Add preview slot to NodeDefinition; show translucent shape during move

User feedback: the move tool's CursorSphere is just a vertical line,
hard to tell what you're moving. Placement gets a translucent shape
that follows the cursor; move should too.

NodeDefinition.preview?: () => Promise<{ default: ComponentType<{ node }> }>
opt-in lazy component that renders a translucent ghost of the node.
Used by:
- The placement tool (ShelfTool) — renders the preview at the cursor
  position so the user sees the shape they're placing.
- The move tool (MoveRegistryNodeTool) — renders the preview at the
  drag target alongside the CursorSphere. Plus the original node is
  also dragged via live transforms, so the user sees both: the actual
  node moving + a translucent ghost at the same spot.

Implementation:
- New nodes/shelf/preview.tsx: ShelfPreview component. Renders the
  same shape as ShelfRenderer but `transparent: true, opacity: 0.5`.
- shelfDefinition.preview = () => import('./preview').
- ShelfTool's placement preview now uses <ShelfPreview node={defaults} />
  instead of an inline copy of the box geometry.
- MoveRegistryNodeTool lazy-loads `def.preview` (cached by loader,
  Suspense-wrapped). If a kind doesn't define `preview`, only the
  CursorSphere shows — matches today's behavior.

Phase 4 may merge `preview` with `renderer` behind an `opacity` prop
so kinds don't duplicate JSX between the solid and translucent
versions; until then defining `preview` is opt-in and one extra file.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/core/src/registry/types.ts

@@ -32,6 +32,15 @@ export type NodeDefinition<S extends ZodObject<any>> = {
   tool?: LazyComponent
   affordances?: Affordance<z.infer<S>>[]
 
+  /**
+   * Optional translucent preview of the node — used by the move tool to
+   * show where the node will land, and by the placement tool's cursor.
+   * Receives the partially-resolved node (or a default-shaped stub during
+   * placement before any commit has happened). Phase 4 may merge this with
+   * the renderer behind an `opacity` prop.
+   */
+  preview?: () => Promise<{ default: ComponentType<{ node: z.infer<S> }> }>
+
   presentation?: Presentation
   mcp?: McpOverrides
 }

packages/editor/src/components/tools/registry/move-registry-node-tool.tsx

@@ -12,7 +12,15 @@ import {
   useLiveTransforms,
   useScene,
 } from '@pascal-app/core'
-import { useCallback, useEffect, useState } from 'react'
+import {
+  type ComponentType,
+  lazy,
+  Suspense,
+  useCallback,
+  useEffect,
+  useMemo,
+  useState,
+} from 'react'
 import { markToolCancelConsumed } from '../../../hooks/use-keyboard'
 import { sfxEmitter } from '../../../lib/sfx-bus'
 import useEditor from '../../../store/use-editor'
@@ -20,21 +28,44 @@ import { CursorSphere } from '../shared/cursor-sphere'
 
 const roundToHalf = (value: number) => Math.round(value * 2) / 2
 
+// Cache lazy preview components keyed by their module loader so React.lazy
+// isn't re-invoked across renders.
+const previewCache = new WeakMap<() => Promise<unknown>, ComponentType<{ node: AnyNode }>>()
+
+function loadPreview(node: AnyNode): ComponentType<{ node: AnyNode }> | null {
+  const def = nodeRegistry.get(node.type)
+  if (!def?.preview) return null
+  const cached = previewCache.get(def.preview)
+  if (cached) return cached
+  const Comp = lazy(def.preview as () => Promise<{ default: ComponentType<{ node: AnyNode }> }>)
+  previewCache.set(def.preview, Comp)
+  return Comp
+}
+
 /**
- * Generic move tool for any registry-backed kind. Mirrors MoveColumnTool's
- * shape but parses re-creation through `nodeRegistry.get(kind).schema`
- * instead of a hardcoded schema reference. Used as the fallback in
- * `<MoveTool>` for kinds without a bespoke mover.
+ * Generic move tool for any registry-backed kind.
  *
- * Phase 4 may consolidate this with the per-kind movers if they all
- * collapse to the same position+rotation shape — until then they live
- * side by side.
+ * Behavior mirrors MoveColumnTool's shape:
+ * - Pauses scene history on activation, resumes on commit / cancel / unmount.
+ * - On each `grid:move`, applies a live transform to the original node so it
+ *   visibly follows the cursor (no second copy of the node).
+ * - On `grid:click`, commits the position to the scene store.
+ * - If the kind exposes a `preview` component on its NodeDefinition, render
+ *   it as a translucent ghost at the cursor too — the user sees the shape
+ *   they're moving (better UX than just CursorSphere's line).
+ *
+ * Phase 4 may merge the preview slot with the renderer behind an `opacity`
+ * prop. Until then, defining `preview` on a NodeDefinition gives nice move
+ * + placement UX for free.
  */
 export function MoveRegistryNodeTool({ node }: { node: AnyNode }) {
-  const initialPosition: [number, number, number] =
-    'position' in node && Array.isArray((node as { position?: unknown }).position)
-      ? ((node as { position: [number, number, number] }).position ?? [0, 0, 0])
-      : [0, 0, 0]
+  const initialPosition: [number, number, number] = useMemo(
+    () =>
+      'position' in node && Array.isArray((node as { position?: unknown }).position)
+        ? ((node as { position: [number, number, number] }).position ?? [0, 0, 0])
+        : [0, 0, 0],
+    [node],
+  )
   const [previewPosition, setPreviewPosition] = useState<[number, number, number]>(initialPosition)
 
