Phase 5 depth-first: spawn C, fence B+C, slab B+C, ceiling C

Depth-first session: drive registered kinds through Stage B (pure
def.geometry, drop system re-export) and Stage C (def.floorplan,
short-circuit legacy inline rendering in floorplan-panel.tsx).

spawn → C
 - buildSpawnFloorplan wired on definition (was written but deferred
   to avoid double-render).
 - floorplan-panel.tsx's floorplanSpawnEntries useMemo short-circuits
   to [] when nodeRegistry.has('spawn').

fence → B
 - generateFenceGeometry exported from viewer; buildFenceGeometry
   wraps it in a Group+Mesh with DEFAULT_STAIR_MATERIAL.
 - def.geometry set; renderer + system fields dropped.
 - Deleted nodes/src/fence/{renderer.tsx,system.tsx}.

fence → C
 - buildFenceFloorplan: polyline along centerline (sampled for curved
   fences via sampleWallCenterline from core). Stroke width = node.thickness.
 - floorplan-panel.tsx's floorplanFenceEntries short-circuits.

slab → B
 - generateSlabGeometry exported from viewer; buildSlabGeometry wraps
   it in a Group+Mesh + cached material (preset / custom / default
   pattern preserved from legacy renderer).
 - def.geometry set; renderer + system fields dropped.
 - Deleted nodes/src/slab/{renderer.tsx,system.tsx}.

slab → C
 - buildSlabFloorplan: SVG path with outer polygon + hole subpaths
   (uses getRenderableSlabPolygon from core for wall-clipping parity).
 - floorplan-panel.tsx's slabPolygons short-circuits.

ceiling → B INTENTIONALLY SKIPPED
 - Ceiling renderer renders React children (hosted items) + uses TSL
   shader materials + named meshes that other systems poke
   (getObjectByName('ceiling-grid')). Pure def.geometry can't preserve
   that. Ceiling keeps def.renderer (the custom escape hatch) — same
   pattern item uses. Documented in ceiling/definition.ts.

ceiling → C
 - buildCeilingFloorplan: dashed-outline path with hole subpaths
   (visually distinct from slab since ceilings are above).
 - floorplan-panel.tsx's ceilingPolygons short-circuits.

Per-kind progress after this session:
 - shelf: B ✅ C ✅ (Stage E since brand-new)
 - spawn: A ✅ C ✅
 - wall: A ✅ (B blocked on ctx.levelData design)
 - fence: A ✅ B ✅ C ✅
 - slab: A ✅ B ✅ C ✅
 - ceiling: A ✅ C ✅ (B intentionally not applicable)
 - door / window / item: A ✅ (B+C pending in future sessions)

Known test issue: `bun test` in packages/nodes fails to load
`three-bvh-csg` through the viewer's transitive imports (UMD/ESM
mismatch in Bun's test runner). The Next.js editor build works fine
because it bundles differently. Fix requires either dynamic imports
(breaks sync def.geometry contract) or test env config — deferred.
Other tests (schema, geometry, parity) pass.

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

packages/editor/src/components/editor/floorplan-panel.tsx

@@ -8440,9 +8440,13 @@ export function FloorplanPanel() {
 
     return hasPreviewWalls ? nextFloorplanWallById : floorplanWallById
   }, [displayWallById, floorplanWallById, wallCurveDraft, wallEndpointDraft])
-  const floorplanFenceEntries = useMemo(
-    () =>
-      fences.flatMap((fence) => {
+  const floorplanFenceEntries = useMemo(() => {
+    // Fence migrated to def.floorplan (Phase 5 Stage C). When registered,
+    // FloorplanRegistryLayer renders the fence polyline; this legacy
+    // path short-circuits to avoid double-render. Removed entirely in
+    // Phase 6 cleanup.
+    if (nodeRegistry.has('fence')) return []
+    return fences.flatMap((fence) => {
       const live = useLiveTransforms.getState().get(fence.id)
       const fenceCenterX = (fence.start[0] + fence.end[0]) / 2
       const fenceCenterZ = (fence.start[1] + fence.end[1]) / 2
@@ -8480,9 +8484,8 @@ export function FloorplanPanel() {
       })
 
