[iOS] Inconsistent unmount lifecycle/cleanup triggered on App Kill when Keyboard is (or was) active

Description

A breaking change in lifecycle behavior has been observed in versions 0.83.4 and 0.84.1.

On iOS, when a user force-quits (kills) the app, React components normally do not trigger their unmount lifecycles (componentWillUnmount or useEffect cleanup) because the JS engine is terminated abruptly.

However, in these specific versions, if the keyboard was currently open or had been opened and then closed during the session, the unmount lifecycle is triggered upon the app being killed. If the keyboard was never opened during the app's session, the unmount lifecycle is not triggered (matching traditional behavior).

This inconsistency causes side effects, such as unexpected API calls or local storage wipes, to run during a process termination where they previously did not.

This behavior doesn't happen on Android and creates inconsistency between platforms.

Steps to reproduce

Since app is killed debugger is detached. AsyncStorage is used to save timestamp of unmount called

1. Open the application.

2. Observe a component that logs to the console useEffect and class component unmount timestamp

3. Scenario A (No Keyboard): Kill the app via the iOS App Switcher.
   Result: No logs appear on next launch (Expected behavior).

4. Scenario B (Keyboard Active): Reopen the app, tap a TextInput to bring up the keyboard. Kill the app via the App Switcher.
   Result: The unmount logs appear next launch (Inconsistent behavior).

5. Scenario C (Keyboard Dismissed): Reopen the app, open the keyboard, close the keyboard. Kill the app via the App Switcher.
   Result: The unmount logs appear next launch (Inconsistent behavior).

React Native Version

0.83.4, 0.84.1

Affected Platforms

Runtime - iOS

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

System:
  OS: macOS 26.1
  CPU: (12) arm64 Apple M4 Pro
  Memory: 380.42 MB / 24.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 22.15.0
    path: /Users/stas/.nvm/versions/node/v22.15.0/bin/node
  Yarn:
    version: 1.22.22
    path: /Users/stas/.nvm/versions/node/v22.15.0/bin/yarn
  npm:
    version: 10.9.2
    path: /Users/stas/.nvm/versions/node/v22.15.0/bin/npm
  Watchman:
    version: 2026.01.12.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.16.2
    path: /opt/homebrew/bin/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: Not Found
IDEs:
  Android Studio: 2024.3 AI-243.25659.59.2432.13423653
  Xcode:
    version: 26.3/17C529
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 21.0.6
    path: /usr/bin/javac
  Ruby:
    version: 3.4.3
    path: /Users/stas/.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

Stacktrace or Logs

Not a crash so no specific log is present

MANDATORY Reproducer

https://github.com/worksnk/rn_ios_unmount_breaking_change

Screenshots and Videos

Video shows 3 scenarios in described in steps with logs

https://github.com/user-attachments/assets/cd11d754-182c-4d2e-b9f0-99ee9190d3a5

Bắt đầu với reproducer bắt buộc tại rn_ios_unmount_breaking_change và xác minh ba kịch bản bàn phím trên React Native 0.83.4 hoặc 0.84.1 cho iOS. So sánh các timestamp unmount sau khi buộc thoát ứng dụng, khi có và không mở bàn phím; được xem là hoàn tất khi đã hiểu hành vi và việc cleanup ngoài ý muốn khi kill ứng dụng không còn được kích hoạt, với coverage hồi quy khi phù hợp.