[Android][Fabric] addViewAt hard-crashes on a placeholder ViewState synthesised by updateEventEmitter

Description

On Android, SurfaceMountingManager.addViewAt throws a fatal IllegalStateException on a ViewState whose view is null:

java.lang.IllegalStateException: Unable to find view for viewState
  ViewState [3548] - isRoot: false - props: null - viewManager: null - isLayoutOnly: true and tag 3548

The ViewState was not created by createViewUnsafe. It was synthesised by updateEventEmitter, because an UPDATE EVENTEMITTER mutation for that tag arrived before any Create for it.

That placeholder is what makes this fatal. addViewAt already handles a missing ViewState with a soft exception and an early return (line 322), but the placeholder makes the lookup succeed, so the guard is skipped and checkNotNull(view) at line 330 tears down the surface.

props: null identifies the construction site uniquely. There are exactly three ViewState(...) construction sites in SurfaceMountingManager.kt on 0.87.1:

Line	Site	Would print
134	root view	isRoot: true
590	createViewUnsafe	props: non-null: currentProps = propMap is assigned unconditionally, before the isLayoutable branch
978	updateEventEmitter, tagToViewState.getOrPut(reactTag) { ViewState(reactTag) }	isRoot: false - props: null - viewManager: null, view null

Only line 978 matches. And nothing nulls these fields after creation: across the file the only assignments are view/viewManager at 134 and 607 to 609, and currentProps at 591, 666 and 668. So this is not a view-recycling or delete-path artefact, and it is not an ordinary flattened node either, since a flattened node still goes through createViewUnsafe and therefore still has currentProps.

The getOrPut at 978 is intentional (it carries the T62717437 TODO about virtual nodes needing event emitters without a view). The problem is only that the placeholder it leaves behind is indistinguishable from a real ViewState at every later lookup.

Steps to reproduce

I do not have an app-level deterministic reproducer: this is a production crash, and the underlying mutation ordering (an UPDATE EVENTEMITTER reaching a tag with no Create) is a race I cannot trigger on demand. #58265 reports what appears to be the same missing-Create cause.

The failure itself is deterministic and can be driven against SurfaceMountingManager directly, without reproducing the race:

1. Start a surface and mount a parent ViewGroup tag normally.
2. Call updateEventEmitter(tag) for a tag that has had no createView call. This registers a bare ViewState(tag) via the getOrPut at line 978.
3. Call addViewAt(parentTag, tag, 0) for that same tag.
4. The getNullableViewState(tag) check at line 321 succeeds, the soft-exception early return is skipped, and checkNotNull(view) at line 330 throws.

Step 3 is exactly what the mount batch does when the Create is missing, so whether or not the race that drops the Create is fixed separately, this branch should degrade rather than kill the surface.

React Native Version

0.87.1

Affected Platforms

Runtime - Android

Areas

Fabric - The New Renderer

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

System:
  OS: macOS 26.5.2
  CPU: (10) arm64 Apple M2 Pro
  Memory: 192.73 MB / 16.00 GB
Binaries:
  Node: 24.16.0
  npm: 11.13.0
  Watchman: 2026.07.27.00
Managers:
  CocoaPods: 1.17.0
IDEs:
  Android Studio: 2025.3 AI-253.30387.90.2532.14935130
Languages:
  Java: 21.0.9
npmPackages:
  react: 19.2.8
  react-native: 0.87.1
Android:
  hermesEnabled: true
  newArchEnabled: true

Crashing device: HONOR REA-NX9, Android 15, arm64. Production build, main thread.

Stacktrace or Logs

java.lang.IllegalStateException: Unable to find view for viewState ViewState [3548] - isRoot: false - props: null - viewManager: null - isLayoutOnly: true and tag 3548
  at com.facebook.react.fabric.mounting.SurfaceMountingManager.addViewAt (SurfaceMountingManager.kt:330)
  at com.facebook.react.fabric.mounting.mountitems.IntBufferBatchMountItem.execute (IntBufferBatchMountItem.kt:122)
  at com.facebook.react.fabric.mounting.MountItemDispatcher.executeOrEnqueue (MountItemDispatcher.kt:379)
  at com.facebook.react.fabric.mounting.MountItemDispatcher.dispatchMountItems$lambda$7$lambda$6 (MountItemDispatcher.kt:269)
  at com.facebook.react.internal.tracing.PerformanceTracer.trace (PerformanceTracer.java:46)
  at com.facebook.react.fabric.mounting.MountItemDispatcher.dispatchMountItems (MountItemDispatcher.kt:250)
  at com.facebook.react.fabric.mounting.MountItemDispatcher.tryDispatchMountItems (MountItemDispatcher.kt:94)
  at com.facebook.react.fabric.FabricUIManager$DispatchUIFrameCallback.doFrameGuarded (FabricUIManager.java:1622)
  at com.facebook.react.uimanager.GuardedFrameCallback.doFrame (GuardedFrameCallback.kt:42)
  at com.facebook.react.modules.core.ReactChoreographer.frameCallback$lambda$1 (ReactChoreographer.java:58)
  at android.view.Choreographer$CallbackRecord.run (Choreographer.java:2329)
  at android.view.Choreographer.doCallbacks (Choreographer.java:1499)
  at android.os.Handler.handleCallback (Handler.java:997)

Reproducer

No public reproducer app, for the reason given under Steps to reproduce. The proposed fix is defensive and does not depend on reproducing the race:

val view = viewState.view
if (view == null) {
  ReactSoftExceptionLogger.logSoftException(
      ReactSoftExceptionLogger.Categories.SURFACE_MOUNTING_MANAGER_MISSING_VIEWSTATE,
      ReactNoCrashSoftException("Unable to find view for viewState for tag: [$tag] for addViewAt"),
  )
  return
}

This matches the recovery pattern already used in this file, and the one taken in #56389 and #57181 for their branches.

Screenshots and Videos

Not applicable.

Inizia in SurfaceMountingManager.kt, in addViewAt, quindi confronta la gestione del ViewState mancante con il placeholder creato da updateEventEmitter. Riproduci la sequenza updateEventEmitter/addViewAt descritta e verifica che la view mancante venga gestita senza mandare in crash la surface; il completamento deve preservare il comportamento esistente di recupero dalle soft-exception.