Merge remote-tracking branch 'origin/main' into feat/baked-glb-export

# Conflicts:
#	packages/editor/src/components/editor/export-manager.tsx

README.md

@@ -17,12 +17,13 @@ https://github.com/user-attachments/assets/8b50e7cf-cebe-4579-9cf3-8786b35f7b6b
 This is a Turborepo monorepo with three main packages:
 
 ```
-editor-v2/
+editor/
 ├── apps/
 │   └── editor/          # Next.js application
 ├── packages/
 │   ├── core/            # Schema definitions, state management, systems
-│   └── viewer/          # 3D rendering components
+│   ├── viewer/          # 3D rendering components
+│   └── ui/              # Shared UI components
 ```
 
 ### Separation of Concerns

apps/editor/README.md

@@ -7,7 +7,7 @@ A 3D building editor built with React Three Fiber and WebGPU.
 This is a Turborepo monorepo with three main packages:
 
 ```
-editor-v2/
+editor/
 ├── apps/
 │   └── editor/          # Next.js application (this package)
 ├── packages/

apps/editor/components/build-tab.tsx

@@ -168,7 +168,8 @@ export function BuildTab() {
   const ductContext =
     mode === 'build' && (activeTool === 'duct-segment' || activeTool === 'duct-fitting')
   const pipeContext =
-    mode === 'build' && (activeTool === 'pipe-segment' || activeTool === 'pipe-fitting')
+    mode === 'build' &&
+    (activeTool === 'pipe-segment' || activeTool === 'pipe-fitting' || activeTool === 'pipe-trap')
   const liquidLineContext = mode === 'build' && activeTool === 'liquid-line'
 
   const isMepItemActive = (item: MepItem) =>
@@ -421,6 +422,30 @@ export function BuildTab() {
                 />
                 Add Fitting
               </button>
+              <button
+                className={cn(
+                  'flex items-center gap-2 rounded-lg px-3 py-2 text-sm transition-all duration-200',
+                  activeTool === 'pipe-trap'
+                    ? 'bg-primary/10 ring-1 ring-primary/50'
+                    : 'bg-muted/40 hover:bg-muted',
+                )}
+                onClick={() => {
+                  triggerSFX('sfx:menu-click')
+                  activateBuildTool(activeTool === 'pipe-trap' ? 'pipe-segment' : 'pipe-trap')
+                }}
+                onMouseEnter={() => triggerSFX('sfx:menu-hover')}
+                type="button"
+              >
+                <Image
+                  alt=""
+                  aria-hidden
+                  className="size-4 object-contain"
+                  height={16}
+                  src="/icons/dwv-pipes.png"
+                  width={16}
+                />
+                Add Trap
+              </button>
             </div>
           ) : null}
 

apps/editor/components/viewer-toolbar.tsx

@@ -119,11 +119,12 @@ const levelModeLabels: Record<string, string> = {
   solo: 'Solo',
 }
 
-const wallModeOrder = ['cutaway', 'up', 'down'] as const
+const wallModeOrder = ['cutaway', 'up', 'down', 'translucent'] as const
 const wallModeConfig: Record<string, { icon: string; label: string }> = {
   up: { icon: '/icons/room.webp', label: 'Full height' },
   cutaway: { icon: '/icons/wallcut.webp', label: 'Cutaway' },
   down: { icon: '/icons/walllow.webp', label: 'Low' },
+  translucent: { icon: '/icons/wall.webp', label: 'Translucent' },
 }
 
 const SHADING_OPTIONS = [

apps/ifc-converter/components/PreviewToolbar.tsx

@@ -14,7 +14,7 @@ import { Box, Grid2x2, Layers, Layers2, Maximize, ScanLine, Square } from 'lucid
 import { type ReactNode, useMemo } from 'react'
 
 const levelModes = ['stacked', 'solo', 'exploded', 'manual'] as const
-const wallModes = ['up', 'cutaway', 'down'] as const
+const wallModes = ['up', 'cutaway', 'down', 'translucent'] as const
 
 const levelLabel: Record<(typeof levelModes)[number], string> = {
   stacked: 'Stack',
@@ -27,6 +27,7 @@ const wallLabel: Record<(typeof wallModes)[number], string> = {
   up: 'Full',
   cutaway: 'Cutaway',
   down: 'Down',
+  translucent: 'Translucent',
 }
 
 function cycle<T>(list: readonly T[], current: T): T {

packages/core/src/material-library.ts

@@ -4193,7 +4193,7 @@ export function getLibraryMaterialIdFromRef(materialRef?: string | null) {
 }
 
 export function getSceneMaterialIdFromRef(materialRef?: string | null): string | null {
-  if (!materialRef || !materialRef.startsWith(SCENE_MATERIAL_REF_PREFIX)) return null
+  if (!materialRef?.startsWith(SCENE_MATERIAL_REF_PREFIX)) return null
   return materialRef.slice(SCENE_MATERIAL_REF_PREFIX.length)
 }
 

packages/core/src/registry/handles.ts

@@ -182,6 +182,25 @@ export type LinearResizeHandle<N> = {
    * the roof shell below it. Only consulted when `shape === 'tracker'`.
    */
   trackerBaseY?: (node: N, sceneApi: SceneApi) => number
+  /**
+   * Stand the chevron blade up into the node's facing plane instead of
+   * leaving it flat in the local XZ plane. For an `axis: 'x'` handle on a
+   * wall-mounted opening (door / window), the local XZ plane is horizontal,
+   * so the default blade is seen edge-on from the front — rotating it 90°
+   * about its pointing axis lays it in the wall face (local XY) so it reads
+   * face-on toward the camera. Chevron shape only; `axis: 'y'` handles are
+   * already stood up unconditionally so this is a no-op for them.
+   */
+  faceNormal?: boolean
+  /**
+   * Gate this arrow behind a click-to-latch cube. When set, the arrow is
+   * hidden until the user clicks the {@link LatchHandle} cube declaring the
+   * same `group` name; clicking the cube again hides it. Lets a node keep a
+   * dense cluster (e.g. a dormer's window width/height arrows) collapsed
+   * behind a single grip until the user opts in. The latch state is local to
+   * the selection and resets when the node is deselected.
+   */
+  latchGroup?: string
 }
 
 /**
@@ -365,6 +384,25 @@ export type TranslateHandle<N = any> = {
   portal?: HandlePortal
 }
 
+/**
+ * Click-to-latch cube. Renders a small persistent cube at `placement` that
+ * toggles the visibility of every handle tagged with the matching
+ * {@link LinearResizeHandle.latchGroup} `group`. Clicking the cube once shows
+ * the group's arrows; clicking again hides them. The latch state is local to
+ * the current selection and resets on deselect.
+ *
+ * Mirrors the duct-fitting selection cube but driven by descriptor data so any
+ * node can collapse a dense arrow cluster behind one grip — e.g. a dormer's
+ * window width/height arrows latch behind a cube at the window center.
+ */
+export type LatchHandle<N = any> = {
+  kind: 'latch'
+  /** The `latchGroup` name whose arrows this cube reveals / hides. */
+  group: string
+  placement: HandlePlacement<N>
+  portal?: HandlePortal
+}
+
 export type HandleDescriptor<N = any> =
   | LinearResizeHandle<N>
   | RadialResizeHandle<N>
@@ -372,6 +410,7 @@ export type HandleDescriptor<N = any> =
   | EndpointMoveHandle<N>
   | TapActionHandle<N>
   | TranslateHandle<N>
+  | LatchHandle<N>
 
 /**
  * Static array, or a function for shape-dependent cases (column

packages/core/src/registry/index.ts

@@ -9,6 +9,7 @@ export type {
   HandleList,
   HandlePlacement,
   HandlePortal,
+  LatchHandle,
   LinearResizeHandle,
   RadialResizeHandle,
   TapActionHandle,

packages/core/src/registry/types.ts

@@ -1584,6 +1584,23 @@ export type ParametricDescriptor<N> = {
    * `updateNodes`.
    */
   reconcile?: (prev: N, next: N) => Array<{ id: AnyNodeId; data: Partial<AnyNode> }>
+  /**
+   * Deletion companion to `reconcile`: when a node of this kind is about
+   * to be removed, return patches for OTHER nodes that must follow to
+   * undo whatever the node imposed on its neighbours — e.g. an
+   * auto-inserted elbow re-extends the duct runs it trimmed back onto the
+   * corner it replaced. Called with the node and the live scene `nodes`
+   * map BEFORE the deletion lands; patches targeting nodes also being
+   * deleted are ignored. Applied in the same `set` as the delete so it's
+   * one undo step. Fires only on `deleteNodes` (user-intent deletes) —
+   * NOT on `applyNodeChanges`, whose deletes are internal re-routes that
+   * rewrite neighbours explicitly in the same batch and would fight a
+   * restore.
+   */
+  onDelete?: (
+    node: N,
+    nodes: Record<AnyNodeId, AnyNode>,
+  ) => Array<{ id: AnyNodeId; data: Partial<AnyNode> }>
   customPanel?: () => Promise<{ default: ComponentType<{ node: N }> }>
   /**
    * Extra buttons rendered in the inspector's Actions section

packages/core/src/schema/material.test.ts

@@ -0,0 +1,49 @@
+import { describe, expect, test } from 'bun:test'
+import { MaterialSchema } from './material'
+
+describe('MaterialSchema', () => {
+  describe('preset', () => {
+    test('valid preset passes through unchanged', () => {
+      const result = MaterialSchema.parse({ preset: 'brick' })
+      expect(result.preset).toBe('brick')
+    })
+
+    test('every enum preset is accepted', () => {
+      const presets = [
+        'white',
+        'brick',
+        'concrete',
+        'wood',
+        'glass',
+        'metal',
+        'plaster',
+        'tile',
+        'marble',
+        'custom',
+      ] as const
+      for (const preset of presets) {
+        expect(MaterialSchema.parse({ preset }).preset).toBe(preset)
+      }
+    })
+
+    test("unknown preset coerces to 'custom' instead of throwing (Sentry MONOREPO-EDITOR-DB)", () => {
+      const result = MaterialSchema.parse({ preset: 'stone' })
+      expect(result.preset).toBe('custom')
+    })
+
+    test("non-string preset coerces to 'custom'", () => {
+      const result = MaterialSchema.parse({ preset: 42 })
+      expect(result.preset).toBe('custom')
+    })
+
+    test('missing preset stays undefined', () => {
+      const result = MaterialSchema.parse({})
+      expect(result.preset).toBeUndefined()
+    })
+
+    test('explicit undefined preset stays undefined', () => {
+      const result = MaterialSchema.parse({ preset: undefined })
+      expect(result.preset).toBeUndefined()
+    })
+  })
+})

packages/core/src/schema/material.ts

@@ -27,7 +27,8 @@ export type MaterialProperties = z.infer<typeof MaterialProperties>
 
 export const MaterialSchema = z.object({
   id: z.string().optional(),
-  preset: MaterialPreset.optional(),
+  // Coerce unknown presets (legacy/AI-generated data) to 'custom' instead of throwing.
+  preset: MaterialPreset.catch('custom').optional(),
   properties: MaterialProperties.optional(),
   texture: z
     .object({

packages/core/src/schema/nodes/dormer.ts

@@ -91,7 +91,7 @@ export const DormerNode = BaseNode.extend({
   windowCornerRadii: z
     .tuple([z.number(), z.number(), z.number(), z.number()])
     .default(DEFAULT_CORNER_RADII),
-  windowSill: z.boolean().default(true),
+  windowSill: z.boolean().default(false),
   windowSillDepth: z.number().default(DORMER_DEFAULTS.WINDOW_SILL_DEPTH),
   windowSillThickness: z.number().default(DORMER_DEFAULTS.WINDOW_SILL_THICKNESS),
 }).describe(

packages/core/src/schema/nodes/duct-fitting.ts

@@ -45,7 +45,7 @@ export const DuctFittingNode = BaseNode.extend({
   // matching the trunk the fitting sits in. Reducers ignore the shape.
   // When non-round, `diameter` carries the area-equivalent round size
   // (drives leg lengths + advertised ports).
-  shape: z.enum(['round', 'rect', 'oval']).default('round'),
+  shape: z.enum(['round', 'rect', 'oval']).default('rect'),
   // Rect / oval run-leg profile in inches (used when shape ≠ 'round').
   width: z.number().min(4).max(60).default(14),
   height: z.number().min(3).max(40).default(8),
@@ -53,13 +53,15 @@ export const DuctFittingNode = BaseNode.extend({
   // rect / oval profile matching the duct drawn off the tap. When
   // non-round, `diameter2` carries the branch's area-equivalent round
   // size. A cross's two opposed branches share this one profile.
-  shape2: z.enum(['round', 'rect', 'oval']).default('round'),
+  shape2: z.enum(['round', 'rect', 'oval']).default('rect'),
   // Rect / oval branch profile in inches (used when shape2 ≠ 'round').
   width2: z.number().min(4).max(60).default(14),
   height2: z.number().min(3).max(40).default(8),
   // Elbow turn angle in degrees. Residential sheet-metal elbows come in
-  // 90° and 45°; adjustable elbows cover the range between.
-  angle: z.number().min(15).max(90).default(90),
+  // 90° and 45°; adjustable elbows cover the range between. 0° is a
+  // straight coupling — what an elbow flattens to when its run is dragged
+  // into line with the fixed collar.
+  angle: z.number().min(0).max(90).default(90),
   // Tee branch angle in degrees, measured off the +X (outlet) axis: 90°
   // is a square straight tee, <90° a lateral whose branch sweeps
   // downstream toward the outlet (flow merges), >90° leans the branch
@@ -72,6 +74,7 @@ export const DuctFittingNode = BaseNode.extend({
   diameter2: z.number().min(2).max(48).default(6),
   ductMaterial: z.enum(['sheet-metal', 'flex', 'duct-board']).default('sheet-metal'),
   system: z.enum(['supply', 'return']).default('supply'),
+  slots: z.record(z.string(), z.string()).optional(),
 }).describe(
   dedent`
   Duct fitting - elbow, tee, cross, reducer, or square-to-round transition between duct runs.

packages/core/src/schema/nodes/duct-segment.ts

@@ -58,6 +58,7 @@ export const DuctSegmentNode = BaseNode.extend({
   // Which side of the air loop this segment belongs to. Drives visual tint
   // and (in later slices) System graph membership.
   system: z.enum(['supply', 'return']).default('supply'),
+  slots: z.record(z.string(), z.string()).optional(),
 }).describe(
   dedent`
   Duct segment - polyline of 3D points connected by duct sections.

packages/core/src/schema/nodes/pipe-fitting.ts

@@ -24,8 +24,10 @@ export const PipeFittingNode = BaseNode.extend({
   rotation: z.tuple([z.number(), z.number(), z.number()]).default([0, 0, 0]),
   fittingType: z.enum(['elbow', 'wye', 'sanitary-tee', 'cross']).default('elbow'),
   // Elbow turn in degrees — DWV bends ship as 22.5 / 45 / 90 ("long
-  // sweep" for drains); adjustable range matches the duct elbow.
-  angle: z.number().min(15).max(90).default(90),
+  // sweep" for drains); adjustable range matches the duct elbow. 0° is a
+  // straight coupling — what an elbow flattens to when its run is dragged
+  // into line with the fixed collar.
+  angle: z.number().min(0).max(90).default(90),
   // Run nominal size in inches.
   diameter: z.number().min(1.25).max(8).default(2),
   // Branch collar size (wye / sanitary-tee).

packages/core/src/schema/nodes/pipe-trap.ts

@@ -21,7 +21,7 @@ export const PipeTrapNode = BaseNode.extend({
   // Yaw in radians (the arm direction in plan).
   rotation: z.number().default(0),
   // Trap size in inches — matches the fixture drain it serves.
-  diameter: z.number().min(1.25).max(4).default(1.5),
+  diameter: z.number().min(1.25).max(4).default(2),
   pipeMaterial: z.enum(['pvc', 'abs', 'cast-iron']).default('pvc'),
   // Developed length of the trap arm (trap weir → vent) in meters. The
   // draw tool measures it when the arm is drawn; editable in the

packages/core/src/services/index.ts

@@ -43,6 +43,8 @@ export {
 } from './hosting'
 export {
   DEFAULT_LEVEL_HEIGHT,
+  getCeilingAt,
+  getCeilingHeightAt,
   getLevelHeight,
 } from './level-height'
 export {

packages/core/src/services/level-height.ts

@@ -1,3 +1,4 @@
+import { pointInPolygon } from '../hooks/spatial-grid/spatial-grid-manager'
 import type { CeilingNode, LevelNode, WallNode } from '../schema'
 import type { AnyNode, AnyNodeId } from '../schema/types'
 
@@ -40,3 +41,46 @@ export function getLevelHeight(
 
   return maxTop > 0 ? maxTop : DEFAULT_LEVEL_HEIGHT
 }
+
+/**
+ * The ceiling covering level-local point `[x, z]`, or `null` when none
+ * sits over it. Points inside a ceiling's hole are treated as uncovered.
+ * When ceilings overlap, the lowest one wins — that's the surface a duct
+ * would actually hang from.
+ */
+export function getCeilingAt(
+  levelId: string,
+  nodes: Record<AnyNodeId, AnyNode>,
+  x: number,
+  z: number,
+): CeilingNode | null {
+  const level = nodes[levelId as LevelNode['id']] as LevelNode | undefined
+  if (!level) return null
+
+  let best: CeilingNode | null = null
+  for (const childId of level.children) {
+    const child = nodes[childId as keyof typeof nodes]
+    if (child?.type !== 'ceiling') continue
+    const ceiling = child as CeilingNode
+    if (ceiling.polygon.length < 3 || !pointInPolygon(x, z, ceiling.polygon)) continue
+    if (ceiling.holes.some((hole) => hole.length >= 3 && pointInPolygon(x, z, hole))) continue
+    const h = ceiling.height ?? DEFAULT_LEVEL_HEIGHT
+    if (best === null || h < (best.height ?? DEFAULT_LEVEL_HEIGHT)) best = ceiling
+  }
+  return best
+}
+
+/**
+ * Underside elevation (meters above the level floor) of the ceiling
+ * covering level-local point `[x, z]`, or `null` when no ceiling sits
+ * over that point. See {@link getCeilingAt}.
+ */
+export function getCeilingHeightAt(
+  levelId: string,
+  nodes: Record<AnyNodeId, AnyNode>,
+  x: number,
+  z: number,
+): number | null {
+  const ceiling = getCeilingAt(levelId, nodes, x, z)
+  return ceiling ? (ceiling.height ?? DEFAULT_LEVEL_HEIGHT) : null
+}

packages/core/src/services/port-connectivity.test.ts

@@ -0,0 +1,349 @@
+import { describe, expect, test } from 'bun:test'
+import type { AnyNodeDefinition, DistributionRole, NodePort } from '../registry'
+import { registerNode } from '../registry'
+import type { AnyNode, AnyNodeId } from '../schema'
+import { analyzePortConnectivity, resolveConnectivityUpdates } from './port-connectivity'
+
+type Point = [number, number, number]
+
+// Stub registrations mirroring the real kinds' port + role conventions
+// without importing the nodes package (which pulls in CSG and can't load
+// under the test runner). A run exposes start/end at its path tips; the
+// fitting here is a simple two-collar elbow at ±X around its position.
+function stubDef(
+  kind: string,
+  distributionRole: DistributionRole,
+  ports: (node: AnyNode) => NodePort[],
+): void {
+  registerNode({
+    kind,
+    schemaVersion: 1,
+    schema: {},
+    category: 'utility',
+    distributionRole,
+    defaults: () => ({}),
+    capabilities: {},
+    ports,
+  } as unknown as AnyNodeDefinition)
+}
+
+stubDef('duct-segment', 'run', (node) => {
+  const path = (node as unknown as { path: Point[] }).path
+  const system = (node as unknown as { system: string }).system
+  return [
+    { id: 'start', position: path[0]!, direction: [-1, 0, 0], diameter: 6, system },
+    { id: 'end', position: path[path.length - 1]!, direction: [1, 0, 0], diameter: 6, system },
+  ]
+})
+stubDef('duct-fitting', 'fitting', (node) => {
+  const position = (node as unknown as { position: Point }).position
+  const system = (node as unknown as { system: string }).system
+  return [
+    {
+      id: 'inlet',
+      position: [position[0] - 0.2, position[1], position[2]],
+      direction: [-1, 0, 0],
+      diameter: 6,
+      system,
+    },
+    {
+      id: 'outlet',
+      position: [position[0] + 0.2, position[1], position[2]],
+      direction: [1, 0, 0],
+      diameter: 6,
+      system,
+    },
+  ]
+})
+stubDef('duct-tee', 'fitting', (node) => {
+  const position = (node as unknown as { position: Point }).position
+  const system = (node as unknown as { system: string }).system
+  return [
+    {
+      id: 'inlet',
+      position: [position[0] - 0.2, position[1], position[2]],
+      direction: [-1, 0, 0],
+      diameter: 6,
+      system,
+    },
+    {
+      id: 'outlet',
+      position: [position[0] + 0.2, position[1], position[2]],
+      direction: [1, 0, 0],
+      diameter: 6,
+      system,
+    },
+    {
+      id: 'branch',
+      position: [position[0], position[1], position[2] + 0.2],
+      direction: [0, 0, 1],
+      diameter: 6,
+      system,
+    },
+  ]
+})
+
+let nextId = 0
+function makeNode(type: string, fields: Record<string, unknown>): AnyNode {
+  nextId += 1
+  return { id: `${type}_${nextId}`, type, object: 'node', parentId: null, ...fields } as AnyNode
+}
+
+function sceneOf(...nodes: AnyNode[]): Record<AnyNodeId, AnyNode> {
+  return Object.fromEntries(nodes.map((n) => [n.id, n])) as Record<AnyNodeId, AnyNode>
+}
+
+function expectPointClose(actual: Point, expected: Point) {
+  expect(actual[0]).toBeCloseTo(expected[0], 6)
+  expect(actual[1]).toBeCloseTo(expected[1], 6)
+  expect(actual[2]).toBeCloseTo(expected[2], 6)
+}
+
+describe('port connectivity — joint follow (stretch vs translate)', () => {
+  // Layout: duct A ends at the fitting's inlet (−0.2,0,0); duct B starts at the
+  // fitting's outlet (+0.2,0,0). Both runs lie on the X axis. Dragging A's
+  // mated endpoint carries the fitting and duct B; how B reacts depends on
+  // whether the drag is along its axis (stretch) or across it (translate).
+  function joint() {
+    const fitting = makeNode('duct-fitting', { position: [0, 0, 0], system: 'supply' })
+    const ductA = makeNode('duct-segment', {
+      path: [
+        [-3, 0, 0],
+        [-0.2, 0, 0],
+      ],
+      system: 'supply',
+    })
+    const ductB = makeNode('duct-segment', {
+      path: [
+        [0.2, 0, 0],
+        [3, 0, 0],
+      ],
+      system: 'supply',
+    })
+    return { fitting, ductA, ductB }
+  }
+
+  function movedA(end: Point): AnyNode {
+    const { ductA } = joint()
+    return { ...(ductA as Record<string, unknown>), path: [[-3, 0, 0], end] } as AnyNode
+  }
+
+  test('the fitting and sibling run are picked up as carried connections', () => {
+    const { fitting, ductA, ductB } = joint()
+    const connectivity = analyzePortConnectivity(ductA, sceneOf(fitting, ductA, ductB))
+    expect(
+      connectivity.connections.find((c) => c.kind === 'rigid-node' && c.nodeId === fitting.id),
+    ).toBeDefined()
+    expect(
+      connectivity.connections.find((c) => c.kind === 'run' && c.nodeId === ductB.id),
+    ).toBeDefined()
+  })
+
+  test('perpendicular drag translates the WHOLE sibling run (no skew)', () => {
+    const { fitting, ductA, ductB } = joint()
+    const nodes = sceneOf(fitting, ductA, ductB)
+    const connectivity = analyzePortConnectivity(ductA, nodes)
+
+    // Move A's mated end +1 in Z — perpendicular to B's X axis.
+    const updates = resolveConnectivityUpdates(connectivity, movedA([-0.2, 0, 1]))
+
+    expect(
+      (updates.find((u) => u.id === fitting.id)!.data as { position: Point }).position,
+    ).toEqual([0, 0, 1])
+    const bPath = (updates.find((u) => u.id === ductB.id)!.data as { path: Point[] }).path
+    // Both ends ride +1 in Z: the run keeps its length and direction.
+    expect(bPath[0]).toEqual([0.2, 0, 1])
+    expect(bPath[1]).toEqual([3, 0, 1])
+  })
+
+  test('parallel drag stretches the sibling run (only the near end slides)', () => {
+    const { fitting, ductA, ductB } = joint()
+    const nodes = sceneOf(fitting, ductA, ductB)
+    const connectivity = analyzePortConnectivity(ductA, nodes)
+
+    // Move A's mated end +0.5 in X — along B's axis (the fitting slides toward B).
+    const updates = resolveConnectivityUpdates(connectivity, movedA([0.3, 0, 0]))
+
+    const bPath = (updates.find((u) => u.id === ductB.id)!.data as { path: Point[] }).path
+    // Near end slid +0.5 in X; far end stayed put → the run shortened.
+    expect(bPath[0]).toEqual([0.7, 0, 0])
+    expect(bPath[1]).toEqual([3, 0, 0])
+  })
+
+  test('perpendicular slide propagates through the sibling run to its far joint', () => {
+    // Extend the chain: duct B's far end (3,0,0) meets a second elbow, and duct
+    // C hangs off that elbow. A perpendicular drag should carry the whole chain.
+    const { fitting, ductA, ductB } = joint()
+    const elbow2 = makeNode('duct-fitting', { position: [3.2, 0, 0], system: 'supply' })
+    // elbow ports are ±0.2 on X around its position → inlet at (3,0,0) meets B.
+    const ductC = makeNode('duct-segment', {
+      path: [
+        [3.4, 0, 0],
+        [6, 0, 0],
+      ],
+      system: 'supply',
+    })
+    const nodes = sceneOf(fitting, ductA, ductB, elbow2, ductC)
+    const connectivity = analyzePortConnectivity(ductA, nodes)
+
+    const updates = resolveConnectivityUpdates(connectivity, movedA([-0.2, 0, 1]))
+
+    // Whole chain rode +1 in Z.
+    const bPath = (updates.find((u) => u.id === ductB.id)!.data as { path: Point[] }).path
+    expect(bPath[1]).toEqual([3, 0, 1])
+    expect((updates.find((u) => u.id === elbow2.id)!.data as { position: Point }).position).toEqual(
+      [3.2, 0, 1],
+    )
+    const cPath = (updates.find((u) => u.id === ductC.id)!.data as { path: Point[] }).path
+    expect(cPath[0]).toEqual([3.4, 0, 1])
+    expect(cPath[1]).toEqual([6, 0, 1])
+  })
+
+  test('a run reached from both ends applies both endpoint deltas', () => {
+    const moved = makeNode('duct-segment', {
+      path: [
+        [0, 0, 0],
+        [3, 0, 0],
+      ],
+      system: 'supply',
+    })
+    const follower = makeNode('duct-segment', {
+      path: [
+        [0, 0, 0],
+        [3, 0, 0],
+      ],
+      system: 'supply',
+    })
+    const nodes = sceneOf(moved, follower)
+    const connectivity = analyzePortConnectivity(moved, nodes)
+    const preview = {
+      ...(moved as Record<string, unknown>),
+      path: [
+        [0, 0, 1],
+        [3, 0, 2],
+      ],
+    } as AnyNode
+
+    const updates = resolveConnectivityUpdates(connectivity, preview)
+
+    const path = (updates.find((u) => u.id === follower.id)!.data as { path: Point[] }).path
+    expect(path[0]).toEqual([0, 0, 1])
+    expect(path[1]).toEqual([3, 0, 2])
+  })
+
+  test('a polyline run reached from both ends preserves interior bend shape', () => {
+    const moved = makeNode('duct-segment', {
+      path: [
+        [0, 0, 0],
+        [3, 0, 3],
+      ],
+      system: 'supply',
+    })
+    const follower = makeNode('duct-segment', {
+      path: [
+        [0, 0, 0],
+        [1, 0, 0],
+        [1, 0, 3],
+        [3, 0, 3],
+      ],
+      system: 'supply',
+    })
+    const nodes = sceneOf(moved, follower)
+    const connectivity = analyzePortConnectivity(moved, nodes)
+    const preview = {
+      ...(moved as Record<string, unknown>),
+      path: [
+        [-0.5, 0, 0],
+        [3.5, 0, 3],
+      ],
+    } as AnyNode
+
+    const updates = resolveConnectivityUpdates(connectivity, preview)
+
+    const path = (updates.find((u) => u.id === follower.id)!.data as { path: Point[] }).path
+    expect(path).toEqual([
+      [-0.5, 0, 0],
+      [1, 0, 0],
+      [1, 0, 3],
+      [3.5, 0, 3],
+    ])
+  })
+
+  test('a fitting reached from both collars rebroadcasts its final compatible rigid delta', () => {
+    const moved = makeNode('duct-segment', {
+      path: [
+        [-0.2, 0, 0],
+        [0.2, 0, 0],
+      ],
+      system: 'supply',
+    })
+    const fitting = makeNode('duct-tee', { position: [0, 0, 0], system: 'supply' })
+    const downstream = makeNode('duct-segment', {
+      path: [
+        [0, 0, 0.2],
+        [3, 0, 0.2],
+      ],
+      system: 'supply',
+    })
+    const nodes = sceneOf(moved, fitting, downstream)
+    const connectivity = analyzePortConnectivity(moved, nodes)
+    const preview = {
+      ...(moved as Record<string, unknown>),
+      path: [
+        [-0.2, 0, 1],
+        [0.2, 0, 1.00005],
+      ],
+    } as AnyNode
+
+    const updates = resolveConnectivityUpdates(connectivity, preview)
+
+    expectPointClose(
+      (updates.find((u) => u.id === fitting.id)!.data as { position: Point }).position,
+      [0, 0, 1.000025],
+    )
+    const path = (updates.find((u) => u.id === downstream.id)!.data as { path: Point[] }).path
+    expectPointClose(path[0]!, [0, 0, 1.200025])
+    expectPointClose(path[1]!, [3, 0, 1.200025])
+  })
+
+  test('a fitting reached from incompatible collars merges constraints deterministically', () => {
+    const moved = makeNode('duct-segment', {
+      path: [
+        [-0.2, 0, 0],
+        [0.2, 0, 0],
+      ],
+      system: 'supply',
+    })
+    const fitting = makeNode('duct-fitting', { position: [0, 0, 0], system: 'supply' })
+    const nodes = sceneOf(moved, fitting)
+    const connectivity = analyzePortConnectivity(moved, nodes)
+    const preview = {
+      ...(moved as Record<string, unknown>),
+      path: [
+        [-0.2, 0, 1],
+        [0.2, 0, -1],
+      ],
+    } as AnyNode
+
+    const updates = resolveConnectivityUpdates(connectivity, preview)
+
+    expectPointClose(
+      (updates.find((u) => u.id === fitting.id)!.data as { position: Point }).position,
+      [0, 0, 0],
+    )
+  })
+
+  test('an unrelated run not on the fitting is left alone', () => {
+    const { fitting, ductA, ductB } = joint()
+    const distant = makeNode('duct-segment', {
+      path: [
+        [10, 0, 0],
+        [13, 0, 0],
+      ],
+      system: 'supply',
+    })
+    const nodes = sceneOf(fitting, ductA, ductB, distant)
+    const connectivity = analyzePortConnectivity(ductA, nodes)
+    expect(connectivity.connections.find((c) => c.nodeId === distant.id)).toBeUndefined()
+  })
+})

packages/core/src/services/port-connectivity.ts

@@ -13,14 +13,29 @@ import type { AnyNode, AnyNodeId } from '../schema'
  *
  * Pure logic: it asks each node for its ports via `def.ports` (level-local
  * meters) and does arithmetic. No Three.js, no rendering — it lives in
- * core and is consumed by the editor's move tool and the duct-segment
- * system alike.
+ * core and is consumed by the editor's move tool and the duct/pipe
+ * selection affordances alike.
  *
- * Propagation is intentionally **one hop**: a moved fitting stretches the
- * ducts touching it (their near endpoint follows) and rigidly drags any
- * fitting mated collar-to-collar, but it does NOT chase the far end of
- * those ducts or anything beyond. Bounded and predictable — no runaway
- * network rearrangement.
+ * ## Propagation model
+ *
+ * The joint graph is snapshotted once at drag start (`analyzePortConnectivity`)
+ * and walked every frame (`resolveConnectivityUpdates`) given the moved node's
+ * live transform. Deltas flow outward from the moved node through coincident
+ * ports:
+ *
+ * - **Fitting** (rigid): a collar pushed by delta `d` translates the whole
+ *   fitting by `d`; every other collar carries that same `d` onward.
+ * - **Run** (stretch + slide, never skew): an endpoint pushed by delta `d` is
+ *   split against the run's own axis. The *parallel* part slides only that
+ *   endpoint (the run lengthens / shortens); the *perpendicular* part
+ *   translates the entire run (so its direction is preserved). The far
+ *   endpoint therefore moves by just the perpendicular part, and that part
+ *   propagates onward to whatever is mated to the far endpoint.
+ *
+ * Propagation walks the whole connected component so a joint stays welded all
+ * the way down the chain, with a visited guard so cycles (looped runs) and
+ * shared joints terminate. First-reached (shortest path) wins on a node
+ * reachable two ways.
  */
 
 type Point = readonly [number, number, number]
@@ -30,36 +45,55 @@ type Point = readonly [number, number, number]
  *  generous slack for grid-snapped hand placement without false matches. */
 const COINCIDENT_EPS_M = 0.05
 
-/** A node attached to one of the moved node's ports, plus how it follows. */
+/** Below this (meters) a propagated delta is treated as zero — stops the
+ *  walk from chasing sub-millimeter perpendicular residue. */
+const DELTA_EPS_M = 1e-4
+const PROPAGATION_EPS_M = 1e-9
+
+/** A node carried by the edit, plus the snapshot needed to revert it. Kept
+ *  deliberately small: the move tools read only `kind` + `nodeId` and the
+ *  matching start snapshot to revert before the single tracked commit. */
 export type PortConnection =
   | {
-      /** Partner is a duct run: the endpoint touching the moved port slides
-       *  to track it (one hop — the far endpoint stays put, stretching the
-       *  run). */
-      kind: 'duct-endpoint'
-      nodeId: AnyNodeId
-      /** Index in the duct's `path` that tracks the moved port. */
-      pathIndex: number
-      /** The moved node's port id this endpoint follows. */
-      movedPortId: string
-      /** The duct's full path at edit-start (other points are preserved). */
-      startPath: Point[]
-    }
-  | {
-      /** Partner is another fitting mated collar-to-collar: it translates
-       *  rigidly so its collar stays on the moved collar. */
+      /** A fitting mated collar-to-collar: it translates rigidly. */
       kind: 'rigid-node'
       nodeId: AnyNodeId
-      movedPortId: string
-      /** Partner node's `position` at edit-start. */
+      /** Node's `position` at edit-start. */
       startPosition: Point
     }
+  | {
+      /** A run whose endpoint(s) ride the edit: it stretches and/or
+       *  translates, never skews. */
+      kind: 'run'
+      nodeId: AnyNodeId
+      /** The run's full `path` at edit-start. */
+      startPath: Point[]
+    }
+
+/** One node in the snapshotted joint graph (everything reachable from the
+ *  moved node, excluding the moved node itself). */
+type GraphNode = {
+  id: AnyNodeId
+  role: 'run' | 'fitting'
+  ports: ReadonlyArray<{ id: string; position: Point; system?: string }>
+  startPath?: Point[]
+  startPosition?: Point
+}
+
+/** Who else sits on a given node's port, keyed `nodeId` → `portId` → mates. */
+type Adjacency = Record<string, Record<string, Array<{ nodeId: AnyNodeId; portId: string }>>>
 
 export type PortConnectivity = {
   movedNodeId: AnyNodeId
-  /** The moved node's port world positions at edit-start, keyed by port id.
-   *  Used as the reference each connection's delta is measured from. */
+  /** The moved node's port world positions at edit-start, keyed by port id —
+   *  the reference each frame's delta is measured from. */
   startMovedPorts: Record<string, Point>
+  /** Reachable run/fitting nodes (excludes the moved node), keyed by id. */
+  graph: Record<string, GraphNode>
+  /** Port coincidence edges across the moved node + every graph node. */
+  adjacency: Adjacency
+  /** Flat list of carried nodes for the move tools' revert + "anything to
+   *  follow?" check. Derived from `graph`. */
   connections: PortConnection[]
 }
 
@@ -83,85 +117,225 @@ function distSq(a: Point, b: Point): number {
   return dx * dx + dy * dy + dz * dz
 }
 
+/** Two ports mate when they coincide AND don't cross incompatible systems
+ *  (a supply duct and a waste pipe that merely touch must not fuse). */
+function portsMate(
+  a: { position: Point; system?: string },
+  b: { position: Point; system?: string },
+  epsSq: number,
+): boolean {
+  if (distSq(a.position, b.position) > epsSq) return false
+  if (a.system && b.system && a.system !== b.system) return false
+  return true
+}
+
 /**
- * Snapshot which nodes are connected to `movedNode`'s ports, taken at the
+ * Snapshot the joint graph reachable from `movedNode`'s ports, taken at the
  * start of a move/resize. Call once before the drag; feed the result to
  * `resolveConnectivityUpdates` on every frame.
  *
- * Only `run`-role partners (segments — endpoint stretch) and `fitting`-role
- * partners (rigid follow) are tracked — terminals and equipment usually mount
- * to a surface and shouldn't be yanked off it when an adjacent fitting nudges.
+ * Only `run`-role partners (segments) and `fitting`-role partners are walked —
+ * terminals and equipment usually mount to a surface and shouldn't be yanked
+ * off it when an adjacent fitting nudges. Fittings that declare
+ * `portConnectivityFollow: false` are anchored fixtures (e.g. pipe-trap) and
+ * are skipped, so a connected run stretches against them instead.
  */
 export function analyzePortConnectivity(
   movedNode: AnyNode,
   nodes: Record<string, AnyNode>,
 ): PortConnectivity {
-  const movedPorts = portsOf(movedNode) ?? []
-  const startMovedPorts: Record<string, Point> = {}
-  const movedPortSystem: Record<string, string | undefined> = {}
-  for (const p of movedPorts) {
-    startMovedPorts[p.id] = p.position
-    movedPortSystem[p.id] = p.system
-  }
-
-  const connections: PortConnection[] = []
   const epsSq = COINCIDENT_EPS_M * COINCIDENT_EPS_M
 
+  const movedPorts = portsOf(movedNode) ?? []
+  const startMovedPorts: Record<string, Point> = {}
+  for (const p of movedPorts) startMovedPorts[p.id] = p.position
+
+  // Candidate partners: every run + every following fitting in the scene.
+  const candidates: GraphNode[] = []
   for (const other of Object.values(nodes)) {
     if (!other || other.id === movedNode.id) continue
-    // Generalised across every distribution family (HVAC duct + DWV pipe):
-    // `run` partners stretch an endpoint, `fitting` partners follow rigidly.
-    // Terminals/equipment mount to surfaces and are intentionally NOT dragged.
-    // Fittings that declare `portConnectivityFollow: false` are anchored
-    // fixtures (e.g. pipe-trap) — moving a connected run stretches the arm.
-    const otherRole = roleOf(other)
-    if (otherRole !== 'run' && otherRole !== 'fitting') continue
-    const otherDef = nodeRegistry.get(other.type)
-    if (otherRole === 'fitting' && otherDef?.portConnectivityFollow === false) continue
-    const otherPorts = portsOf(other)
-    if (!otherPorts) continue
+    const role = roleOf(other)
+    if (role !== 'run' && role !== 'fitting') continue
+    if (role === 'fitting' && nodeRegistry.get(other.type)?.portConnectivityFollow === false) {
+      continue
+    }
+    const ports = portsOf(other)
+    if (!ports) continue
+    const startPath =
+      role === 'run'
+        ? (other as unknown as { path?: Point[] }).path?.map((p) => [...p] as Point)
+        : undefined
+    if (role === 'run' && (!startPath || startPath.length < 2)) continue
+    const startPosition =
+      role === 'fitting'
+        ? (() => {
+            const pos = (other as unknown as { position?: Point }).position
+            return pos ? ([pos[0], pos[1], pos[2]] as Point) : undefined
+          })()
+        : undefined
+    if (role === 'fitting' && !startPosition) continue
+    candidates.push({ id: other.id as AnyNodeId, role, ports, startPath, startPosition })
+  }
 
-    for (const op of otherPorts) {
-      // Find which of the moved node's ports this partner port sits on.
-      let matchedId: string | null = null
-      for (const mp of movedPorts) {
-        if (distSq(op.position, mp.position) > epsSq) continue
-        // Don't fuse ports from incompatible systems (e.g. a supply duct
-        // and a waste pipe that happen to cross): only mate when both
-        // ports declare the same system, or at least one is unscoped.
-        const ms = movedPortSystem[mp.id]
-        if (ms && op.system && ms !== op.system) continue
-        matchedId = mp.id
-        break
-      }
-      if (!matchedId) continue
+  // Walk outward from the moved node, collecting every node reachable through
+  // coincident ports. The adjacency records each port's mates so the resolver
+  // can replay the same edges with live deltas.
+  const adjacency: Adjacency = {}
+  const addEdge = (nodeId: string, portId: string, mate: { nodeId: AnyNodeId; portId: string }) => {
+    const byPort = adjacency[nodeId] ?? {}
+    adjacency[nodeId] = byPort
+    const mates = byPort[portId] ?? []
+    byPort[portId] = mates
+    mates.push(mate)
+  }
 
-      if (otherRole === 'run') {
-        const path = (other as unknown as { path?: Point[] }).path
-        if (!Array.isArray(path) || path.length < 2) continue
-        // Port id 'start' → first point, 'end' → last point.
-        const pathIndex = op.id === 'start' ? 0 : path.length - 1
-        connections.push({
-          kind: 'duct-endpoint',
-          nodeId: other.id,
-          pathIndex,
-          movedPortId: matchedId,
-          startPath: path.map((p) => [...p] as Point),
-        })
-      } else {
-        const position = (other as unknown as { position?: Point }).position
-        if (!position) continue
-        connections.push({
-          kind: 'rigid-node',
-          nodeId: other.id,
-          movedPortId: matchedId,
-          startPosition: [position[0], position[1], position[2]],
-        })
+  const graph: Record<string, GraphNode> = {}
+  const visited = new Set<string>([movedNode.id])
+
+  // Seed: the moved node's own ports.
+  const queue: Array<{
+    id: string
+    ports: ReadonlyArray<{ id: string; position: Point; system?: string }>
+  }> = [{ id: movedNode.id, ports: movedPorts }]
+
+  while (queue.length > 0) {
+    const { id, ports } = queue.shift()!
+    for (const port of ports) {
+      for (const cand of candidates) {
+        if (cand.id === id) continue
+        for (const cp of cand.ports) {
+          if (!portsMate(port, cp, epsSq)) continue
+          addEdge(id, port.id, { nodeId: cand.id, portId: cp.id })
+          addEdge(cand.id, cp.id, { nodeId: id as AnyNodeId, portId: port.id })
+          if (!visited.has(cand.id)) {
+            visited.add(cand.id)
+            graph[cand.id] = cand
+            queue.push({ id: cand.id, ports: cand.ports })
+          }
+        }
       }
     }
   }
 
-  return { movedNodeId: movedNode.id as AnyNodeId, connections, startMovedPorts }
+  const connections: PortConnection[] = Object.values(graph).map((g) =>
+    g.role === 'fitting'
+      ? { kind: 'rigid-node', nodeId: g.id, startPosition: g.startPosition! }
+      : { kind: 'run', nodeId: g.id, startPath: g.startPath! },
+  )
+
+  return {
+    movedNodeId: movedNode.id as AnyNodeId,
+    startMovedPorts,
+    graph,
+    adjacency,
+    connections,
+  }
+}
+
+function add(a: Point, b: Point): Point {
+  return [a[0] + b[0], a[1] + b[1], a[2] + b[2]]
+}
+
+function sub(a: Point, b: Point): Point {
+  return [a[0] - b[0], a[1] - b[1], a[2] - b[2]]
+}
+
+function lenSq(v: Point): number {
+  return v[0] * v[0] + v[1] * v[1] + v[2] * v[2]
+}
+
+/** Split `delta` into the component along unit `axis` and the remainder. */
+function decompose(delta: Point, axis: Point): { parallel: Point; perp: Point } {
+  const dot = delta[0] * axis[0] + delta[1] * axis[1] + delta[2] * axis[2]
+  const parallel: Point = [axis[0] * dot, axis[1] * dot, axis[2] * dot]
+  return { parallel, perp: sub(delta, parallel) }
+}
+
+function scale(v: Point, scalar: number): Point {
+  return [v[0] * scalar, v[1] * scalar, v[2] * scalar]
+}
+
+function average(deltas: Point[]): Point {
+  const sum = deltas.reduce<Point>((acc, delta) => add(acc, delta), [0, 0, 0])
+  return scale(sum, 1 / deltas.length)
+}
+
+function nearlyEqual(a: Point, b: Point): boolean {
+  return lenSq(sub(a, b)) <= DELTA_EPS_M * DELTA_EPS_M
+}
+
+function propagationEqual(a: Point, b: Point): boolean {
+  return lenSq(sub(a, b)) <= PROPAGATION_EPS_M * PROPAGATION_EPS_M
+}
+
+function effectivePortDeltas(
+  constraints: Record<string, Record<string, Point>>,
+): Record<string, Point> {
+  return Object.fromEntries(
+    Object.entries(constraints).map(([portId, bySource]) => [
+      portId,
+      average(Object.values(bySource)),
+    ]),
+  )
+}
+
+/** Unit direction of the run's segment adjacent to its `start` / `end` tip. */
+function endpointAxis(path: Point[], portId: string): Point {
+  const n = path.length
+  const [a, b] = portId === 'start' ? [path[1]!, path[0]!] : [path[n - 2]!, path[n - 1]!]