   const exitMoveMode = useCallback(() => {
@@ -67,15 +98,11 @@ export function MoveRegistryNodeTool({ node }: { node: AnyNode }) {
       const nodeId = node.id
 
       if (nodeId && useScene.getState().nodes[nodeId]) {
-        // Existing node — just update its position.
         committed = true
         useLiveTransforms.getState().clear(nodeId)
         useScene.temporal.getState().resume()
         useScene.getState().updateNode(nodeId, { position } as Partial<AnyNode>)
       } else if (node.parentId) {
-        // Orphan re-create path — re-parse the node fresh via the kind's
-        // schema in the registry. Mirrors MoveColumnTool's behavior for
-        // registry-supplied kinds.
         const def = nodeRegistry.get(node.type)
         if (def) {
           const reparsed = def.schema.parse({
@@ -124,9 +151,18 @@ export function MoveRegistryNodeTool({ node }: { node: AnyNode }) {
     }
   }, [exitMoveMode, initialPosition, node])
 
-  // Cursor color from the def's presentation if available, else a neutral fallback.
-  const def = nodeRegistry.get(node.type)
-  const cursorColor = def?.presentation?.icon.kind === 'iconify' ? '#a78bfa' : '#a78bfa'
+  const Preview = loadPreview(node)
 
-  return <CursorSphere color={cursorColor} height={2.5} position={previewPosition} />
+  return (
+    <>
+      <CursorSphere color="#a78bfa" height={2.5} position={previewPosition} />
+      {Preview && (
+        <Suspense fallback={null}>
+          <group position={previewPosition}>
+            <Preview node={node} />
+          </group>
+        </Suspense>
+      )}
+    </>
+  )
 }

packages/nodes/src/shelf/definition.ts

@@ -46,6 +46,7 @@ export const shelfDefinition: NodeDefinition<typeof ShelfNode> = {
     kind: 'parametric',
     module: () => import('./renderer'),
   },
+  preview: () => import('./preview'),
   tool: () => import('./tool'),
 
   presentation: {

packages/nodes/src/shelf/preview.tsx

@@ -0,0 +1,50 @@
+'use client'
+
+import { useMemo } from 'react'
+import { Color } from 'three'
+import type { ShelfNode } from './schema'
+
+/**
+ * Translucent preview of a shelf. Used by:
+ * - The placement tool's cursor (ShelfTool) — at the cursor position
+ * - The move tool (MoveRegistryNodeTool) — at the drag target position
+ *
+ * Renders the same primitives as the actual ShelfRenderer, but with
+ * `transparent: true, opacity: 0.5` so the user can see what they're
+ * placing/moving without it being a hard solid.
+ */
+const ShelfPreview = ({ node }: { node: ShelfNode }) => {
+  const color = useMemo(() => new Color(node.color), [node.color])
+  const topY = node.height + node.thickness / 2
+
+  const inset = Math.min(0.12, node.width / 6)
+  const bracketHeight = Math.max(0.01, node.height)
+  const bracketWidth =
+    node.bracketStyle === 'industrial'
+      ? Math.max(0.04, node.depth * 0.2)
+      : Math.max(0.02, node.depth * 0.12)
+  const bracketDepth = node.bracketStyle === 'industrial' ? node.depth * 0.95 : node.depth * 0.7
+
+  return (
+    <group>
+      <mesh position={[0, topY, 0]}>
+        <boxGeometry args={[node.width, node.thickness, node.depth]} />
+        <meshStandardMaterial color={color} transparent opacity={0.5} />
+      </mesh>
+      {node.bracketStyle !== 'hidden' && (
+        <>
+          <mesh position={[-(node.width / 2 - inset), bracketHeight / 2, 0]}>
+            <boxGeometry args={[bracketWidth, bracketHeight, bracketDepth]} />
+            <meshStandardMaterial color={color} transparent opacity={0.5} />
+          </mesh>
+          <mesh position={[node.width / 2 - inset, bracketHeight / 2, 0]}>
+            <boxGeometry args={[bracketWidth, bracketHeight, bracketDepth]} />
+            <meshStandardMaterial color={color} transparent opacity={0.5} />
+          </mesh>
+        </>
+      )}
+    </group>
+  )
+}
+
+export default ShelfPreview