       return [{ fence: displayFence, centerline, markerFrames, path }]
-      }),
-    [fences, movingFloorplanNodeRevision],
-  )
+    })
+  }, [fences, movingFloorplanNodeRevision])
   const wallPolygons = useMemo(
     () =>
       walls.map((wall) => {
@@ -8579,9 +8582,13 @@ export function FloorplanPanel() {
       }),
     [displayFloorplanWallById, movingFloorplanNodeRevision, movingNode, openings],
   )
-  const slabPolygons = useMemo(
-    () =>
-      slabs.flatMap((slab) => {
+  const slabPolygons = useMemo(() => {
+    // Slab migrated to def.floorplan (Phase 5 Stage C). When registered,
+    // FloorplanRegistryLayer renders the slab polygon; this legacy
+    // path short-circuits to avoid double-render. Removed entirely in
+    // Phase 6 cleanup.
+    if (nodeRegistry.has('slab')) return []
+    return slabs.flatMap((slab) => {
       const polygon = toFloorplanPolygon(slab.polygon)
       if (polygon.length < 3) {
         return []
@@ -8603,9 +8610,8 @@ export function FloorplanPanel() {
           path: formatPolygonPath(visualPolygon, visualHoles),
         },
       ]
-      }),
-    [slabs],
-  )
+    })
+  }, [slabs])
   const displaySlabPolygons = useMemo(() => {
     if (!(slabBoundaryDraft || slabHoleBoundaryDraft || slabHoleMoveDraft)) {
       return slabPolygons
@@ -8662,9 +8668,12 @@ export function FloorplanPanel() {
       return nextEntry
     })
   }, [slabBoundaryDraft, slabHoleBoundaryDraft, slabHoleMoveDraft, slabPolygons])
-  const ceilingPolygons = useMemo(
-    () =>
-      ceilings.flatMap((ceiling) => {
+  const ceilingPolygons = useMemo(() => {
+    // Ceiling migrated to def.floorplan (Phase 5 Stage C). When registered,
+    // FloorplanRegistryLayer renders the ceiling polygon; this legacy
+    // path short-circuits. Removed entirely in Phase 6 cleanup.
+    if (nodeRegistry.has('ceiling')) return []
+    return ceilings.flatMap((ceiling) => {
       const polygon = toFloorplanPolygon(ceiling.polygon)
       if (polygon.length < 3) {
         return []
@@ -8682,9 +8691,8 @@ export function FloorplanPanel() {
           path: formatPolygonPath(polygon, holes),
         },
       ]
-      }),
-    [ceilings],
-  )
+    })
+  }, [ceilings])
   const displayCeilingPolygons = useMemo(() => {
     if (!(ceilingBoundaryDraft || ceilingHoleBoundaryDraft || ceilingHoleMoveDraft)) {
       return ceilingPolygons
@@ -8802,13 +8810,18 @@ export function FloorplanPanel() {
       ),
     [levelDescendantNodes],
   )
-  const floorplanSpawnEntries = useMemo<FloorplanSpawnEntry[]>(
-    () =>
-      spawns
+  const floorplanSpawnEntries = useMemo<FloorplanSpawnEntry[]>(() => {
+    // Spawn migrated to the registry-driven floor-plan layer (Phase 5
+    // Stage C). When registered, FloorplanRegistryLayer renders the
+    // spawn marker via def.floorplan; FloorplanRegistryActionMenu
+    // handles select / move / delete. Returning [] here skips the
+    // legacy rendering + action menu paths to avoid double-render.
+    // Removed entirely in Phase 6 cleanup.
+    if (nodeRegistry.has('spawn')) return []
+    return spawns
       .filter((spawn) => spawn.visible !== false)
       .map((spawn) => {
         const live = useLiveTransforms.getState().get(spawn.id)
-
         return {
           spawn,
           position: {
@@ -8817,9 +8830,8 @@ export function FloorplanPanel() {
           },
           rotation: live?.rotation ?? spawn.rotation,
         }
-        }),
-    [movingFloorplanNodeRevision, spawns],
-  )
+      })
+  }, [movingFloorplanNodeRevision, spawns])
   const floorplanItemEntries = useMemo(() => {
     const transformCache = new Map<string, SharedFloorplanNodeTransform | null>()
 

packages/nodes/src/ceiling/definition.ts

@@ -1,20 +1,23 @@
 import type { NodeDefinition } from '@pascal-app/core'
+import { buildCeilingFloorplan } from './floorplan'
 import { ceilingParametrics } from './parametrics'
 import { CeilingNode } from './schema'
 
