Description

When a node moves to a different parent in the same transaction (for example, wrapping an image in a link via $toggleLink), the reconciler destroyed the old DOM and created a fresh one in the new parent. For DecoratorNode this swapped the React portal target, so useDecorators unmounted and remounted the rendered
component. On Safari this shows up as a 1-frame flicker for image links (#8420).

The same destroy-then-create produced a secondary symptom too: floating-UI plugins that measured the reference element during this window saw the wrapper span collapsed to its line-height, so the toolbar appeared at the wrong position on the first toggle.

Fix

Reconciler (packages/lexical)

$createNode now detects cross-parent moves by comparing prevNode.__parent to node.__parent. When they differ and the prev DOM is still in activePrevKeyToDOMMap, the existing DOM is reused and reconciled via $reconcileNode instead of being recreated. This keeps the DOM identity intact, which React portals and contentEditable selection both rely on. The reuse branch is gated on slot !== null so call sites that pass a null slot (used for in-place replacements) keep their existing behavior, and $reconcileNode is never invoked with parentDOM=null.

Supporting changes:

• $destroyNode short-circuits when the key still exists in activeNextNodeMap (the node moved). It only detaches from the old parent; mutation marking and child destruction are skipped. The mutation marker stays 'updated', since setMutatedNode already folded 'destroyed' + 'created' to 'updated', and listeners that branch on mutation type now see a single event instead of a fold-pair.
• $reconcileNode re-evaluates element direction when __parent changes, because $getReconciledDirection's implicit 'auto' depends on the parent. Otherwise the reused DOM would keep its old dir="auto" after moving away from a root child.
• The prev=1, next=1 fast path in $reconcileChildren falls back to slot.insertChild when lastDOM was reused inside replacementDOM. At that point lastDOM.parentNode is no longer the slot element, so replaceChild would throw.

lexical-list (packages/lexical-list)

The reuse path exposed two latent fragilities in ListItemNode:

• $setListItemThemeClassNames now removes all variable theme classes (listitemChecked, listitemUnchecked, nested.listitem) before re-adding the ones that should be present. Previously, the className string only ended up in canonical order on a fresh createDOM call, since classList.add is a no-op for existing classes. After a list-type toggle (which reparents items), the reused DOM kept classes in their original insertion order.
• updateListItemChecked now sets aria-checked unconditionally inside the isCheckbox branch, mirroring role and tabIndex. The previous conditional only set the attribute when the node's own __checked changed, so a list item moved into a check list ended up missing aria-checked.

While #8420 is the immediate motivation, the change applies to all cross-parent moves, including drag/drop into a different paragraph, list indent/outdent, and list-type toggles.

Test plan

• pnpm test-unit — 2386 pass. New tests in
  LexicalReconciler.test.ts cover decorator reuse, multi-level
  element subtree reuse, the single-'updated' mutation event, the
  slot !== null guard via a cross-parent swap with
  updateDOM=true, and a same-parent reorder regression.
• pnpm test-e2e-chromium — local run of List.spec.mjs
  passes the two scenarios that originally failed CI:
  • Nested List > Can toggle format for multi-line list of each type without losing indentation state
  • Nested List > Can create check list, toggle it to bullet-list and back
• Manual playground (Safari + Chrome):
  • Image link wrap/unwrap (5x toggle): no flicker, single
    'updated' listener event.
  • Image drag and drop across paragraphs: image preserved, resize
    handles work.
  • List indent / outdent (Tab / Shift+Tab 5x): text and cursor
    preserved.
  • Image link undo / redo (5x, repeated with accumulated state):
    no DOM divergence.
  • Korean IME input followed by link toggle: no character loss.
  • Equation node wrapped in a link: no flicker.
• CI e2e (chromium / firefox / webkit, including collab).

Fixes: #8420