+  const dir = sub(b, a)
+  const l2 = lenSq(dir)
+  if (l2 < 1e-12) return [0, 0, 0]
+  const l = Math.sqrt(l2)
+  return [dir[0] / l, dir[1] / l, dir[2] / l]
+}
+
+function runPathFromSinglePortDelta(
+  startPath: Point[],
+  portId: 'start' | 'end',
+  delta: Point,
+): Point[] {
+  const nearIdx = portId === 'start' ? 0 : startPath.length - 1
+  const axis = endpointAxis(startPath, portId)
+  const { parallel, perp } = decompose(delta, axis)
+  const path = startPath.map((p) => add(p, perp))
+  path[nearIdx] = add(path[nearIdx]!, parallel)
+  return path
+}
+
+function runEndpointDeltas(startPath: Point[], path: Point[]): Record<string, Point> {
+  return {
+    start: sub(path[0]!, startPath[0]!),
+    end: sub(path[path.length - 1]!, startPath[startPath.length - 1]!),
+  }
+}
+
+function runPathFromPortDeltas(startPath: Point[], portDeltas: Record<string, Point>): Point[] {
+  const startDelta = portDeltas.start
+  const endDelta = portDeltas.end
+  if (startDelta && endDelta) {
+    if (startPath.length === 2) {
+      return [add(startPath[0]!, startDelta), add(startPath[1]!, endDelta)]
+    }
+
+    if (nearlyEqual(startDelta, endDelta)) {
+      return startPath.map((p) => add(p, startDelta))
+    }
+
+    const startParts = decompose(startDelta, endpointAxis(startPath, 'start'))
+    const endParts = decompose(endDelta, endpointAxis(startPath, 'end'))
+    const commonPerp = average([startParts.perp, endParts.perp])
+    const path = startPath.map((p) => add(p, commonPerp))
+    path[0] = add(path[0]!, startParts.parallel)
+    path[path.length - 1] = add(path[path.length - 1]!, endParts.parallel)
+    return path
+  }
+
+  return runPathFromSinglePortDelta(
+    startPath,
+    startDelta ? 'start' : 'end',
+    (startDelta ?? endDelta)!,
+  )
 }
 
 /**
@@ -169,45 +343,103 @@ export function analyzePortConnectivity(
  * that keep every connected node attached. `previewNode` is the moved node
  * with its current drag position/rotation applied so its ports recompute.
  *
- * - Duct endpoint: set the tracked path point to the moved port's new
- *   position (the joint stays welded; the run stretches).
- * - Rigid fitting: translate by the moved port's delta so its mated collar
- *   rides along.
+ * Walks the snapshotted graph, propagating each port delta outward: fittings
+ * translate rigidly, runs stretch along their axis and translate across it
+ * (never skew when driven from one end), and effective port movement carries on
+ * to neighbouring joints. Port-level output guards bound cycles while still
+ * allowing a looped/shared run to accept constraints at both endpoints.
  */
 export function resolveConnectivityUpdates(
   connectivity: PortConnectivity,
   previewNode: AnyNode,
 ): { id: AnyNodeId; data: Partial<AnyNode> }[] {
+  const { graph, adjacency, startMovedPorts, movedNodeId } = connectivity
+  if (Object.keys(graph).length === 0) return []
+
   const newPorts = portsOf(previewNode) ?? []
-  const newById: Record<string, Point> = {}
-  for (const p of newPorts) newById[p.id] = p.position
+  const newMovedPos: Record<string, Point> = {}
+  for (const p of newPorts) newMovedPos[p.id] = p.position
 
-  const updates: { id: AnyNodeId; data: Partial<AnyNode> }[] = []
-  for (const conn of connectivity.connections) {
-    const start = connectivity.startMovedPorts[conn.movedPortId]
-    const now = newById[conn.movedPortId]
-    if (!start || !now) continue
+  // Each queue item drives a node's port by a delta ("this collar / endpoint
+  // must move by this much").
+  const queue: Array<{ nodeId: AnyNodeId; portId: string; delta: Point; sourceKey: string }> = []
+  const results: Record<string, { id: AnyNodeId; data: Partial<AnyNode> }> = {}
+  const constrainedPorts: Record<string, Record<string, Record<string, Point>>> = {}
+  const propagatedPorts: Record<string, Record<string, Point>> = {}
 
-    if (conn.kind === 'duct-endpoint') {
-      const path = conn.startPath.map((p, i) =>
-        i === conn.pathIndex ? ([now[0], now[1], now[2]] as Point) : ([...p] as Point),
-      )
-      updates.push({ id: conn.nodeId, data: { path } as Partial<AnyNode> })
-    } else {
-      const dx = now[0] - start[0]
-      const dy = now[1] - start[1]
-      const dz = now[2] - start[2]
-      updates.push({
-        id: conn.nodeId,
-        data: {
-          position: [
-            conn.startPosition[0] + dx,
-            conn.startPosition[1] + dy,
-            conn.startPosition[2] + dz,
-          ],
-        } as Partial<AnyNode>,
+  const enqueueMates = (nodeId: string, portId: string, delta: Point) => {
+    const byPort = propagatedPorts[nodeId] ?? {}
+    propagatedPorts[nodeId] = byPort
+    const previous = byPort[portId]
+    if (previous && propagationEqual(previous, delta)) return
+    byPort[portId] = delta
+
+    for (const mate of adjacency[nodeId]?.[portId] ?? []) {
+      if (mate.nodeId === movedNodeId) continue
+      queue.push({
+        nodeId: mate.nodeId,
+        portId: mate.portId,
+        delta,
+        sourceKey: `${nodeId}:${portId}`,
       })
     }
   }
-  return updates
+
+  const acceptPortDelta = (
+    nodeId: AnyNodeId,
+    portId: string,
+    sourceKey: string,
+    delta: Point,
+  ): boolean => {
+    const byPort = constrainedPorts[nodeId] ?? {}
+    constrainedPorts[nodeId] = byPort
+    const bySource = byPort[portId] ?? {}
+    byPort[portId] = bySource
+    const existing = bySource[sourceKey]
+    if (existing && propagationEqual(existing, delta)) {
+      return false
+    }
+    bySource[sourceKey] = delta
+    return true
+  }
+
+  // Seed from the moved node's live port deltas.
+  for (const [portId, start] of Object.entries(startMovedPorts)) {
+    const now = newMovedPos[portId]
+    if (!now) continue
+    const delta = sub(now, start)
+    if (lenSq(delta) <= DELTA_EPS_M * DELTA_EPS_M) continue
+    enqueueMates(movedNodeId, portId, delta)
+  }
+
+  while (queue.length > 0) {
+    const { nodeId, portId, delta, sourceKey } = queue.shift()!
+    const node = graph[nodeId]
+    if (!node) continue
+    if (!acceptPortDelta(nodeId, portId, sourceKey, delta)) continue
+    const portDeltas = effectivePortDeltas(constrainedPorts[nodeId]!)
+
+    if (node.role === 'fitting') {
+      const start = node.startPosition!
+      const effectiveDelta = average(Object.values(portDeltas))
+      results[nodeId] = {
+        id: nodeId,
+        data: { position: add(start, effectiveDelta) } as Partial<AnyNode>,
+      }
+      // Rigid: every collar carries the effective body translation onward.
+      for (const p of node.ports) {
+        enqueueMates(nodeId, p.id, effectiveDelta)
+      }
+    } else {
+      const startPath = node.startPath!
+      const path = runPathFromPortDeltas(startPath, portDeltas)
+      results[nodeId] = { id: nodeId, data: { path } as Partial<AnyNode> }
+      for (const [nextPortId, nextDelta] of Object.entries(runEndpointDeltas(startPath, path))) {
+        if (lenSq(nextDelta) <= DELTA_EPS_M * DELTA_EPS_M) continue
+        enqueueMates(nodeId, nextPortId, nextDelta)
+      }
+    }
+  }
+
+  return Object.values(results)
 }

packages/core/src/store/actions/node-actions.ts

@@ -1,3 +1,4 @@
+import { nodeRegistry } from '../../registry/registry'
 import {
   type AnyNode,
   type AnyNodeId,
@@ -1010,6 +1011,24 @@ export const deleteNodesAction = (
     }
     for (const id of allIds) deletedIds.add(id)
 
+    // Let each deleted kind undo what it imposed on its neighbours (e.g. an
+    // auto-inserted elbow re-extends the duct runs it trimmed back onto the
+    // corner it replaced). Read against pre-deletion `nextNodes`; skip
+    // patches that target a node also being deleted.
+    for (const id of allIds) {
+      const node = nextNodes[id]
+      if (!node) continue
+      const onDelete = nodeRegistry.get(node.type)?.parametrics?.onDelete
+      if (!onDelete) continue
+      for (const { id: targetId, data } of onDelete(node, nextNodes)) {
+        if (allIds.has(targetId)) continue
+        const target = nextNodes[targetId]
+        if (!target) continue
+        nextNodes[targetId] = { ...target, ...data } as AnyNode
+        nodesToMarkDirty.add(targetId)
+      }
+    }
+
     for (const plan of mergePlans) {
       const primaryWall = nextNodes[plan.primaryWallId]
       if (!(primaryWall && primaryWall.type === 'wall') || allIds.has(plan.primaryWallId)) {

packages/core/src/store/use-scene.ts

@@ -547,9 +547,18 @@ function migrateNodes(nodes: Record<string, any>): {
   // any per-type migration runs, so already-saved scenes load cleanly.
   const { nodes: healed } = healSceneNodes(nodes)
   const patchedNodes = { ...healed } as Record<string, any>
+
   // Scene materials minted while moving legacy wall fields onto `node.slots`;
   // merged into the scene material map by the caller (`setScene`).
   const mintedMaterials: Record<SceneMaterialId, SceneMaterial> = {}
+
+  // Pass 1: all node types except elevator.
+  // Elevator migration (migrateElevatorParent) mutates level.children to remove
+  // the elevator ID. If the elevator is processed before its parent level in
+  // Object.entries order, the level migration in this same pass would then see
+  // a children array that still contains the elevator ID and filter it out as
+  // "missing" — corrupting the level. Running elevators in a second pass after
+  // all levels are stable avoids the race entirely.
   for (const [id, node] of Object.entries(patchedNodes)) {
     // 1. Item scale migration
     if (node.type === 'item' && !('scale' in node)) {
@@ -682,14 +691,6 @@ function migrateNodes(nodes: Record<string, any>): {
       )
     }
 
-    if (node.type === 'elevator') {
-      const parentMigrated = migrateElevatorParent(id, node, patchedNodes)
-      const normalized = normalizeElevatorNode(parentMigrated)
-      if (normalized) {
-        patchedNodes[id] = normalized
-      }
-    }
-
     // Roof-segment hosting was added in this migration cycle (the same
     // pattern as shelf above). Older segments saved before the schema
     // gained `children` need the field initialised so
@@ -778,7 +779,59 @@ function migrateNodes(nodes: Record<string, any>): {
         patchedNodes[id] = { ...node, children: flattened }
       }
     }
+
+    // Level children normalization.
+    // Pre-0.9.1 JSONs may carry child IDs that no longer exist in the node
+    // map (e.g. elevator IDs that lived under a level before the elevator
+    // parent migration moved them up to building). If those dangling IDs are
+    // left in place, collectReachableNodeIds marks the level as having
+    // reachable children that don't exist, which corrupts the scene graph
+    // traversal and leaves the LevelNode in a broken state — making floors
+    // impossible to drag or delete after import.
+    // We intentionally do NOT filter by type prefix here; being permissive
+    // about which types are allowed as children prevents data loss when new
+    // child types are added to the schema in the future.
+    if (node.type === 'level') {
+      const rawChildren = getStringArray(node.children)
+      const validChildren = rawChildren.filter((childId) => {
+        const exists = Boolean(patchedNodes[childId])
+        if (!exists) {
+          console.warn(
+            '[migrateNodes] level',
+            id,
+            'references missing child',
+            childId,
+            '— dropping',
+          )
+        }
+        return exists
+      })
+      const levelNumber = getFiniteNumber(node.level, 0)
+      patchedNodes[id] = {
+        ...node,
+        level: levelNumber,
+        children: validChildren,
+      }
+    }
   }
+
+  // Pass 2: elevator migration.
+  // migrateElevatorParent mutates the parent level's children array (removes
+  // the elevator ID from it). Running this after Pass 1 guarantees that the
+  // level normalization above has already seen a clean children list — if we
+  // ran elevator migration inside Pass 1, the order of Object.entries
+  // iteration would be non-deterministic: processing an elevator before its
+  // parent level would mutate the level's children mid-iteration, potentially
+  // causing the level branch above to see a stale node reference.
+  for (const [id, node] of Object.entries(patchedNodes)) {
+    if (node.type !== 'elevator') continue
+    const parentMigrated = migrateElevatorParent(id, node, patchedNodes)
+    const normalized = normalizeElevatorNode(parentMigrated)
+    if (normalized) {
+      patchedNodes[id] = normalized
+    }
+  }
+
   return { nodes: patchedNodes as Record<string, AnyNode>, mintedMaterials }
 }
 

packages/editor/src/components/editor/handles/handle-arrow.tsx

@@ -51,6 +51,13 @@ const CHEVRON_DEPTH = 0.08
 const CHEVRON_BEVEL_THICKNESS = 0.035
 const CHEVRON_BEVEL_SIZE = 0.03
 const CHEVRON_BEVEL_SEGMENTS = 10
+// Slimmer extrude profile matching the legacy wall side handles
+// (`wall-move-side-handles.tsx`) — opt-in via the `thin` prop so the chunkier
+// default is preserved for every other handle that uses the shared chevron.
+const CHEVRON_THIN_DEPTH = 0.045
+const CHEVRON_THIN_BEVEL_THICKNESS = 0.018
+const CHEVRON_THIN_BEVEL_SIZE = 0.02
+const CHEVRON_THIN_BEVEL_SEGMENTS = 8
 const MOVE_CROSS_HALF_LENGTH = 0.36
 const MOVE_CROSS_SHAFT_HALF_WIDTH = 0.03
 const MOVE_CROSS_HEAD_HALF_WIDTH = 0.12
@@ -64,7 +71,7 @@ const ROTATE_HANDLE_HALF_SWEEP = Math.PI / 3
 const ROTATE_RIBBON_HALF_WIDTH = 0.02
 const ROTATE_HEAD_HALF_WIDTH = 0.045
 const TRACKER_CUBE_SIZE = 0.16
-export const CORNER_HEX_RADIUS = 0.16
+export const CORNER_HEX_RADIUS = 0.11
 
 export type HandleArrowShape = 'chevron' | 'cross' | 'curved-arrow' | 'tracker' | 'corner-picker'
 export type HandleArrowInputShape = HandleArrowShape | 'arrow' | 'move-cross'
@@ -90,6 +97,8 @@ export type HandleArrowProps = {
   indicatorRotation?: readonly [number, number, number]
   onPointerEnter?: PointerHandler
   onPointerLeave?: PointerHandler
+  // Extrude the slimmer wall-handle chevron profile (chevron shape only).
+  thin?: boolean
 }
 
 function normalizeHandleArrowShape(shape: HandleArrowInputShape, cursor: Cursor): HandleArrowShape {
@@ -179,8 +188,9 @@ export function createRotateArrowHandleGeometry() {
 
 // Reused chevron+shaft silhouette. The chevron points along +X by default;
 // callers rotate it around Y for Z-axis handles and into a vertical frame for
-// Y-axis handles.
-export function createArrowHandleGeometry() {
+// Y-axis handles. `thin` extrudes the slimmer wall-handle profile.
+export function createArrowHandleGeometry(thin = false) {
+  const depth = thin ? CHEVRON_THIN_DEPTH : CHEVRON_DEPTH
   const shape = new Shape()
   shape.moveTo(CHEVRON_MAX_X, 0)
   shape.lineTo(CHEVRON_NOTCH_X, CHEVRON_HALF_WIDTH)
@@ -191,16 +201,16 @@ export function createArrowHandleGeometry() {
   shape.lineTo(CHEVRON_NOTCH_X, -CHEVRON_HALF_WIDTH)
   shape.lineTo(CHEVRON_MAX_X, 0)
   const geometry = new ExtrudeGeometry(shape, {
-    depth: CHEVRON_DEPTH,
+    depth,
     bevelEnabled: true,
-    bevelThickness: CHEVRON_BEVEL_THICKNESS,
-    bevelSize: CHEVRON_BEVEL_SIZE,
+    bevelThickness: thin ? CHEVRON_THIN_BEVEL_THICKNESS : CHEVRON_BEVEL_THICKNESS,
+    bevelSize: thin ? CHEVRON_THIN_BEVEL_SIZE : CHEVRON_BEVEL_SIZE,
     bevelOffset: 0,
-    bevelSegments: CHEVRON_BEVEL_SEGMENTS,
+    bevelSegments: thin ? CHEVRON_THIN_BEVEL_SEGMENTS : CHEVRON_BEVEL_SEGMENTS,
     curveSegments: 16,
     steps: 1,
   })
-  geometry.translate(0, 0, -CHEVRON_DEPTH / 2)
+  geometry.translate(0, 0, -depth / 2)
   geometry.rotateX(-Math.PI / 2)
   geometry.computeVertexNormals()
   geometry.computeBoundingSphere()
@@ -314,8 +324,8 @@ export function createEndpointHitAreaGeometry(radius: number) {
   return geometry
 }
 
-function createHandleArrowGeometry(shape: HandleArrowShape) {
-  if (shape === 'chevron') return createArrowHandleGeometry()
+function createHandleArrowGeometry(shape: HandleArrowShape, thin = false) {
+  if (shape === 'chevron') return createArrowHandleGeometry(thin)
   if (shape === 'cross') return createMoveCrossHandleGeometry()
   if (shape === 'curved-arrow') return createRotateArrowHandleGeometry()
   if (shape === 'tracker') {
@@ -459,9 +469,10 @@ export function HandleArrow({
   onPointerDown,
   onPointerEnter,
   onPointerLeave,
+  thin = false,
 }: HandleArrowProps) {
   const visualShape = normalizeHandleArrowShape(shape, cursor)
-  const geometry = useMemo(() => createHandleArrowGeometry(visualShape), [visualShape])
+  const geometry = useMemo(() => createHandleArrowGeometry(visualShape, thin), [visualShape, thin])
   const hitGeometry = useMemo(() => createHandleArrowHitGeometry(visualShape), [visualShape])
   const indicatorMaterial = useHandleArrowMaterial(visualShape)
   const hitMaterial = useInvisibleHitAreaMaterial()

packages/editor/src/components/editor/index.tsx

@@ -1147,6 +1147,7 @@ export default function Editor({
       <CeilingSystem />
       <RoofEditSystem />
       <StairEditSystem />
+      {isFirstPersonMode && <FirstPersonControls />}
       <CustomCameraControls />
       <ThumbnailGenerator onThumbnailCapture={onThumbnailCapture} />
       <InteractiveSystem />
@@ -1205,8 +1206,14 @@ export default function Editor({
 
         {!isLoading && isPreviewMode ? (
           <div className="dark flex h-full w-full flex-col bg-neutral-100 text-foreground">
-            <ViewerOverlay onBack={() => useEditor.getState().setPreviewMode(false)} />
-            <div className="h-full w-full">{previewViewerContent}</div>
+            {isFirstPersonMode ? (
+              <FirstPersonOverlay onExit={() => useEditor.getState().setFirstPersonMode(false)} />
+            ) : (
+              <ViewerOverlay onBack={() => useEditor.getState().setPreviewMode(false)} />
+            )}
+            <div className="h-full w-full" data-pascal-viewer-3d>
+              {previewViewerContent}
+            </div>
           </div>
         ) : (
           <>
@@ -1270,8 +1277,14 @@ export default function Editor({
 
       {!isLoading && isPreviewMode ? (
         <>
-          <ViewerOverlay onBack={() => useEditor.getState().setPreviewMode(false)} />
-          <div className="h-full w-full">{previewViewerContent}</div>
+          {isFirstPersonMode ? (
+            <FirstPersonOverlay onExit={() => useEditor.getState().setFirstPersonMode(false)} />
+          ) : (
+            <ViewerOverlay onBack={() => useEditor.getState().setPreviewMode(false)} />
+          )}
+          <div className="h-full w-full" data-pascal-viewer-3d>
+            {previewViewerContent}
+          </div>
         </>
       ) : (
         <>

packages/editor/src/components/editor/node-arrow-handles.tsx

@@ -9,6 +9,7 @@ import {
   DEFAULT_ANGLE_STEP,
   type HandleDescriptor,
   type HandlePortal,
+  type LatchHandle,
   type LinearResizeHandle,
   nodeRegistry,
   type RadialResizeHandle,
@@ -109,11 +110,16 @@ export {
   ARROW_COLOR,
   ARROW_HOVER_COLOR,
   ARROW_SCALE,
+  createArrowHandleGeometry,
   createArrowHitAreaGeometry,
   createEndpointHitAreaGeometry,
   createMoveCrossHandleGeometry,
   createRotateArrowHandleGeometry,
   createRotateArrowHitAreaGeometry,
+  HandleArrow,
+  type HandleArrowInputShape,
+  type HandleArrowPlacement,
+  type HandleArrowProps,
   HIT_AREA_MARGIN,
   InvisibleHandleHitArea,
   NO_RAYCAST,
@@ -369,6 +375,21 @@ function NodeArrowHandlesForNode({
   // hook count between renders and trip React's rules-of-hooks check.
   const [activeIndex, setActiveIndex] = useState<number | null>(null)
   const [preDragNode, setPreDragNode] = useState<AnyNode | null>(null)
+  // Latch groups currently toggled open. A `latch` cube descriptor flips its
+  // group here on click; arrows tagged with a `latchGroup` only render while
+  // their group is in this set. Local to this mount, so it resets on deselect
+  // (the rig remounts per selection — see the `key` on NodeArrowHandlesForNode).
+  const [openLatchGroups, setOpenLatchGroups] = useState<ReadonlySet<string>>(() => new Set())
+  const toggleLatchGroup = useMemo(
+    () => (group: string) =>
+      setOpenLatchGroups((prev) => {
+        const next = new Set(prev)
+        if (next.has(group)) next.delete(group)
+        else next.add(group)
+        return next
+      }),
+    [],
+  )
   const dragControls = useMemo<HandleDragControls>(
     () => ({
       onStart: (index: number, snapshot: AnyNode) => {
@@ -399,21 +420,36 @@ function NodeArrowHandlesForNode({
   // here, or they'd lag behind the moving item.
   const activeIsTranslate = activeIndex !== null && descriptors[activeIndex]?.kind === 'translate'
 
-  const arrows = descriptors.map((descriptor, index) => (
-    <ArrowHandle
-      activeIndex={activeIndex}
-      descriptor={descriptor}
-      dragControls={dragControls}
-      handleIndex={index}
-      // Descriptors come from a per-node-kind static list, so index is a
-      // stable identity within this node's selection cycle.
-      key={index}
-      liveNode={node}
-      preDragNode={preDragNode}
-      rideObject={arrowFrame}
-      suppressFreeze={activeIsTranslate}
-    />
-  ))
+  const arrows = descriptors.map((descriptor, index) => {
+    // A `latch` cube toggles its group's visibility; render it always.
+    if (descriptor.kind === 'latch') {
+      return (
+        <LatchCube
+          descriptor={descriptor}
+          key={index}
+          node={node}
+          onToggle={toggleLatchGroup}
+          open={openLatchGroups.has(descriptor.group)}
+        />
+      )
+    }
+    // Arrows tagged with a latch group stay hidden until that group is open.
+    const latchGroup = descriptor.kind === 'linear-resize' ? descriptor.latchGroup : undefined
+    if (latchGroup && !openLatchGroups.has(latchGroup)) return null
+    return (
+      <ArrowHandle
+        activeIndex={activeIndex}
+        descriptor={descriptor}
+        dragControls={dragControls}
+        handleIndex={index}
+        key={index}
+        liveNode={node}
+        preDragNode={preDragNode}
+        rideObject={arrowFrame}
+        suppressFreeze={activeIsTranslate}
+      />
+    )
+  })
 
   return createPortal(
     <group ref={outerRef}>
@@ -668,6 +704,11 @@ function LinearArrow({
               ? 1
               : -1
 
+      // Last value an emitted resize tick fired at — a new tick fires only
+      // when the (snapped + clamped) value actually changes, so the cue
+      // tracks real size steps instead of every sub-pixel pointer jitter.
+      let lastTickValue = initialValue
+
       return {
         overrideId,
         onBegin: () => {
@@ -695,6 +736,10 @@ function LinearArrow({
               ? snapScalar(rawNext, gridSnapStep)
               : rawNext
           const next = Math.min(maxBound, Math.max(minBound, snappedNext))
+          if (next !== lastTickValue) {
+            lastTickValue = next
+            sfxEmitter.emit('sfx:resize')
+          }
           const patch = descriptor.apply(initialNode as never, next, sceneApi) as Partial<AnyNode>
           // Let the kind publish live guides for the edge being resized.
           onDrag?.({ ...(initialNode as object), ...patch } as AnyNode, sceneApi)
@@ -708,10 +753,19 @@ function LinearArrow({
   // X+Z rotation chain matching DoorHeightArrowHandle. When the handle
   // sits below the node (placement Y < 0, e.g. window bottom arrow),
   // flip the Z rotation so the chevron points outward (downward).
+  //
+  // For axis === 'x' with `faceNormal` (wall-mounted opening width arrows),
+  // roll the blade 90° about its own pointing (X) axis so it stands up from
+  // the horizontal XZ plane into the node's facing plane (XY = the wall
+  // face) — otherwise the blade is seen edge-on from the front.
+  const faceNormalX =
+    descriptor.kind === 'linear-resize' && descriptor.axis === 'x' && descriptor.faceNormal === true
   const innerRotation: [number, number, number] =
     descriptor.axis === 'y'
       ? [0, Math.PI / 2, position[1] < 0 ? -Math.PI / 2 : Math.PI / 2]
-      : [0, 0, 0]
+      : faceNormalX
+        ? [Math.PI / 2, 0, 0]
+        : [0, 0, 0]
 
   // Optional guide decoration — linear handles use it for curved-stair
   // width / inner-radius rings; radial handles use it for the column's
@@ -797,6 +851,7 @@ function LinearArrow({
         onPointerDown={activate}
         placement={{ position, rotation: [0, rotationY, 0], baseScale }}
         shape="chevron"
+        thin
       >
         {showLabel ? <DimensionLabel position={[0, 0.22, 0]} text={labelText} /> : null}
       </HandleArrow>
@@ -1192,6 +1247,7 @@ function ArcArrow({
           baseScale,
         }}
         shape={isRotateShape ? 'curved-arrow' : 'chevron'}
+        thin
       />
     </>
   )
@@ -1314,6 +1370,56 @@ function TapActionArrow({
       onPointerDown={onActivate}
       placement={{ position, rotation, baseScale }}
       shape={shape === 'move-cross' ? 'move-cross' : 'chevron'}
+      thin
+    />
+  )
+}
+
+// Click-to-latch cube. A persistent grip (the `tracker` cube) that toggles
+// the visibility of every arrow tagged with its `latchGroup` on click. Sized
+// to match the duct selection cube (`baseScale = zoom`, full TRACKER_CUBE_SIZE)
+// so every latch grip reads the same across the app. Stays highlighted while
+// its group is open so the user can tell it's engaged.
+function LatchCube({
+  descriptor,
+  node,
+  open,
+  onToggle,
+}: {
+  descriptor: LatchHandle<AnyNode>
+  node: AnyNode
+  open: boolean
+  onToggle: (group: string) => void
+}) {
+  const [isHovered, setIsHovered] = useState(false)
+  const { camera } = useThree()
+  const zoom = camera instanceof OrthographicCamera ? 1 / camera.zoom : 1
+  const baseScale = zoom
+
+  const placementSceneApi = useMemo(() => createSceneApi(useScene), [])
+  const position = descriptor.placement.position(node, placementSceneApi)
+  const rotationY = descriptor.placement.rotationY?.(node, placementSceneApi) ?? 0
+
+  // Route through the shared tap path so the cube click is swallowed before it
+  // reaches the select tool — stops R3F propagation, suppresses box-select, and
+  // eats the trailing DOM click that would otherwise select the host node.
+  const onPointerDown = useHandleDrag({
+    kind: 'tap',
+    onTap: () => {
+      setIsHovered(false)
+      onToggle(descriptor.group)
+    },
+  })
+
+  return (
+    <HandleArrow
+      cursor="grab"
+      hover={isHovered || open}
+      hoverScale={1.15}
+      onHoverChange={setIsHovered}
+      onPointerDown={onPointerDown}
+      placement={{ position, rotation: [0, rotationY, 0], baseScale }}
+      shape="tracker"
     />
   )
 }

packages/editor/src/components/editor/wall-move-side-handles.tsx

@@ -54,7 +54,7 @@ const ARROW_HOVER_COLOR = '#a5b4fc'
 // Match the door arrows: scale the rendered chevron down to ~two-thirds
 // so the in-world handles read as a single UI family.
 const ARROW_SCALE = 0.65
-const CORNER_HEX_RADIUS = 0.16
+const CORNER_HEX_RADIUS = 0.11
 const CORNER_DASH_SIZE = 0.1
 const CORNER_GAP_SIZE = 0.07
 const CORNER_DASH_THICKNESS = 0.006

packages/editor/src/components/tools/shared/cursor-sphere.tsx

@@ -12,12 +12,28 @@ interface CursorSphereProps extends Omit<ThreeElements['group'], 'ref'> {
   depthWrite?: boolean
   showTooltip?: boolean
   height?: number
+  /**
+   * Put the bright marker dot at the TIP of the vertical line (y = height)
+   * instead of on the ground ring. Used when the point being placed hangs
+   * above the floor (e.g. duct drawn against the ceiling): the dot rides at
+   * the cursor / placement point while the line drops to a floor ring that
+   * keeps the plan position readable.
+   */
+  dotAtTip?: boolean
   /** Custom tooltip content — overrides the auto-detected build tool icon */
   tooltipContent?: React.ReactNode
 }
 
 export const CursorSphere = forwardRef<Group, CursorSphereProps>(function CursorSphere(
-  { color = '#818cf8', showTooltip = true, height = 2.5, visible = true, tooltipContent, ...props },
+  {
+    color = '#818cf8',
+    showTooltip = true,
+    height = 2.5,
+    dotAtTip = false,
+    visible = true,
+    tooltipContent,
+    ...props
+  },
   ref,
 ) {
   const tool = useEditor((s) => s.tool)
@@ -39,19 +55,23 @@ export const CursorSphere = forwardRef<Group, CursorSphereProps>(function Cursor
 
   return (
     <group ref={ref} {...props} visible={isVisible}>
-      {/* Flat marker on the ground */}
+      {/* Flat marker on the ground. The bright center dot moves to the tip
+          of the line in `dotAtTip` mode (the placement point hangs above the
+          floor), leaving a faint ring here so the plan position stays read. */}
       <group rotation={[-Math.PI / 2, 0, 0]}>
-        {/* Center dot */}
-        <mesh layers={EDITOR_LAYER} renderOrder={2}>
-          <circleGeometry args={[0.06, 32]} />
-          <meshBasicMaterial
-            color={color}
-            depthTest={false}
-            depthWrite={false}
-            opacity={0.9}
-            transparent
-          />
-        </mesh>
+        {/* Center dot — at the ground unless the placement point is elevated */}
+        {!dotAtTip && (
+          <mesh layers={EDITOR_LAYER} renderOrder={2}>
+            <circleGeometry args={[0.06, 32]} />
+            <meshBasicMaterial
+              color={color}
+              depthTest={false}
+              depthWrite={false}
+              opacity={0.9}
+              transparent
+            />
+          </mesh>
+        )}
 
         {/* Outer ring / glow */}
         <mesh layers={EDITOR_LAYER} renderOrder={2}>
@@ -60,7 +80,7 @@ export const CursorSphere = forwardRef<Group, CursorSphereProps>(function Cursor
             color={color}
             depthTest={false}
             depthWrite={false}
-            opacity={0.25}
+            opacity={dotAtTip ? 0.2 : 0.25}
             transparent
           />
         </mesh>
@@ -80,6 +100,15 @@ export const CursorSphere = forwardRef<Group, CursorSphereProps>(function Cursor
         </mesh>
       )}
 
+      {/* Bright marker dot at the tip of the line — the actual placement
+          point, riding at the cursor while the line drops to the floor. */}
+      {dotAtTip && height > 0 && (
+        <mesh layers={EDITOR_LAYER} position={[0, height, 0]} renderOrder={2}>
+          <sphereGeometry args={[0.08, 20, 14]} />
+          <meshBasicMaterial color={color} depthTest={false} depthWrite={false} />
+        </mesh>
+      )}
+
       {/* Tool Icon Tooltip at the top of the line */}
       {isVisible && showTooltip && (activeToolConfig || tooltipContent) && (
         <Html

packages/editor/src/components/ui/command-palette/editor-commands.tsx

@@ -245,10 +245,10 @@ export function EditorCommands() {
         label: 'Wall Mode',
         group: 'Viewer Controls',
         icon: <Layers className="h-4 w-4" />,
-        keywords: ['wall', 'cutaway', 'up', 'down', 'view'],
+        keywords: ['wall', 'cutaway', 'up', 'down', 'translucent', 'view'],
         badge: () => {
           const mode = useViewer.getState().wallMode
-          return { cutaway: 'Cutaway', up: 'Up', down: 'Down' }[mode]
+          return { cutaway: 'Cutaway', up: 'Up', down: 'Down', translucent: 'Translucent' }[mode]
         },
         navigate: true,
         execute: () => navigateTo('wall-mode'),

packages/editor/src/components/ui/command-palette/index.tsx

@@ -244,10 +244,11 @@ export function CommandPalette({ emptyAction }: { emptyAction?: CommandPaletteEm
     setOpen(false)
   }
 
-  const wallModeLabel: Record<'cutaway' | 'up' | 'down', string> = {
+  const wallModeLabel: Record<'cutaway' | 'up' | 'down' | 'translucent', string> = {
     cutaway: 'Cutaway',
     up: 'Up',
     down: 'Down',
+    translucent: 'Translucent',
   }
   const levelModeLabel: Record<'manual' | 'stacked' | 'exploded' | 'solo', string> = {
     manual: 'Manual',
@@ -373,7 +374,7 @@ export function CommandPalette({ emptyAction }: { emptyAction?: CommandPaletteEm
               {/* ── Wall Mode sub-page ────────────────────────────────────── */}
               {page === 'wall-mode' && (
                 <Command.Group heading="Wall Mode">
-                  {(['cutaway', 'up', 'down'] as const).map((mode) => (
+                  {(['cutaway', 'up', 'down', 'translucent'] as const).map((mode) => (
                     <OptionItem
                       isActive={wallMode === mode}
                       key={mode}

packages/editor/src/components/ui/helpers/helper-manager.tsx

@@ -72,17 +72,23 @@ export function HelperManager() {
         .filter((node): node is AnyNode => node !== undefined),
     ),
   )
-  const selectModeHints = useMemo(
-    () =>
-      resolveSelectModeHelpHints({
-        selectedCount: selectedNodes.length,
-        hasMovableSelection: selectedNodes.some((node) => canDirectMoveNode(node)),
-        hasRotatableSelection: selectedNodes.some((node) => canDirectRotateNode(node)),
-        commandPressed: modifiers.command,
-        shiftPressed: modifiers.shift,
-      }),
-    [modifiers.command, modifiers.shift, selectedNodes],
-  )
+  const selectModeHints = useMemo(() => {
+    const single = selectedNodes.length === 1 ? selectedNodes[0] : null
+    const mepSelection =
+      single?.type === 'duct-segment' || single?.type === 'pipe-segment'
+        ? 'run'
+        : single?.type === 'duct-fitting' || single?.type === 'pipe-fitting'
+          ? 'fitting'
+          : null
+    return resolveSelectModeHelpHints({
+      selectedCount: selectedNodes.length,
+      hasMovableSelection: selectedNodes.some((node) => canDirectMoveNode(node)),
+      hasRotatableSelection: selectedNodes.some((node) => canDirectRotateNode(node)),
+      commandPressed: modifiers.command,
+      shiftPressed: modifiers.shift,
+      mepSelection,
+    })
+  }, [modifiers.command, modifiers.shift, selectedNodes])
 
   // Helpers are keyboard-driven hints (Esc, R, etc.) — irrelevant on touch.
   if (isMobile) return null

packages/editor/src/components/viewer-overlay.tsx

@@ -25,6 +25,7 @@ import {
   Check,
   ChevronRight,
   Diamond,
+  Footprints,
   Layers,
   Palette,
   PenLine,
@@ -32,8 +33,10 @@ import {
   Square,
 } from 'lucide-react'
 import Link from 'next/link'
+import { flushSync } from 'react-dom'
 import { useShallow } from 'zustand/react/shallow'
 import { cn } from '../lib/utils'
+import useEditor from '../store/use-editor'
 import { ActionButton } from './ui/action-menu/action-button'
 import {
   DropdownMenu,
@@ -51,6 +54,24 @@ type ProjectOwner = {
   image: string | null
 }
 
+function requestWalkthroughPointerLock() {
+  const canvas = document.querySelector<HTMLCanvasElement>('[data-pascal-viewer-3d] canvas')
+  if (!canvas) return
+
+  if (!canvas.hasAttribute('tabindex')) {
+    canvas.tabIndex = -1
+  }
+  canvas.focus({ preventScroll: true })
+
+  if (document.pointerLockElement === canvas) return
+
+  try {
+    canvas.requestPointerLock?.()
+  } catch {
+    return
+  }
+}
+
 const levelModeLabels: Record<'stacked' | 'exploded' | 'solo', string> = {
   stacked: 'Stacked',
   exploded: 'Exploded',
@@ -83,6 +104,12 @@ const wallModeConfig = {
     ),
     label: 'Low',
   },
+  translucent: {
+    icon: (props: any) => (
+      <img alt="Translucent" height={28} src="/icons/wall.png" width={28} {...props} />
+    ),
+    label: 'Translucent',
+  },
 }
 
 const SHADING_OPTIONS = [
@@ -580,7 +607,12 @@ export const ViewerOverlay = ({
               }
               label={`Walls: ${wallModeConfig[wallMode as keyof typeof wallModeConfig].label}`}
               onClick={() => {
-                const modes: ('cutaway' | 'up' | 'down')[] = ['cutaway', 'up', 'down']
+                const modes: ('cutaway' | 'up' | 'down' | 'translucent')[] = [
+                  'cutaway',
+                  'up',
+                  'down',
+                  'translucent',
+                ]
                 const nextIndex = (modes.indexOf(wallMode as any) + 1) % modes.length
                 useViewer.getState().setWallMode(modes[nextIndex] ?? 'cutaway')
               }}
@@ -641,6 +673,23 @@ export const ViewerOverlay = ({
                 src="/icons/topview.webp"
               />
             </ActionButton>
+
+            <div className="mx-1 h-5 w-px bg-border/40" />
+
+            {/* First-person walkthrough */}
+            <ActionButton
+              className="hover:bg-white/5 hover:text-emerald-400"
+              label="Walkthrough"
+              onClick={() => {
+                flushSync(() => useEditor.getState().setFirstPersonMode(true))
+                requestWalkthroughPointerLock()
+              }}
+              size="icon"
+              tooltipSide="top"
+              variant="ghost"
+            >
+              <Footprints className="h-6 w-6" />
+            </ActionButton>
           </div>
         </TooltipProvider>
       </div>

packages/editor/src/index.tsx

@@ -40,7 +40,27 @@ export {
   formatMeasurement,
   MeasurementPill,
 } from './components/editor/measurement-pill'
-export { NodeArrowHandles } from './components/editor/node-arrow-handles'
+// In-world arrow handle primitives (chevron geometry, invisible hit area,
+// shared material, palette + scale constants). Re-exported so kind-owned
+// 3D selection affordances in `@pascal-app/nodes` (duct side-move / height /
+// extend arrows) reuse the same UI family as the wall / fence side handles.
+export {
+  ARROW_COLOR,
+  ARROW_HOVER_COLOR,
+  ARROW_SCALE,
+  createArrowHandleGeometry,
+  createArrowHitAreaGeometry,
+  HandleArrow,
+  type HandleArrowInputShape,
+  type HandleArrowPlacement,
+  type HandleArrowProps,
+  InvisibleHandleHitArea,
+  NO_RAYCAST,
+  NodeArrowHandles,
+  swallowNextClick,
+  useArrowMaterial,
+  useInvisibleHitAreaMaterial,
+} from './components/editor/node-arrow-handles'
 export {
   type SnapshotCameraData,
   ThumbnailGenerator,

packages/editor/src/lib/contextual-help.ts

@@ -10,12 +10,19 @@ export type SelectModeHelpContext = {
   hasRotatableSelection: boolean
   commandPressed: boolean
   shiftPressed: boolean
+  // When a single MEP node is selected its in-world handle rig (click a dot to
+  // reveal move arrows) is the real editing path, so the panel leads with the
+  // handle-specific hints instead of just the generic Cmd-drag tips.
+  mepSelection?: 'run' | 'fitting' | null
 }
 
 const COMMAND_KEY = 'Cmd/Ctrl'
 const LEFT_CLICK = 'Left click'
 const RIGHT_CLICK = 'Right click'
 const SHIFT_KEY = 'Shift'
+const CLICK = 'Click'
+const ALT_KEY = 'Alt'
+const ROTATE_KEYS = 'R / T'
 
 export function resolveSelectModeHelpHints({
   selectedCount,
@@ -23,6 +30,7 @@ export function resolveSelectModeHelpHints({
   hasRotatableSelection,
   commandPressed,
   shiftPressed,
+  mepSelection = null,
 }: SelectModeHelpContext): ContextualShortcutHint[] {
   const hints: ContextualShortcutHint[] = []
 
@@ -37,6 +45,20 @@ export function resolveSelectModeHelpHints({
     return hints
   }
 
+  // MEP handle workflow — duct/pipe runs and fittings are edited through the
+  // in-world arrow rig that a click on the handle dot reveals, so surface those
+  // hints first. A run endpoint's side / up-down arrows swing the run and Alt
+  // detaches the joint mid-drag; a fitting's cluster adds rotate arcs, with
+  // R / T (and Alt to switch axis) for keyboard rotation.
+  if (mepSelection === 'run') {
+    hints.push({ keys: [CLICK], label: 'Click a handle dot to show move arrows' })
+    hints.push({ keys: [ALT_KEY], label: 'Detach the joint while dragging an arrow' })
+  } else if (mepSelection === 'fitting') {
+    hints.push({ keys: [CLICK], label: 'Click the handle dot to show move + rotate handles' })
+    hints.push({ keys: [ROTATE_KEYS], label: 'Rotate ±45°' })
+    hints.push({ keys: [ALT_KEY], label: 'Switch the rotation axis (Y → X → Z)' })
+  }
+
   if (commandPressed) {
     if (hasMovableSelection) {
       hints.push({

packages/editor/src/lib/sfx-bus.ts

@@ -10,6 +10,7 @@ type SFXEvents = {
   'sfx:item-pick': undefined
   'sfx:item-place': undefined
   'sfx:item-rotate': undefined
+  'sfx:resize': undefined
   'sfx:structure-build-start': undefined
   'sfx:structure-build': undefined
   'sfx:structure-delete': undefined
@@ -40,6 +41,7 @@ export function initSFXBus() {
   sfxEmitter.on('sfx:item-pick', () => playSFX('itemPick'))
   sfxEmitter.on('sfx:item-place', () => playSFX('itemPlace'))
   sfxEmitter.on('sfx:item-rotate', () => playSFX('itemRotate'))
+  sfxEmitter.on('sfx:resize', () => playSFX('resize'))
   sfxEmitter.on('sfx:structure-build-start', () => playSFX('structureBuildStart'))
   sfxEmitter.on('sfx:structure-build', () => playSFX('structureBuildEnd'))
   sfxEmitter.on('sfx:structure-delete', () => playSFX('structureDelete'))

packages/editor/src/lib/sfx-player.ts

@@ -59,6 +59,16 @@ export const SFX: Record<string, SFXConfig> = {
     volumeRange: [0.92, 1.0],
     panJitter: 0.15,
   },
+  // Ticks as a resize handle is dragged across snap steps. Fires in rapid
+  // succession, so it mirrors gridSnap: three variations cycled round-robin
+  // with pitch/pan jitter and a gap so the run reads as texture, not a tone.