 /**
- * Ceiling — Phase 5 batch kind, polygon-based. Structurally identical
- * to slab but mounted at `height` rather than `elevation`.
+ * Ceiling — Phase 5 batch kind, polygon-based. Structurally similar to
+ * slab but with React-rendered hosted children + TSL shader materials +
+ * named meshes that other systems poke (`getObjectByName('ceiling-grid')`).
  *
- * Capabilities:
- *  - **No `movable`**: ceiling move is bespoke via legacy `MoveCeilingTool`
- *    + the floor-plan boundary / hole editors. Capability-driven dispatch
- *    keeps the legacy mover (preserves polygon-aware behavior).
- *  - **`surfaces.top`**: items host on the ceiling at `height`.
- *  - `selectable`, `duplicable`, `deletable` standard.
+ * **Stage B intentionally skipped**: pure `def.geometry` extraction
+ * would lose the React children rendering (hosted items) and the
+ * named-mesh structure. Ceiling keeps `def.renderer` as the custom
+ * escape hatch (per plans/editor-node-registry.md "custom-behavior
+ * escape hatch"). Renderer wraps the legacy CeilingRenderer; system
+ * wraps the legacy CeilingSystem.
  *
- * Relations: `hosts: ['item']` for ceiling-mounted items (lights, fans).
- * `cascadeDelete: 'descendants'` removes hosted items on ceiling delete.
+ * **Stage C completed**: `def.floorplan` builder draws the ceiling
+ * polygon as a dashed outline in floor plan; legacy `ceilingPolygons`
+ * short-circuits to [] when ceiling is registered.
  */
 export const ceilingDefinition: NodeDefinition<typeof CeilingNode> = {
   kind: 'ceiling',
@@ -59,6 +62,7 @@ export const ceilingDefinition: NodeDefinition<typeof CeilingNode> = {
     module: () => import('./system'),
     priority: 4,
   },
+  floorplan: buildCeilingFloorplan,
 
   toolHints: [
     { key: 'Left click', label: 'Trace ceiling outline' },

packages/nodes/src/ceiling/floorplan.ts

@@ -0,0 +1,37 @@
+import type { CeilingNode, FloorplanGeometry, FloorplanPoint } from '@pascal-app/core'
+
+/**
+ * Stage C floor-plan builder for ceiling. Renders the polygon outline
+ * as a dashed boundary (ceilings are above and would visually obscure
+ * the slab/walls if drawn solid). Same shape as slab but visually
+ * distinct.
+ */
+export function buildCeilingFloorplan(node: CeilingNode): FloorplanGeometry | null {
+  const polygon = node.polygon
+  if (!polygon || polygon.length < 3) return null
+
+  const outer: FloorplanPoint[] = polygon.map(([x, z]) => [x, z] as FloorplanPoint)
+
+  const ring = (points: FloorplanPoint[]) => {
+    const [first, ...rest] = points
+    if (!first) return ''
+    return [`M ${first[0]} ${first[1]}`, ...rest.map(([x, y]) => `L ${x} ${y}`), 'Z'].join(' ')
+  }
+
+  const segments: string[] = [ring(outer)]
+  const holes = node.holes ?? []
+  for (const hole of holes) {
+    if (hole.length < 3) continue
+    segments.push(ring(hole.map(([x, z]) => [x, z] as FloorplanPoint)))
+  }
+
+  return {
+    kind: 'path',
+    d: segments.join(' '),
+    fill: 'none',
+    stroke: '#94a3b8',
+    strokeWidth: 0.03,
+    strokeDasharray: '0.15 0.1',
+    opacity: 0.7,
+  }
+}

packages/nodes/src/fence/definition.ts

@@ -1,34 +1,21 @@
 import type { NodeDefinition } from '@pascal-app/core'
+import { buildFenceFloorplan } from './floorplan'
+import { buildFenceGeometry } from './geometry'
 import { fenceParametrics } from './parametrics'
 import { FenceNode } from './schema'
 
 /**
- * Fence — the first Phase 5 batch-migration kind.
+ * Fence — Phase 5 batch kind. Stage B complete: `def.geometry` drives
+ * the rebuild via the generic `<GeometrySystem>`; `<ParametricNodeRenderer>`
+ * mounts the empty group. No per-kind renderer or system file.
  *
- * What this definition encodes:
- *  - **Capabilities**: snappable (other walls/fences/items snap to it),
- *    surfaces (front + back faces host items), selectable, duplicable,
- *    deletable. No `movable` capability — fence move is bespoke
- *    endpoint-drag, same shape as wall (handled by legacy MoveFenceTool
- *    until the affordance port).
- *  - **Relations**: `linkedBy: 'endpoint-match'` for fence-corner cascade.
- *    No `hosts` field — doors/windows don't mount on fences. `affectsSpatial`
- *    omitted: moving a fence doesn't dirty slabs/zones in the legacy
- *    behavior, so the registry stays parity-equivalent until we
- *    explicitly add the cascade (separate decision).
- *  - **Parametrics**: dimensions, posts, style — see `./parametrics.ts`.
- *  - **toolHints**: placement panel hints for the fence-build tool.
- *  - **Renderer + system**: thin placeholder mesh + re-export of the
- *    legacy `FenceSystem`. Same shape as wall milestone B; future Phase 5+
- *    extracts the pure geometry function and migrates to `def.geometry`.
+ * Capabilities:
+ *  - **No `movable`**: fence move is bespoke endpoint-drag. Capability-
+ *    driven dispatch keeps the legacy MoveFenceTool until the
+ *    affordance port (Stage D).
+ *  - `surfaces.sides`, `selectable`, `duplicable`, `deletable` standard.
  *
- * Tool field stays absent: fence has 4 separate tools (build, curve,
- * move, move-endpoint) wired through editor state, not the registry
- * tool dispatch. They keep running unchanged until the affordance port.
- *
- * Migration is gated by `feature-flag.ts`
- * (env: `NEXT_PUBLIC_USE_REGISTRY_FOR_FENCE`). See
- * `plans/editor-node-registry.md#phase-5` for the batch order.
+ * Relations: `linkedBy: 'endpoint-match'` for corner cascade.
  */
 export const fenceDefinition: NodeDefinition<typeof FenceNode> = {
   kind: 'fence',
@@ -71,16 +58,15 @@ export const fenceDefinition: NodeDefinition<typeof FenceNode> = {
 
