[0.82.0] Different behavior of views with position: "absolute" between old and new architecture

Description

In the old React Native architecture, a view with position: "absolute" will overlap a child of its sibling even if that child had a higher zIndex. This meant that box1 (blue) appears below box2 (red):

In the new architecture, the stacking behavior is different — box2, being absolutely positioned outside the sibling hierarchy, will overlap box1:

Steps to reproduce

1. Build and run rn-tester.
2. Open RNTesterPlayground.js with reproducer.

React Native Version

0.82.0

Affected Platforms

Runtime - Android, Runtime - iOS

Areas

Fabric - The New Renderer

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

info Fetching system and libraries information...
System:
  OS: macOS 15.4.1
  CPU: (12) arm64 Apple M3 Pro
  Memory: 164.56 MB / 18.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 22.17.1
    path: /Users/wojciechloboda/.nvm/versions/node/v22.17.1/bin/node
  Yarn:
    version: 1.22.22
    path: /opt/homebrew/bin/yarn
  npm:
    version: 10.9.2
    path: /Users/wojciechloboda/.nvm/versions/node/v22.17.1/bin/npm
  Watchman:
    version: 2025.04.28.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.16.2
    path: /opt/homebrew/bin/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 24.5
      - iOS 18.5
      - macOS 15.5
      - tvOS 18.5
      - visionOS 2.5
      - watchOS 11.5
  Android SDK:
    API Levels:
      - "28"
      - "31"
      - "33"
      - "35"
      - "36"
    Build Tools:
      - 28.0.3
      - 30.0.2
      - 30.0.3
      - 34.0.0
      - 35.0.0
      - 35.0.1
      - 36.0.0
      - 36.0.0
    System Images:
      - android-33 | Google Play ARM 64 v8a
      - android-35 | Google Play ARM 64 v8a
    Android NDK: Not Found
IDEs:
  Android Studio: 2024.2 AI-242.23726.103.2422.12816248
  Xcode:
    version: 16.4/16F6
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.15
    path: /opt/homebrew/opt/openjdk@17/bin/javac
  Ruby:
    version: 2.6.10
    path: /usr/bin/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 20.0.0
    wanted: 20.0.0
  react:
    installed: 19.1.1
    wanted: 19.1.1
  react-native:
    installed: 0.82.0
    wanted: 0.82.0
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: Not found
  newArchEnabled: false

Stacktrace or Logs

.

MANDATORY Reproducer

https://github.com/facebook/react-native/pull/54169

Screenshots and Videos

Old arch:

New arch:

rn-tester erstellen und ausführen und dann RNTesterPlayground.js mit dem in PR 54169 verlinkten Reproducer öffnen. Vergleiche das Stacking absolut positionierter Elemente und von zIndex unter der alten und neuen Architektur auf Android und iOS; als erledigt gilt die Aufgabe, wenn sich das Verhalten in beiden Architekturen konsistent mit der erwarteten Geschwisterhierarchie verhält.