fix: Memory leak when unmounting views mid-animation#9711
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Pull request overview
Fixes an Android memory leak in Fabric mounting where tearing down a view subtree mid-animation could leave removed nodes (and their scheduled CSS animations) registered indefinitely. The mount hook no longer returns early on Reanimated-originated mounts, ensuring removal draining always runs while still only unpausing commits on React-originated mounts.
Changes:
- Compute whether the mount was initiated by Reanimated via
ReanimatedMountTrait, and always unset the trait for cleanliness. - Always call
UpdatesRegistryManager::handleNodeRemovals(even on Reanimated mounts) to prevent leaks during per-frame animation mounts. - Gate
unpauseReanimatedCommits()/requestFlush_()so they only run after React commits.
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tomekzaw
approved these changes
Jun 22, 2026
ReanimatedMountHook skipped handleNodeRemovals on Reanimated's own commits. While CSS animations run, every mount carries the mount trait, so the cleanup never ran for the duration of the animation. Tearing the view tree down mid-animation then leaked the unmounted nodes (and their still-scheduled CSS animations) in all update registries on Android. Always run handleNodeRemovals; gate only the commit-unpause on React commits.
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This was referenced Jun 24, 2026
MatiPl01
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Jul 2, 2026
…ion (#9711) (#9830) ## Summary Cherry-picking for Reanimated 4.3.2 release - #9711 ## Cherry-pick notes Conflict resolution: on 4.3-stable the early return lived directly in the mount-trait block (and 4.3 has no `setLastMountedRoot`, which came with #9715), so the change was applied on 4.3's shape - `handleNodeRemovals` now always runs and only the unpause is gated on the commit not being a Reanimated mount. Same semantics as on main.
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Fixes an Android memory leak: tearing down a view subtree while CSS animations are running left the unmounted nodes (and their still-scheduled animations) in every update registry.
ReanimatedMountHookreturned early on Reanimated's own commits and skippedhandleNodeRemovals, so while an animation runs (every frame is a Reanimated commit) the cleanup never ran. It now always drains removable nodes on mount and only gates the commit-unpause on React commits.