packages/nodes/src/shelf/tool.tsx

@@ -10,8 +10,9 @@ import {
 } from '@pascal-app/core'
 import { triggerSFX } from '@pascal-app/editor'
 import { useViewer } from '@pascal-app/viewer'
-import { useEffect, useRef } from 'react'
+import { useEffect, useMemo, useRef } from 'react'
 import { type Group, Vector3 } from 'three'
+import ShelfPreview from './preview'
 
 const worldVector = new Vector3()
 const GRID_STEP = 0.5
@@ -36,22 +37,19 @@ function getLevelLocalPosition(levelId: string, event: GridEvent): [number, numb
   return [sx, worldVector.y, sz]
 }
 
-// Cursor preview dimensions — match the shelf's default schema dimensions.
-// Once the shelf has user-tunable defaults in the inspector, this can pull
-// from the active draft.
-const PREVIEW_WIDTH = 1.2
-const PREVIEW_DEPTH = 0.3
-const PREVIEW_THICKNESS = 0.04
-const PREVIEW_HEIGHT = 0.9
-const PREVIEW_INSET = Math.min(0.12, PREVIEW_WIDTH / 6)
-const PREVIEW_BRACKET_WIDTH = Math.max(0.02, PREVIEW_DEPTH * 0.12)
-const PREVIEW_BRACKET_DEPTH = PREVIEW_DEPTH * 0.7
-
 const ShelfTool = () => {
   const activeLevelId = useViewer((state) => state.selection.levelId)
   const cursorRef = useRef<Group>(null)
   const previousSnapRef = useRef<[number, number] | null>(null)
 
+  // Default-shaped shelf for the placement preview. Same shape the move tool
+  // uses (both reach for `shelfDefinition.preview`) so placement and move
+  // look identical.
+  const previewNode = useMemo(
+    () => ShelfNode.parse({ name: 'Shelf', position: [0, 0, 0], rotation: [0, 0, 0] }),
+    [],
+  )
+
   useEffect(() => {
     if (!activeLevelId) return
     previousSnapRef.current = null
@@ -60,8 +58,6 @@ const ShelfTool = () => {
       const [sx, sz] = snapPointToGrid([event.localPosition[0], event.localPosition[2]], GRID_STEP)
       cursorRef.current?.position.set(sx, event.localPosition[1], sz)
 
-      // Fire grid-snap SFX only when the snapped position crosses a cell,
-      // matching the wall / slab / curve tools.
       const prev = previousSnapRef.current
       if (!prev || prev[0] !== sx || prev[1] !== sz) {
         triggerSFX('sfx:grid-snap')
@@ -94,26 +90,12 @@ const ShelfTool = () => {
 
   if (!activeLevelId) return null
 
-  // Cursor preview: ghostly version of the full shelf (top board + brackets)
-  // so the user sees the same shape they're placing. Position is updated
-  // imperatively via the ref; no React state, no re-render cycles.
+  // Cursor preview: defers to the shared ShelfPreview component used by the
+  // move tool too. Position is updated imperatively via the ref; no React
+  // state, no re-render cycles.
   return (
     <group ref={cursorRef}>
-      {/* Top board */}
-      <mesh position={[0, PREVIEW_HEIGHT + PREVIEW_THICKNESS / 2, 0]}>
-        <boxGeometry args={[PREVIEW_WIDTH, PREVIEW_THICKNESS, PREVIEW_DEPTH]} />
-        <meshStandardMaterial color="#a07050" transparent opacity={0.5} />
-      </mesh>
-      {/* Left bracket */}
-      <mesh position={[-(PREVIEW_WIDTH / 2 - PREVIEW_INSET), PREVIEW_HEIGHT / 2, 0]}>
-        <boxGeometry args={[PREVIEW_BRACKET_WIDTH, PREVIEW_HEIGHT, PREVIEW_BRACKET_DEPTH]} />
-        <meshStandardMaterial color="#a07050" transparent opacity={0.5} />
-      </mesh>
-      {/* Right bracket */}
-      <mesh position={[PREVIEW_WIDTH / 2 - PREVIEW_INSET, PREVIEW_HEIGHT / 2, 0]}>
-        <boxGeometry args={[PREVIEW_BRACKET_WIDTH, PREVIEW_HEIGHT, PREVIEW_BRACKET_DEPTH]} />
-        <meshStandardMaterial color="#a07050" transparent opacity={0.5} />
-      </mesh>
+      <ShelfPreview node={previewNode} />
     </group>
   )
 }