+  resize: {
+    src: ['/audios/sfx/resize_0.mp3', '/audios/sfx/resize_1.mp3', '/audios/sfx/resize_2.mp3'],
+    rateRange: [0.98, 1.02],
+    volumeRange: [0.26, 0.34],
+    panJitter: 0.15,
+    minIntervalMs: 80,
+  },
   // Fired when a structure draft begins (first click of a wall/slab/etc).
   structureBuildStart: {
     src: '/audios/sfx/structure_build_start.mp3',

packages/nodes/src/box-vent/move-tool.tsx

@@ -5,6 +5,7 @@ import {
   type BoxVentNode,
   emitter,
   type RoofEvent,
+  type RoofNode,
   type RoofSegmentNode,
   sceneRegistry,
   useScene,
@@ -21,8 +22,14 @@ import {
   createRelativeRoofDrag,
   type RelativeRoofDragTarget,
   roofSegmentLocalToBuildingLocal,
+  snapRelativeRoofDragTarget,
 } from '../shared/relative-roof-drag'
 import { getAnalyticalNormal, surfaceQuatFromNormal } from '../shared/roof-surface'
+import {
+  clearRoofSurfacePlacementGuides,
+  publishRoofSurfaceNodePlacementGuides,
+  snapRoofSurfaceNodeTarget,
+} from '../shared/roof-surface-placement-guides'
 import BoxVentPreview from './preview'
 
 /**
@@ -72,10 +79,21 @@ export default function MoveBoxVentTool({ node }: { node: BoxVentNode }) {
       lastSnap = null
       setPreviewPos(null)
       setPreviewSurfaceQuat(null)
+      clearRoofSurfacePlacementGuides()
+    }
+
+    const resolveSnappedTarget = (event: RoofEvent): RelativeRoofDragTarget | null => {
+      const rawTarget = roofDrag.resolve(event)
+      if (!rawTarget) return null
+      return snapRoofSurfaceNodeTarget({
+        target: snapRelativeRoofDragTarget(rawTarget, event.nativeEvent?.shiftKey === true),
+        node,
+        bypass: event.nativeEvent?.shiftKey === true,
+      })
     }
 
     const updatePreview = (event: RoofEvent) => {
-      const target = roofDrag.resolve(event)
+      const target = resolveSnappedTarget(event)
       if (!target) {
         clearTarget()
         return
@@ -102,12 +120,18 @@ export default function MoveBoxVentTool({ node }: { node: BoxVentNode }) {
           target.localZ,
         ]),
       )
+      publishRoofSurfaceNodePlacementGuides({
+        roof: event.node as RoofNode,
+        segment: target.segment,
+        center: [target.localX, target.localY, target.localZ],
+        node,
+      })
       event.stopPropagation()
     }
 
     const onRoofClick = (event: RoofEvent) => {
       if (committed) return
-      const target = lastTarget ?? roofDrag.resolve(event)
+      const target = lastTarget ?? resolveSnappedTarget(event)
       if (!target) return
       committed = true
       const targetSegmentId = target.segment.id as AnyNodeId
@@ -152,6 +176,7 @@ export default function MoveBoxVentTool({ node }: { node: BoxVentNode }) {
       if (obj) obj.visible = true
 
       triggerSFX('sfx:item-place')
+      clearRoofSurfacePlacementGuides()
       exitMoveMode()
       event.stopPropagation()
     }
@@ -172,6 +197,7 @@ export default function MoveBoxVentTool({ node }: { node: BoxVentNode }) {
         useScene.getState().deleteNode(node.id as AnyNodeId)
         useScene.temporal.getState().resume()
         markToolCancelConsumed()
+        clearRoofSurfacePlacementGuides()
         exitMoveMode()
         return
       }
@@ -191,6 +217,7 @@ export default function MoveBoxVentTool({ node }: { node: BoxVentNode }) {
 
       useScene.temporal.getState().resume()
       markToolCancelConsumed()
+      clearRoofSurfacePlacementGuides()
       exitMoveMode()
     }
 
@@ -223,6 +250,7 @@ export default function MoveBoxVentTool({ node }: { node: BoxVentNode }) {
       // the original mesh visible rather than stranded invisible.
       const obj = sceneRegistry.nodes.get(node.id)
       if (obj) obj.visible = true
+      clearRoofSurfacePlacementGuides()
       useScene.temporal.getState().resume()
     }
   }, [exitMoveMode, node])

packages/nodes/src/box-vent/tool.tsx

@@ -16,6 +16,11 @@ import * as THREE from 'three'
 import { RoofAttachmentFallbackPreview } from '../shared/roof-attachment-fallback-preview'
 import { resolveRoofSegmentHit } from '../shared/roof-segment-hit'
 import { getAnalyticalNormal, getDownSlopeYaw, surfaceQuatFromNormal } from '../shared/roof-surface'
+import {
+  clearRoofSurfacePlacementGuides,
+  publishRoofSurfacePlacementGuides,
+  roofSurfaceFootprintFromNode,
+} from '../shared/roof-surface-placement-guides'
 import { boxVentDefinition } from './definition'
 import BoxVentPreview from './preview'
 
@@ -85,6 +90,15 @@ const BoxVentTool = () => {
       setPreviewYaw((event.node.rotation ?? 0) + (hit.segment.rotation ?? 0))
       setPreviewRotation(getDownSlopeYaw(hit.localX, hit.localZ, hit.segment))
       setPreviewPos(worldToBuildingLocal(wx, wy, wz))
+      publishRoofSurfacePlacementGuides({
+        roof: event.node as RoofNode,
+        segment: hit.segment,
+        center: [hit.localX, hit.localY, hit.localZ],
+        footprint: roofSurfaceFootprintFromNode({
+          ...previewNode,
+          rotation: getDownSlopeYaw(hit.localX, hit.localZ, hit.segment),
+        }),
+      })
       event.stopPropagation()
     }
 
@@ -109,6 +123,7 @@ const BoxVentTool = () => {
       state.dirtyNodes.add(hit.segment.id as AnyNodeId)
       setSelection({ selectedIds: [vent.id] })
       triggerSFX('sfx:item-place')
+      clearRoofSurfacePlacementGuides()
       event.stopPropagation()
     }
 
@@ -120,8 +135,9 @@ const BoxVentTool = () => {
       emitter.off('roof:move', updatePreview)
       emitter.off('roof:enter', updatePreview)
       emitter.off('roof:click', onClick)
+      clearRoofSurfacePlacementGuides()
     }
-  }, [activeBuildingId, setSelection])
+  }, [activeBuildingId, setSelection, previewNode])
 
   return (
     <>
@@ -131,6 +147,7 @@ const BoxVentTool = () => {
         onInvalidTarget={() => {
           setPreviewPos(null)
           setPreviewSurfaceQuat(null)
+          clearRoofSurfacePlacementGuides()
         }}
       />
       {activeBuildingId && previewPos && previewSurfaceQuat && (

packages/nodes/src/chimney/move-tool.tsx

@@ -10,11 +10,25 @@ import {
   sceneRegistry,
   useScene,
 } from '@pascal-app/core'
-import { consumePlacementDragRelease, triggerSFX, useEditor } from '@pascal-app/editor'
+import {
+  consumePlacementDragRelease,
+  markToolCancelConsumed,
+  triggerSFX,
+  useEditor,
+} from '@pascal-app/editor'
 import { useViewer } from '@pascal-app/viewer'
 import { useEffect, useMemo, useRef, useState } from 'react'
 import * as THREE from 'three'
-import { createRelativeRoofDrag, type RelativeRoofDragTarget } from '../shared/relative-roof-drag'
+import {
+  createRelativeRoofDrag,
+  type RelativeRoofDragTarget,
+  snapRelativeRoofDragTarget,
+} from '../shared/relative-roof-drag'
+import {
+  clearRoofSurfacePlacementGuides,
+  publishRoofSurfaceNodePlacementGuides,
+  snapRoofSurfaceNodeTarget,
+} from '../shared/roof-surface-placement-guides'
 import ChimneyPreview from './preview'
 
 const tmpMatrix = new THREE.Matrix4()
@@ -67,6 +81,25 @@ const MoveChimneyTool = ({ node }: { node: ChimneyNode }) => {
 
   useEffect(() => {
     if (!activeBuildingId) return
+    useScene.temporal.getState().pause()
+
+    const original = {
+      position: [...node.position] as [number, number, number],
+      rotation: node.rotation ?? 0,
+      roofSegmentId: node.roofSegmentId,
+      parentId: node.parentId,
+      metadata: node.metadata,
+    }
+    const meta =
+      node.metadata && typeof node.metadata === 'object' && !Array.isArray(node.metadata)
+        ? (node.metadata as Record<string, unknown>)
+        : {}
+    const isNew = !!meta.isNew
+
+    if (node.id) {
+      const chimneyObj = sceneRegistry.nodes.get(node.id)
+      if (chimneyObj) chimneyObj.visible = false
+    }
 
     const computeSegmentXform = (segmentId: string): SegmentTransform | null => {
       const buildingObj = sceneRegistry.nodes.get(activeBuildingId as AnyNodeId)
@@ -84,25 +117,33 @@ const MoveChimneyTool = ({ node }: { node: ChimneyNode }) => {
     }
 
     let lastTarget: RelativeRoofDragTarget | null = null
+    let committed = false
     const roofDrag = createRelativeRoofDrag({
-      position: [...node.position] as [number, number, number],
-      roofSegmentId: node.roofSegmentId,
+      position: original.position,
+      roofSegmentId: original.roofSegmentId,
     })
 
+    const resolveSnappedTarget = (event: RoofEvent): RelativeRoofDragTarget | null => {
+      const rawTarget = roofDrag.resolve(event)
+      if (!rawTarget) return null
+      return snapRoofSurfaceNodeTarget({
+        target: snapRelativeRoofDragTarget(rawTarget, event.nativeEvent?.shiftKey === true),
+        node,
+        bypass: event.nativeEvent?.shiftKey === true,
+      })
+    }
+
     const clearTarget = () => {
       lastTarget = null
       setSegmentXform(null)
       setHitLocal(null)
       setPreviewSegment(null)
+      clearRoofSurfacePlacementGuides()
     }
 
     const updatePreview = (event: RoofEvent) => {
-      const target = roofDrag.resolve(event)
-      if (!target) {
-        clearTarget()
-        return
-      }
-      lastTarget = target
+      const target = resolveSnappedTarget(event)
+      if (!target) return clearTarget()
 
       const sx = Math.round(target.localX * 20) / 20
       const sz = Math.round(target.localZ * 20) / 20
@@ -113,26 +154,32 @@ const MoveChimneyTool = ({ node }: { node: ChimneyNode }) => {
       }
 
       const xform = computeSegmentXform(target.segment.id)
-      if (!xform) return
+      if (!xform) return clearTarget()
+      lastTarget = target
       setSegmentXform(xform)
       setHitLocal([target.localX, target.localY, target.localZ])
       setPreviewSegment(target.segment)
+      publishRoofSurfaceNodePlacementGuides({
+        roof: event.node,
+        segment: target.segment,
+        center: [target.localX, target.localY, target.localZ],
+        node,
+      })
       event.stopPropagation()
     }
 
     const onClick = (event: RoofEvent) => {
-      const target = lastTarget ?? roofDrag.resolve(event)
+      if (committed) return
+      const target = lastTarget ?? resolveSnappedTarget(event)
       if (!target) return
+      committed = true
       const state = useScene.getState()
 
       // Strip the `isNew` flag — only used to mark a duplicate clone
       // that hasn't been committed yet.
-      const meta =
-        node.metadata && typeof node.metadata === 'object' && !Array.isArray(node.metadata)
-          ? (node.metadata as Record<string, unknown>)
-          : {}
       const { isNew, ...restMeta } = meta as { isNew?: boolean }
       const cleanedMeta = Object.keys(restMeta).length > 0 ? restMeta : undefined
+      const targetSegmentId = target.segment.id as AnyNodeId
 
       // Duplicate (clone with no committed id yet) → create a fresh
       // chimney parented to the hit segment. Plain move (existing id,
@@ -143,29 +190,105 @@ const MoveChimneyTool = ({ node }: { node: ChimneyNode }) => {
           ...node,
           id: undefined as never,
           roofSegmentId: target.segment.id,
+          parentId: target.segment.id,
           position: [target.localX, target.localY, target.localZ],
+          visible: true,
           metadata: cleanedMeta,
         })
-        state.createNode(committed, target.segment.id as AnyNodeId)
-        state.dirtyNodes.add(target.segment.id as AnyNodeId)
+        useScene.temporal.getState().resume()
+        state.applyNodeChanges({
+          delete: node.id ? [node.id as AnyNodeId] : [],
+          create: [{ node: committed, parentId: targetSegmentId }],
+        })
+        state.dirtyNodes.add(targetSegmentId)
         setSelection({ selectedIds: [committed.id] })
+        useScene.temporal.getState().pause()
       } else {
-        const prevSegmentId = node.roofSegmentId as AnyNodeId | undefined
+        const prevSegmentId = original.roofSegmentId as AnyNodeId | undefined
+        const reparenting = Boolean(prevSegmentId && prevSegmentId !== targetSegmentId)
+        // Resume BEFORE any scene edits so the reparent (both segments'
+        // children arrays + the chimney's own host/position update) lands as
+        // one tracked transaction. Otherwise undo reverts the chimney but
+        // leaves the children arrays inconsistent with its parentId.
+        useScene.temporal.getState().resume()
+        if (reparenting) {
+          const oldSeg = state.nodes[prevSegmentId!] as RoofSegmentNode | undefined
+          if (oldSeg) {
+            state.updateNode(prevSegmentId!, {
+              children: (oldSeg.children ?? []).filter((id) => id !== node.id),
+            })
+          }
+          const newSeg = state.nodes[targetSegmentId] as RoofSegmentNode | undefined
+          if (newSeg && !(newSeg.children ?? []).includes(node.id)) {
+            state.updateNode(targetSegmentId, {
+              children: [...(newSeg.children ?? []), node.id],
+            })
+          }
+          state.dirtyNodes.add(prevSegmentId!)
+        }
         state.updateNode(node.id as AnyNodeId, {
           roofSegmentId: target.segment.id,
           parentId: target.segment.id,
           position: [target.localX, target.localY, target.localZ],
+          rotation: original.rotation,
+          visible: true,
           metadata: cleanedMeta,
         })
-        if (prevSegmentId) state.dirtyNodes.add(prevSegmentId)
-        state.dirtyNodes.add(target.segment.id as AnyNodeId)
+        useScene.temporal.getState().pause()
+        state.dirtyNodes.add(targetSegmentId)
+        state.dirtyNodes.add(node.id as AnyNodeId)
         setSelection({ selectedIds: [node.id] })
       }
+      const obj = node.id && !isNew ? sceneRegistry.nodes.get(node.id) : null
+      if (obj) obj.visible = true
+      clearRoofSurfacePlacementGuides()
       setMovingNode(null)
       triggerSFX('sfx:item-place')
       event.stopPropagation()
     }
 
+    const onCancel = () => {
+      if (isNew) {
+        if (node.id) {
+          const parentId = original.roofSegmentId as AnyNodeId | undefined
+          if (parentId) {
+            const parent = useScene.getState().nodes[parentId] as RoofSegmentNode | undefined
+            if (parent) {
+              useScene.getState().updateNode(parentId, {
+                children: (parent.children ?? []).filter((id) => id !== node.id),
+              })
+            }
+          }
+          useScene.getState().deleteNode(node.id as AnyNodeId)
+        }
+        useScene.temporal.getState().resume()
+        markToolCancelConsumed()
+        clearRoofSurfacePlacementGuides()
+        setMovingNode(null)
+        return
+      }
+
+      if (node.id) {
+        useScene.getState().updateNode(node.id as AnyNodeId, {
+          position: original.position,
+          rotation: original.rotation,
+          roofSegmentId: original.roofSegmentId as AnyNodeId | undefined,
+          parentId: original.parentId as AnyNodeId | undefined,
+          metadata: original.metadata,
+        })
+        if (original.roofSegmentId) {
+          useScene.getState().dirtyNodes.add(original.roofSegmentId as AnyNodeId)
+        }
+        const obj = sceneRegistry.nodes.get(node.id)
+        if (obj) obj.visible = true
+      }
+
+      useScene.temporal.getState().resume()
+      markToolCancelConsumed()
+      clearRoofSurfacePlacementGuides()
+      setMovingNode(null)
+    }
+
     const onPlacementDragPointerUp = (event: PointerEvent) => {
       if (!consumePlacementDragRelease(event)) return
       if (!lastTarget) return
@@ -179,6 +302,7 @@ const MoveChimneyTool = ({ node }: { node: ChimneyNode }) => {
     emitter.on('roof:enter', updatePreview)
     emitter.on('roof:click', onClick)
     emitter.on('roof:leave', clearTarget)
+    emitter.on('tool:cancel', onCancel)
     window.addEventListener('pointerup', onPlacementDragPointerUp)
 
     return () => {
@@ -186,7 +310,15 @@ const MoveChimneyTool = ({ node }: { node: ChimneyNode }) => {
       emitter.off('roof:enter', updatePreview)
       emitter.off('roof:click', onClick)
       emitter.off('roof:leave', clearTarget)
+      emitter.off('tool:cancel', onCancel)
       window.removeEventListener('pointerup', onPlacementDragPointerUp)
+
+      if (node.id) {
+        const obj = sceneRegistry.nodes.get(node.id)
+        if (obj) obj.visible = true
+      }
+      clearRoofSurfacePlacementGuides()
+      useScene.temporal.getState().resume()
     }
   }, [activeBuildingId, node, setMovingNode, setSelection])
 

packages/nodes/src/chimney/tool.tsx

@@ -16,6 +16,11 @@ import { useEffect, useMemo, useRef, useState } from 'react'
 import * as THREE from 'three'
 import { RoofAttachmentFallbackPreview } from '../shared/roof-attachment-fallback-preview'
 import { resolveRoofSegmentHit } from '../shared/roof-segment-hit'
+import {
+  clearRoofSurfacePlacementGuides,
+  publishRoofSurfacePlacementGuides,
+  roofSurfaceFootprintFromNode,
+} from '../shared/roof-surface-placement-guides'
 import { chimneyDefinition } from './definition'
 import ChimneyPreview from './preview'
 
@@ -102,6 +107,12 @@ const ChimneyTool = () => {
       setSegmentXform(xform)
       setHitLocal([hit.localX, hit.localY, hit.localZ])
       setPreviewSegment(hit.segment)
+      publishRoofSurfacePlacementGuides({
+        roof: event.node as RoofNode,
+        segment: hit.segment,
+        center: [hit.localX, hit.localY, hit.localZ],
+        footprint: roofSurfaceFootprintFromNode(previewNode, { segment: hit.segment }),
+      })
       event.stopPropagation()
     }
 
@@ -126,6 +137,7 @@ const ChimneyTool = () => {
       state.dirtyNodes.add(hit.segment.id as AnyNodeId)
       setSelection({ selectedIds: [chimney.id] })
       triggerSFX('sfx:item-place')
+      clearRoofSurfacePlacementGuides()
       event.stopPropagation()
     }
 
@@ -137,8 +149,9 @@ const ChimneyTool = () => {
       emitter.off('roof:move', updatePreview)
       emitter.off('roof:enter', updatePreview)
       emitter.off('roof:click', onClick)
+      clearRoofSurfacePlacementGuides()
     }
-  }, [activeBuildingId, setSelection])
+  }, [activeBuildingId, setSelection, previewNode])
 
   return (
     <>
@@ -149,6 +162,7 @@ const ChimneyTool = () => {
           setSegmentXform(null)
           setHitLocal(null)
           setPreviewSegment(null)
+          clearRoofSurfacePlacementGuides()
         }}
       />
       {activeBuildingId && segmentXform && hitLocal && previewSegment && (

packages/nodes/src/column/renderer.tsx

@@ -2404,18 +2404,7 @@ export const ColumnRenderer = ({ node: rawNode }: { node: ColumnNode }) => {
         textures,
         colorPreset,
       }),
-    [
-      shading,
-      textures,
-      colorPreset,
-      node.material,
-      node.material?.preset,
-      node.material?.properties,
-      node.material?.texture,
-      node.materialPreset,
-      node.slots,
-      sceneMaterials,
-    ],
+    [shading, textures, colorPreset, node, sceneMaterials],
   )
 
   useRegistry(node.id, node.type, ref)

packages/nodes/src/cupola/move-tool.tsx

@@ -5,6 +5,7 @@ import {
   type CupolaNode,
   emitter,
   type RoofEvent,
+  type RoofNode,
   type RoofSegmentNode,
   sceneRegistry,
   useScene,
@@ -21,8 +22,14 @@ import {
   createRelativeRoofDrag,
   type RelativeRoofDragTarget,
   roofSegmentLocalToBuildingLocal,
+  snapRelativeRoofDragTarget,
 } from '../shared/relative-roof-drag'
 import { getAnalyticalNormal, surfaceQuatFromNormal } from '../shared/roof-surface'
+import {
+  clearRoofSurfacePlacementGuides,
+  publishRoofSurfaceNodePlacementGuides,
+  snapRoofSurfaceNodeTarget,
+} from '../shared/roof-surface-placement-guides'
 import CupolaPreview from './preview'
 
 /**
@@ -70,10 +77,21 @@ export default function MoveCupolaTool({ node }: { node: CupolaNode }) {
       lastSnap = null
       setPreviewPos(null)
       setPreviewSurfaceQuat(null)
+      clearRoofSurfacePlacementGuides()
+    }
+
+    const resolveSnappedTarget = (event: RoofEvent): RelativeRoofDragTarget | null => {
+      const rawTarget = roofDrag.resolve(event)
+      if (!rawTarget) return null
+      return snapRoofSurfaceNodeTarget({
+        target: snapRelativeRoofDragTarget(rawTarget, event.nativeEvent?.shiftKey === true),
+        node,
+        bypass: event.nativeEvent?.shiftKey === true,
+      })
     }
 
     const updatePreview = (event: RoofEvent) => {
-      const target = roofDrag.resolve(event)
+      const target = resolveSnappedTarget(event)
       if (!target) {
         clearTarget()
         return
@@ -100,12 +118,18 @@ export default function MoveCupolaTool({ node }: { node: CupolaNode }) {
           target.localZ,
         ]),
       )
+      publishRoofSurfaceNodePlacementGuides({
+        roof: event.node as RoofNode,
+        segment: target.segment,
+        center: [target.localX, target.localY, target.localZ],
+        node,
+      })
       event.stopPropagation()
     }
 
     const onRoofClick = (event: RoofEvent) => {
       if (committed) return
-      const target = lastTarget ?? roofDrag.resolve(event)
+      const target = lastTarget ?? resolveSnappedTarget(event)
       if (!target) return
       committed = true
       const targetSegmentId = target.segment.id as AnyNodeId
@@ -146,6 +170,7 @@ export default function MoveCupolaTool({ node }: { node: CupolaNode }) {
       if (obj) obj.visible = true
 
       triggerSFX('sfx:item-place')
+      clearRoofSurfacePlacementGuides()
       exitMoveMode()
       event.stopPropagation()
     }
@@ -164,6 +189,7 @@ export default function MoveCupolaTool({ node }: { node: CupolaNode }) {
         useScene.getState().deleteNode(node.id as AnyNodeId)
         useScene.temporal.getState().resume()
         markToolCancelConsumed()
+        clearRoofSurfacePlacementGuides()
         exitMoveMode()
         return
       }
@@ -183,6 +209,7 @@ export default function MoveCupolaTool({ node }: { node: CupolaNode }) {
 
       useScene.temporal.getState().resume()
       markToolCancelConsumed()
+      clearRoofSurfacePlacementGuides()
       exitMoveMode()
     }
 
@@ -212,6 +239,7 @@ export default function MoveCupolaTool({ node }: { node: CupolaNode }) {
 
       const obj = sceneRegistry.nodes.get(node.id)
       if (obj) obj.visible = true
+      clearRoofSurfacePlacementGuides()
       useScene.temporal.getState().resume()
     }
   }, [exitMoveMode, node])

packages/nodes/src/cupola/tool.tsx

@@ -16,6 +16,11 @@ import * as THREE from 'three'
 import { RoofAttachmentFallbackPreview } from '../shared/roof-attachment-fallback-preview'
 import { resolveRoofSegmentHit } from '../shared/roof-segment-hit'
 import { getAnalyticalNormal, surfaceQuatFromNormal } from '../shared/roof-surface'
+import {
+  clearRoofSurfacePlacementGuides,
+  publishRoofSurfacePlacementGuides,
+  roofSurfaceFootprintFromNode,
+} from '../shared/roof-surface-placement-guides'
 import { cupolaDefinition } from './definition'
 import CupolaPreview from './preview'
 
@@ -77,6 +82,12 @@ const CupolaTool = () => {
       setPreviewSurfaceQuat(surfaceQuatFromNormal(normal, new THREE.Quaternion()))
       setPreviewYaw((event.node.rotation ?? 0) + (hit.segment.rotation ?? 0))
       setPreviewPos(worldToBuildingLocal(wx, wy, wz))
+      publishRoofSurfacePlacementGuides({
+        roof: event.node as RoofNode,
+        segment: hit.segment,
+        center: [hit.localX, hit.localY, hit.localZ],
+        footprint: roofSurfaceFootprintFromNode(previewNode),
+      })
       event.stopPropagation()
     }
 
@@ -101,6 +112,7 @@ const CupolaTool = () => {
       state.dirtyNodes.add(hit.segment.id as AnyNodeId)
       setSelection({ selectedIds: [cupola.id] })
       triggerSFX('sfx:item-place')
+      clearRoofSurfacePlacementGuides()
       event.stopPropagation()
     }
 
@@ -112,8 +124,9 @@ const CupolaTool = () => {
       emitter.off('roof:move', updatePreview)
       emitter.off('roof:enter', updatePreview)
       emitter.off('roof:click', onClick)
+      clearRoofSurfacePlacementGuides()
     }
-  }, [activeBuildingId, setSelection])
+  }, [activeBuildingId, setSelection, previewNode])
 
   return (
     <>
@@ -123,6 +136,7 @@ const CupolaTool = () => {
         onInvalidTarget={() => {
           setPreviewPos(null)
           setPreviewSurfaceQuat(null)
+          clearRoofSurfacePlacementGuides()
         }}
       />
       {activeBuildingId && previewPos && previewSurfaceQuat && (

packages/nodes/src/door/preview.tsx

@@ -29,7 +29,7 @@ const DoorPreview = ({
     const m = buildDoorPreviewMesh(node)
     m.layers.set(EDITOR_LAYER)
     return m
-  }, [node.width, node.height, node.frameDepth, node.openingShape, node.doorType, node.leafCount])
+  }, [node])
 
   // Ghost treatment (clone + tint + raycast-off) re-applies if the tint flips;
   // its cleanup only disposes the clones it made.

packages/nodes/src/dormer/__tests__/schema.test.ts

@@ -12,7 +12,7 @@ describe('DormerNode schema', () => {
     expect(parsed.height).toBe(0)
     expect(parsed.roofType).toBe('gable')
     expect(parsed.windowShape).toBe('rectangle')
-    expect(parsed.windowSill).toBe(true)
+    expect(parsed.windowSill).toBe(false)
   })
 
   test('windowColumns / windowRows clamped to [1, 8]', () => {

packages/nodes/src/dormer/definition.ts

@@ -33,6 +33,9 @@ const MAX_SKIRT = 6
 const WINDOW_SIDE_HANDLE_OFFSET = 0.15
 const WINDOW_HEIGHT_HANDLE_OFFSET = 0.15
 const WINDOW_FACE_Z_OFFSET = 0.05
+// The four window-edge arrows latch behind a cube at the window center;
+// they stay hidden until the user clicks that cube to open the group.
+const WINDOW_LATCH_GROUP = 'dormer-window'
 // Lower clamp for window dims matches the geometry's internal clamp
 // in `getDormerSkirtWindowDims` (0.1m). Upper clamps depend on the
 // dormer dimensions and are resolved per-handle via the function form
@@ -109,21 +112,43 @@ function dormerWidthHandle(side: 'left' | 'right'): HandleDescriptor<DormerNodeT
   }
 }
 
-// Depth arrow on the +Z side. Symmetric (anchor 'center') to match
-// chimney's known-working handle count — splitting depth into asymmetric
-// front + back chevrons puts the dormer over the per-node MRT/TSL
-// budget that chimney already documents (see `chimneyHandles` factory).
-// Re-evaluate the split once that pipeline issue is pinned down.
-function dormerDepthHandle(): HandleDescriptor<DormerNodeType> {
+// Depth arrow on the +Z (front) or -Z (back) side. Asymmetric resize:
+// dragging one arrow grows the dormer outward from its own edge while
+// the opposite edge stays world-fixed in segment frame — same pattern
+// as `dormerWidthHandle`, just on the Z axis. `apply` recomputes
+// `position` so the anchored edge stays at the same segment-local point
+// even when the dormer is Y-rotated: project the dormer's local +Z onto
+// segment frame via (sin r, cos r), find the anchored edge's segment-
+// local XZ from the pre-drag node, then place the new center half a new-
+// depth away from that anchor in the same direction.
+function dormerDepthHandle(side: 'front' | 'back'): HandleDescriptor<DormerNodeType> {
+  const sign = side === 'front' ? 1 : -1
   return {
     kind: 'linear-resize',
     axis: 'z',
-    anchor: 'center',
+    // 'min' = -Z edge anchored (front arrow grows the +Z edge outward).
+    // 'max' = +Z edge anchored (back arrow grows the -Z edge outward).
+    anchor: side === 'front' ? 'min' : 'max',
     min: MIN_DIM,
     currentValue: (n) => n.depth,
-    apply: (_n, newValue) => ({ depth: newValue }),
+    apply: (initial, newDepth) => {
+      const rotY = initial.rotation ?? 0
+      const armX = Math.sin(rotY)
+      const armZ = Math.cos(rotY)
+      const anchorX = initial.position[0] - sign * (initial.depth / 2) * armX
+      const anchorZ = initial.position[2] - sign * (initial.depth / 2) * armZ
+      const newCenterX = anchorX + sign * (newDepth / 2) * armX
+      const newCenterZ = anchorZ + sign * (newDepth / 2) * armZ
+      return {
+        depth: newDepth,
+        position: [newCenterX, initial.position[1], newCenterZ],
+      }
+    },
     placement: {
-      position: (n) => [0, getBodyMidY(n), n.depth / 2 + SIDE_HANDLE_OFFSET],
+      position: (n) => [0, getBodyMidY(n), sign * (n.depth / 2 + SIDE_HANDLE_OFFSET)],
+      // The renderer auto-yaws axis-'z' chevrons by -π/2 so the default
+      // points +Z (front). Flip the back chevron 180° to point -Z.
+      rotationY: () => (side === 'front' ? 0 : Math.PI),
     },
   }
 }
@@ -273,6 +298,11 @@ function dormerWindowWidthHandle(side: 'left' | 'right'): HandleDescriptor<Dorme
   return {
     kind: 'linear-resize',
     axis: 'x',
+    // Stand the blade up into the gable face so it reads flat-on like the
+    // top/bottom window-height arrows instead of edge-on.
+    faceNormal: true,
+    // Hidden until the user clicks the window-center latch cube.
+    latchGroup: WINDOW_LATCH_GROUP,
     anchor: side === 'right' ? 'min' : 'max',
     min: MIN_WINDOW_DIM,
     // Cap at the dormer's window field — keep a 0.1m gap on each side
@@ -317,6 +347,8 @@ function dormerWindowHeightHandle(side: 'top' | 'bottom'): HandleDescriptor<Dorm
   return {
     kind: 'linear-resize',
     axis: 'y',
+    // Hidden until the user clicks the window-center latch cube.
+    latchGroup: WINDOW_LATCH_GROUP,
     // 'min' = bottom edge anchored (top arrow grows the top edge up).
     // 'max' = top edge anchored (bottom arrow drops the bottom edge).
     anchor: side === 'top' ? 'min' : 'max',
@@ -350,12 +382,37 @@ function dormerWindowHeightHandle(side: 'top' | 'bottom'): HandleDescriptor<Dorm
   }
 }
 
+// Window-center latch cube. Sits at the window center on the exposed
+// gable face; clicking it reveals / hides the four window edge arrows
+// (width L/R + height top/bottom) tagged with `WINDOW_LATCH_GROUP`.
+// Mirrors the duct-fitting selection cube but driven by the shared
+// latch descriptor so the dense window cluster stays collapsed behind
+// one grip until the user opts in.
+function dormerWindowLatchHandle(): HandleDescriptor<DormerNodeType> {
+  return {
+    kind: 'latch',
+    group: WINDOW_LATCH_GROUP,
+    placement: {
+      position: (n, sceneApi) => {
+        const faceSign = getExposedFaceZSign(n, sceneApi)
+        return [
+          n.windowOffsetX,
+          getWindowCenterY(n),
+          faceSign * (n.depth / 2 + WINDOW_FACE_Z_OFFSET),
+        ]
+      },
+    },
+  }
+}
+
 const dormerHandles: HandleDescriptor<DormerNodeType>[] = [
   dormerWidthHandle('right'),
   dormerWidthHandle('left'),
-  dormerDepthHandle(),
+  dormerDepthHandle('front'),
+  dormerDepthHandle('back'),
   dormerWallHeightHandle(),
   dormerRotateHandle(),
+  dormerWindowLatchHandle(),
   dormerWindowWidthHandle('right'),
   dormerWindowWidthHandle('left'),
   dormerWindowHeightHandle('top'),

packages/nodes/src/dormer/move-tool.tsx

@@ -11,6 +11,7 @@ import {
 import { useEditor } from '@pascal-app/editor'
 import { useViewer } from '@pascal-app/viewer'
 import { useEffect, useMemo } from 'react'
+import { DormerPlacementGuides } from './placement-guides'
 import DormerPreview from './preview'
 import { useDormerPlacement } from './use-dormer-placement'
 
@@ -74,84 +75,95 @@ const MoveDormerTool = ({ node }: { node: DormerNode }) => {
     }
   }, [node.id, isNew])
 
-  const { activeBuildingId, segmentXform, hitLocal, ghostRotation } = useDormerPlacement({
-    initialRotation: originalRotation,
-    relativeStart: {
-      position: [...node.position] as [number, number, number],
-      roofSegmentId: node.roofSegmentId,
-    },
-    onCommit: (hit, rotation) => {
-      const state = useScene.getState()
+  const { activeBuildingId, segmentXform, hitSegment, hitLocal, ghostRotation } =
+    useDormerPlacement({
+      initialRotation: originalRotation,
+      relativeStart: {
+        position: [...node.position] as [number, number, number],
+        roofSegmentId: node.roofSegmentId,
+      },
+      onCommit: (hit, rotation) => {
+        const state = useScene.getState()
 
-      // Strip the `isNew` / `isTransient` flags — only used to mark a
-      // clone or in-flight move that hasn't been committed yet.
-      const cleanedMeta = (() => {
-        const m =
-          node.metadata && typeof node.metadata === 'object' && !Array.isArray(node.metadata)
-            ? (node.metadata as Record<string, unknown>)
-            : {}
-        const {
-          isNew: _isNew,
-          isTransient: _isTransient,
-          ...rest
-        } = m as {
-          isNew?: boolean
-          isTransient?: boolean
-        }
-        return Object.keys(rest).length > 0 ? rest : undefined
-      })()
+        // Strip the `isNew` / `isTransient` flags — only used to mark a
+        // clone or in-flight move that hasn't been committed yet.
+        const cleanedMeta = (() => {
+          const m =
+            node.metadata && typeof node.metadata === 'object' && !Array.isArray(node.metadata)
+              ? (node.metadata as Record<string, unknown>)
+              : {}
+          const {
+            isNew: _isNew,
+            isTransient: _isTransient,
+            ...rest
+          } = m as {
+            isNew?: boolean
+            isTransient?: boolean
+          }
+          return Object.keys(rest).length > 0 ? rest : undefined
+        })()
 
-      if (isNew || !node.id) {
-        const { id: _id, ...rest } = node
-        const committed = DormerNodeSchema.parse({
-          ...rest,
-          roofSegmentId: hit.segment.id,
-          parentId: hit.segment.id,
-          position: [hit.localX, hit.localY, hit.localZ],
-          rotation,
-          metadata: cleanedMeta,
-        })
-        state.createNode(committed, hit.segment.id as AnyNodeId)
-        state.dirtyNodes.add(hit.segment.id as AnyNodeId)
-        setSelection({ selectedIds: [committed.id] })
-      } else {
-        const prevSegmentId = node.roofSegmentId as AnyNodeId | undefined
-        state.updateNode(node.id as AnyNodeId, {
-          roofSegmentId: hit.segment.id,
-          parentId: hit.segment.id,
-          position: [hit.localX, hit.localY, hit.localZ],
-          rotation,
-          metadata: cleanedMeta,
-        })
-        if (prevSegmentId) state.dirtyNodes.add(prevSegmentId)
-        state.dirtyNodes.add(hit.segment.id as AnyNodeId)
-        // Unlist from previous segment's children and add to the new one.
-        if (prevSegmentId && prevSegmentId !== (hit.segment.id as AnyNodeId)) {
-          const prevSeg = state.nodes[prevSegmentId] as RoofSegmentNode | undefined
-          if (prevSeg) {
-            state.updateNode(prevSegmentId, {
-              children: (prevSeg.children ?? []).filter((id) => id !== node.id),
-            })
-          }
-          const newSeg = state.nodes[hit.segment.id as AnyNodeId] as RoofSegmentNode | undefined
-          if (newSeg && !(newSeg.children ?? []).includes(node.id)) {
-            state.updateNode(hit.segment.id as AnyNodeId, {
-              children: [...(newSeg.children ?? []), node.id],
-            })
+        if (isNew || !node.id) {
+          const { id: _id, ...rest } = node
+          const committed = DormerNodeSchema.parse({
+            ...rest,
+            roofSegmentId: hit.segment.id,
+            parentId: hit.segment.id,
+            position: [hit.localX, hit.localY, hit.localZ],
+            rotation,
+            metadata: cleanedMeta,
+          })
+          state.createNode(committed, hit.segment.id as AnyNodeId)
+          state.dirtyNodes.add(hit.segment.id as AnyNodeId)
+          setSelection({ selectedIds: [committed.id] })
+        } else {
+          const prevSegmentId = node.roofSegmentId as AnyNodeId | undefined
+          state.updateNode(node.id as AnyNodeId, {
+            roofSegmentId: hit.segment.id,
+            parentId: hit.segment.id,
+            position: [hit.localX, hit.localY, hit.localZ],
+            rotation,
+            metadata: cleanedMeta,
+          })
+          if (prevSegmentId) state.dirtyNodes.add(prevSegmentId)
+          state.dirtyNodes.add(hit.segment.id as AnyNodeId)
+          // Unlist from previous segment's children and add to the new one.
+          if (prevSegmentId && prevSegmentId !== (hit.segment.id as AnyNodeId)) {
+            const prevSeg = state.nodes[prevSegmentId] as RoofSegmentNode | undefined
+            if (prevSeg) {
+              state.updateNode(prevSegmentId, {
+                children: (prevSeg.children ?? []).filter((id) => id !== node.id),
+              })
+            }
+            const newSeg = state.nodes[hit.segment.id as AnyNodeId] as RoofSegmentNode | undefined
+            if (newSeg && !(newSeg.children ?? []).includes(node.id)) {
+              state.updateNode(hit.segment.id as AnyNodeId, {
+                children: [...(newSeg.children ?? []), node.id],
+              })
+            }
           }
+          setSelection({ selectedIds: [node.id] })
         }
-        setSelection({ selectedIds: [node.id] })
-      }
-      const dormerObj = sceneRegistry.nodes.get(node.id)
-      if (dormerObj) dormerObj.visible = true
-      setMovingNode(null)
-    },
-  })
+        const dormerObj = sceneRegistry.nodes.get(node.id)
+        if (dormerObj) dormerObj.visible = true
+        setMovingNode(null)
+      },
+    })
 
   if (!activeBuildingId || !segmentXform || !hitLocal) return null
 
   return (
     <group position={segmentXform.position} quaternion={segmentXform.quaternion}>
+      {hitSegment && (
+        <DormerPlacementGuides
+          center={hitLocal}
+          depth={previewNode.depth}
+          movingId={node.id}
+          rotation={ghostRotation}
+          segment={hitSegment}
+          width={previewNode.width}
+        />
+      )}
       <group position={hitLocal}>
         <group rotation-y={ghostRotation}>
           <DormerPreview node={previewNode} />

packages/nodes/src/dormer/placement-guides.tsx

@@ -0,0 +1,273 @@
+'use client'
+
+import type { RoofSegmentNode } from '@pascal-app/core'
+import { EDITOR_LAYER, formatMeasurement } from '@pascal-app/editor'
+import { useViewer } from '@pascal-app/viewer'
+import { Html } from '@react-three/drei'
+import { useEffect, useMemo } from 'react'
+import { BufferGeometry, Float32BufferAttribute, Line as ThreeLine } from 'three'
+import { LineBasicNodeMaterial } from 'three/webgpu'
+import { getRoofSurfaceFaceBoundsAt } from '../shared/roof-surface'
+import {
+  roofFaceKey,
+  roofGuideBounds,
+  roofSiblingSpacing,
+} from '../shared/roof-surface-placement-guides'
+
+// Indigo — matches the wall/window 3D proximity guide accent so every
+// "distance to edge" readout reads the same across the app.
+const GUIDE_COLOR = 0x81_8c_f8
+const ALIGN_COLOR = 0xef_44_44
+const PILL_BG = '#6366f1'
+const BADGE_BG = '#ec4899'
+// Lift the lines a hair off the sloped surface so they don't z-fight the
+// roof + dormer ghost.
+const SURFACE_LIFT = 0.02
+// Hide a gap that has collapsed (dormer edge flush to / past the roof edge)
+// so we don't draw a degenerate "0m" pill.
+const MIN_GAP_M = 0.02
+
+const guideMaterial = new LineBasicNodeMaterial({
+  color: GUIDE_COLOR,
+  depthTest: false,
+  depthWrite: false,
+  toneMapped: false,
+  transparent: true,
+})
+const alignMaterial = new LineBasicNodeMaterial({
+  color: ALIGN_COLOR,
+  depthTest: false,
+  depthWrite: false,
+  toneMapped: false,
+  transparent: true,
+})
+
+type Vec3 = [number, number, number]
+type DormerGuide =
+  | {
+      id: string
+      from: Vec3
+      to: Vec3
+      kind: 'align-line' | 'dimension'
+      value?: number
+    }
+  | {
+      id: string
+      at: Vec3
+      kind: 'badge'
+      value: number
+    }
+
+/**
+ * Live "distance to roof edge" guides shown while a dormer ghost is being
+ * placed or dragged — the roof-plane analog of the window's sill/head +
+ * edge-proximity pills. Renders measured lines from each side-center of
+ * the dormer's occupied roof area out to the active roof face edges, each
+ * with a distance pill at its midpoint.
+ *
+ * Mounted as a sibling of `<DormerPreview>` INSIDE the segment-local frame
+ * (the `segmentXform` group) but OUTSIDE the dormer's `hitLocal` + rotation
+ * groups, so its coordinates are segment-local. The roof-face boundary is
+ * resolved from the actual visible top face under `center`, not from the
+ * wall footprint dimensions.
+ *
+ * Normal roof accessories use side-center readouts. Linear accessories
+ * like ridge vents and gutters use their own two-end guide mode.
