fix: Drop Android CSS transition animators when the React context goes

[MatiPl01]

The pre-draw listeners are registered on the window's ViewTreeObserver, which survives a React context teardown, so nothing removed them: after a reload they kept running every frame and retained the dead context through the manager.

NativeProxy.invalidate() now tears the manager down alongside pseudoSelectorManager, cancelling the animators, dropping the pending starts and removing the listeners. The reconciler keeps observer -> listener pairs so removal is possible at all; a HashSet of observers gave nothing to pass to removeOnPreDrawListener.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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Reviewing files that changed from the base of the PR and between ca4506b and 3cdb9b0.

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• packages/react-native-reanimated/android/src/main/java/com/swmansion/reanimated/css/CSSPlatformTransitionsManager.kt

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📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes
  • Improved cleanup of CSS-based transitions when views or animation systems are reset.
  • Prevented stale transition listeners from remaining attached after invalidation.
  • Ensured active transitions are cancelled and pending transitions are cleared during cleanup.
  • Improved reliability when views are recreated, detached, or otherwise become unavailable.

Walkthrough

CSS platform transition cleanup now tracks listener instances, rejects stale observers, blocks work after invalidation, cancels active animators, clears pending transitions, and runs from NativeProxy.invalidate().

Changes

CSS transition invalidation

Layer / File(s)	Summary
Reconciler listener cleanup packages/react-native-reanimated/android/src/main/java/com/swmansion/reanimated/css/CSSPlatformTransitionReconciler.kt	The reconciler tracks listener identities, removes stale observers, retires listeners, and clears live listeners during invalidation.
Manager and native cleanup packages/react-native-reanimated/android/src/main/java/com/swmansion/reanimated/css/CSSPlatformTransitionsManager.kt, packages/react-native-reanimated/android/src/main/java/com/swmansion/reanimated/NativeProxy.kt	The manager blocks transition work after invalidation, clears pending starts, cancels active animators on the UI thread, and invalidates the reconciler. NativeProxy.invalidate() invokes this cleanup.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant NativeProxy
  participant CSSPlatformTransitionsManager
  participant ActiveAnimators
  participant CSSPlatformTransitionReconciler
  NativeProxy->>CSSPlatformTransitionsManager: invalidate()
  CSSPlatformTransitionsManager->>CSSPlatformTransitionsManager: mark invalidated and clear pending starts
  CSSPlatformTransitionsManager->>ActiveAnimators: cancel active animators on UI thread
  CSSPlatformTransitionsManager->>CSSPlatformTransitionReconciler: invalidate()
  CSSPlatformTransitionReconciler->>CSSPlatformTransitionReconciler: remove tracked pre-draw listeners

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Possibly related PRs

• software-mansion/react-native-reanimated#10090: Modifies the same transition manager lifecycle.
• software-mansion/react-native-reanimated#10092: Modifies the same transition reconciler and manager lifecycle.
• software-mansion/react-native-reanimated#10170: Overlaps in NativeProxy, the reconciler, and the transition manager.

Suggested reviewers: pawicao, tjzel

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly describes the Android CSS transition animator teardown during React context teardown.
Description check	✅ Passed	The description explains how the changes remove listeners, cancel animators, and prevent retention after React context teardown.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch @matipl01/android-css-transition-teardown

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[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In
`@packages/react-native-reanimated/android/src/main/java/com/swmansion/reanimated/css/CSSPlatformTransitionReconciler.kt`:
- Around line 15-22: Update the tracking flow around track, invalidate, and
retire to resolve and retain the post-attachment window ViewTreeObserver as the
listener owner before pruning dead observers, ensuring listeners are removed
even when the temporary detached observer is invalidated. Preserve the
one-listener-per-window behavior and add a regression test covering detached
tracking, attachment, and invalidate().

In
`@packages/react-native-reanimated/android/src/main/java/com/swmansion/reanimated/css/CSSPlatformTransitionsManager.kt`:
- Around line 94-104: Make CSSPlatformTransitionsManager invalidation terminal
by adding a flag set before the UI-thread cleanup is posted. Guard
animateTransition() at entry and again inside its UI-thread lambda, returning
when invalidated so queued work cannot repopulate startTokens, create animators,
or call reconciler.track() after invalidate().

🪄 Autofix

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 1891504d-ceed-479e-ab50-7a768a274e65

📥 Commits

Reviewing files that changed from the base of the PR and between a874e64 and c5a0a61.

📒 Files selected for processing (3)

• packages/react-native-reanimated/android/src/main/java/com/swmansion/reanimated/NativeProxy.kt
• packages/react-native-reanimated/android/src/main/java/com/swmansion/reanimated/css/CSSPlatformTransitionReconciler.kt
• packages/react-native-reanimated/android/src/main/java/com/swmansion/reanimated/css/CSSPlatformTransitionsManager.kt