   parametrics: fenceParametrics,
 
-  renderer: {
-    kind: 'parametric',
-    module: () => import('./renderer'),
-  },
-  system: {
-    module: () => import('./system'),
-    // Same frame priority as the legacy FenceSystem (4 — runs after door/
-    // window animations at 2-3, before zone/level systems at 6+).
-    priority: 4,
-  },
+  // Stage B: pure geometry function. Generic <GeometrySystem> rebuilds
+  // on dirtyNodes; <ParametricNodeRenderer> mounts the empty group.
+  // `renderer` + `system` fields dropped along with their files.
+  geometry: buildFenceGeometry,
+  // Stage C: floor-plan rendering. FloorplanRegistryLayer iterates kinds
+  // with `floorplan` set and renders via FloorplanGeometryRenderer.
+  // Legacy `floorplanFenceEntries` short-circuits to [] when fence is
+  // registered (see floorplan-panel.tsx).
+  floorplan: buildFenceFloorplan,
 
   toolHints: [
     { key: 'Left click', label: 'Set fence start / end' },

packages/nodes/src/fence/floorplan.ts

@@ -0,0 +1,32 @@
+import type { FloorplanGeometry, FloorplanPoint } from '@pascal-app/core'
+import { isCurvedWall, sampleWallCenterline } from '@pascal-app/core'
+import type { FenceNode } from './schema'
+
+/**
+ * Stage C floor-plan builder for fence. Draws the fence centerline as
+ * a polyline; thickness becomes the stroke width.
+ *
+ * Curved fences sample the centerline at 24 segments — same density the
+ * legacy `floorplanFenceEntries` useMemo uses, so straight + curved
+ * fences look comparable to the legacy rendering.
+ *
+ * Visual nuances the legacy ships (side hatching to indicate thickness
+ * direction, post markers along the centerline) are deferred — Phase 5
+ * Stage D will revisit if real visual parity is needed.
+ */
+export function buildFenceFloorplan(node: FenceNode): FloorplanGeometry {
+  const points: FloorplanPoint[] = isCurvedWall(node)
+    ? sampleWallCenterline(node, 24).map((p) => [p.x, p.y] as FloorplanPoint)
+    : [
+        [node.start[0], node.start[1]],
+        [node.end[0], node.end[1]],
+      ]
+
+  return {
+    kind: 'polyline',
+    points,
+    stroke: node.color || '#475569',
+    strokeWidth: Math.max(node.thickness, 0.05),
+    opacity: 0.9,
+  }
+}

packages/nodes/src/fence/geometry.ts

@@ -0,0 +1,29 @@
+import { DEFAULT_STAIR_MATERIAL, generateFenceGeometry } from '@pascal-app/viewer'
+import { Group, Mesh } from 'three'
+import type { FenceNode } from './schema'
+
+/**
+ * Stage B builder for fence. Reuses the legacy `generateFenceGeometry`
+ * (pure function from viewer that returns a merged BufferGeometry of
+ * posts + base + top rail + curve spans) and wraps it in a Mesh-in-Group
+ * shape the generic `<GeometrySystem>` expects.
+ *
+ * Material is a single shared reference — fences look the same regardless
+ * of instance, so we don't clone per node. If per-fence material
+ * customization lands later (color picker on the panel maps to a real
+ * material), this becomes a per-node lookup.
+ *
+ * Phase 6 cleanup moves the 280 lines of geometry math out of the
+ * legacy `viewer/src/systems/fence/fence-system.tsx` into this folder
+ * once the legacy system file is deleted. Until then `generateFenceGeometry`
+ * is publicly re-exported from viewer.
+ */
+export function buildFenceGeometry(node: FenceNode): Group {
+  const group = new Group()
+  const geometry = generateFenceGeometry(node)
+  const mesh = new Mesh(geometry, DEFAULT_STAIR_MATERIAL)
+  mesh.castShadow = true
+  mesh.receiveShadow = true
+  group.add(mesh)
+  return group
+}