+ */
+export function DormerPlacementGuides({
+  segment,
+  center,
+  width,
+  depth,
+  rotation,
+  movingId,
+}: {
+  segment: RoofSegmentNode
+  center: Vec3
+  width: number
+  depth: number
+  rotation: number
+  movingId?: string
+}) {
+  const unit = useViewer((s) => s.unit)
+
+  const [cx, , cz] = center
+  const faceBounds = getRoofSurfaceFaceBoundsAt(segment, cx, cz)
+  const halfW = Math.max(0, width) / 2
+  const halfD = Math.max(0, depth) / 2
+  const cos = Math.cos(rotation)
+  const sin = Math.sin(rotation)
+  const halfX = Math.abs(cos) * halfW + Math.abs(sin) * halfD
+  const halfZ = Math.abs(sin) * halfW + Math.abs(cos) * halfD
+  const movingBounds = roofGuideBounds(center, { width, depth, rotation })
+
+  const surfaceY = (x: number, z: number): number => faceBounds.surfaceYAt(x, z) + SURFACE_LIFT
+
+  const xInterval = faceBounds.xIntervalAtZ(cz)
+  const zInterval = faceBounds.zIntervalAtX(cx)
+
+  const guides: DormerGuide[] = []
+  const push = (id: string, ax: number, az: number, bx: number, bz: number) => {
+    const from: Vec3 = [ax, surfaceY(ax, az), az]
+    const to: Vec3 = [bx, surfaceY(bx, bz), bz]
+    const value = Math.hypot(to[0] - from[0], to[1] - from[1], to[2] - from[2])
+    if (value < MIN_GAP_M) return
+    guides.push({
+      id,
+      from,
+      to,
+      kind: 'dimension',
+      value,
+    })
+  }
+  const siblingSpacing = roofSiblingSpacing<DormerGuide>({
+    segment,
+    movingId,
+    movingBounds,
+    faceKey: roofFaceKey(faceBounds.polygon),
+    dimension: (id, [ax, az], [bx, bz]) => {
+      const from: Vec3 = [ax, surfaceY(ax, az), az]
+      const to: Vec3 = [bx, surfaceY(bx, bz), bz]
+      const value = Math.hypot(to[0] - from[0], to[1] - from[1], to[2] - from[2])
+      if (value < MIN_GAP_M) return null
+      return { id, from, to, kind: 'dimension', value }
+    },
+    alignLine: (id, [ax, az], [bx, bz]) => {
+      const from: Vec3 = [ax, surfaceY(ax, az), az]
+      const to: Vec3 = [bx, surfaceY(bx, bz), bz]
+      const value = Math.hypot(to[0] - from[0], to[1] - from[1], to[2] - from[2])
+      if (value < MIN_GAP_M) return null
+      return { id, from, to, kind: 'align-line' }
+    },
+    badge: (id, [x, z], value) => {
+      if (value < MIN_GAP_M) return null
+      return {
+        id,
+        at: [x, surfaceY(x, z), z],
+        kind: 'badge',
+        value,
+      }
+    },
+    measure: ([ax, az], [bx, bz]) => {
+      const ay = surfaceY(ax, az)
+      const by = surfaceY(bx, bz)
+      return Math.hypot(bx - ax, by - ay, bz - az)
+    },
+  })
+  if (xInterval) {
+    const [faceMinX, faceMaxX] = xInterval
+    const itemMinX = Math.max(faceMinX, Math.min(faceMaxX, cx - halfX))
+    const itemMaxX = Math.max(faceMinX, Math.min(faceMaxX, cx + halfX))
+    if (!siblingSpacing.blockedSides.left && itemMinX > faceMinX + MIN_GAP_M) {
+      push('left', faceMinX, cz, itemMinX, cz)
+    }
+    if (!siblingSpacing.blockedSides.right && itemMaxX < faceMaxX - MIN_GAP_M) {
+      push('right', itemMaxX, cz, faceMaxX, cz)
+    }
+  }
+  if (zInterval) {
+    const [faceMinZ, faceMaxZ] = zInterval
+    const itemMinZ = Math.max(faceMinZ, Math.min(faceMaxZ, cz - halfZ))
+    const itemMaxZ = Math.max(faceMinZ, Math.min(faceMaxZ, cz + halfZ))
+    if (!siblingSpacing.blockedSides.bottom && itemMinZ > faceMinZ + MIN_GAP_M) {
+      push('back', cx, faceMinZ, cx, itemMinZ)
+    }
+    if (!siblingSpacing.blockedSides.top && itemMaxZ < faceMaxZ - MIN_GAP_M) {
+      push('front', cx, itemMaxZ, cx, faceMaxZ)
+    }
+  }
+  guides.push(...siblingSpacing.guides)
+
+  return (
+    <>
+      {guides.map((g) => (
+        <Guide key={g.id} guide={g} unit={unit} />
+      ))}
+    </>
+  )
+}
+
+function Guide({ guide, unit }: { guide: DormerGuide; unit: 'metric' | 'imperial' }) {
+  if (guide.kind === 'badge') {
+    return <GuideBadge at={guide.at} pill={`= ${formatMeasurement(guide.value, unit)}`} />
+  }
+
+  return (
+    <GuideLine
+      from={guide.from}
+      kind={guide.kind}
+      pill={guide.value === undefined ? undefined : formatMeasurement(guide.value, unit)}
+      to={guide.to}
+    />
+  )
+}
+
+function GuideBadge({ at, pill }: { at: Vec3; pill: string }) {
+  return (
+    <Html
+      center
+      position={at}
+      style={{ pointerEvents: 'none', userSelect: 'none' }}
+      zIndexRange={[20, 0]}
+    >
+      <div
+        className="whitespace-nowrap rounded-[3px] px-[5px] py-[2px] font-semibold font-sans text-[11px] text-white"
+        style={{ backgroundColor: BADGE_BG }}
+      >
+        {pill}
+      </div>
+    </Html>
+  )
+}
+
+function GuideLine({
+  from,
+  to,
+  pill,
+  kind,
+}: {
+  from: Vec3
+  to: Vec3
+  pill?: string
+  kind: DormerGuide['kind']
+}) {
+  const { line, position } = useMemo(() => {
+    const position = new Float32BufferAttribute(new Float32Array(6), 3)
+    const geometry = new BufferGeometry()
+    geometry.setAttribute('position', position)
+    const line = new ThreeLine(geometry, kind === 'align-line' ? alignMaterial : guideMaterial)
+    line.frustumCulled = false
+    line.layers.set(EDITOR_LAYER)
+    line.renderOrder = 1000
+    return { line, position }
+  }, [kind])
+
+  position.setXYZ(0, from[0], from[1], from[2])
+  position.setXYZ(1, to[0], to[1], to[2])
+  position.needsUpdate = true
+
+  useEffect(() => () => line.geometry.dispose(), [line])
+
+  const mid: Vec3 = [(from[0] + to[0]) / 2, (from[1] + to[1]) / 2, (from[2] + to[2]) / 2]
+
+  return (
+    <>
+      <primitive object={line} />
+      {pill ? (
+        <Html
+          center
+          position={mid}
+          style={{ pointerEvents: 'none', userSelect: 'none' }}
+          zIndexRange={[20, 0]}
+        >
+          <div
+            className="whitespace-nowrap rounded-[3px] px-[5px] py-[2px] font-medium font-sans text-[11px] text-white"
+            style={{ backgroundColor: PILL_BG }}
+          >
+            {pill}
+          </div>
+        </Html>
+      ) : null}
+    </>
+  )
+}

packages/nodes/src/dormer/tool.tsx

@@ -5,6 +5,7 @@ import { useViewer } from '@pascal-app/viewer'
 import { useMemo } from 'react'
 import { RoofAttachmentFallbackPreview } from '../shared/roof-attachment-fallback-preview'
 import { dormerDefinition } from './definition'
+import { DormerPlacementGuides } from './placement-guides'
 import DormerPreview from './preview'
 import { useDormerPlacement } from './use-dormer-placement'
 
@@ -48,7 +49,7 @@ const DormerTool = () => {
     [],
   )
 
-  const { activeBuildingId, clearPreview, segmentXform, hitLocal, ghostRotation } =
+  const { activeBuildingId, clearPreview, segmentXform, hitSegment, hitLocal, ghostRotation } =
     useDormerPlacement({
       onCommit: (hit, rotation) => {
         const state = useScene.getState()
@@ -78,6 +79,15 @@ const DormerTool = () => {
       />
       {activeBuildingId && segmentXform && hitLocal && (
         <group position={segmentXform.position} quaternion={segmentXform.quaternion}>
+          {hitSegment && (
+            <DormerPlacementGuides
+              center={hitLocal}
+              depth={previewNode.depth}
+              rotation={ghostRotation}
+              segment={hitSegment}
+              width={previewNode.width}
+            />
+          )}
           <group position={hitLocal}>
             <group rotation-y={ghostRotation}>
               <DormerPreview node={previewNode} />

packages/nodes/src/dormer/use-dormer-placement.ts

@@ -60,12 +60,14 @@ export function useDormerPlacement(opts: {
   activeBuildingId: string | undefined
   clearPreview: () => void
   segmentXform: DormerSegmentTransform | null
+  hitSegment: RoofSegmentNode | null
   hitLocal: [number, number, number] | null
   ghostRotation: number
 } {
   const activeBuildingId = useViewer((s) => s.selection.buildingId)
 
   const [segmentXform, setSegmentXform] = useState<DormerSegmentTransform | null>(null)
+  const [hitSegment, setHitSegment] = useState<RoofSegmentNode | null>(null)
   const [hitLocal, setHitLocal] = useState<[number, number, number] | null>(null)
   const [ghostRotation, setGhostRotation] = useState(opts.initialRotation ?? 0)
   const lastSnapRef = useRef<[number, number] | null>(null)
@@ -81,6 +83,7 @@ export function useDormerPlacement(opts: {
 
   const clearPreview = () => {
     setSegmentXform(null)
+    setHitSegment(null)
     setHitLocal(null)
   }
 
@@ -136,6 +139,7 @@ export function useDormerPlacement(opts: {
       const xform = computeSegmentXform(hit.segment.id)
       if (!xform) return
       setSegmentXform(xform)
+      setHitSegment(hit.segment)
       // Lift the ghost to the actual roof-surface Y at the cursor so
       // it tracks the mouse along the slope. The CSG inside
       // `generateDormerGeometry` carves the dormer against the host
@@ -200,6 +204,7 @@ export function useDormerPlacement(opts: {
     activeBuildingId: activeBuildingId ?? undefined,
     clearPreview,
     segmentXform,
+    hitSegment,
     hitLocal,
     ghostRotation,
   }

packages/nodes/src/duct-fitting/definition.ts

@@ -1,4 +1,5 @@
 import type { NodeDefinition } from '@pascal-app/core'
+import { ductBodyPaint, ductBodySlots } from '../shared/duct-body-paint'
 import { rotateFittingNode } from '../shared/fitting-rotation'
 import { buildDuctFittingFloorplan } from './floorplan'
 import { buildDuctFittingGeometry } from './geometry'
@@ -29,16 +30,16 @@ export const ductFittingDefinition: NodeDefinition<typeof DuctFittingNode> = {
     position: [0, 0, 0],
     rotation: [0, 0, 0],
     fittingType: 'elbow',
-    shape: 'round',
+    shape: 'rect',
     width: 14,
     height: 8,
-    shape2: 'round',
+    shape2: 'rect',
     width2: 14,
     height2: 8,
     angle: 90,
     branchAngle: 90,
-    diameter: 6,
-    diameter2: 6,
+    diameter: 12,
+    diameter2: 12,
     ductMaterial: 'sheet-metal',
     system: 'supply',
   }),
@@ -51,6 +52,8 @@ export const ductFittingDefinition: NodeDefinition<typeof DuctFittingNode> = {
     movable: { axes: ['x', 'y', 'z'], gridSnap: true, cursorAttached: true },
     duplicable: true,
     deletable: true,
+    slots: () => ductBodySlots(),
+    paint: ductBodyPaint,
   },
 
   parametrics: ductFittingParametrics,
@@ -75,6 +78,7 @@ export const ductFittingDefinition: NodeDefinition<typeof DuctFittingNode> = {
       n.diameter2,
       n.ductMaterial,
       n.system,
+      n.slots,
     ]),
 
   ports: getDuctFittingPorts,

packages/nodes/src/duct-fitting/geometry.ts

@@ -1,3 +1,5 @@
+import type { GeometryContext } from '@pascal-app/core'
+import type { ColorPreset, RenderShading } from '@pascal-app/viewer'
 import {
   BufferGeometry,
   CylinderGeometry,
@@ -5,8 +7,8 @@ import {
   Euler,
   Float32BufferAttribute,
   Group,
+  type Material,
   Mesh,
-  type MeshStandardMaterial,
   SphereGeometry,
   TorusGeometry,
   Vector3,
@@ -18,6 +20,7 @@ import {
   createDuctMaterial,
   INCHES_TO_METERS,
 } from '../duct-segment/geometry'
+import { DUCT_BODY_SLOT_ID } from '../shared/duct-body-paint'
 import { localFittingPorts } from './ports'
 import type { DuctFittingNode } from './schema'
 
@@ -76,7 +79,7 @@ function buildMiteredElbow(
   sweepM: number,
   cheekM: number,
   profileShape: 'rect' | 'oval',
-  material: MeshStandardMaterial,
+  material: Material,
 ): Mesh {
   const travelIn = inletPos.clone().multiplyScalar(-1).normalize() // inlet → junction
   const travelOut = outletPos.clone().normalize() // junction → outlet
@@ -155,7 +158,7 @@ function buildRectToRoundLoft(
   widthM: number,
   heightM: number,
   radius: number,
-  material: MeshStandardMaterial,
+  material: Material,
 ): Mesh {
   const hw = widthM / 2
   const hh = heightM / 2
@@ -212,9 +215,23 @@ function buildRectToRoundLoft(
  * height rides local +Y — for the horizontal-plane orientations trunks
  * are drawn in, that's world-vertical.
  */
-export function buildDuctFittingGeometry(node: DuctFittingNode): Group {
+export function buildDuctFittingGeometry(
+  node: DuctFittingNode,
+  ctx?: GeometryContext,
+  shading: RenderShading = 'rendered',
+  textures = true,
+  colorPreset: ColorPreset = 'clay',
+  sceneTheme?: string,
+): Group {
   const group = new Group()
-  const material = createDuctMaterial(node)
+  const material = createDuctMaterial(
+    node,
+    ctx?.materials,
+    shading,
+    textures,
+    colorPreset,
+    sceneTheme,
+  )
   const radiusMain = (node.diameter * INCHES_TO_METERS) / 2
   const ports = localFittingPorts(node)
   const widthM = node.width * INCHES_TO_METERS
@@ -459,5 +476,10 @@ export function buildDuctFittingGeometry(node: DuctFittingNode): Group {
     group.add(collar)
   }
 
+  group.traverse((object) => {
+    const mesh = object as Mesh
+    if (mesh.isMesh) mesh.userData.slotId = DUCT_BODY_SLOT_ID
+  })
+
   return group
 }

packages/nodes/src/duct-fitting/inspector-editors.tsx

@@ -0,0 +1,38 @@
+'use client'
+
+import { ActionButton } from '@pascal-app/editor'
+import { ArrowLeftRight } from 'lucide-react'
+import type { DuctFittingNode } from './schema'
+
+const WIDTH_MIN = 4
+const WIDTH_MAX = 60
+const HEIGHT_MIN = 3
+const HEIGHT_MAX = 40
+
+function clamp(value: number, min: number, max: number) {
+  return Math.min(max, Math.max(min, value))
+}
+
+export function DuctFittingSizeSwapEditor({
+  node,
+  onUpdate,
+}: {
+  node: DuctFittingNode
+  onUpdate: (patch: Partial<DuctFittingNode>) => void
+}) {
+  const nextWidth = clamp(node.height, WIDTH_MIN, WIDTH_MAX)
+  const nextHeight = clamp(node.width, HEIGHT_MIN, HEIGHT_MAX)
+
+  return (
+    <div className="px-2">
+      <ActionButton
+        className="h-8 w-full flex-none"
+        icon={<ArrowLeftRight className="h-3.5 w-3.5" />}
+        label="Swap W/H"
+        onClick={() => onUpdate({ width: nextWidth, height: nextHeight })}
+        title="Swap width and height"
+        type="button"
+      />
+    </div>
+  )
+}

packages/nodes/src/duct-fitting/move-tool.tsx

@@ -11,6 +11,7 @@ import {
   useScene,
 } from '@pascal-app/core'
 import {
+  consumePlacementDragRelease,
   DragBoundingBox,
   EDITOR_LAYER,
   markToolCancelConsumed,
@@ -22,11 +23,13 @@ import {
 import { useViewer } from '@pascal-app/viewer'
 import { useEffect, useMemo, useState } from 'react'
 import { Box3, Euler, type Material, type Mesh, MeshBasicMaterial, Vector3 } from 'three'
+import { autoOffsetInvalidationUpdates } from '../shared/auto-offset-tag'
 import {
   type Aabb2D,
   collectGhostAlignmentCandidates,
   resolveGhostAlignment,
 } from '../shared/ghost-alignment'
+import { type RunMoveConnectivity, startRunMoveConnectivity } from '../shared/run-move-connectivity'
 import { buildDuctFittingGeometry } from './geometry'
 
 type Vec3 = [number, number, number]
@@ -174,11 +177,27 @@ export const MoveDuctFittingTool: React.FC<{ node: AnyNode }> = ({ node }) => {
     }
     if (existedAtStart) setMeshHidden(true)
 
+    // Carry connected ducts as the fitting slides: the part of the move along
+    // a run's axis stretches it, the part across translates the whole run (and
+    // propagates to its far joint). Snapshot once at drag start; only existing
+    // fittings are mated to anything.
+    const connectivity: RunMoveConnectivity | null = existedAtStart
+      ? startRunMoveConnectivity(node)
+      : null
+
     let lastPos: Vec3 = originalPosition
+    // Tracks whether the last frame held Alt: the fitting is detached from its
+    // connected ducts for the drag, so they stay put (no follow) and the
+    // commit omits their updates. Mirrors the duct endpoint's Alt-detach.
+    let lastDetached = false
 
     const onMove = (event: GridEvent) => {
       const bypass = event.nativeEvent?.shiftKey === true
+      // Alt = detach: drop the connected-duct follow so the fitting moves on
+      // its own, leaving every mated run where it sits.
+      const detached = event.nativeEvent?.altKey === true
       const snap = bypass ? (v: number) => v : snapToGridStep
+
       let x = snap(event.localPosition[0])
       let z = snap(event.localPosition[2])
 
@@ -198,17 +217,27 @@ export const MoveDuctFittingTool: React.FC<{ node: AnyNode }> = ({ node }) => {
       } else {
         useAlignmentGuides.getState().clear()
       }
+      const next: Vec3 = [x, lastPos[1], z]
 
-      const next: Vec3 = [x, originalPosition[1], z]
-      if (next[0] !== lastPos[0] || next[2] !== lastPos[2]) triggerSFX('sfx:grid-snap')
+      if (next[0] !== lastPos[0] || next[1] !== lastPos[1] || next[2] !== lastPos[2]) {
+        triggerSFX('sfx:grid-snap')
+      }
       lastPos = next
+      lastDetached = detached
       hasMoved = true
       setCursorPos(next)
+      // Detached: keep the followers at their origin (drop any live overrides
+      // from a prior non-detached frame). Otherwise preview the follow.
+      if (detached) connectivity?.clear()
+      else connectivity?.preview({ position: next })
     }
 
-    const commit = (event: GridEvent) => {
+    const commit = (event: GridEvent, fromDragRelease = false) => {
       if (committed) return
-      if (Date.now() - activatedAt < 150) {
+      // The 150ms debounce only guards click-to-place against the arming click
+      // double-firing; a press-drag release is a distinct pointerup gesture, so
+      // it skips the guard (a quick drag-flick still commits).
+      if (!fromDragRelease && Date.now() - activatedAt < 150) {
         event.nativeEvent?.stopPropagation?.()
         return
       }
@@ -230,10 +259,24 @@ export const MoveDuctFittingTool: React.FC<{ node: AnyNode }> = ({ node }) => {
         useScene.getState().createNode(created as AnyNode, node.parentId as AnyNodeId)
         selectId = created.id as AnyNodeId
       } else {
-        useScene.getState().updateNode(nodeId, { position: lastPos } as Partial<AnyNode>)
-        useScene.getState().markDirty(nodeId)
+        // Fold connected-duct / sibling-run follow-updates into the SAME batch
+        // as the moved fitting so the whole joint is one undo step. Detached
+        // (Alt on the final frame): the joint is broken, so nothing follows.
+        const followUpdates = lastDetached
+          ? []
+          : (connectivity?.commitUpdates({ position: lastPos }) ?? [])
+        const scene = useScene.getState()
+        scene.updateNodes([
+          { id: nodeId, data: { position: lastPos } as Partial<AnyNode> },
+          ...followUpdates,
+          ...autoOffsetInvalidationUpdates(scene.nodes, nodeId),
+        ])
+        scene.markDirty(nodeId)
       }
       useScene.temporal.getState().pause()
+      // Followers are committed to the store — drop their live overrides so
+      // renderers read the canonical path/position.
+      connectivity?.clear()
       setMeshHidden(false)
 
       useAlignmentGuides.getState().clear()
@@ -245,6 +288,7 @@ export const MoveDuctFittingTool: React.FC<{ node: AnyNode }> = ({ node }) => {
     }
 
     const onCancel = () => {
+      connectivity?.clear()
       if (existedAtStart) {
         setMeshHidden(false)
         useViewer.getState().setSelection({ selectedIds: [nodeId] })
@@ -256,14 +300,39 @@ export const MoveDuctFittingTool: React.FC<{ node: AnyNode }> = ({ node }) => {
       useEditor.getState().setMovingNode(null)
     }
 
+    // Press-drag-release: when the move was engaged by the drag gesture (the
+    // selection rig's move cross or a future floating drag), `placementDragMode`
+    // is set, so commit on pointer-up at the last previewed position instead of
+    // waiting for a second click — same contract as every other move tool.
+    const onPlacementDragPointerUp = (event: PointerEvent) => {
+      if (!consumePlacementDragRelease(event)) return
+      // A press-release that never moved isn't a placement — back out cleanly
+      // (drop the ghost, re-select the fitting) instead of leaving the tool
+      // armed waiting for a click.
+      if (!hasMoved) {
+        onCancel()
+        return
+      }
+      commit(
+        {
+          nativeEvent: event,
+          stopPropagation: () => event.stopPropagation(),
+        } as unknown as GridEvent,
+        true,
+      )
+    }
+
     emitter.on('grid:move', onMove)
     emitter.on('grid:click', commit)
     emitter.on('tool:cancel', onCancel)
+    window.addEventListener('pointerup', onPlacementDragPointerUp)
 
     return () => {
       emitter.off('grid:move', onMove)
       emitter.off('grid:click', commit)
       emitter.off('tool:cancel', onCancel)
+      window.removeEventListener('pointerup', onPlacementDragPointerUp)
+      connectivity?.clear()
       useAlignmentGuides.getState().clear()
       if (existedAtStart) setMeshHidden(false)
       useScene.temporal.getState().resume()

packages/nodes/src/duct-fitting/parametrics.test.ts

@@ -0,0 +1,271 @@
+import { beforeAll, beforeEach, describe, expect, mock, test } from 'bun:test'
+import {
+  type AnyNode,
+  type AnyNodeId,
+  DuctFittingNode,
+  DuctSegmentNode,
+  useScene,
+} from '@pascal-app/core'
+import { readAutoOffsetTag, withAutoOffsetTag } from '../shared/auto-offset-tag'
+import { getDuctFittingPorts } from './ports'
+
+let ductFittingParametrics: typeof import('./parametrics')['ductFittingParametrics']
+
+type Point = [number, number, number]
+
+function equivalentDiameterIn(widthIn: number, heightIn: number): number {
+  return 2 * Math.sqrt((widthIn * heightIn) / Math.PI)
+}
+
+function rectElbow() {
+  return DuctFittingNode.parse({
+    id: 'duct-fitting_resize' as AnyNodeId,
+    object: 'node',
+    parentId: null,
+    visible: true,
+    metadata: {},
+    name: 'Resize elbow',
+    fittingType: 'elbow',
+    shape: 'rect',
+    width: 14,
+    height: 8,
+    diameter: equivalentDiameterIn(14, 8),
+    diameter2: equivalentDiameterIn(14, 8),
+    ductMaterial: 'sheet-metal',
+    system: 'supply',
+    position: [0, 0, 0],
+    rotation: [0, 0, 0],
+    angle: 90,
+  })
+}
+
+function verticalRectRunFrom(point: Point, roll: number) {
+  return DuctSegmentNode.parse({
+    id: 'duct-segment_vertical' as AnyNodeId,
+    object: 'node',
+    parentId: null,
+    visible: true,
+    metadata: {},
+    name: 'Drawn vertical run',
+    path: [point, [point[0], point[1] + 3, point[2]]],
+    shape: 'rect',
+    width: 14,
+    height: 8,
+    diameter: equivalentDiameterIn(14, 8),
+    roll,
+    ductMaterial: 'sheet-metal',
+    insulationR: 0,
+    system: 'supply',
+  })
+}
+
+describe('ductFittingParametrics', () => {
+  beforeAll(async () => {
+    mock.module('@pascal-app/editor', () => ({
+      ActionButton: () => null,
+    }))
+    ;({ ductFittingParametrics } = await import('./parametrics'))
+  })
+
+  beforeEach(() => {
+    useScene.setState({
+      nodes: {},
+      rootNodeIds: [],
+      dirtyNodes: new Set(),
+      collections: {},
+      readOnly: false,
+    } as never)
+    useScene.temporal.getState().clear()
+  })
+
+  test('resizing a fitting retrims connected ducts without changing their roll', () => {
+    const fitting = rectElbow()
+    const outlet = getDuctFittingPorts(fitting).find((p) => p.id === 'outlet')!
+    const originalRoll = 0.37
+    const duct = verticalRectRunFrom([...outlet.position] as Point, originalRoll)
+
+    useScene.setState({
+      nodes: {
+        [fitting.id]: fitting as AnyNode,
+        [duct.id]: duct as AnyNode,
+      },
+      rootNodeIds: [fitting.id, duct.id],
+      dirtyNodes: new Set(),
+      collections: {},
+      readOnly: false,
+    } as never)
+
+    const patch = { width: 20 }
+    const derived = ductFittingParametrics.derive?.({ ...fitting, ...patch }, patch) ?? {}
+    const next = DuctFittingNode.parse({ ...fitting, ...patch, ...derived })
+    const updates = ductFittingParametrics.reconcile?.(fitting, next) ?? []
+    const ductUpdate = updates.find((u) => u.id === duct.id)
+
+    expect(ductUpdate).toBeDefined()
+    expect((ductUpdate?.data as Partial<DuctSegmentNode>).path).toBeDefined()
+    expect((ductUpdate?.data as Partial<DuctSegmentNode>).roll).toBeUndefined()
+  })
+
+  test('resizing a fitting refreshes a connected duct auto-offset base path', () => {
+    const fitting = rectElbow()
+    const outlet = getDuctFittingPorts(fitting).find((p) => p.id === 'outlet')!
+    const duct = verticalRectRunFrom([...outlet.position] as Point, 0)
+    const taggedDuct = DuctSegmentNode.parse({
+      ...duct,
+      metadata: withAutoOffsetTag(duct.metadata, {
+        group: 'aoff_resize',
+        dy: 1,
+        minted: ['duct-fitting_minted' as AnyNodeId],
+        base: [{ id: duct.id, data: { path: duct.path } }],
+      }),
+    })
+
+    useScene.setState({
+      nodes: {
+        [fitting.id]: fitting as AnyNode,
+        [taggedDuct.id]: taggedDuct as AnyNode,
+      },
+      rootNodeIds: [fitting.id, taggedDuct.id],
+      dirtyNodes: new Set(),
+      collections: {},
+      readOnly: false,
+    } as never)
+
+    const patch = { width: 20 }
+    const derived = ductFittingParametrics.derive?.({ ...fitting, ...patch }, patch) ?? {}
+    const next = DuctFittingNode.parse({ ...fitting, ...patch, ...derived })
+    const updates = ductFittingParametrics.reconcile?.(fitting, next) ?? []
+    const ductUpdate = updates.find((u) => u.id === taggedDuct.id)
+    const nextOutlet = getDuctFittingPorts(next).find((p) => p.id === 'outlet')!
+    const nextTag = readAutoOffsetTag({ metadata: ductUpdate?.data.metadata })
+    const basePath = nextTag?.base.find((b) => b.id === taggedDuct.id)?.data.path as
+      | Point[]
+      | undefined
+
+    expect(basePath?.[0]).toEqual([...nextOutlet.position])
+  })
+
+  test('deleting an elbow re-extends mated runs back onto the junction', () => {
+    const fitting = rectElbow()
+    const ports = getDuctFittingPorts(fitting)
+    const outlet = ports.find((p) => p.id === 'outlet')!
+    const inlet = ports.find((p) => p.id === 'inlet')!
+    // Two runs meeting the elbow's collars — the L-shape the elbow trimmed.
+    const outletRun = verticalRectRunFrom([...outlet.position] as Point, 0)
+    const inletRun = DuctSegmentNode.parse({
+      ...verticalRectRunFrom([...inlet.position] as Point, 0),
+      id: 'duct-segment_inlet' as AnyNodeId,
+      path: [
+        [...inlet.position] as Point,
+        [inlet.position[0] - 3, inlet.position[1], inlet.position[2]],
+      ],
+    })
+
+    const nodes: Record<AnyNodeId, AnyNode> = {
+      [fitting.id]: fitting as AnyNode,
+      [outletRun.id]: outletRun as AnyNode,
+      [inletRun.id]: inletRun as AnyNode,
+    }
+
+    const updates = ductFittingParametrics.onDelete?.(fitting, nodes) ?? []
+    const outletUpdate = updates.find((u) => u.id === outletRun.id)
+    const inletUpdate = updates.find((u) => u.id === inletRun.id)
+
+    // Both mated endpoints snap back to the junction (the original corner).
+    expect((outletUpdate?.data as Partial<DuctSegmentNode>).path?.[0]).toEqual([
+      ...fitting.position,
+    ])
+    expect((inletUpdate?.data as Partial<DuctSegmentNode>).path?.[0]).toEqual([...fitting.position])
+  })
+
+  test('delete repair matches the 5 cm live connectivity mate tolerance', () => {
+    const fitting = rectElbow()
+    const outlet = getDuctFittingPorts(fitting).find((p) => p.id === 'outlet')!
+    const nearOutlet: Point = [outlet.position[0], outlet.position[1], outlet.position[2] + 0.04]
+    const outletRun = DuctSegmentNode.parse({
+      ...verticalRectRunFrom(nearOutlet, 0),
+      id: 'duct-segment_outlet_gap' as AnyNodeId,
+    })
+    const nodes: Record<AnyNodeId, AnyNode> = {
+      [fitting.id]: fitting as AnyNode,
+      [outletRun.id]: outletRun as AnyNode,
+    }
+
+    const updates = ductFittingParametrics.onDelete?.(fitting, nodes) ?? []
+    const outletUpdate = updates.find((u) => u.id === outletRun.id)
+
+    expect((outletUpdate?.data as Partial<DuctSegmentNode>).path?.[0]).toEqual([
+      ...fitting.position,
+    ])
+  })
+
+  test('deleting a generated elbow clears the owner duct auto-offset tag', () => {
+    const fitting = rectElbow()
+    const outlet = getDuctFittingPorts(fitting).find((p) => p.id === 'outlet')!
+    const duct = verticalRectRunFrom([...outlet.position] as Point, 0)
+    const taggedDuct = DuctSegmentNode.parse({
+      ...duct,
+      metadata: withAutoOffsetTag(duct.metadata, {
+        group: 'aoff_deleted_elbow',
+        dy: 1,
+        minted: [fitting.id],
+        base: [{ id: duct.id, data: { path: duct.path } }],
+      }),
+    })
+    const nodes: Record<AnyNodeId, AnyNode> = {
+      [fitting.id]: fitting as AnyNode,
+      [taggedDuct.id]: taggedDuct as AnyNode,
+    }
+
+    const updates = ductFittingParametrics.onDelete?.(fitting, nodes) ?? []
+    const finalDuctUpdate = updates.filter((u) => u.id === taggedDuct.id).at(-1)
+
+    expect(readAutoOffsetTag({ metadata: finalDuctUpdate?.data.metadata })).toBeNull()
+  })
+
+  test('deleting a tee leaves mated runs untouched', () => {
+    const tee = DuctFittingNode.parse({ ...rectElbow(), fittingType: 'tee' })
+    const outlet = getDuctFittingPorts(tee).find((p) => p.id === 'outlet')!
+    const duct = verticalRectRunFrom([...outlet.position] as Point, 0)
+    const nodes: Record<AnyNodeId, AnyNode> = {
+      [tee.id]: tee as AnyNode,
+      [duct.id]: duct as AnyNode,
+    }
+
+    expect(ductFittingParametrics.onDelete?.(tee, nodes) ?? []).toEqual([])
+  })
+
+  test('resizing a generated fitting clears the owner duct auto-offset tag', () => {
+    const fitting = rectElbow()
+    const outlet = getDuctFittingPorts(fitting).find((p) => p.id === 'outlet')!
+    const duct = verticalRectRunFrom([...outlet.position] as Point, 0)
+    const taggedDuct = DuctSegmentNode.parse({
+      ...duct,
+      metadata: withAutoOffsetTag(duct.metadata, {
+        group: 'aoff_generated_fit',
+        dy: 1,
+        minted: [fitting.id],
+        base: [{ id: duct.id, data: { path: duct.path } }],
+      }),
+    })
+
+    useScene.setState({
+      nodes: {
+        [fitting.id]: fitting as AnyNode,
+        [taggedDuct.id]: taggedDuct as AnyNode,
+      },
+      rootNodeIds: [fitting.id, taggedDuct.id],
+      dirtyNodes: new Set(),
+      collections: {},
+      readOnly: false,
+    } as never)
+
+    const patch = { width: 20 }
+    const derived = ductFittingParametrics.derive?.({ ...fitting, ...patch }, patch) ?? {}
+    const next = DuctFittingNode.parse({ ...fitting, ...patch, ...derived })
+    const updates = ductFittingParametrics.reconcile?.(fitting, next) ?? []
+    const finalDuctUpdate = updates.filter((u) => u.id === taggedDuct.id).at(-1)
+
+    expect(readAutoOffsetTag({ metadata: finalDuctUpdate?.data.metadata })).toBeNull()
+  })
+})

packages/nodes/src/duct-fitting/parametrics.ts

@@ -7,19 +7,41 @@ import {
 } from '@pascal-app/core'
 import { Vector3 } from 'three'
 import {
-  ductPortDiameterIn,
-  equivalentDiameterIn,
-  ovalEquivalentDiameterIn,
-  rollToContinueAcrossElbow,
-} from '../duct-segment/geometry'
+  autoOffsetInvalidationUpdates,
+  readAutoOffsetTag,
+  withAutoOffsetTag,
+} from '../shared/auto-offset-tag'
+import { DuctFittingSizeSwapEditor } from './inspector-editors'
 import { getDuctFittingPorts } from './ports'
 import type { DuctFittingNode } from './schema'
 
 /** Schema bounds for `diameter` / `diameter2`. */
 const clampDiameter = (d: number) => Math.min(48, Math.max(2, d))
 
+const equivalentDiameterIn = (widthIn: number, heightIn: number): number =>
+  2 * Math.sqrt((widthIn * heightIn) / Math.PI)
+
+const ovalEquivalentDiameterIn = (widthIn: number, heightIn: number): number => {
+  const minor = Math.min(widthIn, heightIn)
+  const major = Math.max(widthIn, heightIn)
+  const area = (major - minor) * minor + Math.PI * (minor / 2) ** 2
+  return 2 * Math.sqrt(area / Math.PI)
+}
+
+const ductPortDiameterIn = (node: DuctSegmentNode): number => {
+  if (node.shape === 'rect' && node.width && node.height) {
+    return equivalentDiameterIn(node.width, node.height)
+  }
+  if (node.shape === 'oval' && node.width && node.height) {
+    return ovalEquivalentDiameterIn(node.width, node.height)
+  }
+  return node.diameter
+}
+
 /** A duct endpoint sitting this close to a collar counts as mated. */
-const MATE_TOL_M = 0.03
+const MATE_TOL_M = 0.05
+
+type Point = [number, number, number]
 
 type DuctMate = { duct: DuctSegmentNode; endIndex: number }
 
@@ -28,10 +50,13 @@ type DuctMate = { duct: DuctSegmentNode; endIndex: number }
  * port id. Auto-minted joints place duct ends exactly on the collar, so
  * a tight distance check is enough — no connectivity graph yet.
  */
-function matedDucts(fitting: DuctFittingNode): Map<string, DuctMate> {
+function matedDucts(
+  fitting: DuctFittingNode,
+  nodes: Record<AnyNodeId, AnyNode> = useScene.getState().nodes,
+): Map<string, DuctMate> {
   const mates = new Map<string, DuctMate>()
   const ports = getDuctFittingPorts(fitting)
-  for (const node of Object.values(useScene.getState().nodes)) {
+  for (const node of Object.values(nodes)) {
     if (node.type !== 'duct-segment') continue
     const duct = node as DuctSegmentNode
     for (const endIndex of [0, duct.path.length - 1]) {
@@ -51,6 +76,25 @@ function matedDucts(fitting: DuctFittingNode): Map<string, DuctMate> {
   return mates
 }
 
+function refreshedAutoOffsetMetadata(
+  duct: DuctSegmentNode,
+  endIndex: number,
+  target: Point,
+): Record<string, unknown> | null {
+  const tag = readAutoOffsetTag(duct)
+  if (!tag) return null
+  let changed = false
+  const base = tag.base.map((patch) => {
+    if (patch.id !== duct.id || !Array.isArray(patch.data.path)) return patch
+    const path = patch.data.path.map((p) => (Array.isArray(p) ? [...p] : p))
+    if (!Array.isArray(path[endIndex])) return patch
+    path[endIndex] = [...target]
+    changed = true
+    return { ...patch, data: { ...patch.data, path } }
+  })
+  return changed ? withAutoOffsetTag(duct.metadata, { ...tag, base }) : null
+}
+
 export const ductFittingParametrics: ParametricDescriptor<DuctFittingNode> = {
   // Switching the run legs round↔rect flips the whole fitting and sizes
   // the new profile off the ducts actually mated to its collars, so the
@@ -127,34 +171,48 @@ export const ductFittingParametrics: ParametricDescriptor<DuctFittingNode> = {
         path[mate.endIndex] = [...target.position]
         data.path = path
       }
-      // Steep rect / oval runs also re-derive their cross-section roll
-      // so a riser's profile stays continuous through the fitting (same
-      // continuity the draw tool computes; runs flipped to rect after
-      // drawing never got it). Horizontal runs are left alone — their
-      // roll-0 orientation is canonical and re-deriving it from a
-      // possibly-stale riser roll would corrupt it.
-      if (next.shape !== 'round' && mate.duct.shape !== 'round') {
-        const away = mate.duct.path[mate.endIndex === 0 ? 1 : mate.duct.path.length - 2]
-        const source = getDuctFittingPorts(next).find(
-          (p) => p.id !== portId && p.id !== 'branch' && p.id !== 'branch2',
-        )
-        if (away && source) {
-          const newDir = new Vector3(away[0] - end[0], away[1] - end[1], away[2] - end[2])
-          if (newDir.lengthSq() >= 1e-10) {
-            newDir.normalize()
-            if (Math.abs(newDir.y) >= Math.SQRT1_2) {
-              const srcMate = mates.get(source.id)
-              const srcRoll = srcMate && srcMate.duct.shape !== 'round' ? srcMate.duct.roll : 0
-              const srcDir = new Vector3(...source.direction)
-              const roll = rollToContinueAcrossElbow(srcDir, srcRoll, srcDir, newDir)
-              if (Math.abs(roll - mate.duct.roll) > 1e-6) data.roll = roll
-            }
-          }
-        }
-      }
+      const metadata = refreshedAutoOffsetMetadata(
+        mate.duct,
+        mate.endIndex,
+        target.position as Point,
+      )
+      if (metadata) data.metadata = metadata as DuctSegmentNode['metadata']
       if (Object.keys(data).length > 0) updates.push({ id: mate.duct.id, data })
     }
-    return updates
+    return [...updates, ...autoOffsetInvalidationUpdates(useScene.getState().nodes, next.id)]
+  },
+
+  // Deleting an auto-inserted elbow restores the corner it replaced: both
+  // mated runs were pulled back one leg onto its collars, with the
+  // junction (the fitting's position) sitting exactly on the corner they
+  // originally met at. Re-extend each mated endpoint back to that junction
+  // so the L-shape returns to its pre-fitting length. Scoped to elbows —
+  // tees / crosses split a trunk into two separate nodes, which can't be
+  // re-joined by moving an endpoint.
+  onDelete: (fitting, nodes) => {
+    const invalidations = autoOffsetInvalidationUpdates(nodes, fitting.id)
+    if (fitting.fittingType !== 'elbow') return invalidations
+    const junction = new Vector3(...fitting.position)
+    const updates: Array<{ id: AnyNodeId; data: Partial<AnyNode> }> = []
+    for (const mate of matedDucts(fitting, nodes).values()) {
+      const end = mate.duct.path[mate.endIndex]
+      if (!end) continue
+      const dx = end[0] - junction.x
+      const dy = end[1] - junction.y
+      const dz = end[2] - junction.z
+      if (dx * dx + dy * dy + dz * dz < 1e-12) continue
+      const path = mate.duct.path.map((p) => [...p] as Point)
+      path[mate.endIndex] = [junction.x, junction.y, junction.z]
+      const data: Partial<DuctSegmentNode> = { path }
+      const metadata = refreshedAutoOffsetMetadata(mate.duct, mate.endIndex, [
+        junction.x,
+        junction.y,
+        junction.z,
+      ])
+      if (metadata) data.metadata = metadata as DuctSegmentNode['metadata']
+      updates.push({ id: mate.duct.id, data })
+    }
+    return [...updates, ...invalidations]
   },
   groups: [
     {
@@ -170,7 +228,7 @@ export const ductFittingParametrics: ParametricDescriptor<DuctFittingNode> = {
           key: 'angle',
           kind: 'number',
           unit: '°',
-          min: 15,
+          min: 0,
           max: 90,
           step: 15,
           visibleIf: (n) => n.fittingType === 'elbow',
@@ -236,6 +294,13 @@ export const ductFittingParametrics: ParametricDescriptor<DuctFittingNode> = {
           visibleIf: (n) =>
             n.fittingType === 'transition' || (n.shape !== 'round' && n.fittingType !== 'reducer'),
         },
+        {
+          key: 'swapWidthHeight',
+          kind: 'custom',
+          component: DuctFittingSizeSwapEditor,
+          visibleIf: (n) =>
+            n.fittingType === 'transition' || (n.shape !== 'round' && n.fittingType !== 'reducer'),
+        },
         {
           key: 'shape2',
           kind: 'enum',

packages/nodes/src/duct-fitting/ports.ts

@@ -1,8 +1,9 @@
 import type { NodePort } from '@pascal-app/core'
 import { Euler, Vector3 } from 'three'
-import { INCHES_TO_METERS } from '../duct-segment/geometry'
 import type { DuctFittingNode } from './schema'
 
+const INCHES_TO_METERS = 0.0254
+
 /**
  * Collar stub length in meters — how far each port sticks out from the
  * fitting's junction center. Scales with the duct so big trunks get

packages/nodes/src/duct-fitting/selection.tsx

@@ -1,27 +1,299 @@
 'use client'
 
-import { type AnyNodeId, useScene } from '@pascal-app/core'
+import {
+  type AnyNode,
+  type AnyNodeId,
+  analyzePortConnectivity,
+  type Cursor,
+  type DuctFittingNode,
+  type PortConnectivity,
+  pauseSceneHistory,
+  resolveConnectivityUpdates,
+  resumeSceneHistory,
+  sceneRegistry,
+  useScene,
+} from '@pascal-app/core'
+import {
+  ARROW_COLOR,
+  EDITOR_LAYER,
+  swallowNextClick,
+  triggerSFX,
+  useEditor,
+} from '@pascal-app/editor'
 import { useViewer } from '@pascal-app/viewer'
-import { useEffect } from 'react'
-import { cycleRotationAxis } from '../shared/fitting-rotation'
+import { createPortal, type ThreeEvent, useFrame, useThree } from '@react-three/fiber'
+import { useEffect, useMemo, useState } from 'react'
+import {
+  BufferGeometry,
+  Euler,
+  Float32BufferAttribute,
+  type Group,
+  LineSegments,
+  type Object3D,
+  OrthographicCamera,
+  Plane,
+  Quaternion,
+  Raycaster,
+  SphereGeometry,
+  Vector2,
+  Vector3,
+} from 'three'
+import { LineBasicNodeMaterial, MeshBasicNodeMaterial } from 'three/webgpu'
+import { INCHES_TO_METERS } from '../duct-segment/geometry'
+import { autoOffsetInvalidationUpdates } from '../shared/auto-offset-tag'
+import {
+  AXIS_VECTORS,
+  cycleRotationAxis,
+  ROTATE_STEP_RAD,
+  type RotationAxis,
+} from '../shared/fitting-rotation'
+import { HandleCube, MoveChevron, RotateArc } from '../shared/selection-handles'
+import { fittingLegLength } from './ports'
+
+type Point = [number, number, number]
+
+/** Stand-off (meters) from the fitting body to each arrow. */
+const ARROW_GAP = 0.14
+const RESIZE_HANDLE_GAP = 0.18
+const RESIZE_STEP_IN = 1
+const RESIZE_GUIDE_DASH = 0.07
+const RESIZE_GUIDE_GAP = 0.045
+const RESIZE_SPHERE_RADIUS = 0.065
+const RESIZE_HIT_RADIUS = 0.13
+
+const UP = new Vector3(0, 1, 0)
+
+function snap(value: number, step: number): number {
+  if (step <= 0) return value
+  return Math.round(value / step) * step
+}
+
+function clamp(value: number, min: number, max: number): number {
+  return Math.min(max, Math.max(min, value))
+}
+
+/** Rough body radius (meters) — the larger of the fitting's two collar reaches,
+ *  used to stand the handles clear of the geometry. */
+function fittingExtentM(node: DuctFittingNode): number {
+  const d2 = (node as { diameter2?: number }).diameter2 ?? node.diameter
+  return Math.max(fittingLegLength(node.diameter), fittingLegLength(d2))
+}
+
+/** The transform a drag frame writes onto the fitting. */
+type FittingTransform = { position?: Point; rotation?: Point }
+type FittingDimension = 'width' | 'height'
+
+function fittingParameterPatch(node: DuctFittingNode): Partial<DuctFittingNode> {
+  return {
+    fittingType: node.fittingType,
+    shape: node.shape,
+    width: node.width,
+    height: node.height,
+    shape2: node.shape2,
+    width2: node.width2,
+    height2: node.height2,
+    angle: node.angle,
+    branchAngle: node.branchAngle,
+    diameter: node.diameter,
+    diameter2: node.diameter2,
+    ductMaterial: node.ductMaterial,
+    system: node.system,
+  }
+}
+
+function preserveFittingParameters(
+  node: DuctFittingNode,
+  data: Partial<DuctFittingNode>,
+): Partial<AnyNode> {
+  return { ...fittingParameterPatch(node), ...data } as Partial<AnyNode>
+}
+
+function canResizeRunProfile(node: DuctFittingNode): boolean {
+  return (
+    node.fittingType === 'transition' || (node.fittingType !== 'reducer' && node.shape !== 'round')
+  )
+}
+
+function dimensionBounds(dimension: FittingDimension): { min: number; max: number } {
+  return dimension === 'width' ? { min: 4, max: 60 } : { min: 3, max: 40 }
+}
+
+function closestAxisParameterToRay(
+  axisOrigin: Vector3,
+  axisDirection: Vector3,
+  ray: Raycaster['ray'],
+) {
+  const originToRay = axisOrigin.clone().sub(ray.origin)
+  const b = axisDirection.dot(ray.direction)
+  const d = axisDirection.dot(originToRay)
+  const e = ray.direction.dot(originToRay)
+  const denominator = 1 - b * b
+  if (Math.abs(denominator) < 1e-6) return -d
+  const axisParameter = (b * e - d) / denominator
+  const rayParameter = e + b * axisParameter
+  return rayParameter < 0 ? -d : axisParameter
+}
+
+function DashedResizeGuide({ from, to }: { from: Point; to: Point }) {
+  const line = useMemo(() => {
+    const a = new Vector3(from[0], from[1], from[2])
+    const b = new Vector3(to[0], to[1], to[2])
+    const span = b.clone().sub(a)
+    const length = span.length()
+    const points: number[] = []
+    if (length > 1e-4) {
+      const dir = span.clone().normalize()
+      let t = 0
+      while (t < length) {
+        const start = a.clone().addScaledVector(dir, t)
+        const end = a.clone().addScaledVector(dir, Math.min(t + RESIZE_GUIDE_DASH, length))
+        points.push(start.x, start.y, start.z, end.x, end.y, end.z)
+        t += RESIZE_GUIDE_DASH + RESIZE_GUIDE_GAP
+      }
+    }
+    const geometry = new BufferGeometry()
+    geometry.setAttribute('position', new Float32BufferAttribute(new Float32Array(points), 3))
+    const material = new LineBasicNodeMaterial({
+      color: ARROW_COLOR,
+      transparent: true,
+      opacity: 0.8,
+      depthWrite: false,
+    })
+    const next = new LineSegments(geometry, material)
+    next.frustumCulled = false
+    next.layers.set(EDITOR_LAYER)
+    next.renderOrder = 1002
+    next.raycast = () => {}
+    return next
+  }, [from, to])
+
+  useEffect(
+    () => () => {
+      line.geometry.dispose()
+      ;(line.material as LineBasicNodeMaterial).dispose()
+    },
+    [line],
+  )
+
+  return <primitive object={line} />
+}
+
+function ResizeSphereHandle({
+  cursor,
+  onPointerDown,
+  position,
+}: {
+  cursor: Cursor
+  onPointerDown: (event: ThreeEvent<PointerEvent>) => void
+  position: Point
+}) {
+  const { camera } = useThree()
+  const [hovered, setHovered] = useState(false)
+  const zoom = camera instanceof OrthographicCamera ? 1 / camera.zoom : 1
+  const sphereGeometry = useMemo(() => new SphereGeometry(RESIZE_SPHERE_RADIUS, 18, 12), [])
+  const hitGeometry = useMemo(() => new SphereGeometry(RESIZE_HIT_RADIUS, 12, 8), [])
+  const sphereMaterial = useMemo(
+    () =>
+      new MeshBasicNodeMaterial({
+        color: ARROW_COLOR,
+        transparent: true,
+        opacity: 0.92,
+        depthTest: false,
+        depthWrite: false,
+      }),
+    [],
+  )
+  const hitMaterial = useMemo(
+    () =>
+      new MeshBasicNodeMaterial({
+        color: ARROW_COLOR,
+        transparent: true,
+        opacity: 0,
+        depthTest: false,
+        depthWrite: false,
+      }),
+    [],
+  )
+
+  useEffect(() => {
+    sphereMaterial.opacity = hovered ? 1 : 0.92
+  }, [sphereMaterial, hovered])
+  useEffect(
+    () => () => {
+      hitGeometry.dispose()
+      sphereGeometry.dispose()
+      sphereMaterial.dispose()
+      hitMaterial.dispose()
+    },
+    [hitGeometry, hitMaterial, sphereGeometry, sphereMaterial],
+  )
+
+  const consumePress = (event: ThreeEvent<PointerEvent>) => {
+    event.stopPropagation()
+    event.nativeEvent.stopPropagation()
+    event.nativeEvent.stopImmediatePropagation()
+    swallowNextClick()
+    onPointerDown(event)
+  }
+
+  return (
+    <group position={position} scale={zoom}>
+      <mesh
+        geometry={hitGeometry}
+        material={hitMaterial}
+        onPointerDown={consumePress}
+        onPointerEnter={(event) => {
+          event.stopPropagation()
+          setHovered(true)
+          document.body.style.cursor = cursor
+        }}
+        onPointerLeave={(event) => {
+          event.stopPropagation()
+          setHovered(false)
+          if (document.body.style.cursor === cursor) document.body.style.cursor = ''
+        }}
+      />
+      <mesh geometry={sphereGeometry} material={sphereMaterial} renderOrder={1004} />
+    </group>
+  )
+}
 
 /**
- * Selection-time rotation support for placed fittings, mounted by the
- * editor's SelectionAffordanceManager (`def.affordanceTools.selection`).
- * The R/T rotation itself lives in `def.keyboardActions` (the editor's
- * keyboard hook dispatches it); this contributes the piece that hook
- * can't: **Alt cycles the active rotation axis** while a single fitting
- * is selected. The axis lives on `useEditor.rotationAxis`, which the
- * floating action menu reads to show the axis pill above the selected
- * fitting — so this component renders nothing.
+ * Selection-time affordances for a placed duct fitting — the 3D twin of the
+ * duct-segment selection rig. A CLICK-to-latch cube sits at the fitting center;
+ * clicking it opens (click again to close) a cluster of:
+ *
+ *  - **Six move arrows** (±X / ±Y / ±Z): translate the whole fitting along one
+ *    world axis. Connected runs follow via port connectivity.
+ *  - **Three rotation arcs** (X / Y / Z): spin the fitting about each world
+ *    axis. Connected runs re-aim via port follow.
