes on startup with the following error:

[runtime not ready]: TypeError: Cannot read property 'OS' of undefined

Steps to reproduce

A minimal reproduction repository is available at Capstan/reproducer-react-native-settings on branch repro/settings-circular-dependency.

You can clone it, checkout the branch, and run:

yarn install
yarn test

Alternatively, you can minimally reproduce this crash by placing the following Jest unit test inside packages/react-native/Libraries/Settings/__tests__/Settings-test.js and running it:

/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow strict-local
 * @format
 * @oncall react_native
 */

'use strict';

describe('Settings', () => {
  beforeEach(() => {
    jest.resetModules();
  });

  it('should not throw due to circular dependency during Platform initialization', () => {
    // Intercept NativePlatformConstantsIOS (which Platform.ios requires during load)
    // to simulate another module requiring Settings during Platform's initialization phase.
    jest.mock('../../Utilities/NativePlatformConstantsIOS', () => {
      // Accessing Settings while Platform is loading
      require('../Settings.js');
      return {
        getConstants() {
          return {
            interfaceIdiom: 'phone',
            isTesting: true,
            osVersion: '16.0',
            systemName: 'iOS',
          };
        },
      };
    });

    expect(() => {
      require('../../Utilities/Platform');
    }).not.toThrow();
  });
});

React Native Version

0.85.3

Affected Platforms

Runtime - Android, Runtime - iOS

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

System:
  OS: macOS 26.5
  CPU: (10) arm64 Apple M1 Max
  Memory: 2.55 GB / 64.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 26.0.0
    path: /opt/homebrew/bin/node
  Yarn: Not Found
  npm:
    version: 11.12.1
    path: /opt/homebrew/bin/npm
  Watchman: Not Found
Managers:
  CocoaPods:
    version: 1.16.2
    path: /opt/homebrew/lib/ruby/gems/4.0.0/bin/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 25.5
      - iOS 26.5
      - macOS 26.5
      - tvOS 26.5
      - visionOS 26.5
      - watchOS 26.5
  Android SDK:
    API Levels:
      - "36"
      - "36"
    Build Tools:
      - 35.0.0
      - 36.0.0
      - 36.1.0
      - 37.0.0
    System Images:
      - android-34 | Google APIs ARM 64 v8a
      - android-35 | Google Play ARM 64 v8a
    Android NDK: Not Found
IDEs:
  Android Studio: 2025.3 AI-253.32098.37.2534.15336583
  Xcode:
    version: 26.5/17F42
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 26.0.1
    path: /opt/homebrew/opt/openjdk/bin/javac
  Ruby:
    version: 4.0.5
    path: /opt/homebrew/opt/ruby/bin/ruby

Stacktrace or Logs

Error name:    "TypeError"
Error message: "Cannot read properties of undefined (reading 'OS')"

  at Object.OS (node_modules/react-native/Libraries/Settings/Settings.js:21:14)
  at require (__tests__/SettingsCircularDependency.test.ts:17:7)
  at Object.require (node_modules/react-native/Libraries/Utilities/Platform.ios.js:13:1)

MANDATORY Reproducer

https://github.com/Capstan/reproducer-react-native-settings/tree/repro/settings-circular-dependency

Screenshots and Videos

No response

Libraries/Settings/Settings.js と Utilities/Platform.ios.js から始め、次に yarn install と yarn test を使ってブランチ repro/settings-circular-dependency で reproducer を実行してください。既存の Settings circular-dependency test は、Platform の初期化時のクラッシュや、OS が未定義であることによる TypeError なしにパスするはずです。