packages/nodes/src/fence/renderer.tsx

@@ -1,44 +0,0 @@
-'use client'
-
-import { type FenceNode, useRegistry, useScene } from '@pascal-app/core'
-import { DEFAULT_STAIR_MATERIAL, useNodeEvents } from '@pascal-app/viewer'
-import { useLayoutEffect, useMemo, useRef } from 'react'
-import type { Mesh } from 'three'
-
-/**
- * Thin fence renderer — registers an empty mesh, marks the node dirty so
- * `FenceSystem` (re-exported via `./system`) fills the geometry next
- * frame, and wires pointer events through `useNodeEvents`.
- *
- * Behaviorally identical to the legacy `FenceRenderer` in
- * `@pascal-app/viewer/components/renderers/fence/fence-renderer.tsx`.
- * Phase 0 shims pick which one mounts based on `nodeRegistry.has('fence')`.
- *
- * Material is `DEFAULT_STAIR_MATERIAL` (legacy reuse; fence and stairs
- * share the wood-tone preset).
- */
-const FenceRenderer = ({ node }: { node: FenceNode }) => {
-  const ref = useRef<Mesh>(null!)
-  const handlers = useNodeEvents(node, 'fence')
-  const material = useMemo(() => DEFAULT_STAIR_MATERIAL, [])
-
-  useRegistry(node.id, 'fence', ref)
-  useLayoutEffect(() => {
-    useScene.getState().markDirty(node.id)
-  }, [node.id])
-
-  return (
-    <mesh
-      castShadow
-      material={material}
-      receiveShadow
-      ref={ref}
-      visible={node.visible}
-      {...handlers}
-    >
-      <boxGeometry args={[0, 0, 0]} />
-    </mesh>
-  )
-}
-
-export default FenceRenderer

packages/nodes/src/fence/system.tsx

@@ -1,26 +0,0 @@
-'use client'
-
-import { FenceSystem } from '@pascal-app/viewer'
-
-/**
- * Registry-driven fence system bundle.
- *
- * Wraps the legacy `FenceSystem` (re-exported from viewer) so it mounts
- * via `RegisteredSystems` when fence is registry-driven. The legacy
- * `<LegacySystem kind="fence">` wrapper around `<FenceSystem />` in
- * `viewer/components/viewer/index.tsx` short-circuits whenever
- * `nodeRegistry.has('fence')` is true — same pattern wall uses.
- *
- * Phase 6 deletes the legacy mount point; until then this bundle is the
- * single mount surface for fence's per-frame work when registry-driven.
- *
- * Future Phase 5+ work: extract fence geometry out of `FenceSystem`'s
- * useFrame body into a pure `buildFenceGeometry(node, ctx)` and migrate
- * to `def.geometry`. The generic `<GeometrySystem>` will then handle
- * the rebuild loop and this bundle can be deleted.
- */
-const FenceSystems = () => {
-  return <FenceSystem />
-}
-
-export default FenceSystems

packages/nodes/src/slab/definition.ts

@@ -1,29 +1,24 @@
 import type { NodeDefinition } from '@pascal-app/core'
+import { buildSlabFloorplan } from './floorplan'
+import { buildSlabGeometry } from './geometry'
 import { slabParametrics } from './parametrics'
 import { SlabNode } from './schema'
 
 /**
- * Slab — Phase 5 batch kind, polygon-based.
+ * Slab — Phase 5 batch kind, polygon-based. Stage B: `def.geometry`
+ * drives the rebuild via generic <GeometrySystem>; <ParametricNodeRenderer>
+ * mounts the empty group. No per-kind renderer or system file.
  *
  * Capabilities:
  *  - **No `movable`**: slab's "move" today is whole-slab translation via
  *    legacy `MoveSlabTool`, which integrates with the floor-plan boundary /
- *    hole editors. Per the capability-driven dispatch rule, omitting
- *    `movable` keeps the legacy mover (preserves polygon-aware behavior).
- *    Migration to the generic mover is possible in a later milestone if
- *    the legacy mover proves equivalent.
+ *    hole editors. Capability-driven dispatch keeps the legacy mover.
  *  - **`surfaces.top`**: items host on the slab top at `elevation`.
  *  - `selectable`, `duplicable`, `deletable` standard.
  *
  * Relations:
  *  - `hosts: ['item']` — items mount on the slab top.
  *  - `cascadeDelete: 'descendants'` — deleting a slab removes hosted items.
- *
- * Renderer + system: thin renderer + re-export of the legacy `SlabSystem`.
- * Same shape as wall / fence runtime port.
- *
- * Tool field absent: slab has 3 tools (slab-tool, boundary-editor, hole-
- * editor) wired through editor state, not registry dispatch.
  */
 export const slabDefinition: NodeDefinition<typeof SlabNode> = {
   kind: 'slab',
@@ -59,14 +54,11 @@ export const slabDefinition: NodeDefinition<typeof SlabNode> = {
 
   parametrics: slabParametrics,
 
-  renderer: {
-    kind: 'parametric',
-    module: () => import('./renderer'),
-  },
-  system: {
-    module: () => import('./system'),
-    priority: 4,
-  },
+  // Stage B: pure geometry function.
+  geometry: buildSlabGeometry,
+  // Stage C: floor-plan rendering. Legacy `slabPolygons` short-circuits
+  // to [] when slab is registered (see floorplan-panel.tsx).
+  floorplan: buildSlabFloorplan,
 
   toolHints: [
     { key: 'Left click', label: 'Trace slab outline' },

packages/nodes/src/slab/floorplan.ts

@@ -0,0 +1,52 @@
+import {
+  type FloorplanGeometry,
+  type FloorplanPoint,
+  getRenderableSlabPolygon,
+  type SlabNode,
+} from '@pascal-app/core'
+
+/**
+ * Stage C floor-plan builder for slab. Renders the slab polygon as a
+ * filled path with holes cut out.
+ *
+ * Uses `getRenderableSlabPolygon` (the same helper the legacy
+ * floorplan-panel.tsx uses) to compute the visual polygon — accounts
+ * for wall-clipping when a slab is auto-generated from walls.
+ */
+export function buildSlabFloorplan(node: SlabNode): FloorplanGeometry | null {
+  const polygon = node.polygon
+  if (!polygon || polygon.length < 3) return null
+
+  const visualPolygon = getRenderableSlabPolygon(node)
+  if (!visualPolygon || visualPolygon.length < 3) return null
+
+  const outer: FloorplanPoint[] = visualPolygon.map(([x, z]) => [x, z] as FloorplanPoint)
+
+  // SVG path with outer ring + hole subpaths. Each subpath uses M/L
+  // commands + Z to close. Holes follow the outer ring; FloorplanGeometry
+  // 'path' kind supports this natively (renderer passes the `d` string
+  // straight to the SVG <path>).
+  const segments: string[] = []
+  const ring = (points: FloorplanPoint[]) => {
+    const [first, ...rest] = points
+    if (!first) return ''
+    return [`M ${first[0]} ${first[1]}`, ...rest.map(([x, y]) => `L ${x} ${y}`), 'Z'].join(' ')
+  }
+  segments.push(ring(outer))
+
+  const holes = node.holes ?? []
+  for (const hole of holes) {
+    if (hole.length < 3) continue
+    const holePts: FloorplanPoint[] = hole.map(([x, z]) => [x, z] as FloorplanPoint)
+    segments.push(ring(holePts))
+  }
+
+  return {
+    kind: 'path',
+    d: segments.join(' '),
+    fill: '#cbd5e1',
+    stroke: '#475569',
+    strokeWidth: 0.03,
+    opacity: 0.85,
+  }
+}

packages/nodes/src/slab/geometry.ts

@@ -0,0 +1,61 @@
+import { getMaterialPresetByRef, type SlabNode } from '@pascal-app/core'
+import {
+  applyMaterialPresetToMaterials,
+  createMaterial,
+  DEFAULT_SLAB_MATERIAL,
+  generateSlabGeometry,
+} from '@pascal-app/viewer'
+import { DoubleSide, Group, Mesh, MeshStandardMaterial } from 'three'
+
+/**
+ * Stage B builder for slab. Reuses `generateSlabGeometry` (pure
+ * triangulation + hole CSG from viewer) and the same material cache
+ * pattern the legacy slab renderer used.
+ *
+ * Materials are cached by `{material, materialPreset}` signature so
+ * slabs sharing settings share the GPU resource. Cached entry mutation
+ * (preset apply) is preserved — async texture loads still update the
+ * rendered material after re-mount.
+ */
+const slabMaterialCache = new Map<string, MeshStandardMaterial>()
+
+function getSlabMaterial(node: SlabNode): MeshStandardMaterial {
+  const cacheKey = JSON.stringify({
+    material: node.material ?? null,
+    materialPreset: node.materialPreset ?? null,
+  })
+  const cached = slabMaterialCache.get(cacheKey)
+  if (cached) return cached
+
+  const preset = getMaterialPresetByRef(node.materialPreset)
+  const material = preset
+    ? new MeshStandardMaterial()
+    : node.material
+      ? createMaterial(node.material).clone()
+      : DEFAULT_SLAB_MATERIAL.clone()
+
+  if (preset) {
+    applyMaterialPresetToMaterials(material, preset)
+  }
+
+  material.transparent = false
+  material.opacity = 1
+  material.alphaMap = null
+  material.side = DoubleSide
+  material.depthWrite = true
+  material.needsUpdate = true
+
+  slabMaterialCache.set(cacheKey, material)
+  return material
+}
+
+export function buildSlabGeometry(node: SlabNode): Group {
+  const group = new Group()
+  const geometry = generateSlabGeometry(node)
+  const material = getSlabMaterial(node)
+  const mesh = new Mesh(geometry, material)
+  mesh.castShadow = true
+  mesh.receiveShadow = true
+  group.add(mesh)
+  return group
+}

packages/nodes/src/slab/renderer.tsx

@@ -1,116 +0,0 @@
-'use client'
-
-import { getMaterialPresetByRef, type SlabNode, useRegistry, useScene } from '@pascal-app/core'
-import {
-  applyMaterialPresetToMaterials,
-  createMaterial,
-  DEFAULT_SLAB_MATERIAL,
-  useNodeEvents,
-} from '@pascal-app/viewer'
-import { useEffect, useLayoutEffect, useMemo, useRef } from 'react'
-import type { Mesh } from 'three'
-import * as THREE from 'three'
-
-/**
- * Thin slab renderer. Mounts a placeholder mesh, registers it with
- * `sceneRegistry`, and marks the node dirty so `SlabSystem` fills the
- * geometry next frame.
- *
- * Behaviorally identical to the legacy `SlabRenderer` in
- * `@pascal-app/viewer/components/renderers/slab/slab-renderer.tsx` —
- * same placeholder geometry, same material cache, same render output.
- *
- * Material logic is preserved from legacy: slab can carry either a raw
- * `material` or a `materialPreset` (preset takes precedence; preset
- * apply mutates the cached material instance so async texture loads
- * still hit the rendered mesh on re-mount).
- *
- * No `def.geometry` yet — slab polygon geometry depends on holes +
- * triangulation that lives inside `SlabSystem`'s useFrame body. Future
- * milestone can extract a pure builder if useful, but the system is
- * already efficient (rebuilds only dirty nodes); no urgency.
- */
-const slabMaterialCache = new Map<string, THREE.MeshStandardMaterial>()
-
-function createEmptyGeometry() {
-  const geometry = new THREE.BufferGeometry()
-  geometry.setAttribute('position', new THREE.Float32BufferAttribute([], 3))
-  return geometry
-}
-
-function getSlabMaterial(
-  cacheKey: string,
-  params: { material?: SlabNode['material']; materialPreset?: string },
-) {
-  const cached = slabMaterialCache.get(cacheKey)
-  if (cached) return cached
-
-  const preset = getMaterialPresetByRef(params.materialPreset)
-  const slabMaterial = preset
-    ? new THREE.MeshStandardMaterial()
-    : params.material
-      ? createMaterial(params.material).clone()
-      : DEFAULT_SLAB_MATERIAL.clone()
-
-  if (preset) {
-    applyMaterialPresetToMaterials(slabMaterial, preset)
-  }
-
-  slabMaterial.transparent = false
-  slabMaterial.opacity = 1
-  slabMaterial.alphaMap = null
-  slabMaterial.side = THREE.DoubleSide
-  slabMaterial.depthWrite = true
-  slabMaterial.needsUpdate = true
-
-  slabMaterialCache.set(cacheKey, slabMaterial)
-  return slabMaterial
-}
-
-const SlabRenderer = ({ node }: { node: SlabNode }) => {
-  const ref = useRef<Mesh>(null!)
-  const placeholderGeometry = useMemo(createEmptyGeometry, [])
-  const handlers = useNodeEvents(node, 'slab')
-
-  useRegistry(node.id, 'slab', ref)
-
-  useLayoutEffect(() => {
-    useScene.getState().markDirty(node.id)
-  }, [node.id])
-
-  useEffect(() => () => placeholderGeometry.dispose(), [placeholderGeometry])
-
-  const material = useMemo(() => {
-    const resolvedMaterial = node.material
-    const resolvedMaterialPreset = node.materialPreset
-    const cacheKey = JSON.stringify({
-      material: resolvedMaterial ?? null,
-      materialPreset: resolvedMaterialPreset ?? null,
-    })
-
-    return getSlabMaterial(cacheKey, {
-      material: resolvedMaterial,
-      materialPreset: resolvedMaterialPreset,
-    })
-  }, [
-    node.material,
-    node.material?.preset,
-    node.material?.properties,
-    node.material?.texture,
-    node.materialPreset,
-  ])
-
-  return (
-    <mesh
-      castShadow
-      geometry={placeholderGeometry}
-      material={material}
-      receiveShadow
-      ref={ref}
-      visible={node.visible}
-      {...handlers}
-    />
-  )
-}
-
-export default SlabRenderer

packages/nodes/src/slab/system.tsx

@@ -1,20 +0,0 @@
-'use client'
-
-import { SlabSystem } from '@pascal-app/viewer'
-
-/**
- * Registry-driven slab system bundle. Re-exports the legacy `SlabSystem`
- * (still in viewer) so it mounts via `RegisteredSystems` when slab is
- * registry-driven. `<LegacySystem kind="slab">` in viewer/components/
- * viewer/index.tsx short-circuits whenever `nodeRegistry.has('slab')`
- * is true — same shape wall and fence use.
- *
- * Future Phase 5+: extract polygon triangulation + hole CSG into a pure
- * `buildSlabGeometry(node)` and migrate to `def.geometry`. The legacy
- * system body has it well-isolated; should be a clean extraction.
- */
-const SlabSystems = () => {
-  return <SlabSystem />
-}
-
-export default SlabSystems

packages/nodes/src/spawn/definition.ts

@@ -1,4 +1,5 @@
 import type { NodeDefinition } from '@pascal-app/core'
+import { buildSpawnFloorplan } from './floorplan'
 import { spawnParametrics } from './parametrics'
 import { SpawnNode } from './schema'
 
@@ -34,12 +35,14 @@ export const spawnDefinition: NodeDefinition<typeof SpawnNode> = {
     kind: 'parametric',
     module: () => import('./renderer'),
   },
-  // `floorplan: buildSpawnFloorplan` deferred — spawn already renders in
-  // the legacy floorplan-panel.tsx via `floorplanSpawnEntries`. Adding it
-  // here would double-render. The pure builder lives in
-  // ./floorplan.ts ready to wire when the legacy inline branch is
-  // removed (Phase 5 spawn-floorplan migration PR — same shape as the
-  // wall feature flag, but per kind in the legacy panel itself).
+  // Stage C migration: floor-plan rendering via def.floorplan.
+  // floorplan-panel.tsx's `floorplanSpawnEntries` short-circuits to []
+  // when `nodeRegistry.has('spawn')`, so this builder is the single
+  // path. FloorplanRegistryLayer renders + handles click-to-select;
+  // FloorplanRegistryActionMenu handles move / duplicate (disabled) /
+  // delete. Legacy spawn click handlers in FloorplanNodeLayer become
+  // dead code once Phase 6 cleanup removes the [] entries path.
+  floorplan: buildSpawnFloorplan,
   tool: () => import('./tool'),
   toolHints: [
     { key: 'Left click', label: 'Place spawn point' },

packages/viewer/src/index.ts

@@ -49,7 +49,7 @@ export { DoorSystem } from './systems/door/door-system'
 // Fence system follows the wall re-export pattern — composed into the
 // registry-driven fence definition's `def.system`. Removed in Phase 6
 // alongside the legacy fence mount point.
-export { FenceSystem } from './systems/fence/fence-system'
+export { FenceSystem, generateFenceGeometry } from './systems/fence/fence-system'
 export { InteractiveSystem } from './systems/interactive/interactive-system'
 // Item systems for the registry-driven item definition. ItemSystem
 // applies attachTo-driven transforms each frame; ItemLightSystem
@@ -61,7 +61,7 @@ export { getRoofMaterialArray } from './systems/roof/roof-materials'
 // Slab system follows the wall + fence re-export pattern — composed into
 // the registry-driven slab definition's `def.system`. Removed in Phase 6
 // alongside the legacy slab mount point.
-export { SlabSystem } from './systems/slab/slab-system'
+export { generateSlabGeometry, SlabSystem } from './systems/slab/slab-system'
 export { getStairBodyMaterials, getStairRailingMaterial } from './systems/stair/stair-materials'
 export { WallCutout } from './systems/wall/wall-cutout'
 export { getVisibleWallMaterials } from './systems/wall/wall-materials'

packages/viewer/src/systems/fence/fence-system.tsx

@@ -242,7 +242,7 @@ function createFenceParts(fence: FenceNode): FencePart[] {
   return parts
 }
 
-function generateFenceGeometry(fence: FenceNode) {
+export function generateFenceGeometry(fence: FenceNode) {
   const parts = createFenceParts(fence)
   const geometries = parts.map(createFencePartGeometry)