+ *  - **Two profile cubes** on the fitting's visible side/top faces: resize
+ *    non-round fitting width and height without occupying the inside corner.
+ *
+ * The handle rig is PORTALED into the fitting group's PARENT — never the
+ * fitting group itself — because the selection outliner (`MergedOutlineNode`)
+ * traces every descendant mesh of the SELECTED node, so a hit-area cylinder
+ * parented under the fitting would be swept into its selection outline. Walls /
+ * doors / windows dodge it the same way. The fitting's local `position` is
+ * expressed in the parent's frame, so an identity group under the parent lets
+ * us place handles at absolute level-local coords with world-aligned axes.
+ *
+ * History does the single-undo dance: paused during the drag (live ticks are
+ * untracked), reverted on release, resumed, then the final transform re-applied
+ * as one tracked change so the whole joint is one undo step.
  */
 const DuctFittingSelectionAffordance = () => {
   const selectedIds = useViewer((s) => s.selection.selectedIds)
-  const hasSelectedFitting = useScene((s) => {
-    if (selectedIds.length !== 1) return false
-    return s.nodes[selectedIds[0] as AnyNodeId]?.type === 'duct-fitting'
+  const fitting = useScene((s) => {
+    if (selectedIds.length !== 1) return null
+    const node = s.nodes[selectedIds[0] as AnyNodeId]
+    return node?.type === 'duct-fitting' ? (node as DuctFittingNode) : null
   })
 
+  // Alt cycles the active rotation axis for the R / T keyboard rotate while a
+  // single fitting is selected (the gizmo's three arcs cover every axis on
+  // their own; this only keeps the keyboard action meaningful).
+  const hasSelectedFitting = !!fitting
   useEffect(() => {
     if (!hasSelectedFitting) return
     const onKeyDown = (e: KeyboardEvent) => {
@@ -31,13 +303,586 @@ const DuctFittingSelectionAffordance = () => {
       e.preventDefault()
       cycleRotationAxis()
     }
-    // Bubble phase — when the placement tool is active its capture-phase
-    // handler stops propagation, so the two never double-cycle.
     window.addEventListener('keydown', onKeyDown)
     return () => window.removeEventListener('keydown', onKeyDown)
   }, [hasSelectedFitting])
 
-  return null
+  // Portal target: the fitting's registered group. Resolved with a rAF retry
+  // because registration lands on the renderer's mount, a frame after select.
+  const fittingId = fitting?.id ?? null
+  const [target, setTarget] = useState<Object3D | null>(null)
+  useEffect(() => {
+    if (!fittingId) {
+      setTarget(null)
+      return
+    }
+    let frameId = 0
+    const resolve = () => {
+      const next = sceneRegistry.nodes.get(fittingId as AnyNodeId) ?? null
+      setTarget((cur) => (cur === next ? cur : next))
+      if (!next) frameId = window.requestAnimationFrame(resolve)
+    }
+    resolve()
+    return () => window.cancelAnimationFrame(frameId)
+  }, [fittingId])
+
+  if (!fitting || !target) return null
+  const mount = target.parent ?? target
+  return createPortal(<FittingHandles fitting={fitting} target={target} />, mount, undefined)
+}
+
+const FittingHandles = ({ fitting, target }: { fitting: DuctFittingNode; target: Object3D }) => {
+  const { camera, gl } = useThree()
+  const [frame, setFrame] = useState<Group | null>(null)
+  // True while the cluster is latched open. Click the center cube to toggle.
+  const [open, setOpen] = useState(false)
+  // True while a move / rotate drag is live — the arrows hide (the window
+  // pointer handlers own the gesture), exactly like the duct-segment rig.
+  const [dragging, setDragging] = useState(false)
+  const [sideSign, setSideSign] = useState(1)
+
+  const makeRay = (clientX: number, clientY: number) => {
+    const rect = gl.domElement.getBoundingClientRect()
+    const ndc = new Vector2(
+      ((clientX - rect.left) / rect.width) * 2 - 1,
+      -((clientY - rect.top) / rect.height) * 2 + 1,
+    )
+    const raycaster = new Raycaster()
+    raycaster.setFromCamera(ndc, camera)
+    return raycaster.ray
+  }
+  const intersect = (clientX: number, clientY: number, plane: Plane): Vector3 | null => {
+    const hit = new Vector3()
+    return makeRay(clientX, clientY).intersectPlane(plane, hit) ? hit : null
+  }
+  const sampleAxisParameter = (
+    clientX: number,
+    clientY: number,
+    axisOrigin: Vector3,
+    axisDirection: Vector3,
+  ): number => closestAxisParameterToRay(axisOrigin, axisDirection, makeRay(clientX, clientY))
+  /** World hit on a vertical, camera-facing plane through `anchorWorld`,
+   *  returned as a level-local Y (the frame is axis-aligned to the parent). */
+  const intersectVerticalY = (
+    clientX: number,
+    clientY: number,
+    anchorWorld: Vector3,
+  ): number | null => {
+    if (!frame) return null
+    const forward = camera.getWorldDirection(new Vector3())
+    forward.y = 0
+    if (forward.lengthSq() < 1e-6) forward.set(0, 0, 1)
+    forward.normalize()
+    const plane = new Plane().setFromNormalAndCoplanarPoint(forward, anchorWorld)
+    const hit = intersect(clientX, clientY, plane)
+    return hit ? frame.worldToLocal(hit.clone()).y : null
+  }
+
+  const toWorld = (p: Point): Vector3 =>
+    frame ? frame.localToWorld(new Vector3(p[0], p[1], p[2])) : new Vector3(p[0], p[1], p[2])
+  const axisToWorld = (origin: Point, axis: Vector3): Vector3 => {
+    const originWorld = toWorld(origin)
+    const tipWorld = frame
+      ? frame.localToWorld(new Vector3(origin[0] + axis.x, origin[1] + axis.y, origin[2] + axis.z))
+      : new Vector3(origin[0] + axis.x, origin[1] + axis.y, origin[2] + axis.z)
+    return tipWorld.sub(originWorld).normalize()
+  }
+
+  /** Cursor's coordinate on one world axis, in the frame's local space. For Y
+   *  it rides a camera-facing vertical plane; for X / Z it projects onto the
+   *  horizontal plane through the fitting and reads back the local component. */
+  const sampleAxis = (
+    axis: RotationAxis,
+    clientX: number,
+    clientY: number,
+    anchorWorld: Vector3,
+  ): number | null => {
+    if (axis === 'y') return intersectVerticalY(clientX, clientY, anchorWorld)
+    const plane = new Plane().setFromNormalAndCoplanarPoint(UP, anchorWorld)
+    const hit = intersect(clientX, clientY, plane)
+    if (!hit || !frame) return null
+    const local = frame.worldToLocal(hit.clone())
+    return axis === 'x' ? local.x : local.z
+  }
+
+  // Follow-updates for runs / fittings mated to this fitting, given a preview
+  // transform. Endpoints whose ports didn't move resolve to a zero delta.
+  const connectivityUpdates = (
+    connectivity: PortConnectivity | null,
+    transform: FittingTransform,
+  ): { id: AnyNodeId; data: Partial<AnyNode> }[] => {
+    if (!connectivity) return []
+    const preview = { ...(fitting as Record<string, unknown>), ...transform } as AnyNode
+    const nodes = useScene.getState().nodes
+    return resolveConnectivityUpdates(connectivity, preview)
+      .filter((u) => nodes[u.id])
+      .map((u) => {
+        const node = nodes[u.id]
+        if (node?.type !== 'duct-fitting') return u
+        return {
+          id: u.id,
+          data: preserveFittingParameters(
+            node as DuctFittingNode,
+            u.data as Partial<DuctFittingNode>,
+          ),
+        }
+      })
+  }
+
+  /**
+   * Shared lifecycle for the move / rotate drags. `makeCompute` is built at
+   * pointer-down so it can capture the grab anchor (cursor's start coord /
+   * bearing) and avoid a teleport. Each frame `compute` turns the cursor into
+   * the fitting's next transform; the fitting writes it and any mated runs
+   * follow via port connectivity. Lands as one undo step.
+   */
+  const beginDrag =
+    (
+      cursor: Cursor,
+      makeCompute: (
+        e: ThreeEvent<PointerEvent>,
+      ) => (event: PointerEvent) => FittingTransform | null,
+    ) =>
+    (e: ThreeEvent<PointerEvent>) => {
+      e.stopPropagation()
+      const initialPosition = [...fitting.position] as Point
+      const initialRotation = [...fitting.rotation] as Point
+      const connectivity = analyzePortConnectivity(fitting as AnyNode, useScene.getState().nodes)
+      const compute = makeCompute(e)
+      pauseSceneHistory(useScene)
+      useViewer.getState().setInputDragging(true)
+      setDragging(true)
+      document.body.style.cursor = cursor
+      let current: FittingTransform | null = null
+
+      const buildBatch = (t: FittingTransform): { id: AnyNodeId; data: Partial<AnyNode> }[] => [
+        {
+          id: fitting.id as AnyNodeId,
+          data: preserveFittingParameters(fitting, t as Partial<DuctFittingNode>),
+        },
+        ...connectivityUpdates(connectivity, t),
+      ]
+
+      const onMove = (event: PointerEvent) => {
+        const next = compute(event)
+        if (!next) return
+        current = next
+        useScene.getState().updateNodes(buildBatch(next))
+      }
+
+      const cleanup = () => {
+        window.removeEventListener('pointermove', onMove)
+        window.removeEventListener('pointerup', onUp)
+        window.removeEventListener('pointercancel', onUp)
+        useViewer.getState().setInputDragging(false)
+        setDragging(false)
+        if (document.body.style.cursor === cursor) document.body.style.cursor = ''
+      }
+
+      const onUp = () => {
+        // Swallow the trailing synthetic click so it doesn't reach the
+        // background-click deselect handler (cleanup drops `inputDragging`
+        // synchronously here).
+        swallowNextClick()
+        cleanup()
+        // Single-undo dance: revert the fitting AND its followers to the
+        // pre-drag state while history is still paused, resume, then re-apply
+        // the final transform as one tracked change.
+        const reverts: { id: AnyNodeId; data: Partial<AnyNode> }[] = (
+          connectivity?.connections ?? []
+        ).map((conn) => {
+          if (conn.kind !== 'rigid-node') {
+            return { id: conn.nodeId, data: { path: conn.startPath } as Partial<AnyNode> }
+          }
+          const node = useScene.getState().nodes[conn.nodeId]
+          return {
+            id: conn.nodeId,
+            data:
+              node?.type === 'duct-fitting'
+                ? preserveFittingParameters(node as DuctFittingNode, {
+                    position: conn.startPosition as Point,
+                  })
+                : ({ position: conn.startPosition } as Partial<AnyNode>),
+          }
+        })
+        useScene.getState().updateNodes([
+          {
+            id: fitting.id as AnyNodeId,
+            data: preserveFittingParameters(fitting, {
+              position: initialPosition,
+              rotation: initialRotation,
+            }),
+          },
+          ...reverts.filter((u) => useScene.getState().nodes[u.id]),
+        ])
+        resumeSceneHistory(useScene)
+        if (current) {
+          const scene = useScene.getState()
+          scene.updateNodes([
+            ...buildBatch(current),
+            ...autoOffsetInvalidationUpdates(scene.nodes, fitting.id as AnyNodeId),
+          ])
+        }
+      }
+
+      window.addEventListener('pointermove', onMove)
+      window.addEventListener('pointerup', onUp)
+      window.addEventListener('pointercancel', onUp)
+    }
+
+  // Move: translate the fitting along one world axis, anchored to the cursor's
+  // start coord so it doesn't jump on grab. Y is clamped at the floor; Shift
+  // bypasses grid snapping.
+  const moveCompute =
+    (axis: RotationAxis) =>
+    (e: ThreeEvent<PointerEvent>): ((event: PointerEvent) => FittingTransform | null) => {
+      const anchorWorld = toWorld(fitting.position as Point)
+      const start = sampleAxis(axis, e.nativeEvent.clientX, e.nativeEvent.clientY, anchorWorld)
+      const base = [...fitting.position] as Point
+      const axisIndex = axis === 'x' ? 0 : axis === 'y' ? 1 : 2
+      let lastDelta = Number.NaN
+      return (event: PointerEvent): FittingTransform | null => {
+        if (start === null) return null
+        const s = sampleAxis(axis, event.clientX, event.clientY, anchorWorld)
+        if (s === null) return null
+        const step = event.shiftKey ? 0 : useEditor.getState().gridSnapStep
+        const delta = snap(s - start, step)
+        if (delta === lastDelta) return null
+        lastDelta = delta
+        if (step > 0) triggerSFX('sfx:grid-snap')
+        const next = [...base] as Point
+        next[axisIndex] = (
+          axis === 'y' ? Math.max(0, base[axisIndex] + delta) : base[axisIndex] + delta
+        ) as number
+        return { position: next }
+      }
+    }
+
+  // Rotate: spin the fitting about one world axis. The cursor's bearing in the
+  // plane perpendicular to that axis (through the body center) drives the
+  // angle; world-frame premultiply so the axis means the screen X/Y/Z the user
+  // expects regardless of how the fitting is already turned.
+  const rotateCompute =
+    (axis: RotationAxis) =>
+    (e: ThreeEvent<PointerEvent>): ((event: PointerEvent) => FittingTransform | null) => {
+      const normal = AXIS_VECTORS[axis].clone()
+      const center = toWorld(fitting.position as Point)
+      const ref = axis === 'y' ? new Vector3(1, 0, 0) : new Vector3(0, 1, 0)
+      const u = ref
+        .clone()
+        .sub(normal.clone().multiplyScalar(ref.dot(normal)))
+        .normalize()
+      const v = new Vector3().crossVectors(normal, u)
+      const plane = new Plane().setFromNormalAndCoplanarPoint(normal, center)
+      const bearing = (clientX: number, clientY: number): number | null => {
+        const hit = intersect(clientX, clientY, plane)
+        if (!hit) return null
+        const d = hit.sub(center)
+        return Math.atan2(d.dot(v), d.dot(u))
+      }
+      const startBearing = bearing(e.nativeEvent.clientX, e.nativeEvent.clientY)
+      const startQuat = new Quaternion().setFromEuler(
+        new Euler(fitting.rotation[0], fitting.rotation[1], fitting.rotation[2]),
+      )
+      let lastStep = Number.NaN
+      return (event: PointerEvent): FittingTransform | null => {
+        if (startBearing === null) return null
+        const b = bearing(event.clientX, event.clientY)
+        if (b === null) return null
+        // Snap the turn to 45° steps; Shift = smooth (no snap).
+        const raw = b - startBearing
+        const delta = event.shiftKey ? raw : Math.round(raw / ROTATE_STEP_RAD) * ROTATE_STEP_RAD
+        // Tick the rotate SFX each time a fresh snap step is crossed (snapped
+        // turns only — a smooth Shift-drag has no discrete steps to mark).
+        if (!event.shiftKey) {
+          const step = Math.round(raw / ROTATE_STEP_RAD)
+          if (step !== lastStep) {
+            lastStep = step
+            triggerSFX('sfx:item-rotate')
+          }
+        }
+        const turn = new Quaternion().setFromAxisAngle(normal, delta)
+        const euler = new Euler().setFromQuaternion(turn.multiply(startQuat))
+        return { rotation: [euler.x, euler.y, euler.z] }
+      }
+    }
+
+  const beginDimensionDrag =
+    (dimension: FittingDimension, axisLocal: Vector3, cursor: Cursor) =>
+    (e: ThreeEvent<PointerEvent>) => {
+      e.stopPropagation()
+      const baseValue = fitting[dimension]
+      const initialPatch = { [dimension]: baseValue } as Partial<DuctFittingNode>
+      const centerWorld = toWorld(fitting.position as Point)
+      const axisWorld = axisToWorld(fitting.position as Point, axisLocal)
+      const start = sampleAxisParameter(
+        e.nativeEvent.clientX,
+        e.nativeEvent.clientY,
+        centerWorld,
+        axisWorld,
+      )
+      const { min, max } = dimensionBounds(dimension)
+      pauseSceneHistory(useScene)
+      useViewer.getState().setInputDragging(true)
+      setDragging(true)
+      document.body.style.cursor = cursor
+      let current: Partial<DuctFittingNode> | null = null
+      let lastValue = Number.NaN
+
+      const apply = (patch: Partial<DuctFittingNode>) => {
+        useScene.getState().updateNodes([
+          {
+            id: fitting.id as AnyNodeId,
+            data: preserveFittingParameters(fitting, patch),
+          },
+        ])
+      }
+
+      const onMove = (event: PointerEvent) => {
+        const rawDeltaM =
+          sampleAxisParameter(event.clientX, event.clientY, centerWorld, axisWorld) - start
+        const deltaIn = (rawDeltaM / INCHES_TO_METERS) * 2
+        const nextRaw = baseValue + deltaIn
+        const nextValue = clamp(event.shiftKey ? nextRaw : snap(nextRaw, RESIZE_STEP_IN), min, max)
+        if (nextValue === lastValue) return
+        lastValue = nextValue
+        current = { [dimension]: nextValue } as Partial<DuctFittingNode>
+        if (!event.shiftKey) triggerSFX('sfx:grid-snap')
+        apply(current)
+      }
+
+      const cleanup = () => {
+        window.removeEventListener('pointermove', onMove)
+        window.removeEventListener('pointerup', onUp)
+        window.removeEventListener('pointercancel', onUp)
+        useViewer.getState().setInputDragging(false)
+        setDragging(false)
+        if (document.body.style.cursor === cursor) document.body.style.cursor = ''
+      }
+
+      const onUp = () => {
+        swallowNextClick()
+        cleanup()
+        apply(initialPatch)
+        resumeSceneHistory(useScene)
+        if (current) apply(current)
+      }
+
+      window.addEventListener('pointermove', onMove)
+      window.addEventListener('pointerup', onUp)
+      window.addEventListener('pointercancel', onUp)
+    }
+
+  const extent = useMemo(() => fittingExtentM(fitting), [fitting])
+  const p = fitting.position as Point
+  const base = extent + ARROW_GAP
+  const fittingRotation = useMemo(
+    () => new Euler(fitting.rotation[0], fitting.rotation[1], fitting.rotation[2]),
+    [fitting.rotation],
+  )
+  const profileAxes = useMemo(() => {
+    const hingeAxis = new Vector3(0, 1, 0).applyEuler(fittingRotation).normalize()
+    const sideAxis = new Vector3(0, 0, 1).applyEuler(fittingRotation).normalize()
+    const hingeIsVertical = Math.abs(hingeAxis.y) >= Math.SQRT1_2
+    const hingeDimension: FittingDimension = hingeIsVertical ? 'height' : 'width'
+    const sideDimension: FittingDimension = hingeIsVertical ? 'width' : 'height'
+    const hingeEntry = { key: hingeDimension, axis: hingeAxis }
+    const sideEntry = { key: sideDimension, axis: sideAxis }
+    return Math.abs(hingeAxis.dot(UP)) >= Math.abs(sideAxis.dot(UP))
+      ? { top: hingeEntry, side: sideEntry }
+      : { top: sideEntry, side: hingeEntry }
+  }, [fittingRotation])
+  const topAxis = useMemo(() => {
+    const axis = profileAxes.top.axis.clone()
+    return axis.dot(UP) >= 0 ? axis : axis.multiplyScalar(-1)
+  }, [profileAxes])
+  const baseSideAxis = profileAxes.side.axis
+  const sideAxis = useMemo(
+    () => baseSideAxis.clone().multiplyScalar(sideSign),
+    [baseSideAxis, sideSign],
+  )
+  useFrame(() => {
+    if (!frame) return
+    const cameraPosition = camera.getWorldPosition(new Vector3())
+    const cameraLocal = frame.worldToLocal(cameraPosition)
+    const toCamera = cameraLocal.sub(new Vector3(p[0], p[1], p[2]))
+    const nextSign = baseSideAxis.dot(toCamera) >= 0 ? 1 : -1
+    setSideSign((current) => (current === nextSign ? current : nextSign))
+  })
+  const resizeHandleBase = extent + RESIZE_HANDLE_GAP
+  const resizeHandles: {
+    key: FittingDimension
+    axis: Vector3
+    cursor: Cursor
+    guideFrom: Point
+    guideTo: Point
+    position: Point
+  }[] = canResizeRunProfile(fitting)
+    ? [
+        {
+          key: profileAxes.top.key,
+          axis: topAxis,
+          cursor: 'ns-resize',
+          guideFrom: [
+            p[0] + topAxis.x * resizeHandleBase,
+            p[1] + topAxis.y * resizeHandleBase,
+            p[2] + topAxis.z * resizeHandleBase,
+          ],
+          guideTo: [
+            p[0] + topAxis.x * Math.max(extent * 0.18, 0.04),
+            p[1] + topAxis.y * Math.max(extent * 0.18, 0.04),
+            p[2] + topAxis.z * Math.max(extent * 0.18, 0.04),
+          ],
+          position: [
+            p[0] + topAxis.x * resizeHandleBase,
+            p[1] + topAxis.y * resizeHandleBase,
+            p[2] + topAxis.z * resizeHandleBase,
+          ],
+        },
+        {
+          key: profileAxes.side.key,
+          axis: sideAxis,
+          cursor: 'ew-resize',
+          guideFrom: [
+            p[0] + sideAxis.x * resizeHandleBase,
+            p[1] + sideAxis.y * resizeHandleBase,
+            p[2] + sideAxis.z * resizeHandleBase,
+          ],
+          guideTo: [
+            p[0] + sideAxis.x * Math.max(extent * 0.18, 0.04),
+            p[1] + sideAxis.y * Math.max(extent * 0.18, 0.04),
+            p[2] + sideAxis.z * Math.max(extent * 0.18, 0.04),
+          ],
+          position: [
+            p[0] + sideAxis.x * resizeHandleBase,
+            p[1] + sideAxis.y * resizeHandleBase,
+            p[2] + sideAxis.z * resizeHandleBase,
+          ],
+        },
+      ]
+    : []
+
+  // Six whole-fitting move arrows, one per ± world axis.
+  const moveArrows: {
+    key: string
+    axis: RotationAxis
+    position: Point
+    rotationY: number
+    vertical?: 'up' | 'down'
+    cursor: Cursor
+  }[] = [
+    { key: '+x', axis: 'x', position: [p[0] + base, p[1], p[2]], rotationY: 0, cursor: 'grab' },
+    {
+      key: '-x',
+      axis: 'x',
+      position: [p[0] - base, p[1], p[2]],
+      rotationY: Math.PI,
+      cursor: 'grab',
+    },
+    {
+      key: '+z',
+      axis: 'z',
+      position: [p[0], p[1], p[2] + base],
+      rotationY: -Math.PI / 2,
+      cursor: 'grab',
+    },
+    {
+      key: '-z',
+      axis: 'z',
+      position: [p[0], p[1], p[2] - base],
+      rotationY: Math.PI / 2,
+      cursor: 'grab',
+    },
+    {
+      key: '+y',
+      axis: 'y',
+      position: [p[0], p[1] + base, p[2]],
+      rotationY: 0,
+      vertical: 'up',
+      cursor: 'ns-resize',
+    },
+    {
+      key: '-y',
+      axis: 'y',
+      position: [p[0], p[1] - base, p[2]],
+      rotationY: 0,
+      vertical: 'down',
+      cursor: 'ns-resize',
+    },
+  ]
+
+  // Three rotation arcs, one per world axis. Each arc wraps its axis (the
+  // shared `curved-arrow` wraps world +Y by default; `setFromUnitVectors`
+  // re-aims it) and sits at a diagonal offset in the plane it spins, so the
+  // three don't pile onto the move arrows.
+  const d = base * Math.SQRT1_2
+  const rotateArcs: { key: string; axis: RotationAxis; position: Point; rotation: Point }[] = (
+    ['x', 'y', 'z'] as RotationAxis[]
+  ).map((axis) => {
+    const q = new Quaternion().setFromUnitVectors(UP, AXIS_VECTORS[axis])
+    // Spin the arc in place about its own axis so the grip sits where we want
+    // it without moving its position.
+    if (axis === 'z') {
+      q.premultiply(new Quaternion().setFromAxisAngle(AXIS_VECTORS.z, Math.PI / 4))
+    } else if (axis === 'x') {
+      q.premultiply(new Quaternion().setFromAxisAngle(AXIS_VECTORS.x, (-145 * Math.PI) / 180))
+    } else if (axis === 'y') {
+      q.premultiply(new Quaternion().setFromAxisAngle(AXIS_VECTORS.y, (-45 * Math.PI) / 180))
+    }
+    const e = new Euler().setFromQuaternion(q)
+    const position: Point =
+      axis === 'x'
+        ? [p[0], p[1] + d, p[2] + d]
+        : axis === 'y'
+          ? [p[0] + d, p[1], p[2] + d]
+          : [p[0] + d, p[1] + d, p[2]]
+    return { key: `r${axis}`, axis, position, rotation: [e.x, e.y, e.z] }
+  })
+
+  if (dragging) {
+    return <group ref={setFrame} />
+  }
+  return (
+    <group ref={setFrame}>
+      <HandleCube active={open} onClick={() => setOpen((o) => !o)} position={p} />
+      {!open &&
+        resizeHandles.map((handle) => (
+          <group key={handle.key}>
+            <DashedResizeGuide from={handle.guideFrom} to={handle.guideTo} />
+            <ResizeSphereHandle
+              cursor={handle.cursor}
+              onPointerDown={beginDimensionDrag(handle.key, handle.axis, handle.cursor)}
+              position={handle.position}
+            />
+          </group>
+        ))}
+      {open && (
+        <>
+          {moveArrows.map((a) => (
+            <MoveChevron
+              cursor={a.cursor}
+              key={a.key}
+              onPointerDown={beginDrag(
+                a.axis === 'y' ? 'ns-resize' : 'grabbing',
+                moveCompute(a.axis),
+              )}
+              position={a.position}
+              rotationY={a.rotationY}
+              vertical={a.vertical}
+            />
+          ))}
+          {rotateArcs.map((arc) => (
+            <RotateArc
+              key={arc.key}
+              onPointerDown={beginDrag('grabbing', rotateCompute(arc.axis))}
+              position={arc.position}
+              rotation={arc.rotation}
+            />
+          ))}
+        </>
+      )}
+    </group>
+  )
 }
 
 export default DuctFittingSelectionAffordance

packages/nodes/src/duct-segment/definition.ts

@@ -1,5 +1,7 @@
 import { type AnyNode, type NodeDefinition, useScene } from '@pascal-app/core'
+import { ductBodyPaint, ductBodySlots } from '../shared/duct-body-paint'
 import { createPathPointMoveAffordance } from '../shared/path-point-affordance'
+import { createSegmentMoveAffordance } from '../shared/path-segment-affordance'
 import { buildDuctSegmentFloorplan } from './floorplan'
 import { buildDuctSegmentGeometry, ductPortDiameterIn } from './geometry'
 import { ductSegmentParametrics } from './parametrics'
@@ -71,6 +73,8 @@ export const ductSegmentDefinition: NodeDefinition<typeof DuctSegmentNode> = {
     selectable: { hitVolume: 'bbox' },
     duplicable: true,
     deletable: true,
+    slots: () => ductBodySlots(),
+    paint: ductBodyPaint,
   },
 
   parametrics: ductSegmentParametrics,
@@ -103,6 +107,7 @@ export const ductSegmentDefinition: NodeDefinition<typeof DuctSegmentNode> = {
       n.insulated,
       n.insulationR,
       n.system,
+      n.slots,
     ]),
 
   // Open run ends as typed ports — directions point outward along the
@@ -147,6 +152,9 @@ export const ductSegmentDefinition: NodeDefinition<typeof DuctSegmentNode> = {
   // `endpoint-handle` per path vertex; this drags the matching point.
   floorplanAffordances: {
     'move-path-point': createPathPointMoveAffordance('duct-segment'),
+    // 2D twin of the 3D side-move arrows: slide a segment perpendicular to
+    // itself. (Length editing stays on the per-vertex hex handles.)
+    'move-segment': createSegmentMoveAffordance('duct-segment'),
   },
 
   // Selection-time path-point handles (drag to edit a committed run).
@@ -164,7 +172,7 @@ export const ductSegmentDefinition: NodeDefinition<typeof DuctSegmentNode> = {
   tool: () => import('./tool'),
   toolHints: [
     { key: 'Click', label: 'Start segment' },
-    { key: 'Click again', label: 'Place it (locked to 45°)' },
+    { key: 'Click again', label: 'Place and continue' },
     { key: 'Shift', label: 'Free angle' },
     { key: 'Alt + drag', label: 'Go vertical ↕, click to place' },
     { key: '[ / ]', label: 'Duct diameter down / up' },

packages/nodes/src/duct-segment/floorplan.ts

@@ -5,6 +5,10 @@ import type { DuctSegmentNode } from './schema'
 const SUPPLY_CENTERLINE = '#d4825a'
 const RETURN_CENTERLINE = '#5a8ad4'
 const BODY_COLOR = '#9ca3af'
+/** Move-arrow stand-off past the duct body, in plan meters. */
+const SIDE_ARROW_GAP = 0.27
+/** Below this plan length a segment / end has no usable direction. */
+const MIN_SEGMENT_LEN = 0.05
 
 /**
  * Floor-plan representation of a duct run: the path drawn at the duct's
@@ -96,6 +100,32 @@ export function buildDuctSegmentFloorplan(
         payload: { pointIndex: indexMap[k]! },
       })
     }
+
+    // Side-move arrows: a front / back pair at each segment midpoint, sliding
+    // that segment perpendicular to itself. 2D twin of the 3D side-move
+    // arrows. The arrows stand one duct-radius + gap off the body; `angle`
+    // points each chevron outward along the segment normal.
+    const offset = diameterM / 2 + SIDE_ARROW_GAP
+    for (let k = 0; k < points.length - 1; k++) {
+      const a = points[k]!
+      const b = points[k + 1]!
+      const dx = b[0] - a[0]
+      const dz = b[1] - a[1]
+      const len = Math.hypot(dx, dz)
+      if (len < MIN_SEGMENT_LEN) continue
+      const normal: [number, number] = [-dz / len, dx / len]
+      const mid: FloorplanPoint = [(a[0] + b[0]) / 2, (a[1] + b[1]) / 2]
+      for (const side of [1, -1] as const) {
+        const n: [number, number] = [normal[0] * side, normal[1] * side]
+        children.push({
+          kind: 'move-arrow',
+          point: [mid[0] + n[0] * offset, mid[1] + n[1] * offset],
+          angle: Math.atan2(n[1], n[0]),
+          affordance: 'move-segment',
+          payload: { segmentIndex: indexMap[k]!, normal: n },
+        })
+      }
+    }
   }
 
   return { kind: 'group', children }

packages/nodes/src/duct-segment/geometry.ts

@@ -1,9 +1,18 @@
+import type { GeometryContext } from '@pascal-app/core'
+import {
+  type ColorPreset,
+  createSurfaceRoleMaterial,
+  type RenderShading,
+  resolveMaterialRef,
+  resolveSlotDefaultMaterial,
+} from '@pascal-app/viewer'
 import {
   BoxGeometry,
   CatmullRomCurve3,
   CylinderGeometry,
   ExtrudeGeometry,
   Group,
+  type Material,
   Matrix4,
   Mesh,
   MeshStandardMaterial,
@@ -13,6 +22,7 @@ import {
   TubeGeometry,
   Vector3,
 } from 'three'
+import { DUCT_BODY_SLOT_DEFAULT, DUCT_BODY_SLOT_ID } from '../shared/duct-body-paint'
 import type { DuctSegmentNode } from './schema'
 
 export const INCHES_TO_METERS = 0.0254
@@ -137,7 +147,7 @@ export function buildRectSection(
   end: Vector3,
   widthM: number,
   heightM: number,
-  material: MeshStandardMaterial,
+  material: Material,
   name: string,
   roll = 0,
 ): Mesh | null {
@@ -200,7 +210,7 @@ export function buildOvalSection(
   end: Vector3,
   widthM: number,
   heightM: number,
-  material: MeshStandardMaterial,
+  material: Material,
   name: string,
   roll = 0,
 ): Mesh | null {
@@ -226,7 +236,7 @@ export function buildSection(
   start: Vector3,
   end: Vector3,
   radius: number,
-  material: MeshStandardMaterial,
+  material: Material,
   name: string,
 ): Mesh | null {
   const dir = new Vector3().subVectors(end, start)
@@ -318,6 +328,7 @@ function helixRidgeFor(
 type DuctAppearance = {
   ductMaterial: 'sheet-metal' | 'spiral' | 'flex' | 'duct-board'
   system: 'supply' | 'return'
+  slots?: Record<string, string>
 }
 
 function getSystemTint(node: DuctAppearance): string {
@@ -330,12 +341,25 @@ function getSystemTint(node: DuctAppearance): string {
  * metal. Shared with the fitting builder so connected runs and junctions
  * look like one piece.
  */
-export function createDuctMaterial(_node: DuctAppearance): MeshStandardMaterial {
-  return new MeshStandardMaterial({
-    color: '#ffffff',
-    metalness: 0,
-    roughness: 0.7,
-  })
+export function createDuctMaterial(
+  node: DuctAppearance,
+  sceneMaterials?: GeometryContext['materials'],
+  shading: RenderShading = 'rendered',
+  textures = true,
+  colorPreset: ColorPreset = 'clay',
+  sceneTheme?: string,
+): Material {
+  if (!textures) {
+    return createSurfaceRoleMaterial('furnishing', colorPreset, undefined, sceneTheme)
+  }
+
+  const slotRef = node.slots?.[DUCT_BODY_SLOT_ID]
+  if (slotRef) {
+    const resolved = resolveMaterialRef(slotRef, sceneMaterials, shading)
+    if (resolved) return resolved
+  }
+
+  return resolveSlotDefaultMaterial(DUCT_BODY_SLOT_DEFAULT, shading, 0.7)
 }
 
 /**
@@ -354,7 +378,14 @@ export function createDuctMaterial(_node: DuctAppearance): MeshStandardMaterial
  * identity since the schema has no position field — the path itself is
  * absolute within the level).
  */
-export function buildDuctSegmentGeometry(node: DuctSegmentNode): Group {
+export function buildDuctSegmentGeometry(
+  node: DuctSegmentNode,
+  ctx?: GeometryContext,
+  shading: RenderShading = 'rendered',
+  textures = true,
+  colorPreset: ColorPreset = 'clay',
+  sceneTheme?: string,
+): Group {
   const group = new Group()
   if (node.path.length < 2) return group
 
@@ -363,7 +394,14 @@ export function buildDuctSegmentGeometry(node: DuctSegmentNode): Group {
   const radius = (node.diameter * INCHES_TO_METERS) / 2
   const widthM = node.width * INCHES_TO_METERS
   const heightM = node.height * INCHES_TO_METERS
-  const ductMaterial = createDuctMaterial(node)
+  const ductMaterial = createDuctMaterial(
+    node,
+    ctx?.materials,
+    shading,
+    textures,
+    colorPreset,
+    sceneTheme,
+  )
 
   const points = node.path.map(([x, y, z]) => new Vector3(x, y, z))
 
@@ -371,9 +409,10 @@ export function buildDuctSegmentGeometry(node: DuctSegmentNode): Group {
     half: number,
     rectW: number,
     rectH: number,
-    material: MeshStandardMaterial,
+    material: Material,
     namePrefix: string,
     endInsetM = 0,
+    paintableBody = false,
   ) => {
     for (let i = 0; i < points.length - 1; i++) {
       // Loop bounds + min(2) on the schema guarantee both points exist.
@@ -396,7 +435,10 @@ export function buildDuctSegmentGeometry(node: DuctSegmentNode): Group {
         : isOval
           ? buildOvalSection(a, b, rectW, rectH, material, `${namePrefix}-section-${i}`, node.roll)
           : buildSection(a, b, half, material, `${namePrefix}-section-${i}`)
-      if (mesh) group.add(mesh)
+      if (mesh) {
+        if (paintableBody) mesh.userData.slotId = DUCT_BODY_SLOT_ID
+        group.add(mesh)
+      }
     }
     // Joint caps at interior points only (skip first and last — they're
     // open ends; equipment / terminal / fitting collars cap them). Rect
@@ -410,11 +452,12 @@ export function buildDuctSegmentGeometry(node: DuctSegmentNode): Group {
           : new Mesh(new SphereGeometry(half, RADIAL_SEGMENTS, 12), material)
       joint.name = `${namePrefix}-joint-${i}`
       joint.position.copy(points[i] as Vector3)
+      if (paintableBody) joint.userData.slotId = DUCT_BODY_SLOT_ID
       group.add(joint)
     }
   }
 
-  addRun(radius, widthM, heightM, ductMaterial, 'duct')
+  addRun(radius, widthM, heightM, ductMaterial, 'duct', 0, true)
 
   // Construction body detail: spiral winds its lock seam, flex its wire
   // helix (tight pitch — reads as corrugation) over each round section.

packages/nodes/src/duct-segment/move-tool.tsx

@@ -4,6 +4,7 @@ import {
   type AlignmentAnchor,
   type AnyNode,
   type AnyNodeId,
+  analyzePortConnectivity,
   DuctSegmentNode,
   emitter,
   type GridEvent,
@@ -11,6 +12,7 @@ import {
   useScene,
 } from '@pascal-app/core'
 import {
+  consumePlacementDragRelease,
   DragBoundingBox,
   EDITOR_LAYER,
   markToolCancelConsumed,
@@ -27,6 +29,13 @@ import {
   collectGhostAlignmentCandidates,
   resolveGhostAlignment,
 } from '../shared/ghost-alignment'
+import { DuctSegmentGhost, FittingGhost } from '../shared/mep-ghost'
+import { collectScenePorts, DUCT_PORT_SYSTEMS } from '../shared/ports'
+import { type RunMoveConnectivity, startRunMoveConnectivity } from '../shared/run-move-connectivity'
+import {
+  planRunTranslationOffsets,
+  type RunTranslationOffsetPlan,
+} from '../shared/run-translation-offset'
 import { rectSectionAxes } from './geometry'
 
 type Vec3 = [number, number, number]
@@ -106,6 +115,7 @@ export const MoveDuctSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
     (node.metadata as Record<string, unknown>).isNew === true
 
   const [previewPath, setPreviewPath] = useState<Vec3[]>(originalPathRef.current)
+  const [translationGhost, setTranslationGhost] = useState<RunTranslationOffsetPlan | null>(null)
   const previewPathRef = useRef<Vec3[]>(originalPathRef.current)
   const hasMovedRef = useRef(false)
   const activatedAtRef = useRef<number>(Date.now())
@@ -138,6 +148,26 @@ export const MoveDuctSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
     }
     if (existedAtStart) setMeshHidden(true)
 
+    // Carry connected fittings (+ their other runs) as the whole run slides.
+    // Snapshot once at drag start; only existing runs are mated to anything.
+    const connectivity: RunMoveConnectivity | null = existedAtStart
+      ? startRunMoveConnectivity(node)
+      : null
+    const portConnectivity = existedAtStart
+      ? analyzePortConnectivity(node, useScene.getState().nodes)
+      : null
+    const scenePorts = existedAtStart
+      ? collectScenePorts({ excludeNodeId: nodeId, systems: DUCT_PORT_SYSTEMS })
+      : []
+    const nodesById = useScene.getState().nodes
+    const profile = {
+      shape: duct.shape,
+      diameter: duct.diameter,
+      width: duct.width,
+      height: duct.height,
+    }
+    let lastTranslationPlan: RunTranslationOffsetPlan | null = null
+
     const setPreview = (path: Vec3[]) => {
       previewPathRef.current = path
       setPreviewPath(path)
@@ -177,12 +207,30 @@ export const MoveDuctSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
       }
       prevSnapRef.current = cur
       hasMovedRef.current = true
-      setPreview(originalPath.map(([x, y, z]) => [x + dx, y, z + dz] as Vec3))
+      const nextPath = originalPath.map(([x, y, z]) => [x + dx, y, z + dz] as Vec3)
+      setPreview(nextPath)
+      lastTranslationPlan =
+        existedAtStart && portConnectivity
+          ? planRunTranslationOffsets({
+              duct,
+              translatedPath: nextPath,
+              profile,
+              connections: portConnectivity.connections,
+              scenePorts,
+              nodesById,
+            })
+          : null
+      if (lastTranslationPlan) connectivity?.clear()
+      else connectivity?.preview({ path: nextPath })
+      setTranslationGhost(lastTranslationPlan)
     }
 
-    const commit = (event: GridEvent) => {
+    const commit = (event: GridEvent, fromDragRelease = false) => {
       if (committed) return
-      if (Date.now() - activatedAtRef.current < 150) {
+      // The 150ms debounce only guards click-to-place against the arming click
+      // double-firing; a press-drag release is a distinct pointerup gesture, so
+      // it skips the guard (a quick drag-flick still commits).
+      if (!fromDragRelease && Date.now() - activatedAtRef.current < 150) {
         event.nativeEvent?.stopPropagation?.()
         return
       }
@@ -205,10 +253,44 @@ export const MoveDuctSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
         useScene.getState().createNode(created as AnyNode, node.parentId as AnyNodeId)
         selectId = created.id as AnyNodeId
       } else {
-        useScene.getState().updateNode(nodeId, { path: finalPath } as Partial<AnyNode>)
+        const translationPlan =
+          portConnectivity &&
+          planRunTranslationOffsets({
+            duct,
+            translatedPath: finalPath,
+            profile,
+            connections: portConnectivity.connections,
+            scenePorts,
+            nodesById,
+          })
+        if (translationPlan) {
+          useScene.getState().applyNodeChanges({
+            create: [...translationPlan.fittings, ...translationPlan.connectors].map((created) => ({
+              node: created as AnyNode,
+              parentId: node.parentId as AnyNodeId,
+            })),
+            update: [
+              { id: nodeId, data: { path: translationPlan.ductPath } as Partial<AnyNode> },
+              ...translationPlan.updates,
+            ],
+          })
+        } else {
+          // Fold connected-fitting / sibling-run follow-updates into the SAME
+          // batch as the moved run so the whole joint is one undo step.
+          const followUpdates = connectivity?.commitUpdates({ path: finalPath }) ?? []
+          useScene
+            .getState()
+            .updateNodes([
+              { id: nodeId, data: { path: finalPath } as Partial<AnyNode> },
+              ...followUpdates,
+            ])
+        }
         useScene.getState().markDirty(nodeId)
       }
       useScene.temporal.getState().pause()
+      // Followers are committed to the store — drop their live overrides so
+      // renderers read the canonical path/position.
+      connectivity?.clear()
       setMeshHidden(false)
 
       useAlignmentGuides.getState().clear()
@@ -220,6 +302,8 @@ export const MoveDuctSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
     }
 
     const onCancel = () => {
+      connectivity?.clear()
+      setTranslationGhost(null)
       if (existedAtStart) {
         setMeshHidden(false)
         useViewer.getState().setSelection({ selectedIds: [nodeId] })
@@ -231,14 +315,37 @@ export const MoveDuctSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
       useEditor.getState().setMovingNode(null)
     }
 
+    // Press-drag-release: when the move was engaged by the drag gesture (the
+    // selection rig's move cross), `placementDragMode` is set, so commit on
+    // pointer-up at the last previewed path instead of waiting for a second
+    // click — same contract as the fitting move tool.
+    const onPlacementDragPointerUp = (event: PointerEvent) => {
+      if (!consumePlacementDragRelease(event)) return
+      if (!hasMovedRef.current) {
+        onCancel()
+        return
+      }
+      commit(
+        {
+          nativeEvent: event,
+          stopPropagation: () => event.stopPropagation(),
+        } as unknown as GridEvent,
+        true,
+      )
+    }
+
     emitter.on('grid:move', onMove)
     emitter.on('grid:click', commit)
     emitter.on('tool:cancel', onCancel)
+    window.addEventListener('pointerup', onPlacementDragPointerUp)
 
     return () => {
       emitter.off('grid:move', onMove)
       emitter.off('grid:click', commit)
       emitter.off('tool:cancel', onCancel)
+      window.removeEventListener('pointerup', onPlacementDragPointerUp)
+      connectivity?.clear()
+      setTranslationGhost(null)
       useAlignmentGuides.getState().clear()
       if (existedAtStart) setMeshHidden(false)
       useScene.temporal.getState().resume()
@@ -261,6 +368,16 @@ export const MoveDuctSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
       {segments.map((seg, i) => (
         <GhostSegment a={seg.a} b={seg.b} duct={duct} key={`ghost-${i}`} />
       ))}
+      {translationGhost?.fittings.map((fitting) => (
+        <FittingGhost fitting={fitting} key={`translation-fitting-${fitting.id}`} tint="valid" />
+      ))}
+      {translationGhost?.connectors.map((connector) => (
+        <DuctSegmentGhost
+          duct={connector}
+          key={`translation-connector-${connector.id}`}
+          tint="valid"
+        />
+      ))}
       <DragBoundingBox
         centerY={0}
         nodeId={node.id}

packages/nodes/src/duct-segment/tool.tsx

@@ -2,11 +2,13 @@
 
 import {
   type AnyNode,
+  type CeilingNode,
+  type DuctFittingNode,
   DuctSegmentNode,
   emitter,
   type GridEvent,
-  getLevelHeight,
-  sceneRegistry,
+  getCeilingAt,
+  getCeilingHeightAt,
   useScene,
 } from '@pascal-app/core'
 import {
@@ -19,8 +21,17 @@ import {
 } from '@pascal-app/editor'
 import { useViewer } from '@pascal-app/viewer'
 import { Html } from '@react-three/drei'
-import { useEffect, useRef, useState } from 'react'
-import { type Group, Matrix4, Vector3 } from 'three'
+import { useEffect, useMemo, useRef, useState } from 'react'
+import {
+  type BufferGeometry,
+  DoubleSide,
+  type Group,
+  Matrix4,
+  Path,
+  Shape,
+  ShapeGeometry,
+  Vector3,
+} from 'three'
 import { getDuctFittingPorts } from '../duct-fitting/ports'
 import {
   planCrossAtRunBody,
@@ -30,6 +41,7 @@ import {
 } from '../shared/auto-fitting'
 import { alignDrawPoint, clearDrawAlignment } from '../shared/draw-alignment'
 import { LevelOffsetGroup } from '../shared/level-offset-group'
+import { FittingGhost } from '../shared/mep-ghost'
 import {
   collectScenePorts,
   DUCT_PORT_SYSTEMS,
@@ -40,17 +52,17 @@ import {
   type ScenePort,
 } from '../shared/ports'
 import { ductSegmentDefinition } from './definition'
-import { rectSectionAxes, rollToContinueAcrossElbow } from './geometry'
+import { ductPortDiameterIn, rectSectionAxes, rollToContinueAcrossElbow } from './geometry'
 
 /**
- * One-segment-at-a-time placement tool for round duct segments.
+ * Continuous placement tool for duct segments.
