`ShadowNodeFamily` instance count continuously increases when toggling content

[t0maboro]

Description

In the attached repro, I have a button that mounts and unmounts a large number of components. Based on my observations, ShadowNodeFamily may not be deallocated correctly.

When repeatedly toggling the content, I notice in the Debug Memory Graph in Xcode that the number of ShadowNodeFamily instances keeps increasing. Additionally, when I click "Collect garbage" in the Memory tab of RN DevTools, the number of instances does not decrease.

This suggests that the objects might still be retained somewhere.

Steps to reproduce

1. Press a button that mounts a large subtree of components.
2. Press the button again to unmount the subtree.
3. Repeat that multiple times.
4. Observe the Debug Memory Graph in Xcode.

React Native Version

0.84.1

Affected Platforms

Runtime - iOS

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

System:
  OS: macOS 26.3
  CPU: (10) arm64 Apple M2 Pro
  Memory: 100.70 MB / 16.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 24.3.0
    path: /opt/homebrew/bin/node
  Yarn:
    version: 1.22.22
    path: /opt/homebrew/bin/yarn
  npm:
    version: 11.4.2
    path: /opt/homebrew/bin/npm
  Watchman:
    version: 2025.09.15.00
    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:
    API Levels:
      - "33"
      - "34"
      - "35"
      - "36"
    Build Tools:
      - 29.0.2
      - 33.0.1
      - 34.0.0
      - 35.0.0
      - 36.0.0
      - 36.1.0
      - 36.1.0
    System Images:
      - android-25 | Google APIs ARM 64 v8a
      - android-27 | Google APIs ARM 64 v8a
      - android-28 | Google APIs ARM 64 v8a
      - android-29 | Google APIs ARM 64 v8a
      - android-31 | Google APIs ARM 64 v8a
      - android-33 | Google APIs ARM 64 v8a
      - android-34 | Google Play ARM 64 v8a
      - android-36 | Android TV ARM 64 v8a
      - android-36 | Google Play ARM 64 v8a
    Android NDK: Not Found
IDEs:
  Android Studio: 2025.1 AI-251.26094.121.2512.13840223
  Xcode:
    version: 26.3/17C529
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.15
    path: /usr/bin/javac
  Ruby:
    version: 3.4.2
    path: /Users/tomaszboron/.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

N/A

MANDATORY Reproducer

https://github.com/t0maboro/ShadowNodeFamilyRepro#

Screenshots and Videos

after a few toggles:

after some more toggles: