MVCP rendering issues in Flatlist on Android

Description

When adding items in a flatlist with dynamic heights and having animations with MaintainVisibleContentPosition, there's jittering on the flatlist.

After slowing down the video, i found the flatlist renders the new item in one frame, then removes it and then animates it in properly.

I believe the root cause to be the new fabric engine as this was working on a previous version without new architecture.

I did find 2 potential fixes:

1. Setting a static height on the items, pointing the issue to only variable height items
2. Setting enableFabricCommitBranching to true, but this caused an issue with react navigation/screens going back, where the screen would unrender before the new one finished animating in.

Steps to reproduce

1. Install the reproductiion app on android
2. npm install
3. npm run android
4. Press "Add" multiple times at least 5, notice the jank in the animation

React Native Version

0.85.3

Affected Platforms

Runtime - Android

Areas

Fabric - The New Renderer

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

System:
  OS: macOS 26.4.1
  CPU: (16) arm64 Apple M3 Max
  Memory: 3.33 GB / 64.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 25.9.0
    path: /opt/homebrew/bin/node
  Yarn:
    version: 1.22.19
    path: /Users/humaid/.nvm/versions/node/v24.14.1/bin/yarn
  npm:
    version: 11.12.1
    path: /opt/homebrew/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 25.5
      - iOS 26.5
      - macOS 26.5
      - tvOS 26.5
      - visionOS 26.5
      - watchOS 26.5
  Android SDK:
    API Levels:
      - "30"
      - "34"
      - "35"
      - "36"
      - "37"
    Build Tools:
      - 30.0.3
      - 33.0.0
      - 33.0.1
      - 34.0.0
      - 35.0.0
      - 36.0.0
    System Images:
      - android-34 | Google APIs ARM 64 v8a
    Android NDK: Not Found
IDEs:
  Android Studio: 2025.3 AI-253.30387.90.2532.14935130
  Xcode:
    version: 26.5/17F42
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 21.0.11
    path: /Users/humaid/Library/Java/JavaVirtualMachines/azul-21.0.11/Contents/Home/bin/javac
  Ruby:
    version: 3.3.5
    path: /Users/humaid/.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: 0.85.3
    wanted: 0.85.3
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: true
  newArchEnabled: true

Stacktrace or Logs

No Stack trace

MANDATORY Reproducer

https://github.com/humaidk2/MVCPrepro

Screenshots and Videos

Normal video

https://github.com/user-attachments/assets/e107378d-c108-4423-9a77-18815d6addf9

Slowed down to 10%

https://github.com/user-attachments/assets/8e3a6889-5166-4ca4-a295-874c5b7f9819

Slowed down to 5%

https://github.com/user-attachments/assets/80e6a927-d32d-4bc8-a985-200177413752

Bắt đầu với trình tái hiện bắt buộc tại https://github.com/humaidk2/MVCPrepro: chạy npm install và npm run android, sau đó tái hiện hiện tượng giật trên Android bằng cách nhấn “Add” liên tục. Điều tra hành vi của Flatlist liên quan đến chiều cao động, MaintainVisibleContentPosition và Fabric; hoàn thành khi mục mới được thêm không còn hiển thị trong chốc lát, biến mất rồi lại xuất hiện bằng animation.