  *
  * Mouse-driven model:
  *   - **First click** anchors the segment start (port snap joins onto an
  *     existing run / fitting collar).
- *   - **Second click** commits a two-point duct immediately and re-arms
- *     the tool — no polyline accumulation, no finish gesture. Chain runs
- *     by clicking again near the end you just placed (port snap).
+ *   - **Second click** commits a two-point duct immediately and keeps the
+ *     segment end anchored, so the next click continues the run like wall
+ *     drafting. No polyline accumulation, no finish gesture.
  *   - **Auto-elbow**: when either end snapped onto another RUN's open
  *     port at an angle (15–90°, vertical turns included), an elbow
  *     fitting is minted at the joint and the duct pulls back to its
@@ -69,9 +81,10 @@ import { rectSectionAxes, rollToContinueAcrossElbow } from './geometry'
  *     vertical mouse motion drives Y. Click commits the riser segment.
  *   - **[ / ]** step the duct diameter through nominal US sizes; the
  *     ghost preview and the committed node both use it.
- *   - **C** toggles ceiling-level placement: the start point lands at
- *     the level's ceiling height (duct top hugging the ceiling) instead
- *     of the floor. Subsequent points inherit the start's Y as usual.
+ *   - **C** toggles ceiling-level placement: each point lands just below
+ *     the ceiling actually covering it (duct top hugging that ceiling)
+ *     instead of the floor, so a run tracks per-room ceiling heights.
+ *     Points not under any ceiling fall back to the floor.
  *   - Esc clears an anchored start point.
  */
 const PREVIEW_OPACITY = 0.55
@@ -94,6 +107,11 @@ const ALT_PIXELS_PER_METER = 100
 const ALT_Y_MIN_M = -3
 const ALT_Y_MAX_M = 10
 
+/** green-500 — the project's bounding-box / placeable accent. The cursor
+ *  ring + vertical line recolour to this while the point is snapped onto an
+ *  existing run, so the coincidence reads with the familiar snap green. */
+const SNAP_CURSOR_COLOR = '#22c55e'
+
 function snap(value: number, step: number): number {
   if (step <= 0) return value
   return Math.round(value / step) * step
@@ -163,6 +181,14 @@ function continuityRollFrom(port: ScenePort | null, newDir: Vector3): number | n
   return rollToContinueAcrossElbow(srcDir, srcRoll, srcDir, newDir)
 }
 
+function continuityRollForRun(
+  startPort: ScenePort | null,
+  endPort: ScenePort | null,
+  dir: Vector3,
+): number {
+  return continuityRollFrom(startPort, dir) ?? continuityRollFrom(endPort, dir) ?? 0
+}
+
 /**
  * Nearest typed port — duct run ends, fitting collars, anything whose
  * kind registers `def.ports` — within snap range of `point` on the XZ
@@ -259,6 +285,209 @@ function projectToAngleLock(
   return [from[0] + Math.cos(snapped) * d, from[1], from[2] + Math.sin(snapped) * d]
 }
 
+/** The full set of nodes a drawn segment produces. The drawn `ducts`
+ *  (and any trunk `tails` from a tee / cross split) are previewed by the
+ *  duct ghost already; `fittings` are the auto-inserted elbow / tee /
+ *  cross nodes the ghost preview draws so the user sees them before the
+ *  commit. Shared by `commitSegment` and the live preview so what you see
+ *  is exactly what lands. */
+type DuctDrawPlan = {
+  fittings: DuctFittingNode[]
+  ducts: DuctSegmentNode[]
+  tails: DuctSegmentNode[]
+  updates: { id: AnyNode['id']; data: Partial<AnyNode> }[]
+}
+
+const elbowPlanFor = (
+  port: ScenePort | null,
+  awayDir: [number, number, number],
+  profile: DraftProfile,
+) => {
+  if (!port) return null
+  const owner = useScene.getState().nodes[port.nodeId]
+  if (owner?.type !== 'duct-segment') return null
+  const plan = planElbowAtPort(port, awayDir, profile)
+  if (!plan) return null
+  // Trim the run's snapped endpoint back to the elbow's inlet collar.
+  const path = owner.path.map((p) => [...p] as [number, number, number])
+  const index = port.id === 'start' ? 0 : path.length - 1
+  const neighbor = path[index === 0 ? 1 : index - 1]!
+  const remaining = Math.hypot(
+    plan.trimmedPortPoint[0] - neighbor[0],
+    plan.trimmedPortPoint[1] - neighbor[1],
+    plan.trimmedPortPoint[2] - neighbor[2],
+  )
+  // The trim must leave a real piece of the existing run AND not flip it.
+  const original = path[index]!
+  const originalLen = Math.hypot(
+    original[0] - neighbor[0],
+    original[1] - neighbor[1],
+    original[2] - neighbor[2],
+  )
+  if (remaining < 0.08 || remaining >= originalLen) return null
+  path[index] = plan.trimmedPortPoint
+  return { ...plan, trim: { id: port.nodeId, data: { path } as Partial<AnyNode> } }
+}
+
+const realignPlanFor = (port: ScenePort | null, awayDir: [number, number, number]) => {
+  if (!port) return null
+  const owner = useScene.getState().nodes[port.nodeId]
+  if (owner?.type !== 'duct-fitting') return null
+  return planElbowRealign(owner, port.id, awayDir)
+}
+
+/**
+ * Pure planner for a drawn duct segment: given its endpoints and what
+ * each end snapped onto (an open port, or a run body for a tee / cross
+ * tap), decide every node the commit creates / updates — auto-inserted
+ * elbows / tees / crosses, the drawn run (split in two when it crosses a
+ * trunk), trunk tails, and trim / realign updates. Reads the live scene
+ * graph but mutates nothing, so the live preview can call it each frame
+ * to ghost the fittings before the commit applies the identical plan.
+ */
+function planDuctDraw(
+  start: [number, number, number],
+  end: [number, number, number],
+  startPort: ScenePort | null,
+  startBody: RunBodyHit | null,
+  endPort: ScenePort | null,
+  endBody: RunBodyHit | null,
+  profile: DraftProfile,
+): DuctDrawPlan | null {
+  const length = Math.hypot(end[0] - start[0], end[1] - start[1], end[2] - start[2])
+  if (length < 1e-4) return null
+  const dir: [number, number, number] = [
+    (end[0] - start[0]) / length,
+    (end[1] - start[1]) / length,
+    (end[2] - start[2]) / length,
+  ]
+
+  const startPlan = elbowPlanFor(startPort, dir, profile)
+  const endPlan = elbowPlanFor(endPort, [-dir[0], -dir[1], -dir[2]], profile)
+  const startRealign = startPlan ? null : realignPlanFor(startPort, dir)
+  const endRealign = endPlan ? null : realignPlanFor(endPort, [-dir[0], -dir[1], -dir[2]])
+  const trunkBody = startPlan ? null : startBody
+  const trunkOwner = trunkBody ? useScene.getState().nodes[trunkBody.nodeId] : null
+  const teePlan =
+    trunkBody && trunkOwner?.type === 'duct-segment'
+      ? planTeeAtRunBody(trunkOwner, trunkBody, dir, profile)
+      : null
+  const endTrunkBody = endPlan || endRealign ? null : endBody
+  const endTrunkOwner = endTrunkBody ? useScene.getState().nodes[endTrunkBody.nodeId] : null
+  const endTeePlan =
+    endTrunkBody && endTrunkOwner?.type === 'duct-segment'
+      ? planTeeAtRunBody(endTrunkOwner, endTrunkBody, [-dir[0], -dir[1], -dir[2]], profile)
+      : null
+  let ductStart =
+    startPlan?.collarPoint ?? teePlan?.branchCollar ?? startRealign?.collarPoint ?? start
+  let ductEnd = endPlan?.collarPoint ?? endTeePlan?.branchCollar ?? endRealign?.collarPoint ?? end
+  const remaining = Math.hypot(
+    ductEnd[0] - ductStart[0],
+    ductEnd[1] - ductStart[1],
+    ductEnd[2] - ductStart[2],
+  )
+  let plans = [startPlan, endPlan].filter((p) => p !== null)
+  let tee = teePlan
+  let endTee = endTeePlan && endTrunkBody?.nodeId === trunkBody?.nodeId ? null : endTeePlan
+  if (!endTee && endTeePlan) ductEnd = endRealign?.collarPoint ?? end
+  let realigns = [startRealign, endRealign].filter((p) => p !== null)
+
+  const crossHit = findRunBodyCrossingXZ(start, end, BODY_SNAP_RADIUS_M)
+  const crossOwner = crossHit ? useScene.getState().nodes[crossHit.nodeId] : null
+  const crossTappedElsewhere =
+    crossHit?.nodeId === trunkBody?.nodeId || crossHit?.nodeId === endTrunkBody?.nodeId
+  let cross =
+    crossHit && !crossTappedElsewhere && crossOwner?.type === 'duct-segment'
+      ? planCrossAtRunBody(crossOwner, crossHit, dir, profile)
+      : null
+
+  if (remaining <= 0.08) {
+    plans = []
+    tee = null
+    endTee = null
+    realigns = []
+    cross = null
+    ductStart = start
+    ductEnd = end
+  }
+
+  // Rect / oval continuity: roll the new run's cross-section so its
+  // profile stays continuous with whatever either end joined.
+  let roll = 0
+  if (profile.shape !== 'round') {
+    const newDir = new Vector3(...dir)
+    roll = continuityRollForRun(startPort, endPort, newDir)
+  }
+
+  const defaults = ductSegmentDefinition.defaults()
+  const toolDefaults = useEditor.getState().toolDefaults['duct-segment'] ?? {}
+  const makeDuct = (from: [number, number, number], to: [number, number, number]) =>
+    DuctSegmentNode.parse({
+      ...defaults,
+      ...toolDefaults,
+      name: profile.shape === 'rect' ? 'Trunk' : 'Duct run',
+      path: [from, to],
+      shape: profile.shape,
+      diameter: profile.diameter,
+      width: profile.width,
+      height: profile.height,
+      roll,
+    })
+  const ducts = cross
+    ? [
+        dist2(ductStart, cross.branchCollarNear) > 0.08 * 0.08
+          ? makeDuct(ductStart, cross.branchCollarNear)
+          : null,
+        dist2(cross.branchCollarFar, ductEnd) > 0.08 * 0.08
+          ? makeDuct(cross.branchCollarFar, ductEnd)
+          : null,
+      ].filter((d) => d !== null)
+    : [makeDuct(ductStart, ductEnd)]
+
+  const fittings: DuctFittingNode[] = [
+    ...plans.map((p) => p.fitting),
+    ...(tee ? [tee.fitting] : []),
+    ...(endTee ? [endTee.fitting] : []),
+    ...(cross ? [cross.fitting] : []),
+  ]
+  const tails: DuctSegmentNode[] = [
+    ...(tee ? [tee.trunkTail] : []),
+    ...(endTee ? [endTee.trunkTail] : []),
+    ...(cross ? [cross.trunkTail] : []),
+  ]
+  const updates: { id: AnyNode['id']; data: Partial<AnyNode> }[] = [
+    ...plans.map((p) => p.trim),
+    ...(tee ? [tee.trunkUpdate as { id: AnyNode['id']; data: Partial<AnyNode> }] : []),
+    ...(endTee ? [endTee.trunkUpdate as { id: AnyNode['id']; data: Partial<AnyNode> }] : []),
+    ...(cross ? [cross.trunkUpdate as { id: AnyNode['id']; data: Partial<AnyNode> }] : []),
+    ...realigns.map((p) => p.update as { id: AnyNode['id']; data: Partial<AnyNode> }),
+  ]
+
+  return { fittings, ducts, tails, updates }
+}
+
+function ductEndPort(duct: DuctSegmentNode, id: 'start' | 'end'): ScenePort | null {
+  if (duct.path.length < 2) return null
+  const index = id === 'start' ? 0 : duct.path.length - 1
+  const neighborIndex = id === 'start' ? 1 : duct.path.length - 2
+  const position = duct.path[index]!
+  const neighbor = duct.path[neighborIndex]!
+  const dx = position[0] - neighbor[0]
+  const dy = position[1] - neighbor[1]
+  const dz = position[2] - neighbor[2]
+  const len = Math.hypot(dx, dy, dz)
+  const direction: [number, number, number] =
+    len < 1e-9 ? [1, 0, 0] : [dx / len, dy / len, dz / len]
+  return {
+    id,
+    nodeId: duct.id,
+    position,
+    direction,
+    diameter: ductPortDiameterIn(duct),
+    system: duct.system,
+  }
+}
+
 const DuctSegmentTool = () => {
   const activeLevelId = useViewer((s) => s.selection.levelId)
   const unit = useViewer((s) => s.unit)
@@ -285,12 +514,24 @@ const DuctSegmentTool = () => {
   // Ceiling mode (toggle with C): the first point lands at the level's
   // ceiling height (duct top hugging the ceiling) instead of the floor.
   const [ceilingMode, setCeilingMode] = useState(false)
-  // When the cursor is within snap range of an existing duct's endpoint we
-  // surface a brighter indicator and commit at the endpoint's exact coords.
+  // The shared coordinate when the cursor is within snap range of an existing
+  // duct (null = free placement). Drives the green cursor highlight so the
+  // user sees the next click will join an existing run, not freeform-place.
   const [snapTarget, setSnapTarget] = useState<[number, number, number] | null>(null)
+  // In ceiling mode, the ceiling the cursor is currently under — rendered as
+  // a translucent overlay so the duct reads as hung against a real surface
+  // rather than a dot floating in space. Null when off-ceiling.
+  const [hoverCeiling, setHoverCeiling] = useState<CeilingNode | null>(null)
   // True while Alt is held with a last point on the draft — drives the
   // vertical-cylinder ghost and the cursor HUD label.
   const [altActive, setAltActive] = useState(false)
+  // What the in-flight cursor end currently snaps onto (port end, or a
+  // run body for a tee / cross tap). Drives the auto-fitting GHOST so the
+  // user sees the elbow / tee / cross the next click will mint.
+  const [endSnap, setEndSnap] = useState<{ port: ScenePort | null; body: RunBodyHit | null }>({
+    port: null,
+    body: null,
+  })
   // Mirror into refs so emitter callbacks (closing over the first render's
   // setState) read the latest values without re-subscribing.
   const draftRef = useRef(draftPoints)
@@ -317,246 +558,63 @@ const DuctSegmentTool = () => {
   useEffect(() => {
     if (!activeLevelId) return
 
-    /**
-     * Auto-elbow gate: only joints onto another RUN's open end get a
-     * fitting minted. Ports on fittings / equipment / terminals are
-     * already proper connections — a duct mates straight onto those.
-     *
-     * The elbow's junction sits ON the drawn corner, so the existing run
-     * must trim back one leg to make room (`trim` update). Plans that
-     * would trim the run to (or past) nothing are dropped — that corner
-     * stays a plain butt joint. Guards against the snapped node having
-     * been deleted between clicks.
-     */
-    const elbowPlanFor = (port: ScenePort | null, awayDir: [number, number, number]) => {
-      if (!port) return null
-      const owner = useScene.getState().nodes[port.nodeId]
-      if (owner?.type !== 'duct-segment') return null
-      const plan = planElbowAtPort(port, awayDir, profileRef.current)
-      if (!plan) return null
-
-      // Trim the run's snapped endpoint back to the elbow's inlet collar.
-      const path = owner.path.map((p) => [...p] as [number, number, number])
-      const index = port.id === 'start' ? 0 : path.length - 1
-      const neighbor = path[index === 0 ? 1 : index - 1]!
-      const remaining = Math.hypot(
-        plan.trimmedPortPoint[0] - neighbor[0],
-        plan.trimmedPortPoint[1] - neighbor[1],
-        plan.trimmedPortPoint[2] - neighbor[2],
-      )
-      // The trim must leave a real piece of the existing run AND not flip
-      // it (trimmed point past the neighbor) — otherwise skip the fitting.
-      const original = path[index]!
-      const originalLen = Math.hypot(
-        original[0] - neighbor[0],
-        original[1] - neighbor[1],
-        original[2] - neighbor[2],
-      )
-      if (remaining < 0.08 || remaining >= originalLen) return null
-      path[index] = plan.trimmedPortPoint
-      return { ...plan, trim: { id: port.nodeId, data: { path } as Partial<AnyNode> } }
-    }
-
-    /**
-     * Realign gate: the snapped port belongs to an existing ELBOW's open
-     * collar — re-aim that elbow (junction + mated collar fixed, free
-     * collar swings to the drawn direction). Null when the owner isn't
-     * an elbow or the required turn leaves the 15–90° range.
-     */
-    const realignPlanFor = (port: ScenePort | null, awayDir: [number, number, number]) => {
-      if (!port) return null
-      const owner = useScene.getState().nodes[port.nodeId]
-      if (owner?.type !== 'duct-fitting') return null
-      return planElbowRealign(owner, port.id, awayDir)
-    }
-
-    // One segment per gesture: first click anchors the start, second
-    // click commits a two-point duct immediately. No selection switch —
-    // the tool stays armed so the next click starts the next segment
-    // (port snap joins it onto the end just committed).
+    // Continuous chain: first click anchors the start, each following
+    // click commits one two-point duct and uses that duct's far end as
+    // the next anchor. No selection switch or finish gesture.
     //
-    // When an end of the segment snapped onto another run's open port at
-    // an angle, an elbow fitting is minted at that joint and the duct is
-    // pulled back to the elbow's outlet collar — corners get real
-    // fittings instead of butt joints.
+    // All the auto-fitting decisions (elbow / tee / cross) live in the
+    // shared `planDuctDraw` so the live ghost previews exactly what this
+    // commit applies.
     const commitSegment = (
       start: [number, number, number],
       end: [number, number, number],
       endPort: ScenePort | null = null,
       endBody: RunBodyHit | null = null,
     ) => {
-      const length = Math.hypot(end[0] - start[0], end[1] - start[1], end[2] - start[2])
-      if (length < 1e-4) return
-      const dir: [number, number, number] = [
-        (end[0] - start[0]) / length,
-        (end[1] - start[1]) / length,
-        (end[2] - start[2]) / length,
-      ]
-
-      const startPlan = elbowPlanFor(startPortRef.current, dir)
-      const endPlan = elbowPlanFor(endPort, [-dir[0], -dir[1], -dir[2]])
-      // Existing-fitting joints: re-aim the elbow whose collar was hit so
-      // it faces the drawn run instead of leaving a mismatched butt joint.
-      const startRealign = startPlan ? null : realignPlanFor(startPortRef.current, dir)
-      const endRealign = endPlan ? null : realignPlanFor(endPort, [-dir[0], -dir[1], -dir[2]])
-      // Tee tap: the start snapped onto a run's BODY (not an end port) —
-      // split the trunk and branch from the tee's collar.
-      const trunkBody = startPlan ? null : startBodyRef.current
-      const trunkOwner = trunkBody ? useScene.getState().nodes[trunkBody.nodeId] : null
-      const teePlan =
-        trunkBody && trunkOwner?.type === 'duct-segment'
-          ? planTeeAtRunBody(trunkOwner, trunkBody, dir, profileRef.current)
-          : null
-      // End tee tap: the END landed on a run's BODY — split that trunk and
-      // the new duct ends at the tee's branch collar. The branch leaves
-      // toward the drawn run (back along -dir, since dir points start→end).
-      const endTrunkBody = endPlan || endRealign ? null : endBody
-      const endTrunkOwner = endTrunkBody ? useScene.getState().nodes[endTrunkBody.nodeId] : null
-      const endTeePlan =
-        endTrunkBody && endTrunkOwner?.type === 'duct-segment'
-          ? planTeeAtRunBody(
-              endTrunkOwner,
-              endTrunkBody,
-              [-dir[0], -dir[1], -dir[2]],
-              profileRef.current,
-            )
-          : null
-      let ductStart =
-        startPlan?.collarPoint ?? teePlan?.branchCollar ?? startRealign?.collarPoint ?? start
-      let ductEnd =
-        endPlan?.collarPoint ?? endTeePlan?.branchCollar ?? endRealign?.collarPoint ?? end
-      // The collar pull-back must leave a real piece of duct between the
-      // fittings; if not, fall back to the plain joint.
-      const remaining = Math.hypot(
-        ductEnd[0] - ductStart[0],
-        ductEnd[1] - ductStart[1],
-        ductEnd[2] - ductStart[2],
+      const plan = planDuctDraw(
+        start,
+        end,
+        startPortRef.current,
+        startBodyRef.current,
+        endPort,
+        endBody,
+        profileRef.current,
       )
-      let plans = [startPlan, endPlan].filter((p) => p !== null)
-      let tee = teePlan
-      // Both ends tapping the SAME trunk would split one polyline twice in
-      // a single change (conflicting updates + double tail) — drop the end
-      // tee in that rare case and let the end butt-join instead.
-      let endTee = endTeePlan && endTrunkBody?.nodeId === trunkBody?.nodeId ? null : endTeePlan
-      if (!endTee && endTeePlan) ductEnd = endRealign?.collarPoint ?? end
-      let realigns = [startRealign, endRealign].filter((p) => p !== null)
-
-      // Cross tap: the drawn run passes straight THROUGH a trunk's body
-      // (interior crossing, not an end touch). Split that trunk and the
-      // drawn duct into two halves meeting the cross's opposed branch
-      // collars. Skip a run already tapped by a start / end tee so one
-      // polyline isn't split twice in a single change.
-      const crossHit = findRunBodyCrossingXZ(start, end, BODY_SNAP_RADIUS_M)
-      const crossOwner = crossHit ? useScene.getState().nodes[crossHit.nodeId] : null
-      const crossTappedElsewhere =
-        crossHit?.nodeId === trunkBody?.nodeId || crossHit?.nodeId === endTrunkBody?.nodeId
-      let cross =
-        crossHit && !crossTappedElsewhere && crossOwner?.type === 'duct-segment'
-          ? planCrossAtRunBody(crossOwner, crossHit, dir, profileRef.current)
-          : null
-
-      if (remaining <= 0.08) {
-        plans = []
-        tee = null
-        endTee = null
-        realigns = []
-        cross = null
-        ductStart = start
-        ductEnd = end
-      }
-
-      // Rect / oval continuity: roll the new run's cross-section so its
-      // profile stays continuous with whatever either end joined — run
-      // end or fitting collar, turn or straight continuation (see
-      // `continuityRollFrom`). The start joint wins if both ends join.
-      let roll = 0
-      if (profileRef.current.shape !== 'round') {
-        const newDir = new Vector3(...dir)
-        roll =
-          continuityRollFrom(startPortRef.current, newDir) ??
-          continuityRollFrom(endPort, newDir) ??
-          0
-      }
-
-      const defaults = ductSegmentDefinition.defaults()
-      const toolDefaults = useEditor.getState().toolDefaults['duct-segment'] ?? {}
-      const makeDuct = (from: [number, number, number], to: [number, number, number]) =>
-        DuctSegmentNode.parse({
-          ...defaults,
-          ...toolDefaults,
-          name: profileRef.current.shape === 'rect' ? 'Trunk' : 'Duct run',
-          path: [from, to],
-          shape: profileRef.current.shape,
-          diameter: profileRef.current.diameter,
-          width: profileRef.current.width,
-          height: profileRef.current.height,
-          roll,
-        })
-      // A cross splits the drawn run into two halves that meet its opposed
-      // branch collars; otherwise it's one duct end-to-end. Degenerate
-      // halves (the crossing too near an end) are dropped.
-      const ducts = cross
-        ? [
-            dist2(ductStart, cross.branchCollarNear) > 0.08 * 0.08
-              ? makeDuct(ductStart, cross.branchCollarNear)
-              : null,
-            dist2(cross.branchCollarFar, ductEnd) > 0.08 * 0.08
-              ? makeDuct(cross.branchCollarFar, ductEnd)
-              : null,
-          ].filter((d) => d !== null)
-        : [makeDuct(ductStart, ductEnd)]
+      if (!plan) return
       // One atomic change: trim / split the joined runs, create the
       // fittings + the new duct. Single undo step.
       useScene.getState().applyNodeChanges({
         create: [
-          ...plans.map((plan) => ({ node: plan.fitting, parentId: activeLevelId })),
-          ...(tee
-            ? [
-                { node: tee.fitting, parentId: activeLevelId },
-                { node: tee.trunkTail, parentId: activeLevelId },
-              ]
-            : []),
-          ...(endTee
-            ? [
-                { node: endTee.fitting, parentId: activeLevelId },
-                { node: endTee.trunkTail, parentId: activeLevelId },
-              ]
-            : []),
-          ...(cross
-            ? [
-                { node: cross.fitting, parentId: activeLevelId },
-                { node: cross.trunkTail, parentId: activeLevelId },
-              ]
-            : []),
-          ...ducts.map((node) => ({ node, parentId: activeLevelId })),
-        ],
-        update: [
-          ...plans.map((plan) => plan.trim),
-          ...(tee ? [tee.trunkUpdate as { id: AnyNode['id']; data: Partial<AnyNode> }] : []),
-          ...(endTee ? [endTee.trunkUpdate as { id: AnyNode['id']; data: Partial<AnyNode> }] : []),
-          ...(cross ? [cross.trunkUpdate as { id: AnyNode['id']; data: Partial<AnyNode> }] : []),
-          ...realigns.map((plan) => plan.update as { id: AnyNode['id']; data: Partial<AnyNode> }),
+          ...plan.fittings.map((node) => ({ node, parentId: activeLevelId })),
+          ...plan.tails.map((node) => ({ node, parentId: activeLevelId })),
+          ...plan.ducts.map((node) => ({ node, parentId: activeLevelId })),
         ],
+        update: plan.updates,
       })
+      const nextDuct = plan.ducts.at(-1)
+      const nextStart = nextDuct ? nextDuct.path[nextDuct.path.length - 1]! : end
+      const nextPort = nextDuct ? ductEndPort(nextDuct, 'end') : endPort
       triggerSFX('sfx:item-place')
-      setDraftPoints([])
+      setDraftPoints([nextStart])
       setSnapTarget(null)
-      startPortRef.current = null
-      startBodyRef.current = null
+      setEndSnap({ port: null, body: null })
+      startPortRef.current = nextPort
+      startBodyRef.current = nextPort ? null : endBody
       altAnchorRef.current = null
       setAltActive(false)
     }
 
-    // Base Y for a fresh run's first point: floor (0) by default, or just
-    // below the level's ceiling in ceiling mode so the duct's top hugs the
-    // ceiling (centerline = ceiling height − radius).
-    const resolveBaseY = (): number => {
+    // Y for a point at level-local `[x, z]`. Floor (0) when ceiling mode is
+    // off. In ceiling mode, query the ceiling actually covering that point
+    // and hang the duct just below it (centerline = ceiling underside −
+    // half the duct's vertical dimension) so its top hugs the ceiling. Each
+    // point follows its own ceiling, so a run stepping into a room with a
+    // different ceiling height tracks that change. Points not under any
+    // ceiling fall back to the floor.
+    const resolveCeilingY = (x: number, z: number): number => {
       if (!ceilingModeRef.current) return 0
-      const ceiling = getLevelHeight(
-        activeLevelId,
-        useScene.getState().nodes,
-        (wallId) => sceneRegistry.nodes.get(wallId)?.position.y,
-      )
+      const ceiling = getCeilingHeightAt(activeLevelId, useScene.getState().nodes, x, z)
+      if (ceiling === null) return 0
       const p = profileRef.current
       const verticalIn = p.shape === 'round' ? p.diameter : p.height
       return Math.max(0, ceiling - (verticalIn * 0.0254) / 2)
@@ -571,11 +629,11 @@ const DuctSegmentTool = () => {
       body: RunBodyHit | null
     } => {
       const last = draftRef.current.at(-1)
-      // First point of the run: grid-snapped placement at the base Y (floor,
-      // or ceiling height in ceiling mode). Endpoint snap can still join an
-      // existing run.
+      // First point of the run: grid-snapped placement. Y follows the
+      // ceiling under the cursor in ceiling mode (floor otherwise).
+      // Endpoint snap can still join an existing run.
       if (!last) {
-        const baseY = resolveBaseY()
+        const baseY = resolveCeilingY(event.localPosition[0], event.localPosition[2])
         const raw: [number, number, number] = [
           event.localPosition[0],
           baseY,
@@ -601,15 +659,20 @@ const DuctSegmentTool = () => {
           const body = findNearestRunBodyXZ(probe, BODY_SNAP_RADIUS_M)
           if (body) return { point: body.point, snapped: body.point, port: null, body }
         }
+        const sx = snap(raw[0], step)
+        const sz = snap(raw[2], step)
         return {
-          point: [snap(raw[0], step), baseY, snap(raw[2], step)],
+          point: [sx, resolveCeilingY(sx, sz), sz],
           snapped: null,
           port: null,
           body: null,
         }
       }
       // Subsequent points: angle-locked to 45° from `last` (Shift releases).
-      // Y stays at `last[1]` — depth changes come from Shift+click risers.
+      // Y inherits `last[1]` for the angle/probe math; the free placement
+      // below re-resolves it from the ceiling under the point in ceiling
+      // mode, so a run stepping into a room with a different ceiling height
+      // tracks that change. Depth changes otherwise come from Alt risers.
       const rawXZ: [number, number, number] = [
         event.localPosition[0],
         last[1],
@@ -638,8 +701,11 @@ const DuctSegmentTool = () => {
         const body = findNearestRunBodyXZ(probe, BODY_SNAP_RADIUS_M)
         if (body) return { point: body.point, snapped: body.point, port: null, body }
       }
+      const fx = snap(angled[0], step)
+      const fz = snap(angled[2], step)
+      const fy = ceilingModeRef.current ? resolveCeilingY(fx, fz) : angled[1]
       return {
-        point: [snap(angled[0], step), angled[1], snap(angled[2], step)],
+        point: [fx, fy, fz],
         snapped: null,
         port: null,
         body: null,
@@ -681,6 +747,17 @@ const DuctSegmentTool = () => {
       return { ...r, point }
     }
 
+    // The ceiling the cursor is under (ceiling mode only) — drives the
+    // translucent surface overlay so the in-flight point reads as hung
+    // against a real ceiling. Cleared when off-ceiling or out of mode.
+    const updateHoverCeiling = (x: number, z: number) => {
+      if (!ceilingModeRef.current) {
+        setHoverCeiling(null)
+        return
+      }
+      setHoverCeiling(getCeilingAt(activeLevelId, useScene.getState().nodes, x, z))
+    }
+
     const onMove = (event: GridEvent) => {
       const clientY = (event.nativeEvent as { clientY?: number } | undefined)?.clientY
       if (typeof clientY === 'number') lastClientYRef.current = clientY
@@ -691,12 +768,16 @@ const DuctSegmentTool = () => {
           clearDrawAlignment()
           setCursorPos(point)
           setSnapTarget(null)
+          setEndSnap({ port: null, body: null })
+          updateHoverCeiling(point[0], point[2])
           return
         }
       }
-      const { point, snapped } = resolveAlignedPoint(event)
+      const { point, snapped, port, body } = resolveAlignedPoint(event)
       setCursorPos(point)
       setSnapTarget(snapped)
+      setEndSnap({ port, body: port ? null : body })
+      updateHoverCeiling(point[0], point[2])
     }
 
     const onClick = (event: GridEvent) => {
@@ -783,12 +864,14 @@ const DuctSegmentTool = () => {
         setProfile((p) => ({ ...p, shape: p.shape === 'round' ? 'rect' : 'round' }))
         triggerSFX('sfx:grid-snap')
       } else if (e.key === 'c' || e.key === 'C') {
-        // Toggle ceiling mode. Only the first point reads the base Y, so
-        // toggling mid-run is a no-op until the next fresh segment — flip
-        // it only while unanchored to keep the behaviour predictable.
+        // Toggle ceiling mode: points hang from the ceiling above them
+        // (duct top hugging the ceiling) instead of sitting on the floor.
+        // Only flip while unanchored — already-placed points keep their Y,
+        // so a mid-run toggle would split a run across two height regimes.
         if (draftRef.current.length > 0) return
         e.preventDefault()
         setCeilingMode((m) => !m)
+        setHoverCeiling(null)
         triggerSFX('sfx:grid-snap')
       }
     }
@@ -807,6 +890,8 @@ const DuctSegmentTool = () => {
       setDraftPoints([])
       setCursorPos(null)
       setSnapTarget(null)
+      setEndSnap({ port: null, body: null })
+      setHoverCeiling(null)
       startPortRef.current = null
       startBodyRef.current = null
     }
@@ -838,6 +923,22 @@ const DuctSegmentTool = () => {
     previewSegments.push({ a: last, b: cursorPos })
   }
 
+  // Ghost the auto-inserted fittings (elbow / tee / cross) the next click
+  // will mint, by running the SAME planner the commit uses against the
+  // in-flight endpoints. Skipped in Alt-vertical mode (no XZ tap there).
+  const ghostFittings =
+    last && cursorPos && !altActive
+      ? (planDuctDraw(
+          last,
+          cursorPos,
+          startPortRef.current,
+          startBodyRef.current,
+          endSnap.port,
+          endSnap.body,
+          profile,
+        )?.fittings ?? [])
+      : []
+
   // Wall-style dimension pill above the cursor: absolute world coords before
   // the first point, signed per-axis deltas from the last placed point while
   // a segment is in flight. The actively-driven axis is emphasised — Y in
@@ -868,45 +969,71 @@ const DuctSegmentTool = () => {
           : 'z'
       : undefined
 
+  // When the in-flight point hangs above the floor (ceiling mode, or an
+  // Alt riser), the cursor marker itself rides AT the point (where the
+  // mouse is aiming and the next click commits), and a plumb line drops
+  // straight down to a faint ground ring on the floor below — so the plan
+  // position stays legible from any angle. A floor-level point keeps the
+  // standard fixed-height cursor look.
+  const cursorElevation = cursorPos ? cursorPos[1] : 0
+  const isElevated = cursorElevation > 0.001
+  const cursorGround: [number, number, number] | null = cursorPos
+    ? [cursorPos[0], 0, cursorPos[2]]
+    : null
+
   return (
     <LevelOffsetGroup>
+      {/* Ceiling-mode surface highlight — the ceiling the cursor is under,
+          tinted at its own elevation so the duct reads as hung against a
+          real surface instead of a point floating in space. */}
+      {ceilingMode && hoverCeiling && <CeilingHighlight ceiling={hoverCeiling} />}
       {/* Cursor marker — the same ground ring + vertical line + tool-icon
           badge walls and items show while drawing (icon resolved from the
           active `duct-segment` structure-tools entry). The dimension pill
           rides just above the cursor. */}
-      {cursorPos && (
+      {cursorPos && cursorGround && (
         <>
-          <CursorSphere position={cursorPos} ref={cursorRef} />
+          {/* In ceiling mode (or any elevated point) the ground ring sits on
+              the floor below the cursor and the line rises to the placement
+              point, with the bright dot + tool badge at its tip — exactly
+              where the next click commits. At floor level it's the standard
+              fixed-height cursor. */}
+          {isElevated ? (
+            <CursorSphere
+              color={snapTarget ? SNAP_CURSOR_COLOR : undefined}
+              dotAtTip
+              height={cursorElevation}
+              position={cursorGround}
+              ref={cursorRef}
+            />
+          ) : (
+            <CursorSphere
+              color={snapTarget ? SNAP_CURSOR_COLOR : undefined}
+              position={cursorPos}
+              ref={cursorRef}
+            />
+          )}
           {pillParts && (
             <group position={cursorPos}>
               <Html
                 center
-                position={[0, 0.35, 0]}
+                position={[0, 1.45, 0]}
                 style={{ pointerEvents: 'none', userSelect: 'none' }}
                 zIndexRange={[100, 0]}
               >
-                <div className="flex flex-col items-center gap-1">
-                  <DimensionPill parts={pillParts} primary={pillPrimary} unit={unit} />
+                <div className="flex flex-col items-center gap-2">
                   {ceilingMode && !last && (
                     <div className="whitespace-nowrap rounded-full border border-border/60 bg-background/90 px-3 py-0.5 text-[10px] text-muted-foreground shadow-sm backdrop-blur">
                       Ceiling · C to toggle
                     </div>
                   )}
+                  <DimensionPill parts={pillParts} primary={pillPrimary} unit={unit} />
                 </div>
               </Html>
             </group>
           )}
         </>
       )}
-      {/* Endpoint-snap halo — brighter ring around the target endpoint
-          while the cursor is within snap range, so the user sees that the
-          next click will join an existing duct rather than freeform-place. */}
-      {snapTarget && (
-        <mesh layers={EDITOR_LAYER} position={snapTarget}>
-          <sphereGeometry args={[0.12, 24, 16]} />
-          <meshBasicMaterial color="#818cf8" depthTest={false} opacity={0.35} transparent />
-        </mesh>
-      )}
       {/* Committed point pips */}
       {draftPoints.map((p, i) => (
         <mesh key={`pt-${i}`} layers={EDITOR_LAYER} position={p}>
@@ -919,25 +1046,112 @@ const DuctSegmentTool = () => {
         <PreviewSegment
           a={seg.a}
           b={seg.b}
+          endPort={endSnap.port}
           key={`seg-${i}`}
           profile={profile}
           startPort={startPortRef.current}
         />
       ))}
+      {/* Auto-fitting ghosts — the elbow / tee / cross the next click mints. */}
+      {ghostFittings.map((fitting) => (
+        <FittingGhost fitting={fitting} key={fitting.id} />
+      ))}
     </LevelOffsetGroup>
   )
 }
 
+/**
+ * Build a horizontal `ShapeGeometry` for a ceiling polygon (with holes) in
+ * level-local XZ, laid flat in the XZ plane. Mirrors the ceiling renderer /
+ * move-tool convention (Z negated, then rotated onto the floor plane).
+ */
+function buildCeilingShape(
+  polygon: Array<[number, number]>,
+  holes: Array<Array<[number, number]>>,
+): BufferGeometry | null {
+  if (polygon.length < 3) return null
+  const shape = new Shape()
+  const first = polygon[0]!
+  shape.moveTo(first[0], -first[1])
+  for (let i = 1; i < polygon.length; i++) {
+    const pt = polygon[i]!
+    shape.lineTo(pt[0], -pt[1])
+  }
+  shape.closePath()
+  for (const holePolygon of holes) {
+    if (holePolygon.length < 3) continue
+    const hole = new Path()
+    const hf = holePolygon[0]!
+    hole.moveTo(hf[0], -hf[1])
+    for (let i = 1; i < holePolygon.length; i++) {
+      const pt = holePolygon[i]!
+      hole.lineTo(pt[0], -pt[1])
+    }
+    hole.closePath()
+    shape.holes.push(hole)
+  }
+  const geometry = new ShapeGeometry(shape)
+  geometry.rotateX(-Math.PI / 2)
+  return geometry
+}
+
+/**
+ * Translucent overlay of the ceiling the cursor is under, drawn at the
+ * ceiling's own height. Gives the in-flight duct point a real surface to
+ * read against, so "hung against the ceiling" is visible from any angle
+ * instead of being a dot floating in space.
+ */
+function CeilingHighlight({ ceiling }: { ceiling: CeilingNode }) {
+  const geometry = useMemo(
+    () => buildCeilingShape(ceiling.polygon, ceiling.holes),
+    [ceiling.polygon, ceiling.holes],
+  )
+  const outline = useMemo(() => {
+    if (ceiling.polygon.length < 2) return null
+    const pts = ceiling.polygon.map(([x, z]) => new Vector3(x, 0, z))
+    const f = ceiling.polygon[0]!
+    pts.push(new Vector3(f[0], 0, f[1]))
+    return pts
+  }, [ceiling.polygon])
+  if (!geometry) return null
+  const y = ceiling.height ?? 2.5
+  return (
+    <group position={[0, y, 0]}>
+      <mesh geometry={geometry} layers={EDITOR_LAYER} renderOrder={1}>
+        <meshBasicMaterial
+          color="#818cf8"
+          depthWrite={false}
+          opacity={0.15}
+          side={DoubleSide}
+          transparent
+        />
+      </mesh>
+      {outline && (
+        <line>
+          <bufferGeometry
+            ref={(g) => {
+              if (g) g.setFromPoints(outline)
+            }}
+          />
+          <lineBasicMaterial color="#818cf8" opacity={0.6} transparent />
+        </line>
+      )}
+    </group>
+  )
+}
+
 function PreviewSegment({
   a,
   b,
   profile,
   startPort,
+  endPort,
 }: {
   a: [number, number, number]
   b: [number, number, number]
   profile: DraftProfile
   startPort: ScenePort | null
+  endPort: ScenePort | null
 }) {
   const start = new Vector3(...a)
   const end = new Vector3(...b)
@@ -959,7 +1173,7 @@ function PreviewSegment({
           if (!m) return
           // Same basis AND roll as the commit will use, so the ghost
           // shows the orientation that actually lands.
