[Beta]: Homepage block drag and drop crashes with removeChild RuntimeError

[felixfeng33]

Summary

Dragging the first block in the homepage playground crashes the page instead of moving the block.

Scope

• Browser surface: http://localhost:3000/
• Owner surface: Plate framework/plugin or homepage registry integration
• The homepage runs Plate on the Plite substrate, but the video does not establish whether the defect is in Plate DnD, the Plite DOM layer, or React integration.

Steps to reproduce

1. Check out next at 2938677d265c6fb385f68b5ceefe10ee30243eec.
2. Run pnpm install and pnpm dev.
3. Open http://localhost:3000/ in Chrome.
4. Hover the Welcome to the Plate Playground! block.
5. Drag the block and release it inside the editor.

Expected behavior

The block should move to the selected drop position without crashing the editor.

Actual behavior

The page immediately switches to a RuntimeError screen:

Failed to execute 'removeChild' on 'Node': The node to be removed is not a child of this node.

The supplied recording shows one observed attempt and one crash.

Acceptance criteria

• Dragging and dropping the homepage welcome block moves it to the target location.
• The operation does not throw a DOM removeChild error or replace the editor with the RuntimeError page.
• Add browser regression coverage for the homepage block-DnD path, including the resulting document order and absence of runtime errors.
• Verify follow-up typing and selection still work after the drop.

Regression range

last-known-good: NOT_ENOUGH_INFO
first-known-bad: next@2938677d265c6fb385f68b5ceefe10ee30243eec
evidence: supplied screen recording

Environment

plate: 54.0.0-beta.1
plite: 54.0.0-beta.0
react: 19.2.4
os: macOS 15.7.3
browser: Google Chrome 150.0.7871.126
install: pnpm install / pnpm dev
route: http://localhost:3000/

Public reproduction URL: NOT_ENOUGH_INFO (repo-local route above).

Related issues checked

• NotFoundError: Failed to execute 'removeChild' on 'Node': The node to be removed is not a child of this node. #3531 reports the same DOM exception on Plate 38 but has a different setup and no DnD repro.
• [Bug]: Can't drop element below last line #5000 reports a missing drop below the last line without a crash.
• Table drag & drop does not work #4770 reports table-row/column DnD doing nothing.

None covers this next homepage block-DnD crash.

Video evidence

CleanShot.2026-08-04.at.23.20.56.mp4

[felixfeng33]

[Video source]

[00:00] The user hovers over the "Welcome to the Plate Playground!" text in the editor.
[00:00] The user clicks and drags the text block.
[00:01] The user attempts to drop the text block into the editor area.
[00:02] The screen transitions to a "Runtime RuntimeError" page.
[00:02] The error message "Failed to execute 'removeChild' on 'Node': The node to be removed is not a child of this node." is displayed.
[00:02] The call stack shows an anonymous function error.

[zbeyens]

Fixed locally. This is not committed, in a PR, or shipped.

Root cause: the drop line conditionally unmounted while a direct React DnD drop reordered its target, so React tried to remove the transient node from a stale parent. The fix keeps one inert drop-line DOM node outside the live drop target and toggles only its visibility and edge classes.

Proof:

• The focused Chromium row reproduced the exact removeChild NotFoundError before the fix, then passed three repeat runs after it. It asserts document order, zero runtime errors, follow-up typing, and selection.
• The exact native Chrome drag moved Welcome below the intro paragraph; native typing and selection still worked, with no new error logs.
• www typecheck, lint, registry changelog verification, and scoped P2 autoreview pass.

Leaving the issue open until the local fix is integrated and released.