[Android] With enableFabricCommitBranching, a commit hook's clone in the React revision merge drops the raw props the view is created from

Start from ShadowNode::propsForClonedShadowNode and Props::initializeDynamicProps to see why the source's raw props are dropped once hasBeenMounted_ is set, then follow FabricUIManager's merge callback and FabricMountingManager::getProps. Use the linked reproducer's NativePropsWriter.cpp and its commit=ReactRevisionMerge logcat lines to confirm the clone loses nativeID and backgroundColor. Done means the merge commit creates the view with React's original raw props, so the red box renders with commit branching enabled.

Description

On Android with enableFabricCommitBranching on, a view created by React's commit can mount without the props React gave it. That happens whenever a commit hook clones the node in the merge of React's revision: a background colour, nativeID, testID and everything else React set are missing from the view.

React's commit lands on its branch and runs updateMountedFlag, which marks each node it created as mounted (hasBeenMounted_), although no revision holding those nodes has mounted yet. The merge mounts them later, in FabricUIManager's frame callback. Commit hooks run again in that merge commit (ShadowTreeCommitSource::ReactRevisionMerge). A hook that clones a node passing only the props it writes, as Reanimated's ShadowTreeCloner and the animation backend's commit hook do, gets props whose raw props hold only those props: Props::initializeDynamicProps keeps the raw props of its own parse, and ShadowNode::propsForClonedShadowNode merges the source's raw props in only while the source has not been mounted. The merge then creates the view from those raw props, since FabricMountingManager::getProps sends rawProps at the default flags.

With the flag off, the same hook clones the node in the commit that creates it, before updateMountedFlag, so propsForClonedShadowNode keeps React's raw props and the view mounts complete.

Steps to reproduce

1. Clone https://github.com/YevheniiKotyrlo/react-native-merge-clone-raw-props and install: cd ReproducerApp && yarn install. It is the reproducer template on [email protected], with @react-native-community/[email protected].
2. Build and install it with commit branching on: cd android && ./gradlew assembleRelease -PreactNativeArchitectures=arm64-v8a, then adb install -r app/build/outputs/apk/release/app-release.apk.
3. Launch the app. It installs a C++ commit hook (ReproducerApp/android/app/src/main/jni/NativePropsWriter.cpp) that writes opacity: 1 onto every node whose nativeID starts with written-, then renders a red 200 × 200 view with nativeID and testID written-box.
4. Read adb logcat -s PropsWriter, which logs each clone the hook makes, and look at the screen.
5. Repeat steps 2 to 4 with -PcommitBranching=false added to the Gradle command.

Expected (what step 5 shows): the red box shows.

Actual with the flag on: no box shows. The hook's clone in React's commit keeps the node's raw props; its clone in the merge (commit=ReactRevisionMerge) holds neither nativeID nor backgroundColor, and the merge creates the view from it, so the view has no background colour and none of the props React set. With the flag off, the view is created in React's own commit from the clone that kept them; the later clones there drop them too, but by then the view exists, and an update only applies what changed.

React Native Version

0.89.0-nightly-20261030-4afc5d5b9

Affected Platforms

Runtime - Android, Build - Windows

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

System:
  OS: Windows 11 10.0.26300
  CPU: "(32) x64 AMD Ryzen 9 9950X3D 16-Core Processor          "
  Memory: 148.06 GB / 255.67 GB
Binaries:
  Node:
    version: 26.12.1
    path: C:\Program Files\nodejs\node.EXE
  Yarn:
    version: 1.22.22
    path: C:\Users\yevhe.YEVHENII\AppData\Roaming\npm\yarn.CMD
  npm:
    version: 12.2.1
    path: C:\Program Files\nodejs\npm.CMD
  Watchman: Not Found
SDKs:
  Android SDK:
    API Levels:
      - "33"
      - "35"
      - "35"
      - "35"
      - "36"
      - "37"
      - "37"
    Build Tools:
      - 35.0.0
      - 36.0.0
      - 36.1.0
      - 37.0.0
    System Images:
      - android-26 | Google APIs Intel x86_64 Atom
      - android-28 | Google APIs Intel x86_64 Atom
      - android-29 | Google APIs Intel x86_64 Atom
      - android-30 | Google APIs Intel x86_64 Atom
      - android-31 | Google APIs Intel x86_64 Atom
      - android-32 | Google APIs Intel x86_64 Atom
      - android-33 | Google APIs Intel x86_64 Atom
      - android-34 | Google APIs Intel x86_64 Atom
      - android-35 | Google APIs Intel x86_64 Atom
      - android-36.1 | Google Play Intel x86_64 Atom
      - android-36.1 | Pre-Release 16 KB Page Size Google Play Intel x86_64 Atom
      - android-37.0 | Google APIs Intel x86_64 Atom
    Android NDK: Not Found
  Windows SDK: Not Found
IDEs:
  Android Studio: AI-262.9437.185.2621.16467767
  Visual Studio: Not Found
Languages:
  Java:
    version: 17.0.20.1
    path: C:\Program Files\Microsoft\jdk-17.0.20.101-hotspot\bin\javac.EXE
  Ruby: Not Found
npmPackages:
  "@react-native-community/cli":
    installed: 21.0.0-alpha.1
    wanted: 21.0.0-alpha.1
  react:
    installed: 19.3.0
    wanted: 19.3.0
  react-native:
    installed: 0.89.0-nightly-20261030-4afc5d5b9
    wanted: 0.89.0-nightly-20261030-4afc5d5b9
  react-native-windows: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: Not found
  newArchEnabled: Not found

Stacktrace or Logs

With enableFabricCommitBranching (adb logcat -s PropsWriter):
PropsWriter: commit=React tag=10 source rawProps: nativeID=yes backgroundColor=yes; written rawProps: nativeID=yes backgroundColor=yes
PropsWriter: commit=ReactRevisionMerge tag=10 source rawProps: nativeID=yes backgroundColor=yes; written rawProps: nativeID=no backgroundColor=no
PropsWriter: commit=Unknown tag=10 source rawProps: nativeID=no backgroundColor=no; written rawProps: nativeID=no backgroundColor=no

With -PcommitBranching=false:
PropsWriter: commit=React tag=10 source rawProps: nativeID=yes backgroundColor=yes; written rawProps: nativeID=yes backgroundColor=yes
PropsWriter: commit=Unknown tag=10 source rawProps: nativeID=yes backgroundColor=yes; written rawProps: nativeID=no backgroundColor=no
PropsWriter: commit=Unknown tag=10 source rawProps: nativeID=no backgroundColor=no; written rawProps: nativeID=no backgroundColor=no

MANDATORY Reproducer

https://github.com/YevheniiKotyrlo/react-native-merge-clone-raw-props

Screenshots and Videos

RedMagic NX809J, Android 16, release builds of the reproducer:

-PcommitBranching=false	enableFabricCommitBranching on