-          const roll = continuityRollFrom(startPort, dir) ?? 0
+          const roll = continuityRollForRun(startPort, endPort, dir)
           const { width: x, height: z } = rectSectionAxes(dir, roll)
           m.quaternion.setFromRotationMatrix(new Matrix4().makeBasis(x, dir, z))
         }}

packages/nodes/src/eyebrow-vent/move-tool.tsx

@@ -5,6 +5,7 @@ import {
   type EyebrowVentNode,
   emitter,
   type RoofEvent,
+  type RoofNode,
   type RoofSegmentNode,
   sceneRegistry,
   useScene,
@@ -21,8 +22,14 @@ import {
   createRelativeRoofDrag,
   type RelativeRoofDragTarget,
   roofSegmentLocalToBuildingLocal,
+  snapRelativeRoofDragTarget,
 } from '../shared/relative-roof-drag'
 import { getAnalyticalNormal, surfaceQuatFromNormal } from '../shared/roof-surface'
+import {
+  clearRoofSurfacePlacementGuides,
+  publishRoofSurfaceNodePlacementGuides,
+  snapRoofSurfaceNodeTarget,
+} from '../shared/roof-surface-placement-guides'
 import EyebrowVentPreview from './preview'
 
 /**
@@ -71,10 +78,21 @@ export default function MoveEyebrowVentTool({ node }: { node: EyebrowVentNode })
       lastSnap = null
       setPreviewPos(null)
       setPreviewSurfaceQuat(null)
+      clearRoofSurfacePlacementGuides()
+    }
+
+    const resolveSnappedTarget = (event: RoofEvent): RelativeRoofDragTarget | null => {
+      const rawTarget = roofDrag.resolve(event)
+      if (!rawTarget) return null
+      return snapRoofSurfaceNodeTarget({
+        target: snapRelativeRoofDragTarget(rawTarget, event.nativeEvent?.shiftKey === true),
+        node,
+        bypass: event.nativeEvent?.shiftKey === true,
+      })
     }
 
     const updatePreview = (event: RoofEvent) => {
-      const target = roofDrag.resolve(event)
+      const target = resolveSnappedTarget(event)
       if (!target) {
         clearTarget()
         return
@@ -101,12 +119,18 @@ export default function MoveEyebrowVentTool({ node }: { node: EyebrowVentNode })
           target.localZ,
         ]),
       )
+      publishRoofSurfaceNodePlacementGuides({
+        roof: event.node as RoofNode,
+        segment: target.segment,
+        center: [target.localX, target.localY, target.localZ],
+        node,
+      })
       event.stopPropagation()
     }
 
     const onRoofClick = (event: RoofEvent) => {
       if (committed) return
-      const target = lastTarget ?? roofDrag.resolve(event)
+      const target = lastTarget ?? resolveSnappedTarget(event)
       if (!target) return
       committed = true
       const targetSegmentId = target.segment.id as AnyNodeId
@@ -147,6 +171,7 @@ export default function MoveEyebrowVentTool({ node }: { node: EyebrowVentNode })
       if (obj) obj.visible = true
 
       triggerSFX('sfx:item-place')
+      clearRoofSurfacePlacementGuides()
       exitMoveMode()
       event.stopPropagation()
     }
@@ -165,6 +190,7 @@ export default function MoveEyebrowVentTool({ node }: { node: EyebrowVentNode })
         useScene.getState().deleteNode(node.id as AnyNodeId)
         useScene.temporal.getState().resume()
         markToolCancelConsumed()
+        clearRoofSurfacePlacementGuides()
         exitMoveMode()
         return
       }
@@ -184,6 +210,7 @@ export default function MoveEyebrowVentTool({ node }: { node: EyebrowVentNode })
 
       useScene.temporal.getState().resume()
       markToolCancelConsumed()
+      clearRoofSurfacePlacementGuides()
       exitMoveMode()
     }
 
@@ -213,6 +240,7 @@ export default function MoveEyebrowVentTool({ node }: { node: EyebrowVentNode })
 
       const obj = sceneRegistry.nodes.get(node.id)
       if (obj) obj.visible = true
+      clearRoofSurfacePlacementGuides()
       useScene.temporal.getState().resume()
     }
   }, [exitMoveMode, node])

packages/nodes/src/eyebrow-vent/tool.tsx

@@ -16,6 +16,11 @@ import * as THREE from 'three'
 import { RoofAttachmentFallbackPreview } from '../shared/roof-attachment-fallback-preview'
 import { resolveRoofSegmentHit } from '../shared/roof-segment-hit'
 import { getAnalyticalNormal, getDownSlopeYaw, surfaceQuatFromNormal } from '../shared/roof-surface'
+import {
+  clearRoofSurfacePlacementGuides,
+  publishRoofSurfacePlacementGuides,
+  roofSurfaceFootprintFromNode,
+} from '../shared/roof-surface-placement-guides'
 import { eyebrowVentDefinition } from './definition'
 import EyebrowVentPreview from './preview'
 
@@ -80,6 +85,15 @@ const EyebrowVentTool = () => {
       setPreviewYaw((event.node.rotation ?? 0) + (hit.segment.rotation ?? 0))
       setPreviewRotation(getDownSlopeYaw(hit.localX, hit.localZ, hit.segment))
       setPreviewPos(worldToBuildingLocal(wx, wy, wz))
+      publishRoofSurfacePlacementGuides({
+        roof: event.node as RoofNode,
+        segment: hit.segment,
+        center: [hit.localX, hit.localY, hit.localZ],
+        footprint: roofSurfaceFootprintFromNode({
+          ...previewNode,
+          rotation: getDownSlopeYaw(hit.localX, hit.localZ, hit.segment),
+        }),
+      })
       event.stopPropagation()
     }
 
@@ -104,6 +118,7 @@ const EyebrowVentTool = () => {
       state.dirtyNodes.add(hit.segment.id as AnyNodeId)
       setSelection({ selectedIds: [vent.id] })
       triggerSFX('sfx:item-place')
+      clearRoofSurfacePlacementGuides()
       event.stopPropagation()
     }
 
@@ -115,8 +130,9 @@ const EyebrowVentTool = () => {
       emitter.off('roof:move', updatePreview)
       emitter.off('roof:enter', updatePreview)
       emitter.off('roof:click', onClick)
+      clearRoofSurfacePlacementGuides()
     }
-  }, [activeBuildingId, setSelection])
+  }, [activeBuildingId, setSelection, previewNode])
 
   return (
     <>
@@ -126,6 +142,7 @@ const EyebrowVentTool = () => {
         onInvalidTarget={() => {
           setPreviewPos(null)
           setPreviewSurfaceQuat(null)
+          clearRoofSurfacePlacementGuides()
         }}
       />
       {activeBuildingId && previewPos && previewSurfaceQuat && (

packages/nodes/src/fence/tool.tsx

@@ -552,6 +552,7 @@ export const FenceTool: React.FC = () => {
     }
 
     const onGridClick = (event: GridEvent) => {
+      if (!previewRef.current) return
       if (buildingState.current === 1 && event.nativeEvent.detail >= 2) {
         stopDrafting()
         return

packages/nodes/src/gutter/move-tool.tsx

@@ -17,7 +17,11 @@ import {
   useEditor,
 } from '@pascal-app/editor'
 import { useCallback, useEffect, useState } from 'react'
-import { createRelativeRoofDrag } from '../shared/relative-roof-drag'
+import { createRelativeRoofDrag, snapRelativeRoofDragTarget } from '../shared/relative-roof-drag'
+import {
+  clearRoofSurfacePlacementGuides,
+  publishRoofSurfaceNodePlacementGuides,
+} from '../shared/roof-surface-placement-guides'
 import { type EaveSnap, resolveEaveSnap } from './eave-snap'
 import GutterPreview from './preview'
 
@@ -83,11 +87,13 @@ export default function MoveGutterTool({ node }: { node: GutterNode }) {
       lastTarget = null
       lastSnap = null
       setTarget(null)
+      clearRoofSurfacePlacementGuides()
     }
 
     const resolveTarget = (event: RoofEvent): GutterDragTarget | null => {
-      const target = roofDrag.resolve(event)
-      if (!target) return null
+      const rawTarget = roofDrag.resolve(event)
+      if (!rawTarget) return null
+      const target = snapRelativeRoofDragTarget(rawTarget, event.nativeEvent?.shiftKey === true)
       return {
         segment: target.segment,
         snap: resolveEaveSnap(target.segment, target.localX, target.localZ),
@@ -131,6 +137,13 @@ export default function MoveGutterTool({ node }: { node: GutterNode }) {
         },
         snap,
       })
+      publishRoofSurfaceNodePlacementGuides({
+        roof,
+        segment: target.segment,
+        center: [snap.eaveX, snap.eaveY, snap.eaveZ],
+        node: { ...node, rotation: snap.rotation },
+        mode: 'linear-edge',
+      })
       event.stopPropagation()
     }
 
@@ -178,6 +191,7 @@ export default function MoveGutterTool({ node }: { node: GutterNode }) {
       if (obj) obj.visible = true
 
       triggerSFX('sfx:item-place')
+      clearRoofSurfacePlacementGuides()
       exitMoveMode()
       event.stopPropagation()
     }
@@ -196,6 +210,7 @@ export default function MoveGutterTool({ node }: { node: GutterNode }) {
         useScene.getState().deleteNode(node.id as AnyNodeId)
         useScene.temporal.getState().resume()
         markToolCancelConsumed()
+        clearRoofSurfacePlacementGuides()
         exitMoveMode()
         return
       }
@@ -215,6 +230,7 @@ export default function MoveGutterTool({ node }: { node: GutterNode }) {
 
       useScene.temporal.getState().resume()
       markToolCancelConsumed()
+      clearRoofSurfacePlacementGuides()
       exitMoveMode()
     }
 
@@ -244,6 +260,7 @@ export default function MoveGutterTool({ node }: { node: GutterNode }) {
 
       const obj = sceneRegistry.nodes.get(node.id)
       if (obj) obj.visible = true
+      clearRoofSurfacePlacementGuides()
       useScene.temporal.getState().resume()
     }
   }, [exitMoveMode, node])

packages/nodes/src/gutter/tool.tsx

@@ -13,6 +13,11 @@ import { useViewer } from '@pascal-app/viewer'
 import { useEffect, useMemo, useRef, useState } from 'react'
 import { RoofAttachmentFallbackPreview } from '../shared/roof-attachment-fallback-preview'
 import { resolveRoofSegmentHit } from '../shared/roof-segment-hit'
+import {
+  clearRoofSurfacePlacementGuides,
+  publishRoofSurfacePlacementGuides,
+  roofSurfaceFootprintFromNode,
+} from '../shared/roof-surface-placement-guides'
 import { gutterDefinition } from './definition'
 import { type EaveSnap, resolveEaveSnap } from './eave-snap'
 import GutterPreview from './preview'
@@ -100,6 +105,13 @@ const GutterTool = () => {
         },
         snap,
       })
+      publishRoofSurfacePlacementGuides({
+        roof,
+        segment: hit.segment,
+        center: [snap.eaveX, snap.eaveY, snap.eaveZ],
+        footprint: roofSurfaceFootprintFromNode({ ...previewNode, rotation: snap.rotation }),
+        mode: 'linear-edge',
+      })
       event.stopPropagation()
     }
 
@@ -129,6 +141,7 @@ const GutterTool = () => {
       state.dirtyNodes.add(hit.segment.id as AnyNodeId)
       setSelection({ selectedIds: [gutter.id] })
       triggerSFX('sfx:item-place')
+      clearRoofSurfacePlacementGuides()
       event.stopPropagation()
     }
 
@@ -140,15 +153,19 @@ const GutterTool = () => {
       emitter.off('roof:move', updatePreview)
       emitter.off('roof:enter', updatePreview)
       emitter.off('roof:click', onClick)
+      clearRoofSurfacePlacementGuides()
     }
-  }, [activeBuildingId, setSelection])
+  }, [activeBuildingId, setSelection, previewNode])
 
   return (
     <>
       <RoofAttachmentFallbackPreview
         activeBuildingId={activeBuildingId}
         ghost={<GutterPreview node={previewNode} invalid />}
-        onInvalidTarget={() => setTarget(null)}
+        onInvalidTarget={() => {
+          setTarget(null)
+          clearRoofSurfacePlacementGuides()
+        }}
       />
       {activeBuildingId && target && (
         <group position={target.roof.position} rotation-y={target.roof.rotation}>

packages/nodes/src/item/renderer.tsx

@@ -380,7 +380,7 @@ const ModelRenderer = ({ node }: { node: ItemNode }) => {
       mesh.castShadow = !hasGlass
       mesh.receiveShadow = !hasGlass
     }
-  }, [ref, scene, shading, textures, colorPreset, node.slots, sceneMaterials])
+  }, [shading, textures, colorPreset, node.slots, sceneMaterials])
 
   const interactive = interactiveRef.current
   const animEffect =

packages/nodes/src/lineset/connect.test.ts

@@ -1,124 +0,0 @@
-import { describe, expect, test } from 'bun:test'
-import { planLinesetConnect } from './connect'
-import type { LinesetNode } from './schema'
-
-type Point = [number, number, number]
-
-/** Minimal stand-in — the planner only reads `id` and `path`. */
-function line(id: string, path: Point[]): LinesetNode {
-  return { id, path } as unknown as LinesetNode
-}
-
-describe('planLinesetConnect', () => {
-  test('no shared endpoint → create', () => {
-    const plan = planLinesetConnect(
-      [
-        line('a', [
-          [0, 0, 0],
-          [1, 0, 0],
-        ]),
-      ],
-      [5, 0, 0],
-      [6, 0, 0],
-    )
-    expect(plan).toEqual({
-      kind: 'create',
-      path: [
-        [5, 0, 0],
-        [6, 0, 0],
-      ],
-    })
-  })
-
-  test('new start meets run end → extend, old end becomes interior', () => {
-    const a = line('a', [
-      [0, 0, 0],
-      [1, 0, 0],
-    ])
-    const plan = planLinesetConnect([a], [1, 0, 0], [1, 0, 2])
-    expect(plan).toEqual({
-      kind: 'extend',
-      id: 'a',
-      path: [
-        [0, 0, 0],
-        [1, 0, 0],
-        [1, 0, 2],
-      ],
-    })
-  })
-
-  test('new start meets run start → extend, run reversed so join is interior', () => {
-    const a = line('a', [
-      [0, 0, 0],
-      [1, 0, 0],
-    ])
-    const plan = planLinesetConnect([a], [0, 0, 0], [0, 0, 2])
-    expect(plan).toEqual({
-      kind: 'extend',
-      id: 'a',
-      path: [
-        [1, 0, 0],
-        [0, 0, 0],
-        [0, 0, 2],
-      ],
-    })
-  })
-
-  test('new end meets a run → extend, new segment leads', () => {
-    const a = line('a', [
-      [1, 0, 0],
-      [2, 0, 0],
-    ])
-    const plan = planLinesetConnect([a], [1, 0, 3], [1, 0, 0])
-    expect(plan).toEqual({
-      kind: 'extend',
-      id: 'a',
-      path: [
-        [1, 0, 3],
-        [1, 0, 0],
-        [2, 0, 0],
-      ],
-    })
-  })
-
-  test('both ends meet distinct runs → bridge, second run absorbed', () => {
-    const a = line('a', [
-      [0, 0, 0],
-      [1, 0, 0],
-    ])
-    const b = line('b', [
-      [1, 0, 5],
-      [2, 0, 5],
-    ])
-    const plan = planLinesetConnect([a, b], [1, 0, 0], [1, 0, 5])
-    expect(plan).toEqual({
-      kind: 'bridge',
-      id: 'a',
-      deleteId: 'b',
-      path: [
-        [0, 0, 0],
-        [1, 0, 0],
-        [1, 0, 5],
-        [2, 0, 5],
-      ],
-    })
-  })
-
-  test('both ends meet the SAME run → not a bridge (extends at start)', () => {
-    const a = line('a', [
-      [0, 0, 0],
-      [1, 0, 0],
-    ])
-    const plan = planLinesetConnect([a], [0, 0, 0], [1, 0, 0])
-    expect(plan.kind).toBe('extend')
-  })
-
-  test('float drift within tolerance still coincides', () => {
-    const a = line('a', [
-      [0, 0, 0],
-      [1, 0, 0],
-    ])
-    const plan = planLinesetConnect([a], [1.0000001, 0, 0], [1, 0, 2])
-    expect(plan.kind).toBe('extend')
-  })
-})

packages/nodes/src/lineset/connect.ts

@@ -1,98 +0,0 @@
-import type { LinesetNode } from './schema'
-
-type Point = [number, number, number]
-type LinesetId = LinesetNode['id']
-
-/** Coincidence tolerance (meters) for folding endpoints into one run. The
- * draw tool snaps onto an existing run's endpoint exactly, so this only
- * needs to absorb float drift, not user aim. */
-const COINCIDENT_EPS_M = 1e-3
-
-function samePoint(a: Point, b: Point): boolean {
-  return (
-    Math.abs(a[0] - b[0]) < COINCIDENT_EPS_M &&
-    Math.abs(a[1] - b[1]) < COINCIDENT_EPS_M &&
-    Math.abs(a[2] - b[2]) < COINCIDENT_EPS_M
-  )
-}
-
-/** Which terminal of `line` coincides with `p`, if either. */
-function matchEnd(line: LinesetNode, p: Point): 'start' | 'end' | null {
-  const path = line.path as Point[]
-  if (samePoint(path[0]!, p)) return 'start'
-  if (samePoint(path[path.length - 1]!, p)) return 'end'
-  return null
-}
-
-/** First lineset whose start or end coincides with `p`. */
-function findConnection(
-  existing: LinesetNode[],
-  p: Point,
-): { line: LinesetNode; side: 'start' | 'end' } | null {
-  for (const line of existing) {
-    if (line.path.length < 2) continue
-    const side = matchEnd(line, p)
-    if (side) return { line, side }
-  }
-  return null
-}
-
-/** Path re-ordered so the connecting terminal is its LAST point. */
-function endLast(path: Point[], side: 'start' | 'end'): Point[] {
-  return side === 'end' ? path : [...path].reverse()
-}
-
-/** Path re-ordered so the connecting terminal is its FIRST point. */
-function startFirst(path: Point[], side: 'start' | 'end'): Point[] {
-  return side === 'start' ? path : [...path].reverse()
-}
-
-/**
- * Outcome of committing a new `start`→`end` segment against the existing
- * lineset runs on the same level:
- *   - `create`  — no shared endpoint; place a fresh standalone run.
- *   - `extend`  — one end lands on run `id`; grow that run's path so the old
- *     terminal becomes an interior point (the geometry miters it).
- *   - `bridge`  — both ends land on two *different* runs; weld them plus the
- *     new segment into one path on `id` and delete the absorbed `deleteId`.
- */
-export type LinesetConnectPlan =
-  | { kind: 'create'; path: Point[] }
-  | { kind: 'extend'; id: LinesetId; path: Point[] }
-  | { kind: 'bridge'; id: LinesetId; path: Point[]; deleteId: LinesetId }
-
-/**
- * Decide how a freshly drawn `start`→`end` segment folds into existing
- * lineset runs that share an endpoint coordinate. Pure: returns a plan, the
- * caller mutates the scene. Coords are level-local, so `existing` must be
- * pre-filtered to the segment's level.
- */
-export function planLinesetConnect(
-  existing: LinesetNode[],
-  start: Point,
-  end: Point,
-): LinesetConnectPlan {
-  const atStart = findConnection(existing, start)
-  const atEnd = findConnection(existing, end)
-
-  // Both ends meet distinct runs → weld the three into one path.
-  if (atStart && atEnd && atStart.line.id !== atEnd.line.id) {
-    const left = endLast(atStart.line.path as Point[], atStart.side) // ...→ start
-    const right = startFirst(atEnd.line.path as Point[], atEnd.side) // end →...
-    return {
-      kind: 'bridge',
-      id: atStart.line.id,
-      path: [...left, ...right],
-      deleteId: atEnd.line.id,
-    }
-  }
-  if (atStart) {
-    const base = endLast(atStart.line.path as Point[], atStart.side) // ...→ start
-    return { kind: 'extend', id: atStart.line.id, path: [...base, end] }
-  }
-  if (atEnd) {
-    const base = startFirst(atEnd.line.path as Point[], atEnd.side) // end →...
-    return { kind: 'extend', id: atEnd.line.id, path: [start, ...base] }
-  }
-  return { kind: 'create', path: [start, end] }
-}

packages/nodes/src/lineset/geometry.ts

@@ -46,8 +46,12 @@ function buildRun(
  *
  * One line per node — what the ghost previews is exactly what commits. To run
  * the suction line beside the liquid line, draw them as two separate linesets
- * rather than rendering both together off one path. Joint spheres cap interior
- * corners so turns read as continuous pipe.
+ * rather than rendering both together off one path.
+ *
+ * Each line is a standalone two-point node (no fitting system, unlike ducts),
+ * so a sphere caps BOTH endpoints. On a free end it just rounds the cap; where
+ * two segments share a coordinate the coincident spheres fill the miter gap, so
+ * the turn reads as continuous pipe.
  *
  * Children are level-local meters; `<ParametricNodeRenderer>` owns the
  * node transform (identity today — the path is absolute within the level).
@@ -87,8 +91,10 @@ export function buildLinesetGeometry(node: LinesetNode): Group {
     }
   }
 
-  // Joint caps at interior corners so turns read as continuous pipe.
-  for (let i = 1; i < points.length - 1; i++) {
+  // Spherical caps at every point. Interior corners read as continuous pipe;
+  // endpoint caps round the open ends and, where two separate segments share a
+  // coordinate, the coincident spheres fill the miter so the turn looks welded.
+  for (let i = 0; i < points.length; i++) {
     const joint = new Mesh(new SphereGeometry(copperR, RADIAL_SEGMENTS, 10), copperMat)
     joint.name = `lineset-copper-joint-${i}`
     joint.position.copy(points[i] as Vector3)

packages/nodes/src/lineset/index.ts

@@ -1,4 +1,3 @@
-export { type LinesetConnectPlan, planLinesetConnect } from './connect'
 export { linesetDefinition } from './definition'
 export { buildLinesetGeometry } from './geometry'
 export { LinesetNode } from './schema'

packages/nodes/src/lineset/move-tool.tsx

@@ -27,6 +27,7 @@ import {
   collectGhostAlignmentCandidates,
   resolveGhostAlignment,
 } from '../shared/ghost-alignment'
+import { type RunMoveConnectivity, startRunMoveConnectivity } from '../shared/run-move-connectivity'
 
 type Vec3 = [number, number, number]
 
@@ -137,6 +138,12 @@ export const MoveLinesetTool: React.FC<{ node: AnyNode }> = ({ node }) => {
     }
     if (existedAtStart) setMeshHidden(true)
 
+    // Carry connected fittings (+ their other runs) as the whole run slides.
+    // Snapshot once at drag start; only existing runs are mated to anything.
+    const connectivity: RunMoveConnectivity | null = existedAtStart
+      ? startRunMoveConnectivity(node)
+      : null
+
     const setPreview = (path: Vec3[]) => {
       previewPathRef.current = path
       setPreviewPath(path)
@@ -176,7 +183,9 @@ export const MoveLinesetTool: React.FC<{ node: AnyNode }> = ({ node }) => {
       }
       prevSnapRef.current = cur
       hasMovedRef.current = true
-      setPreview(originalPath.map(([x, y, z]) => [x + dx, y, z + dz] as Vec3))
+      const nextPath = originalPath.map(([x, y, z]) => [x + dx, y, z + dz] as Vec3)
+      setPreview(nextPath)
+      connectivity?.preview({ path: nextPath })
     }
 
     const commit = (event: GridEvent) => {
@@ -204,10 +213,21 @@ export const MoveLinesetTool: React.FC<{ node: AnyNode }> = ({ node }) => {
         useScene.getState().createNode(created as AnyNode, node.parentId as AnyNodeId)
         selectId = created.id as AnyNodeId
       } else {
-        useScene.getState().updateNode(nodeId, { path: finalPath } as Partial<AnyNode>)
+        // Fold connected-fitting / sibling-run follow-updates into the SAME
+        // batch as the moved run so the whole joint is one undo step.
+        const followUpdates = connectivity?.commitUpdates({ path: finalPath }) ?? []
+        useScene
+          .getState()
+          .updateNodes([
+            { id: nodeId, data: { path: finalPath } as Partial<AnyNode> },
+            ...followUpdates,
+          ])
         useScene.getState().markDirty(nodeId)
       }
       useScene.temporal.getState().pause()
+      // Followers are committed to the store — drop their live overrides so
+      // renderers read the canonical path/position.
+      connectivity?.clear()
       setMeshHidden(false)
 
       useAlignmentGuides.getState().clear()
@@ -219,6 +239,7 @@ export const MoveLinesetTool: React.FC<{ node: AnyNode }> = ({ node }) => {
     }
 
     const onCancel = () => {
+      connectivity?.clear()
       if (existedAtStart) {
         setMeshHidden(false)
         useViewer.getState().setSelection({ selectedIds: [nodeId] })
@@ -238,6 +259,7 @@ export const MoveLinesetTool: React.FC<{ node: AnyNode }> = ({ node }) => {
       emitter.off('grid:move', onMove)
       emitter.off('grid:click', commit)
       emitter.off('tool:cancel', onCancel)
+      connectivity?.clear()
       useAlignmentGuides.getState().clear()
       if (existedAtStart) setMeshHidden(false)
       useScene.temporal.getState().resume()

packages/nodes/src/lineset/selection.tsx

@@ -1,282 +1,5 @@
 'use client'
 
-import {
-  type AnyNodeId,
-  type LinesetNode,
-  pauseSceneHistory,
-  resumeSceneHistory,
-  sceneRegistry,
-  useScene,
-} from '@pascal-app/core'
-import { DimensionPill, EDITOR_LAYER, useEditor } from '@pascal-app/editor'
-import { useViewer } from '@pascal-app/viewer'
-import { Html } from '@react-three/drei'
-import { createPortal, type ThreeEvent, useThree } from '@react-three/fiber'
-import { useEffect, useRef, useState } from 'react'
-import { type Object3D, Plane, Raycaster, Vector2, Vector3 } from 'three'
-import { collectScenePorts, findNearestPortXZ, REFRIGERANT_PORT_SYSTEMS } from '../shared/ports'
+import { createRefrigerantLineSelectionAffordance } from '../shared/refrigerant-line-selection'
 
-const HANDLE_RADIUS = 0.08
-const PORT_SNAP_RADIUS_M = 0.4
-
-const UP = new Vector3(0, 1, 0)
-
-function snap(value: number, step: number): number {
-  if (step <= 0) return value
-  return Math.round(value / step) * step
-}
-
-type Point = [number, number, number]
-
-/**
- * Selection-time editing for committed lineset runs: one draggable handle
- * per path point. Mirrors the duct-segment path-handle system, but dragged
- * run endpoints snap onto refrigerant ports only.
- *
- * Handles are PORTALED into the lineset's registered scene group so they
- * share its exact frame. Drag raycasts run in world space and convert hits
- * back into the group's local frame before writing the path.
- */
-const LinesetSelectionAffordance = () => {
-  const selectedIds = useViewer((s) => s.selection.selectedIds)
-  const lineset = useScene((s) => {
-    if (selectedIds.length !== 1) return null
-    const node = s.nodes[selectedIds[0] as AnyNodeId]
-    return node?.type === 'lineset' ? (node as LinesetNode) : null
-  })
-
-  const linesetId = lineset?.id ?? null
-  const [target, setTarget] = useState<Object3D | null>(null)
-  useEffect(() => {
-    if (!linesetId) {
-      setTarget(null)
-      return
-    }
-    let frameId = 0
-    const resolve = () => {
-      const next = sceneRegistry.nodes.get(linesetId as AnyNodeId) ?? null
-      setTarget((cur) => (cur === next ? cur : next))
-      if (!next) frameId = window.requestAnimationFrame(resolve)
-    }
-    resolve()
-    return () => window.cancelAnimationFrame(frameId)
-  }, [linesetId])
-
-  if (!lineset || !target) return null
-  return createPortal(<LinesetPointHandles lineset={lineset} target={target} />, target, undefined)
-}
-
-const LinesetPointHandles = ({ lineset, target }: { lineset: LinesetNode; target: Object3D }) => {
-  const { camera, gl } = useThree()
-  const unit = useViewer((s) => s.unit)
-  const [draggingIndex, setDraggingIndex] = useState<number | null>(null)
-  const [hoverIndex, setHoverIndex] = useState<number | null>(null)
-  const dragRef = useRef<{
-    index: number
-    initialPath: Point[]
-    current: Point
-    cleanup: () => void
-  } | null>(null)
-
-  const makeRay = (clientX: number, clientY: number) => {
-    const rect = gl.domElement.getBoundingClientRect()
-    const ndc = new Vector2(
-      ((clientX - rect.left) / rect.width) * 2 - 1,
-      -((clientY - rect.top) / rect.height) * 2 + 1,
-    )
-    const raycaster = new Raycaster()
-    raycaster.setFromCamera(ndc, camera)
-    return raycaster.ray
-  }
-
-  const intersect = (clientX: number, clientY: number, plane: Plane): Vector3 | null => {
-    const hit = new Vector3()
-    return makeRay(clientX, clientY).intersectPlane(plane, hit) ? hit : null
-  }
-
-  const projectOntoAxis = (
-    clientX: number,
-    clientY: number,
-    anchorWorld: Vector3,
-    axisWorld: Vector3,
-  ): number | null => {
-    const ray = makeRay(clientX, clientY)
-    const w0 = new Vector3().subVectors(ray.origin, anchorWorld)
-    const b = ray.direction.dot(axisWorld)
-    const denom = 1 - b * b
-    if (Math.abs(denom) < 1e-6) return null
-    const d0 = ray.direction.dot(w0)
-    const e0 = axisWorld.dot(w0)
-    return (e0 - b * d0) / denom
-  }
-
-  const toWorld = (p: Point): Vector3 => target.localToWorld(new Vector3(p[0], p[1], p[2]))
-  const toLocal = (world: Vector3): Point => {
-    const local = target.worldToLocal(world.clone())
-    return [local.x, local.y, local.z]
-  }
-
-  const onHandleDown = (index: number) => (e: ThreeEvent<PointerEvent>) => {
-    e.stopPropagation()
-    const initialPath = lineset.path.map((p) => [...p] as Point)
-    const startPoint = initialPath[index]!
-    pauseSceneHistory(useScene)
-    useViewer.getState().setInputDragging(true)
-    document.body.style.cursor = 'grabbing'
-    setDraggingIndex(index)
-
-    const isEndpoint = index === 0 || index === initialPath.length - 1
-
-    const neighbor = initialPath[index === 0 ? 1 : index - 1]!
-    const axisLocal = new Vector3(
-      startPoint[0] - neighbor[0],
-      startPoint[1] - neighbor[1],
-      startPoint[2] - neighbor[2],
-    )
-    if (axisLocal.lengthSq() < 1e-9) axisLocal.set(1, 0, 0)
-    axisLocal.normalize()
-    const anchorWorldStart = toWorld(startPoint)
-    const axisWorld = toWorld([
-      startPoint[0] + axisLocal.x,
-      startPoint[1] + axisLocal.y,
-      startPoint[2] + axisLocal.z,
-    ])
-      .sub(anchorWorldStart)
-      .normalize()
-
-    const onMove = (event: PointerEvent) => {
-      const drag = dragRef.current
-      if (!drag) return
-      const current = drag.current
-      const step = event.shiftKey ? 0 : useEditor.getState().gridSnapStep
-      let next: Point | null = null
-      if (event.altKey) {
-        const plane = new Plane().setFromNormalAndCoplanarPoint(UP, toWorld(current))
-        const hit = intersect(event.clientX, event.clientY, plane)
-        if (hit) {
-          const local = toLocal(hit)
-          next = [snap(local[0], step), current[1], snap(local[2], step)]
-          if (isEndpoint) {
-            const port = findNearestPortXZ(
-              [local[0], current[1], local[2]],
-              collectScenePorts({ excludeNodeId: lineset.id, systems: REFRIGERANT_PORT_SYSTEMS }),
-              PORT_SNAP_RADIUS_M,
-            )
-            if (port) next = [port.position[0], port.position[1], port.position[2]]
-          }
-        }
-      } else {
-        const t = projectOntoAxis(event.clientX, event.clientY, anchorWorldStart, axisWorld)
-        if (t !== null) {
-          const dist = snap(t, step)
-          next = [
-            startPoint[0] + axisLocal.x * dist,
-            Math.max(0, startPoint[1] + axisLocal.y * dist),
-            startPoint[2] + axisLocal.z * dist,
-          ]
-        }
-      }
-      if (!next) return
-      if (next[0] === current[0] && next[1] === current[1] && next[2] === current[2]) return
-      drag.current = next
-      const path = lineset.path.map((p, i) => (i === drag.index ? next! : p)) as Point[]
-      useScene.getState().updateNode(lineset.id, { path })
-    }
-
-    const onUp = () => {
-      const drag = dragRef.current
-      if (!drag) return
-      drag.cleanup()
-      dragRef.current = null
-      setDraggingIndex(null)
-      const finalPath = drag.initialPath.map((p, i) =>
-        i === drag.index ? drag.current : p,
-      ) as Point[]
-      useScene.getState().updateNode(lineset.id, { path: drag.initialPath })
-      resumeSceneHistory(useScene)
-      const moved = finalPath[drag.index]!.some(
-        (v, axis) => v !== drag.initialPath[drag.index]![axis],
-      )
-      if (moved) useScene.getState().updateNode(lineset.id, { path: finalPath })
-    }
-
-    const cleanup = () => {
-      window.removeEventListener('pointermove', onMove)
-      window.removeEventListener('pointerup', onUp)
-      window.removeEventListener('pointercancel', onUp)
-      useViewer.getState().setInputDragging(false)
-      document.body.style.cursor = ''
-    }
-
-    dragRef.current = { index, initialPath, current: startPoint, cleanup }
-    window.addEventListener('pointermove', onMove)
-    window.addEventListener('pointerup', onUp)
-    window.addEventListener('pointercancel', onUp)
-  }
-
-  return (
-    <group>
-      {lineset.path.map((p, i) => {
-        const active = draggingIndex === i
-        const hovered = hoverIndex === i
-        return (
-          <mesh
-            key={`lineset-handle-${i}`}
-            layers={EDITOR_LAYER}
-            onPointerDown={onHandleDown(i)}
-            onPointerEnter={(e) => {
-              e.stopPropagation()
-              setHoverIndex(i)
-              if (draggingIndex === null) document.body.style.cursor = 'grab'
-            }}
-            onPointerLeave={() => {
-              setHoverIndex((prev) => (prev === i ? null : prev))
-              if (draggingIndex === null) document.body.style.cursor = ''
-            }}
-            position={p as Point}
-          >
-            <sphereGeometry args={[HANDLE_RADIUS, 16, 12]} />
-            <meshBasicMaterial
-              color={active || hovered ? '#a5b4fc' : '#818cf8'}
-              depthTest={false}
-              opacity={active ? 1 : 0.85}
-              transparent
-            />
-          </mesh>
-        )
-      })}
-      {draggingIndex !== null &&
-        lineset.path[draggingIndex] &&
-        (() => {
-          const point = lineset.path[draggingIndex]!
-          const origin = dragRef.current?.initialPath[draggingIndex] ?? point
-          const deltas = [point[0] - origin[0], point[1] - origin[1], point[2] - origin[2]]
-          const axes = ['x', 'y', 'z'] as const
-          const primary = axes.reduce((best, axis, i) =>
-            Math.abs(deltas[i]!) > Math.abs(deltas[axes.indexOf(best)]!) ? axis : best,
-          )
-          return (
-            <Html
-              center
-              position={[point[0], point[1] + 0.35, point[2]]}
-              style={{ pointerEvents: 'none', userSelect: 'none' }}
-              zIndexRange={[100, 0]}
-            >
-              <DimensionPill
-                parts={axes.map((axis, i) => ({
-                  key: axis,
-                  prefix: axis.toUpperCase(),
-                  value: deltas[i]!,
-                  signed: true,
-                }))}
-                primary={primary}
-                unit={unit}
-              />
-            </Html>
-          )
-        })()}
-    </group>
-  )
-}
-
-export default LinesetSelectionAffordance
+export default createRefrigerantLineSelectionAffordance('lineset')

packages/nodes/src/lineset/tool.tsx

@@ -1,6 +1,6 @@
 'use client'
 
-import { type AnyNodeId, emitter, type GridEvent, LinesetNode, useScene } from '@pascal-app/core'
+import { emitter, type GridEvent, LinesetNode, useScene } from '@pascal-app/core'
 import {
   CursorSphere,
   DimensionPill,
@@ -16,18 +16,18 @@ import { type Group, Vector3 } from 'three'
 import { alignDrawPoint, clearDrawAlignment } from '../shared/draw-alignment'
 import { LevelOffsetGroup } from '../shared/level-offset-group'
 import { collectScenePorts, findNearestPortXZ, REFRIGERANT_PORT_SYSTEMS } from '../shared/ports'
-import { planLinesetConnect } from './connect'
 import { linesetDefinition } from './definition'
 
 /**
- * One-segment-at-a-time placement tool for refrigerant linesets — the
- * refrigerant-loop sibling of the duct-segment tool.
+ * Continuous placement tool for refrigerant linesets — the refrigerant-loop
+ * sibling of the duct-segment tool.
  *
  * Mouse-driven model:
  *   - **First click** anchors the run start. Within range of a refrigerant
  *     service port (a condenser / coil valve, or another lineset's end) it
  *     snaps onto the port so a run mates flush.
- *   - **Second click** commits a two-point lineset and re-arms the tool.
+ *   - **Second click** commits a two-point lineset and keeps its far end
+ *     anchored, so the next click continues the run like wall / duct drafting.
  *   - The in-flight end is angle-locked to the nearest 45° step in XZ from
  *     the start; Y stays at the start's height. Hold **Shift** to release.
  *   - Hold **Alt** → vertical mode. XZ locks to the start; vertical mouse
@@ -103,32 +103,18 @@ const LinesetTool = () => {
         Math.abs(start[2] - end[2]) < 1e-4
       if (sameSpot) return
 
-      // Fold into any existing run that shares this segment's endpoint, so
-      // two runs meeting at a coordinate become one mitered path instead of
-      // overlapping nodes. Only same-level runs are candidates — lineset
-      // paths are level-local.
-      const scene = useScene.getState()
-      const existing = Object.values(scene.nodes).filter(
-        (n): n is LinesetNode =>
-          n?.type === 'lineset' && (n.parentId as AnyNodeId | null) === activeLevelId,
-      )
-      const plan = planLinesetConnect(existing, start, end)
-
-      if (plan.kind === 'create') {
-        const lineset = LinesetNode.parse({
-          ...linesetDefinition.defaults(),
-          name: 'Lineset',
-          path: plan.path,
-        })
-        scene.createNode(lineset, activeLevelId)
-      } else if (plan.kind === 'extend') {
-        scene.updateNode(plan.id, { path: plan.path })
-      } else {
-        scene.updateNode(plan.id, { path: plan.path })
-        scene.deleteNode(plan.deleteId)
-      }
+      // Each drawn segment is its own standalone two-point lineset node — the
+      // refrigerant-loop sibling of duct-segment. Independent nodes mean each
+      // segment selects and deletes on its own, rather than folding into one
+      // mitered polyline run.
+      const lineset = LinesetNode.parse({
+        ...linesetDefinition.defaults(),
+        name: 'Lineset',
+        path: [start, end],
+      })
+      useScene.getState().createNode(lineset, activeLevelId)
       triggerSFX('sfx:item-place')
-      setDraftPoints([])
+      setDraftPoints([end])
       setSnapTarget(null)
       altAnchorRef.current = null
       setAltActive(false)

packages/nodes/src/liquid-line/connect.ts

@@ -1,98 +0,0 @@
-import type { LiquidLineNode } from './schema'
-
-type Point = [number, number, number]
-type LiquidLineId = LiquidLineNode['id']
-
-/** Coincidence tolerance (meters) for folding endpoints into one run. The
- * draw tool snaps onto an existing run's endpoint exactly, so this only
- * needs to absorb float drift, not user aim. */
-const COINCIDENT_EPS_M = 1e-3
-
-function samePoint(a: Point, b: Point): boolean {
-  return (
-    Math.abs(a[0] - b[0]) < COINCIDENT_EPS_M &&
-    Math.abs(a[1] - b[1]) < COINCIDENT_EPS_M &&
-    Math.abs(a[2] - b[2]) < COINCIDENT_EPS_M
-  )
-}
-
-/** Which terminal of `line` coincides with `p`, if either. */
-function matchEnd(line: LiquidLineNode, p: Point): 'start' | 'end' | null {
-  const path = line.path as Point[]
-  if (samePoint(path[0]!, p)) return 'start'
-  if (samePoint(path[path.length - 1]!, p)) return 'end'
-  return null
-}
-
-/** First liquid line whose start or end coincides with `p`. */
-function findConnection(
-  existing: LiquidLineNode[],
-  p: Point,
-): { line: LiquidLineNode; side: 'start' | 'end' } | null {
-  for (const line of existing) {
-    if (line.path.length < 2) continue
-    const side = matchEnd(line, p)
-    if (side) return { line, side }
-  }
-  return null
-}
-
-/** Path re-ordered so the connecting terminal is its LAST point. */
-function endLast(path: Point[], side: 'start' | 'end'): Point[] {
-  return side === 'end' ? path : [...path].reverse()
-}
-
-/** Path re-ordered so the connecting terminal is its FIRST point. */
-function startFirst(path: Point[], side: 'start' | 'end'): Point[] {
-  return side === 'start' ? path : [...path].reverse()
-}
-
-/**
- * Outcome of committing a new `start`→`end` segment against the existing
- * liquid-line runs on the same level:
- *   - `create`  — no shared endpoint; place a fresh standalone run.
- *   - `extend`  — one end lands on run `id`; grow that run's path so the old
- *     terminal becomes an interior point (the geometry miters it).
- *   - `bridge`  — both ends land on two *different* runs; weld them plus the
- *     new segment into one path on `id` and delete the absorbed `deleteId`.
- */
-export type LiquidLineConnectPlan =
-  | { kind: 'create'; path: Point[] }
-  | { kind: 'extend'; id: LiquidLineId; path: Point[] }
-  | { kind: 'bridge'; id: LiquidLineId; path: Point[]; deleteId: LiquidLineId }
-
-/**
- * Decide how a freshly drawn `start`→`end` segment folds into existing
- * liquid-line runs that share an endpoint coordinate. Pure: returns a plan,
- * the caller mutates the scene. Coords are level-local, so `existing` must be
- * pre-filtered to the segment's level.
- */
-export function planLiquidLineConnect(
-  existing: LiquidLineNode[],
-  start: Point,
-  end: Point,
-): LiquidLineConnectPlan {
-  const atStart = findConnection(existing, start)
-  const atEnd = findConnection(existing, end)
-
-  // Both ends meet distinct runs → weld the three into one path.
-  if (atStart && atEnd && atStart.line.id !== atEnd.line.id) {
-    const left = endLast(atStart.line.path as Point[], atStart.side) // ...→ start
-    const right = startFirst(atEnd.line.path as Point[], atEnd.side) // end →...
-    return {
-      kind: 'bridge',
-      id: atStart.line.id,
-      path: [...left, ...right],
-      deleteId: atEnd.line.id,
-    }
-  }
-  if (atStart) {
-    const base = endLast(atStart.line.path as Point[], atStart.side) // ...→ start
-    return { kind: 'extend', id: atStart.line.id, path: [...base, end] }
-  }
-  if (atEnd) {
-    const base = startFirst(atEnd.line.path as Point[], atEnd.side) // end →...
-    return { kind: 'extend', id: atEnd.line.id, path: [start, ...base] }
-  }
-  return { kind: 'create', path: [start, end] }
-}

packages/nodes/src/liquid-line/geometry.ts

@@ -31,8 +31,12 @@ function buildRun(
 
 /**
  * Pure geometry builder for a standalone liquid line: a single thin bare-copper
- * cylinder following the node path centerline, with joint spheres capping
- * interior corners so turns read as continuous pipe.
+ * cylinder following the node path centerline.
+ *
+ * Each line is a standalone two-point node (no fitting system), so a sphere caps
+ * BOTH endpoints. On a free end it rounds the cap; where two segments share a
+ * coordinate the coincident spheres fill the miter gap, so the turn reads as
+ * continuous pipe.
  *
  * Children are level-local meters; `<ParametricNodeRenderer>` owns the node
  * transform (identity today — the path is absolute within the level).
@@ -55,7 +59,10 @@ export function buildLiquidLineGeometry(node: LiquidLineNode): Group {
     if (run) group.add(run)
   }
 
-  for (let i = 1; i < points.length - 1; i++) {
+  // Spherical caps at every point: interior corners read as continuous pipe,
+  // and endpoint caps round the open ends so two separate segments sharing a
+  // coordinate fill the miter and look welded.
+  for (let i = 0; i < points.length; i++) {
     const joint = new Mesh(new SphereGeometry(radius, RADIAL_SEGMENTS, 10), copperMat)
     joint.name = `liquid-line-joint-${i}`
     joint.position.copy(points[i] as Vector3)

packages/nodes/src/liquid-line/index.ts

@@ -1,4 +1,3 @@
-export { type LiquidLineConnectPlan, planLiquidLineConnect } from './connect'
 export { liquidLineDefinition } from './definition'
 export { buildLiquidLineGeometry } from './geometry'
 export { useLiquidLineToolOptions } from './options'

packages/nodes/src/liquid-line/selection.tsx

@@ -1,282 +1,5 @@
 'use client'
 
-import {
-  type AnyNodeId,
-  type LiquidLineNode,
-  pauseSceneHistory,
-  resumeSceneHistory,
-  sceneRegistry,
-  useScene,
-} from '@pascal-app/core'
-import { DimensionPill, EDITOR_LAYER, useEditor } from '@pascal-app/editor'
-import { useViewer } from '@pascal-app/viewer'
-import { Html } from '@react-three/drei'
-import { createPortal, type ThreeEvent, useThree } from '@react-three/fiber'
-import { useEffect, useRef, useState } from 'react'
-import { type Object3D, Plane, Raycaster, Vector2, Vector3 } from 'three'
-import { collectScenePorts, findNearestPortXZ, REFRIGERANT_PORT_SYSTEMS } from '../shared/ports'
+import { createRefrigerantLineSelectionAffordance } from '../shared/refrigerant-line-selection'
 
-const HANDLE_RADIUS = 0.07
-const PORT_SNAP_RADIUS_M = 0.4
-
-const UP = new Vector3(0, 1, 0)
-
-function snap(value: number, step: number): number {
-  if (step <= 0) return value
-  return Math.round(value / step) * step
-}
-
-type Point = [number, number, number]
-
-/**
- * Selection-time editing for committed liquid-line runs: one draggable handle
- * per path point. Mirrors the lineset path-handle system; dragged run
- * endpoints snap onto refrigerant ports only.
- *
- * Handles are PORTALED into the line's registered scene group so they share
- * its exact frame. Drag raycasts run in world space and convert hits back into
- * the group's local frame before writing the path.
- */
-const LiquidLineSelectionAffordance = () => {
-  const selectedIds = useViewer((s) => s.selection.selectedIds)
-  const line = useScene((s) => {
-    if (selectedIds.length !== 1) return null
-    const node = s.nodes[selectedIds[0] as AnyNodeId]
-    return node?.type === 'liquid-line' ? (node as LiquidLineNode) : null
-  })
-
-  const lineId = line?.id ?? null
-  const [target, setTarget] = useState<Object3D | null>(null)
-  useEffect(() => {
-    if (!lineId) {
-      setTarget(null)
-      return
-    }
-    let frameId = 0
-    const resolve = () => {
-      const next = sceneRegistry.nodes.get(lineId as AnyNodeId) ?? null
-      setTarget((cur) => (cur === next ? cur : next))
-      if (!next) frameId = window.requestAnimationFrame(resolve)
-    }
-    resolve()
-    return () => window.cancelAnimationFrame(frameId)
-  }, [lineId])
-
-  if (!line || !target) return null
-  return createPortal(<LiquidLinePointHandles line={line} target={target} />, target, undefined)
-}
-
-const LiquidLinePointHandles = ({ line, target }: { line: LiquidLineNode; target: Object3D }) => {
-  const { camera, gl } = useThree()
-  const unit = useViewer((s) => s.unit)
-  const [draggingIndex, setDraggingIndex] = useState<number | null>(null)
-  const [hoverIndex, setHoverIndex] = useState<number | null>(null)
-  const dragRef = useRef<{
-    index: number
-    initialPath: Point[]
-    current: Point
-    cleanup: () => void
-  } | null>(null)
-
-  const makeRay = (clientX: number, clientY: number) => {
-    const rect = gl.domElement.getBoundingClientRect()
-    const ndc = new Vector2(
-      ((clientX - rect.left) / rect.width) * 2 - 1,
-      -((clientY - rect.top) / rect.height) * 2 + 1,
-    )
-    const raycaster = new Raycaster()
-    raycaster.setFromCamera(ndc, camera)
-    return raycaster.ray
-  }
-
-  const intersect = (clientX: number, clientY: number, plane: Plane): Vector3 | null => {
-    const hit = new Vector3()
-    return makeRay(clientX, clientY).intersectPlane(plane, hit) ? hit : null
-  }
-
-  const projectOntoAxis = (
-    clientX: number,
-    clientY: number,
-    anchorWorld: Vector3,
-    axisWorld: Vector3,
-  ): number | null => {
-    const ray = makeRay(clientX, clientY)
-    const w0 = new Vector3().subVectors(ray.origin, anchorWorld)
-    const b = ray.direction.dot(axisWorld)
-    const denom = 1 - b * b
-    if (Math.abs(denom) < 1e-6) return null
-    const d0 = ray.direction.dot(w0)
-    const e0 = axisWorld.dot(w0)
-    return (e0 - b * d0) / denom
-  }
-
-  const toWorld = (p: Point): Vector3 => target.localToWorld(new Vector3(p[0], p[1], p[2]))
-  const toLocal = (world: Vector3): Point => {
-    const local = target.worldToLocal(world.clone())
-    return [local.x, local.y, local.z]
-  }
-
-  const onHandleDown = (index: number) => (e: ThreeEvent<PointerEvent>) => {
-    e.stopPropagation()
-    const initialPath = line.path.map((p) => [...p] as Point)
-    const startPoint = initialPath[index]!
-    pauseSceneHistory(useScene)
-    useViewer.getState().setInputDragging(true)
-    document.body.style.cursor = 'grabbing'
-    setDraggingIndex(index)
-
-    const isEndpoint = index === 0 || index === initialPath.length - 1
-
-    const neighbor = initialPath[index === 0 ? 1 : index - 1]!
-    const axisLocal = new Vector3(
-      startPoint[0] - neighbor[0],
-      startPoint[1] - neighbor[1],
-      startPoint[2] - neighbor[2],
-    )
-    if (axisLocal.lengthSq() < 1e-9) axisLocal.set(1, 0, 0)
-    axisLocal.normalize()
-    const anchorWorldStart = toWorld(startPoint)
-    const axisWorld = toWorld([
-      startPoint[0] + axisLocal.x,
-      startPoint[1] + axisLocal.y,
-      startPoint[2] + axisLocal.z,
-    ])
-      .sub(anchorWorldStart)
-      .normalize()
-
-    const onMove = (event: PointerEvent) => {
-      const drag = dragRef.current
-      if (!drag) return
-      const current = drag.current
-      const step = event.shiftKey ? 0 : useEditor.getState().gridSnapStep
-      let next: Point | null = null
-      if (event.altKey) {
-        const plane = new Plane().setFromNormalAndCoplanarPoint(UP, toWorld(current))
-        const hit = intersect(event.clientX, event.clientY, plane)
-        if (hit) {
-          const local = toLocal(hit)
-          next = [snap(local[0], step), current[1], snap(local[2], step)]
-          if (isEndpoint) {
-            const port = findNearestPortXZ(
-              [local[0], current[1], local[2]],
-              collectScenePorts({ excludeNodeId: line.id, systems: REFRIGERANT_PORT_SYSTEMS }),
-              PORT_SNAP_RADIUS_M,
-            )
-            if (port) next = [port.position[0], port.position[1], port.position[2]]
-          }
-        }
-      } else {
-        const t = projectOntoAxis(event.clientX, event.clientY, anchorWorldStart, axisWorld)
-        if (t !== null) {
-          const dist = snap(t, step)
-          next = [
-            startPoint[0] + axisLocal.x * dist,
-            Math.max(0, startPoint[1] + axisLocal.y * dist),
-            startPoint[2] + axisLocal.z * dist,
-          ]
-        }
-      }
-      if (!next) return
-      if (next[0] === current[0] && next[1] === current[1] && next[2] === current[2]) return
-      drag.current = next
-      const path = line.path.map((p, i) => (i === drag.index ? next! : p)) as Point[]
-      useScene.getState().updateNode(line.id, { path })
-    }
-
-    const onUp = () => {
-      const drag = dragRef.current
-      if (!drag) return
-      drag.cleanup()
-      dragRef.current = null
-      setDraggingIndex(null)
-      const finalPath = drag.initialPath.map((p, i) =>
-        i === drag.index ? drag.current : p,
-      ) as Point[]
-      useScene.getState().updateNode(line.id, { path: drag.initialPath })
-      resumeSceneHistory(useScene)
-      const moved = finalPath[drag.index]!.some(
-        (v, axis) => v !== drag.initialPath[drag.index]![axis],
-      )
-      if (moved) useScene.getState().updateNode(line.id, { path: finalPath })
-    }
-
-    const cleanup = () => {
-      window.removeEventListener('pointermove', onMove)
-      window.removeEventListener('pointerup', onUp)
-      window.removeEventListener('pointercancel', onUp)
-      useViewer.getState().setInputDragging(false)
-      document.body.style.cursor = ''
-    }
-
-    dragRef.current = { index, initialPath, current: startPoint, cleanup }
-    window.addEventListener('pointermove', onMove)
-    window.addEventListener('pointerup', onUp)
-    window.addEventListener('pointercancel', onUp)
-  }
-
-  return (
-    <group>
-      {line.path.map((p, i) => {
-        const active = draggingIndex === i
-        const hovered = hoverIndex === i
-        return (
-          <mesh
-            key={`liquid-line-handle-${i}`}
-            layers={EDITOR_LAYER}
-            onPointerDown={onHandleDown(i)}
-            onPointerEnter={(e) => {
-              e.stopPropagation()
-              setHoverIndex(i)
-              if (draggingIndex === null) document.body.style.cursor = 'grab'
-            }}
-            onPointerLeave={() => {
-              setHoverIndex((prev) => (prev === i ? null : prev))
-              if (draggingIndex === null) document.body.style.cursor = ''
-            }}
-            position={p as Point}
-          >
-            <sphereGeometry args={[HANDLE_RADIUS, 16, 12]} />
-            <meshBasicMaterial
-              color={active || hovered ? '#a5b4fc' : '#818cf8'}
-              depthTest={false}
-              opacity={active ? 1 : 0.85}
-              transparent
-            />
-          </mesh>
-        )
-      })}
-      {draggingIndex !== null &&
-        line.path[draggingIndex] &&
-        (() => {
-          const point = line.path[draggingIndex]!
-          const origin = dragRef.current?.initialPath[draggingIndex] ?? point
-          const deltas = [point[0] - origin[0], point[1] - origin[1], point[2] - origin[2]]
-          const axes = ['x', 'y', 'z'] as const
-          const primary = axes.reduce((best, axis, i) =>
-            Math.abs(deltas[i]!) > Math.abs(deltas[axes.indexOf(best)]!) ? axis : best,
-          )
-          return (
-            <Html
-              center
-              position={[point[0], point[1] + 0.35, point[2]]}
-              style={{ pointerEvents: 'none', userSelect: 'none' }}
-              zIndexRange={[100, 0]}
-            >
-              <DimensionPill
-                parts={axes.map((axis, i) => ({
-                  key: axis,
-                  prefix: axis.toUpperCase(),
-                  value: deltas[i]!,
-                  signed: true,
-                }))}
-                primary={primary}
-                unit={unit}
-              />
-            </Html>
-          )
-        })()}
-    </group>
-  )
-}
-
-export default LiquidLineSelectionAffordance
+export default createRefrigerantLineSelectionAffordance('liquid-line')

packages/nodes/src/liquid-line/tool.tsx

@@ -24,17 +24,17 @@ import { alignDrawPoint, clearDrawAlignment } from '../shared/draw-alignment'
 import { LevelOffsetGroup } from '../shared/level-offset-group'
 import { offsetPathHorizontal } from '../shared/path-offset'
 import { collectScenePorts, findNearestPortXZ, REFRIGERANT_PORT_SYSTEMS } from '../shared/ports'
-import { planLiquidLineConnect } from './connect'
 import { liquidLineDefinition } from './definition'
 import { useLiquidLineToolOptions } from './options'
 
 /**
- * One-segment-at-a-time placement tool for standalone liquid lines — the same
- * draw model as the lineset tool (the line it used to be a rail of):
+ * Continuous placement tool for standalone liquid lines — the same draw model
+ * as the lineset tool (the line it used to be a rail of):
  *   - **First click** anchors the run start; within range of a refrigerant
  *     service port it snaps onto it so a run mates flush.
- *   - **Second click** commits a two-point line and re-arms; the in-flight end
- *     is angle-locked to 45° (Shift frees it), Alt drags it vertical.
+ *   - **Second click** commits a two-point line and keeps its far end anchored;
+ *     the in-flight end is angle-locked to 45° (Shift frees it), Alt drags it
+ *     vertical.
  *
  * **Follow mode** (toggled by the MEP panel's Follow button or the `F` key):
  * instead of free-drawing, hover an existing lineset and click — a liquid line
@@ -117,46 +117,138 @@ function traceOffsetMeters(lineset: LinesetNode): number {
   return suctionR + jacket + FOLLOW_GAP_M + GHOST_RADIUS_M
 }
 
-type FollowTarget = { lineset: LinesetNode; sign: number }
+/** Coincidence tolerance (meters) for treating two endpoints as the same joint
+ *  when chaining linesets — the draw tool snaps endpoints exactly, so this only
+ *  needs to absorb float drift. */
+const JOINT_EPS_M = 1e-3
+
+function samePt(a: Vec3, b: Vec3): boolean {
+  return (
+    Math.abs(a[0] - b[0]) < JOINT_EPS_M &&
+    Math.abs(a[1] - b[1]) < JOINT_EPS_M &&
+    Math.abs(a[2] - b[2]) < JOINT_EPS_M
+  )
+}
+
+/** Quantized coordinate key so endpoints sharing a joint hash together. */
+function jointKey(p: Vec3): string {
+  return `${Math.round(p[0] / JOINT_EPS_M)},${Math.round(p[1] / JOINT_EPS_M)},${Math.round(
+    p[2] / JOINT_EPS_M,
+  )}`
+}
 
 /**
- * Nearest lineset whose path passes within `FOLLOW_PICK_RADIUS_M` of the
- * cursor, plus which side of it the cursor is on (`sign`, matching
- * `offsetPathHorizontal`'s side convention). Restricted to the active level.
+ * Whole-run trace target: the assembled centerline of every lineset chained to
+ * the hovered one (each lineset is its own two-point node now), which side the
+ * cursor is on (`sign`, matching `offsetPathHorizontal`'s convention), and a
+ * representative lineset for the offset distance.
+ */
+type FollowTarget = { path: Vec3[]; sign: number; lineset: LinesetNode }
+
+/**
+ * Walk the chain of linesets joined end-to-end at shared joint coordinates,
+ * starting from `start`, into one continuous centerline. Follows a joint only
+ * when it has a single unvisited continuation (degree-2) — a branch / junction
+ * (degree ≥ 3) ends the run so the trace stays a simple path.
+ */
+function assembleRun(start: LinesetNode, linesets: LinesetNode[]): Vec3[] {
+  const byJoint = new Map<string, LinesetNode[]>()
+  for (const ls of linesets) {
+    const a = ls.path[0] as Vec3
+    const b = ls.path[ls.path.length - 1] as Vec3
+    for (const key of [jointKey(a), jointKey(b)]) {
+      const arr = byJoint.get(key)
+      if (arr) arr.push(ls)
+      else byJoint.set(key, [ls])
+    }
+  }
+
+  const visited = new Set<string>([start.id])
+  let points: Vec3[] = (start.path as Vec3[]).map((p) => [...p] as Vec3)
+
+  // Grow the run one lineset at a time off the chosen terminal, until a joint
+  // has no unique continuation. `atEnd` extends after the last point; otherwise
+  // before the first.
+  const grow = (atEnd: boolean) => {
+    for (;;) {
+      const terminal = atEnd ? points[points.length - 1]! : points[0]!
+      const next = (byJoint.get(jointKey(terminal)) ?? []).filter((ls) => !visited.has(ls.id))
+      if (next.length !== 1) break
+      const node = next[0]!
+      visited.add(node.id)
+      const np = (node.path as Vec3[]).map((p) => [...p] as Vec3)
+      if (atEnd) {
+        if (samePt(np[np.length - 1]!, terminal)) np.reverse() // np must start at terminal
+        points = [...points, ...np.slice(1)]
+      } else {
+        if (samePt(np[0]!, terminal)) np.reverse() // np must end at terminal
+        points = [...np.slice(0, np.length - 1), ...points]
+      }
+    }
+  }
+  grow(true)
+  grow(false)
+  return points
+}
+
+/** Cursor side relative to the assembled run's nearest segment, as the offset
+ *  sign for `offsetPathHorizontal`. */
+function sideSign(path: Vec3[], point: Vec3): number {
+  let bestD = Number.POSITIVE_INFINITY
+  let bi = 0
+  for (let i = 0; i < path.length - 1; i++) {
+    const d = distToSegmentXZ(point, path[i]!, path[i + 1]!)
+    if (d < bestD) {
+      bestD = d
+      bi = i
+    }
+  }
+  const a = path[bi]!
+  const b = path[bi + 1]!
+  // Side vector = normalize(heading_xz) × UP = (-hz, 0, hx).
+  const hx = b[0] - a[0]
+  const hz = b[2] - a[2]
+  const hlen = Math.hypot(hx, hz)
+  const sx = hlen > 1e-9 ? -hz / hlen : 0
+  const sz = hlen > 1e-9 ? hx / hlen : 0
+  return (point[0] - a[0]) * sx + (point[2] - a[2]) * sz >= 0 ? 1 : -1
+}
+
+/**
+ * Nearest lineset within `FOLLOW_PICK_RADIUS_M` of the cursor, expanded into
+ * the whole connected run it belongs to. Restricted to the active level.
  */
 function findFollowTarget(point: Vec3, levelId: AnyNodeId): FollowTarget | null {
   const scene = useScene.getState()
-  let best: FollowTarget | null = null
-  let bestD = FOLLOW_PICK_RADIUS_M
+  const linesets: LinesetNode[] = []
   for (const n of Object.values(scene.nodes)) {
     if (!n || n.type !== 'lineset') continue
     if ((n.parentId as AnyNodeId | null) !== levelId) continue
     const ls = n as LinesetNode
-    if (ls.path.length < 2) continue
+    if (ls.path.length >= 2) linesets.push(ls)
+  }
+
+  let hovered: LinesetNode | null = null
+  let bestD = FOLLOW_PICK_RADIUS_M
+  for (const ls of linesets) {
     for (let i = 0; i < ls.path.length - 1; i++) {
-      const a = ls.path[i] as Vec3
-      const b = ls.path[i + 1] as Vec3
-      const d = distToSegmentXZ(point, a, b)
+      const d = distToSegmentXZ(point, ls.path[i] as Vec3, ls.path[i + 1] as Vec3)
       if (d >= bestD) continue
       bestD = d
-      // Side vector = normalize(heading_xz) × UP = (-hz, 0, hx); sign is which
-      // side of the segment the cursor sits on.
-      const hx = b[0] - a[0]
-      const hz = b[2] - a[2]
-      const hlen = Math.hypot(hx, hz)
-      const sx = hlen > 1e-9 ? -hz / hlen : 0
-      const sz = hlen > 1e-9 ? hx / hlen : 0
-      const dot = (point[0] - a[0]) * sx + (point[2] - a[2]) * sz
-      best = { lineset: ls, sign: dot >= 0 ? 1 : -1 }
+      hovered = ls
     }
   }
-  return best
+  if (!hovered) return null
+
+  const path = assembleRun(hovered, linesets)
+  if (path.length < 2) return null
+  return { path, sign: sideSign(path, point), lineset: hovered }
 }
 
-/** The offset path a follow-target would trace, or null if degenerate. */
+/** The offset centerline a follow-target would trace, or null if degenerate. */
 function tracePath(target: FollowTarget): Vec3[] | null {
   const offset = target.sign * traceOffsetMeters(target.lineset)
-  const traced = offsetPathHorizontal(target.lineset.path as Vec3[], offset)
+  const traced = offsetPathHorizontal(target.path, offset)
   return traced.length >= 2 ? traced : null
 }
 
@@ -199,47 +291,39 @@ const LiquidLineTool = () => {
         Math.abs(start[2] - end[2]) < 1e-4
       if (sameSpot) return
 
-      // Fold into any existing run that shares this segment's endpoint, so two
-      // runs meeting at a coordinate become one mitered path instead of
-      // overlapping nodes. Only same-level runs are candidates.
-      const scene = useScene.getState()
-      const existing = Object.values(scene.nodes).filter(
-        (n): n is LiquidLineNode =>
-          n?.type === 'liquid-line' && (n.parentId as AnyNodeId | null) === activeLevelId,
-      )
-      const plan = planLiquidLineConnect(existing, start, end)
-
-      if (plan.kind === 'create') {
-        const line = LiquidLineNode.parse({
-          ...liquidLineDefinition.defaults(),
-          name: 'Liquid Line',
-          path: plan.path,
-        })
-        scene.createNode(line, activeLevelId)
-      } else if (plan.kind === 'extend') {
-        scene.updateNode(plan.id, { path: plan.path })
-      } else {
-        scene.updateNode(plan.id, { path: plan.path })
-        scene.deleteNode(plan.deleteId)
-      }
+      // Each drawn segment is its own standalone two-point liquid-line node.
+      // Independent nodes mean each segment selects and deletes on its own,
+      // rather than folding into one mitered polyline run.
+      const line = LiquidLineNode.parse({
+        ...liquidLineDefinition.defaults(),
+        name: 'Liquid Line',
+        path: [start, end],
+      })
+      useScene.getState().createNode(line, activeLevelId)
       triggerSFX('sfx:item-place')
-      setDraftPoints([])
+      setDraftPoints([end])
       setSnapTarget(null)
       altAnchorRef.current = null
       setAltActive(false)
     }
 
-    // Lay a liquid line beside a lineset, tracing its whole path at the offset.
+    // Lay liquid lines beside the whole connected lineset run, tracing its
+    // assembled centerline at the offset. One two-point node per segment so the
+    // result stays per-segment selectable, matching free-drawn liquid lines.
     const commitTrace = (target: FollowTarget) => {
       const traced = tracePath(target)
       if (!traced) return
-      const scene = useScene.getState()
-      const line = LiquidLineNode.parse({
-        ...liquidLineDefinition.defaults(),
-        name: 'Liquid Line',
-        path: traced,
-      })
-      scene.createNode(line, activeLevelId)
+      const defaults = liquidLineDefinition.defaults()
+      const create = []
+      for (let i = 0; i < traced.length - 1; i++) {
+        const a = traced[i]!
+        const b = traced[i + 1]!
+        if (samePt(a, b)) continue
+        const node = LiquidLineNode.parse({ ...defaults, name: 'Liquid Line', path: [a, b] })
+        create.push({ node, parentId: activeLevelId })
+      }
+      if (create.length === 0) return
+      useScene.getState().applyNodeChanges({ create })
       triggerSFX('sfx:item-place')
       setTraceGhost(null)
       followTargetRef.current = null
@@ -471,7 +555,7 @@ const LiquidLineTool = () => {
                   }}
                 >
                   {followTargetRef.current
-                    ? 'Click to trace this lineset'
+                    ? 'Click to trace this lineset run'
                     : 'Follow: hover a lineset'}
                 </div>
               </Html>

packages/nodes/src/pipe-fitting/definition.ts

@@ -78,6 +78,7 @@ export const pipeFittingDefinition: NodeDefinition<typeof PipeFittingNode> = {
   // editor's SelectionAffordanceManager rather than `def.system`.
   affordanceTools: {
     selection: () => import('./selection'),
+    move: () => import('./move-tool'),
   },
 
   tool: () => import('./tool'),

packages/nodes/src/pipe-fitting/move-tool.tsx

@@ -0,0 +1,361 @@
+'use client'
+
+import {
+  type AlignmentAnchor,
+  type AnyNode,
+  type AnyNodeId,
+  emitter,
+  type GridEvent,
+  PipeFittingNode,
+  sceneRegistry,
+  useScene,
+} from '@pascal-app/core'
+import {
+  DragBoundingBox,
+  EDITOR_LAYER,
+  markToolCancelConsumed,
+  stripPlacementMetadataFlags,
+  triggerSFX,
+  useAlignmentGuides,
+  useEditor,
+} from '@pascal-app/editor'
+import { useViewer } from '@pascal-app/viewer'
+import { useEffect, useMemo, useState } from 'react'
+import { Box3, Euler, type Material, type Mesh, MeshBasicMaterial, Vector3 } from 'three'
+import {
+  type Aabb2D,
+  collectGhostAlignmentCandidates,
+  resolveGhostAlignment,
+} from '../shared/ghost-alignment'
+import { type RunMoveConnectivity, startRunMoveConnectivity } from '../shared/run-move-connectivity'
+import { buildPipeFittingGeometry } from './geometry'
+
+type Vec3 = [number, number, number]
+
+const GHOST_COLOR = '#818cf8'
+const GHOST_OPACITY = 0.5
+
+/** Screen pixels → meters for the Ctrl-vertical (riser) drag — matches the
+ *  pipe draw tool's Alt-vertical feel. 100 px ≈ 1 m. */
+const VERTICAL_PIXELS_PER_METER = 100
+const VERTICAL_Y_MIN_M = -3
+const VERTICAL_Y_MAX_M = 10
+
+/** Snap a coordinate to the editor's live grid step. */
+function snapToGridStep(value: number): number {
+  const step = useEditor.getState().gridSnapStep
+  if (step <= 0) return value
+  return Math.round(value / step) * step
+}
+
+/** World-space size + centre offset of `box` after the fitting's euler
+ *  rotation — the footprint box that wraps the oriented geometry. */
+function rotatedBounds(box: Box3, rotation: Vec3): { size: Vec3; offset: Vec3 } {
+  const euler = new Euler(rotation[0], rotation[1], rotation[2])
+  const min = box.min
+  const max = box.max
+  const corners: Vec3[] = [
+    [min.x, min.y, min.z],
+    [max.x, min.y, min.z],
+    [min.x, max.y, min.z],
+    [min.x, min.y, max.z],
+    [max.x, max.y, min.z],
+    [max.x, min.y, max.z],
+    [min.x, max.y, max.z],
+    [max.x, max.y, max.z],
+  ]
+  const lo: Vec3 = [Number.POSITIVE_INFINITY, Number.POSITIVE_INFINITY, Number.POSITIVE_INFINITY]
+  const hi: Vec3 = [Number.NEGATIVE_INFINITY, Number.NEGATIVE_INFINITY, Number.NEGATIVE_INFINITY]
+  const v = new Vector3()
+  for (const c of corners) {
+    v.set(c[0], c[1], c[2]).applyEuler(euler)
+    lo[0] = Math.min(lo[0], v.x)
+    lo[1] = Math.min(lo[1], v.y)
+    lo[2] = Math.min(lo[2], v.z)
+    hi[0] = Math.max(hi[0], v.x)
+    hi[1] = Math.max(hi[1], v.y)
+    hi[2] = Math.max(hi[2], v.z)
+  }
+  return {
+    size: [hi[0] - lo[0], hi[1] - lo[1], hi[2] - lo[2]],
+    offset: [(lo[0] + hi[0]) / 2, (lo[1] + hi[1]) / 2, (lo[2] + hi[2]) / 2],
+  }
+}
+
+/**
+ * Ghost-preview duplicate / move tool for DWV pipe fittings (elbow / wye /
+ * sanitary tee) — the plumbing sibling of the duct-fitting move tool.
+ *
+ * **Duplicate** (`metadata.isNew`): pure drag-to-place — NOTHING is
+ * inserted into the scene until the commit click. A translucent copy of the
+ * fitting (built from its real geometry, at its own `rotation`, so an elbow
+ * / riser stays properly aligned) rides the cursor inside a footprint
+ * bounding box — the same affordance other items get — and Figma-style
+ * alignment guides snap the box edges to nearby geometry. The commit click
+ * calls `createNode`; Esc discards.
+ *
+ * **Move** (existing fitting): the real node is hidden while the ghost + box
+ * track the cursor; commit writes the new `position` and reveals it.
+ *
+ * Modifiers (mirroring the duct-fitting move):
+ * - **Alt** detaches: the connected-pipe follow drops so the fitting moves
+ *   on its own, leaving every mated run where it sits.
+ * - **Ctrl / Cmd** switches to vertical movement (stack / riser editing): XZ
+ *   holds and the cursor's screen-Y drives the riser height.
+ * - **Shift** bypasses grid snapping / alignment.
+ *
+ * Wired via `def.affordanceTools.move`.
+ */
+export const MovePipeFittingTool: React.FC<{ node: AnyNode }> = ({ node }) => {
+  const fitting = node as PipeFittingNode
+  const originalPosition = (fitting.position ?? [0, 0, 0]) as Vec3
+  const rotation = (fitting.rotation ?? [0, 0, 0]) as Vec3
+  const isNew =
+    typeof node.metadata === 'object' &&
+    node.metadata !== null &&
+    !Array.isArray(node.metadata) &&
+    (node.metadata as Record<string, unknown>).isNew === true
+
+  const [cursorPos, setCursorPos] = useState<Vec3>(originalPosition)
+
+  // Translucent stand-in built from the fitting's real geometry. Rotation is
+  // a geometry input (it decides the elbow's profile roles), so the ghost
+  // matches what lands. Rebuilt only if the source changes.
+  const ghost = useMemo(() => {
+    const group = buildPipeFittingGeometry(fitting)
+    group.traverse((obj) => {
+      const mesh = obj as Mesh
+      if ((mesh as { isMesh?: boolean }).isMesh) {
+        mesh.material = new MeshBasicMaterial({
+          color: GHOST_COLOR,
+          transparent: true,
+          opacity: GHOST_OPACITY,
+          depthTest: false,
+        })
+        mesh.renderOrder = 999
+      }
+      obj.layers.set(EDITOR_LAYER)
+    })
+    return group
+  }, [fitting])
+
+  // Footprint box that wraps the oriented geometry (size + centre offset),
+  // measured once from the ghost.
+  const bounds = useMemo(() => {
+    const box = new Box3().setFromObject(ghost)
+    if (box.isEmpty()) return { size: [0.3, 0.3, 0.3] as Vec3, offset: [0, 0, 0] as Vec3 }
+    return rotatedBounds(box, rotation)
+  }, [ghost, rotation])
+
+  useEffect(() => {
+    return () => {
+      ghost.traverse((obj) => {
+        const mesh = obj as Mesh
+        if ((mesh as { isMesh?: boolean }).isMesh) {
+          mesh.geometry?.dispose?.()
+          const mat = mesh.material as Material | Material[]
+          if (Array.isArray(mat)) for (const m of mat) m.dispose?.()
+          else mat?.dispose?.()
+        }
+      })
+    }
+  }, [ghost])
+
+  useEffect(() => {
+    const nodeId = node.id as AnyNodeId
+    const [hx, , hz] = [bounds.size[0] / 2, 0, bounds.size[2] / 2]
+    const [ox, , oz] = bounds.offset
+
+    useScene.temporal.getState().pause()
+    let committed = false
+    let hasMoved = false
+    const activatedAt = Date.now()
+
+    const candidates: AlignmentAnchor[] = collectGhostAlignmentCandidates(
+      useScene.getState().nodes,
+      nodeId,
+      useViewer.getState().selection.levelId ?? node.parentId,
+    )
+
+    // Moving an existing fitting: hide its 3D MESH imperatively (NOT the
+    // store `visible` flag — the 2D floor plan skips `visible:false` nodes,
+    // so a store hide makes it vanish in 2D / split view). The ghost stands
+    // in until commit; the real mesh is restored on cancel / unmount.
+    const existedAtStart = !isNew && !!useScene.getState().nodes[nodeId]
+    const setMeshHidden = (hidden: boolean) => {
+      const obj = sceneRegistry.nodes.get(nodeId)
+      if (obj) obj.visible = !hidden
+    }
+    if (existedAtStart) setMeshHidden(true)
+
+    // Carry connected pipes as the fitting slides: the part of the move along
+    // a run's axis stretches it, the part across translates the whole run (and
+    // propagates to its far joint). Snapshot once at drag start; only existing
+    // fittings are mated to anything.
+    const connectivity: RunMoveConnectivity | null = existedAtStart
+      ? startRunMoveConnectivity(node)
+      : null
+
+    let lastPos: Vec3 = originalPosition
+    // Tracks whether the last frame held Alt: the fitting is detached from its
+    // connected pipes for the drag, so they stay put (no follow) and the
+    // commit omits their updates. Mirrors the pipe endpoint's Alt-detach.
+    let lastDetached = false
+    // Anchor for the Ctrl-vertical (riser) drag: clientY + base Y captured the
+    // frame Ctrl is first held, so vertical mouse motion maps to Y. Cleared
+    // when Ctrl is released. Mirrors the draw tool's Alt-vertical anchor.
+    let verticalAnchor: { clientY: number; baseY: number } | null = null
+
+    const onMove = (event: GridEvent) => {
+      const bypass = event.nativeEvent?.shiftKey === true
+      // Alt = detach: drop the connected-pipe follow so the fitting moves on
+      // its own, leaving every mated run where it sits.
+      const detached = event.nativeEvent?.altKey === true
+      // Ctrl/Cmd = vertical: XZ locks to where the fitting sits and the cursor's
+      // screen-Y drives the riser height (connected pipes still follow).
+      const vertical = event.nativeEvent?.ctrlKey === true || event.nativeEvent?.metaKey === true
+      const clientY = (event.nativeEvent as { clientY?: number } | undefined)?.clientY
+      const snap = bypass ? (v: number) => v : snapToGridStep
+
+      let next: Vec3
+      if (vertical && typeof clientY === 'number') {
+        if (!verticalAnchor) verticalAnchor = { clientY, baseY: lastPos[1] }
+        // Screen +Y points down, so subtract to map "drag up = raise".
+        const dy = (verticalAnchor.clientY - clientY) / VERTICAL_PIXELS_PER_METER
+        const y = Math.min(
+          VERTICAL_Y_MAX_M,
+          Math.max(VERTICAL_Y_MIN_M, verticalAnchor.baseY + snap(dy)),
+        )
+        next = [lastPos[0], y, lastPos[2]]
+        useAlignmentGuides.getState().clear()
+      } else {
+        verticalAnchor = null
+        let x = snap(event.localPosition[0])
+        let z = snap(event.localPosition[2])
+
+        // Alignment: snap the footprint box edges onto nearby geometry and
+        // publish guides (Alt / Shift bypass).
+        if (!bypass) {
+          const proposed: Aabb2D = {
+            minX: x + ox - hx,
+            maxX: x + ox + hx,
+            minZ: z + oz - hz,
+            maxZ: z + oz + hz,
+          }
+          const { dx, dz, guides } = resolveGhostAlignment(nodeId, proposed, candidates)
+          x += dx
+          z += dz
+          useAlignmentGuides.getState().set(guides)
+        } else {
+          useAlignmentGuides.getState().clear()
+        }
+        next = [x, lastPos[1], z]
+      }
+
+      if (next[0] !== lastPos[0] || next[1] !== lastPos[1] || next[2] !== lastPos[2]) {
+        triggerSFX('sfx:grid-snap')
+      }
+      lastPos = next
+      lastDetached = detached
+      hasMoved = true
+      setCursorPos(next)
+      // Detached: keep the followers at their origin (drop any live overrides
+      // from a prior non-detached frame). Otherwise preview the follow.
+      if (detached) connectivity?.clear()
+      else connectivity?.preview({ position: next })
+    }
+
+    const commit = (event: GridEvent) => {
+      if (committed) return
+      if (Date.now() - activatedAt < 150) {
+        event.nativeEvent?.stopPropagation?.()
+        return
+      }
+      if (!hasMoved) {
+        event.nativeEvent?.stopPropagation?.()
+        return
+      }
+      committed = true
+
+      useScene.temporal.getState().resume()
+      let selectId = nodeId
+      if (isNew && !useScene.getState().nodes[nodeId]) {
+        const created = PipeFittingNode.parse({
+          ...(node as Record<string, unknown>),
+          position: lastPos,
+          metadata: stripPlacementMetadataFlags(node.metadata),
+          visible: true,
+        })
+        useScene.getState().createNode(created as AnyNode, node.parentId as AnyNodeId)
+        selectId = created.id as AnyNodeId
+      } else {
+        // Fold connected-pipe / sibling-run follow-updates into the SAME batch
+        // as the moved fitting so the whole joint is one undo step. Detached
+        // (Alt on the final frame): the joint is broken, so nothing follows.
+        const followUpdates = lastDetached
+          ? []
+          : (connectivity?.commitUpdates({ position: lastPos }) ?? [])
+        useScene
+          .getState()
+          .updateNodes([
+            { id: nodeId, data: { position: lastPos } as Partial<AnyNode> },
+            ...followUpdates,
+          ])
+        useScene.getState().markDirty(nodeId)
+      }
+      useScene.temporal.getState().pause()
+      // Followers are committed to the store — drop their live overrides so
+      // renderers read the canonical path/position.
+      connectivity?.clear()
+      setMeshHidden(false)
+
+      useAlignmentGuides.getState().clear()
+      triggerSFX('sfx:item-place')
+      useViewer.getState().setSelection({ selectedIds: [selectId] })
+      useEditor.getState().setMovingNodeOrigin('3d')
+      useEditor.getState().setMovingNode(null)
+      event.nativeEvent?.stopPropagation?.()
+    }
+
+    const onCancel = () => {
+      connectivity?.clear()
+      if (existedAtStart) {
+        setMeshHidden(false)
+        useViewer.getState().setSelection({ selectedIds: [nodeId] })
+      }
+      useAlignmentGuides.getState().clear()
+      useScene.temporal.getState().resume()
+      markToolCancelConsumed()
+      useEditor.getState().setMovingNodeOrigin('3d')
+      useEditor.getState().setMovingNode(null)
+    }
+
+    emitter.on('grid:move', onMove)
+    emitter.on('grid:click', commit)
+    emitter.on('tool:cancel', onCancel)
+
+    return () => {
+      emitter.off('grid:move', onMove)
+      emitter.off('grid:click', commit)
+      emitter.off('tool:cancel', onCancel)
+      connectivity?.clear()
+      useAlignmentGuides.getState().clear()
+      if (existedAtStart) setMeshHidden(false)
+      useScene.temporal.getState().resume()
+    }
+  }, [bounds, isNew, node, originalPosition])
+
+  return (
+    <group>
+      <primitive object={ghost} position={cursorPos} rotation={rotation} />
+      <DragBoundingBox
+        centerY={bounds.offset[1]}
+        nodeId={node.id}
+        position={[cursorPos[0] + bounds.offset[0], cursorPos[1], cursorPos[2] + bounds.offset[2]]}
+        size={bounds.size}
+      />
+    </group>
+  )
+}
+
+export default MovePipeFittingTool

packages/nodes/src/pipe-fitting/parametrics.test.ts

@@ -0,0 +1,106 @@
+import { describe, expect, test } from 'bun:test'
+import { type AnyNode, type AnyNodeId, PipeFittingNode, PipeSegmentNode } from '@pascal-app/core'
+import { pipeFittingParametrics } from './parametrics'
+import { getPipeFittingPorts } from './ports'
+
+type Point = [number, number, number]
+
+function pipeElbow() {
+  return PipeFittingNode.parse({
+    id: 'pipe-fitting_elbow' as AnyNodeId,
+    object: 'node',
+    parentId: null,
+    visible: true,
+    metadata: {},
+    name: 'DWV bend',
+    fittingType: 'elbow',
+    angle: 90,
+    diameter: 3,
+    diameter2: 3,
+    pipeMaterial: 'pvc',
+    system: 'waste',
+    position: [0, 0, 0],
+    rotation: [0, 0, 0],
+  })
+}
+
+function pipe(id: string, path: Point[]) {
+  return PipeSegmentNode.parse({
+    id: id as AnyNodeId,
+    object: 'node',
+    parentId: null,
+    visible: true,
+    metadata: {},
+    name: 'DWV pipe',
+    path,
+    diameter: 3,
+    pipeMaterial: 'pvc',
+    system: 'waste',
+  })
+}
+
+function add(point: readonly number[], dir: readonly number[], length: number): Point {
+  return [point[0]! + dir[0]! * length, point[1]! + dir[1]! * length, point[2]! + dir[2]! * length]
+}
+
+describe('pipeFittingParametrics', () => {
+  test('deleting an elbow re-extends mated pipe ends back onto the junction', () => {
+    const fitting = pipeElbow()
+    const inlet = getPipeFittingPorts(fitting).find((p) => p.id === 'inlet')!
+    const outlet = getPipeFittingPorts(fitting).find((p) => p.id === 'outlet')!
+    const inletRun = pipe('pipe-segment_inlet', [
+      add(inlet.position, inlet.direction, 3),
+      [...inlet.position] as Point,
+    ])
+    const outletRun = pipe('pipe-segment_outlet', [
+      [...outlet.position] as Point,
+      add(outlet.position, outlet.direction, 3),
+    ])
+    const nodes: Record<AnyNodeId, AnyNode> = {
+      [fitting.id]: fitting as AnyNode,
+      [inletRun.id]: inletRun as AnyNode,
+      [outletRun.id]: outletRun as AnyNode,
+    }
+
+    const updates = pipeFittingParametrics.onDelete?.(fitting, nodes) ?? []
+    const inletUpdate = updates.find((u) => u.id === inletRun.id)
+    const outletUpdate = updates.find((u) => u.id === outletRun.id)
+
+    expect((inletUpdate?.data as Partial<PipeSegmentNode>).path?.[1]).toEqual([...fitting.position])
+    expect((outletUpdate?.data as Partial<PipeSegmentNode>).path?.[0]).toEqual([
+      ...fitting.position,
+    ])
+  })
+
+  test('delete repair matches the 5 cm live connectivity mate tolerance', () => {
+    const fitting = pipeElbow()
+    const inlet = getPipeFittingPorts(fitting).find((p) => p.id === 'inlet')!
+    const inletRun = pipe('pipe-segment_inlet', [
+      add(inlet.position, inlet.direction, 3),
+      add(inlet.position, [0, 0, 1], 0.04),
+    ])
+    const nodes: Record<AnyNodeId, AnyNode> = {
+      [fitting.id]: fitting as AnyNode,
+      [inletRun.id]: inletRun as AnyNode,
+    }
+
+    const updates = pipeFittingParametrics.onDelete?.(fitting, nodes) ?? []
+
+    expect((updates[0]?.data as Partial<PipeSegmentNode>).path?.[1]).toEqual([...fitting.position])
+  })
+
+  test('deleting a branch fitting leaves mated pipe ends untouched', () => {
+    const wye = PipeFittingNode.parse({ ...pipeElbow(), fittingType: 'wye' })
+    const inlet = getPipeFittingPorts(wye).find((p) => p.id === 'inlet')!
+    const inletRun = pipe('pipe-segment_inlet', [
+      add(inlet.position, inlet.direction, 3),
+      [...inlet.position] as Point,
+    ])
+    const nodes: Record<AnyNodeId, AnyNode> = {
+      [wye.id]: wye as AnyNode,
+      [inletRun.id]: inletRun as AnyNode,
+    }
+
+    expect(pipeFittingParametrics.onDelete?.(wye, nodes) ?? []).toEqual([])
+  })
+})

packages/nodes/src/pipe-fitting/parametrics.ts

@@ -1,7 +1,62 @@
-import type { ParametricDescriptor } from '@pascal-app/core'
+import type { AnyNode, AnyNodeId, ParametricDescriptor, PipeSegmentNode } from '@pascal-app/core'
+import { getPipeFittingPorts } from './ports'
 import type { PipeFittingNode } from './schema'
 
+/** A pipe endpoint sitting this close to a fitting hub counts as mated. */
+const MATE_TOL_M = 0.05
+
+type Point = [number, number, number]
+type PipeMate = { pipe: PipeSegmentNode; endIndex: number }
+
+function matedPipes(
+  fitting: PipeFittingNode,
+  nodes: Record<AnyNodeId, AnyNode>,
+): Map<string, PipeMate> {
+  const mates = new Map<string, PipeMate>()
+  const ports = getPipeFittingPorts(fitting)
+  for (const node of Object.values(nodes)) {
+    if (node.type !== 'pipe-segment') continue
+    const pipe = node as PipeSegmentNode
+    for (const endIndex of [0, pipe.path.length - 1]) {
+      const p = pipe.path[endIndex]
+      if (!p) continue
+      for (const port of ports) {
+        if (mates.has(port.id)) continue
+        const dx = p[0] - port.position[0]
+        const dy = p[1] - port.position[1]
+        const dz = p[2] - port.position[2]
+        if (dx * dx + dy * dy + dz * dz <= MATE_TOL_M * MATE_TOL_M) {
+          mates.set(port.id, { pipe, endIndex })
+        }
+      }
+    }
+  }
+  return mates
+}
+
 export const pipeFittingParametrics: ParametricDescriptor<PipeFittingNode> = {
+  // Deleting an auto-inserted DWV bend restores the corner it replaced.
+  // The connected pipe endpoints were pulled back onto the bend collars;
+  // send those endpoints back to the junction so the L-shape regains its
+  // original length.
+  onDelete: (fitting, nodes) => {
+    if (fitting.fittingType !== 'elbow') return []
+    const updates: Array<{ id: AnyNodeId; data: Partial<AnyNode> }> = []
+    for (const mate of matedPipes(fitting, nodes).values()) {
+      const end = mate.pipe.path[mate.endIndex]
+      if (!end) continue
+      const target = fitting.position
+      const dx = end[0] - target[0]
+      const dy = end[1] - target[1]
+      const dz = end[2] - target[2]
+      if (dx * dx + dy * dy + dz * dz < 1e-12) continue
+      const path = mate.pipe.path.map((p) => [...p] as Point)
+      path[mate.endIndex] = [...target]
+      updates.push({ id: mate.pipe.id, data: { path } as Partial<PipeSegmentNode> })
+    }
+    return updates
+  },
+
   groups: [
     {
       label: 'Fitting',
@@ -16,7 +71,7 @@ export const pipeFittingParametrics: ParametricDescriptor<PipeFittingNode> = {
           key: 'angle',
           kind: 'number',
           unit: '°',
-          min: 15,
+          min: 0,
           max: 90,
           step: 7.5,
           visibleIf: (n) => n.fittingType === 'elbow',

packages/nodes/src/pipe-fitting/selection.tsx

@@ -1,27 +1,259 @@
 'use client'
 
-import { type AnyNodeId, useScene } from '@pascal-app/core'
+import {
+  type AnyNode,
+  type AnyNodeId,
+  analyzePortConnectivity,
+  type Cursor,
+  type PipeFittingNode,
+  type PortConnectivity,
+  pauseSceneHistory,
+  resolveConnectivityUpdates,
+  resumeSceneHistory,
+  sceneRegistry,
+  useScene,
+} from '@pascal-app/core'
+import {
+  ARROW_COLOR,
+  EDITOR_LAYER,
+  swallowNextClick,
+  triggerSFX,
+  useEditor,
+} from '@pascal-app/editor'
 import { useViewer } from '@pascal-app/viewer'
-import { useEffect } from 'react'
-import { cycleRotationAxis } from '../shared/fitting-rotation'
+import { createPortal, type ThreeEvent, useFrame, useThree } from '@react-three/fiber'
+import { useEffect, useMemo, useState } from 'react'
+import {
+  BufferGeometry,
+  Euler,
+  Float32BufferAttribute,
+  type Group,
+  LineSegments,
+  type Object3D,
+  OrthographicCamera,
+  Plane,
+  Quaternion,
+  Raycaster,
+  SphereGeometry,
+  Vector2,
+  Vector3,
+} from 'three'
+import { LineBasicNodeMaterial, MeshBasicNodeMaterial } from 'three/webgpu'
+import {
+  AXIS_VECTORS,
+  cycleRotationAxis,
+  ROTATE_STEP_RAD,
+  type RotationAxis,
+} from '../shared/fitting-rotation'
+import { HandleCube, MoveChevron, RotateArc } from '../shared/selection-handles'
+import { pipeFittingLegLength } from './ports'
+
+type Point = [number, number, number]
+type FittingTransform = { position?: Point; rotation?: Point }
+type PipeDimension = 'diameter' | 'diameter2'
+
+const ARROW_GAP = 0.34
+const RESIZE_HANDLE_GAP = 0.3
+const RESIZE_STEP_IN = 0.25
+const RESIZE_GUIDE_DASH = 0.07
+const RESIZE_GUIDE_GAP = 0.045
+const RESIZE_SPHERE_RADIUS = 0.065
+const RESIZE_HIT_RADIUS = 0.13
+const INCHES_TO_METERS = 0.0254
+
+const UP = new Vector3(0, 1, 0)
+
+function snap(value: number, step: number): number {
+  if (step <= 0) return value
+  return Math.round(value / step) * step
+}
+
+function clamp(value: number, min: number, max: number): number {
+  return Math.min(max, Math.max(min, value))
+}
+
+function fittingExtentM(node: PipeFittingNode): number {
+  return Math.max(pipeFittingLegLength(node.diameter), pipeFittingLegLength(node.diameter2))
+}
+
+function fittingParameterPatch(node: PipeFittingNode): Partial<PipeFittingNode> {
+  return {
+    fittingType: node.fittingType,
+    angle: node.angle,
+    diameter: node.diameter,
+    diameter2: node.diameter2,
+    pipeMaterial: node.pipeMaterial,
+    system: node.system,
+  }
+}
+
+function preserveFittingParameters(
+  node: PipeFittingNode,
+  data: Partial<PipeFittingNode>,
+): Partial<AnyNode> {
+  return { ...fittingParameterPatch(node), ...data } as Partial<AnyNode>
+}
+
+function dimensionPatch(
+  fitting: PipeFittingNode,
+  dimension: PipeDimension,
+  value: number,
+): Partial<PipeFittingNode> {
+  if (dimension === 'diameter' && fitting.fittingType === 'elbow') {
+    return { diameter: value, diameter2: value }
+  }
+  return { [dimension]: value } as Partial<PipeFittingNode>
+}
+
+function closestAxisParameterToRay(
+  axisOrigin: Vector3,
+  axisDirection: Vector3,
+  ray: Raycaster['ray'],
+) {
+  const originToRay = axisOrigin.clone().sub(ray.origin)
+  const b = axisDirection.dot(ray.direction)
+  const d = axisDirection.dot(originToRay)
+  const e = ray.direction.dot(originToRay)
+  const denominator = 1 - b * b
+  if (Math.abs(denominator) < 1e-6) return -d
+  const axisParameter = (b * e - d) / denominator
+  const rayParameter = e + b * axisParameter
+  return rayParameter < 0 ? -d : axisParameter
+}
+
+function DashedResizeGuide({ from, to }: { from: Point; to: Point }) {
+  const line = useMemo(() => {
+    const a = new Vector3(from[0], from[1], from[2])
+    const b = new Vector3(to[0], to[1], to[2])
+    const span = b.clone().sub(a)
+    const length = span.length()
+    const points: number[] = []
+    if (length > 1e-4) {
+      const dir = span.clone().normalize()
+      let t = 0
+      while (t < length) {
+        const start = a.clone().addScaledVector(dir, t)
+        const end = a.clone().addScaledVector(dir, Math.min(t + RESIZE_GUIDE_DASH, length))
+        points.push(start.x, start.y, start.z, end.x, end.y, end.z)
+        t += RESIZE_GUIDE_DASH + RESIZE_GUIDE_GAP
+      }
+    }
+    const geometry = new BufferGeometry()
+    geometry.setAttribute('position', new Float32BufferAttribute(new Float32Array(points), 3))
+    const material = new LineBasicNodeMaterial({
+      color: ARROW_COLOR,
+      transparent: true,
+      opacity: 0.8,
+      depthWrite: false,
+    })
+    const next = new LineSegments(geometry, material)
+    next.frustumCulled = false
+    next.layers.set(EDITOR_LAYER)
+    next.renderOrder = 1002
+    next.raycast = () => {}
+    return next
+  }, [from, to])
+
+  useEffect(
+    () => () => {
+      line.geometry.dispose()
+      ;(line.material as LineBasicNodeMaterial).dispose()
+    },
+    [line],
+  )
+
+  return <primitive object={line} />
+}
+
+function ResizeSphereHandle({
+  cursor,
+  onPointerDown,
+  position,
+}: {
+  cursor: Cursor
+  onPointerDown: (event: ThreeEvent<PointerEvent>) => void
+  position: Point
+}) {
+  const { camera } = useThree()
+  const [hovered, setHovered] = useState(false)
+  const zoom = camera instanceof OrthographicCamera ? 1 / camera.zoom : 1
+  const sphereGeometry = useMemo(() => new SphereGeometry(RESIZE_SPHERE_RADIUS, 18, 12), [])
+  const hitGeometry = useMemo(() => new SphereGeometry(RESIZE_HIT_RADIUS, 12, 8), [])
+  const sphereMaterial = useMemo(
+    () =>
+      new MeshBasicNodeMaterial({
+        color: ARROW_COLOR,
+        transparent: true,
+        opacity: 0.92,
+        depthTest: false,
+        depthWrite: false,
+      }),
+    [],
+  )
+  const hitMaterial = useMemo(
+    () =>
+      new MeshBasicNodeMaterial({
+        color: ARROW_COLOR,
+        transparent: true,
+        opacity: 0,
+        depthTest: false,
+        depthWrite: false,
+      }),
+    [],
+  )
+
+  useEffect(() => {
+    sphereMaterial.opacity = hovered ? 1 : 0.92
+  }, [sphereMaterial, hovered])
+  useEffect(
+    () => () => {
+      hitGeometry.dispose()
+      sphereGeometry.dispose()
+      sphereMaterial.dispose()
+      hitMaterial.dispose()
+    },
+    [hitGeometry, hitMaterial, sphereGeometry, sphereMaterial],
+  )
+
+  const consumePress = (event: ThreeEvent<PointerEvent>) => {
+    event.stopPropagation()
+    event.nativeEvent.stopPropagation()
+    event.nativeEvent.stopImmediatePropagation()
+    swallowNextClick()
+    onPointerDown(event)
+  }
+
+  return (
+    <group position={position} scale={zoom}>
+      <mesh
+        geometry={hitGeometry}
+        material={hitMaterial}
+        onPointerDown={consumePress}
+        onPointerEnter={(event) => {
+          event.stopPropagation()
+          setHovered(true)
+          document.body.style.cursor = cursor
+        }}
+        onPointerLeave={(event) => {
+          event.stopPropagation()
+          setHovered(false)
+          if (document.body.style.cursor === cursor) document.body.style.cursor = ''
+        }}
+      />
+      <mesh geometry={sphereGeometry} material={sphereMaterial} renderOrder={1004} />
+    </group>
+  )
+}
 
-/**
- * Selection-time rotation support for placed pipe fittings — mirrors
- * the duct-fitting affordance, mounted by the editor's
- * SelectionAffordanceManager (`def.affordanceTools.selection`). R/T
- * rotation lives in `def.keyboardActions`; this contributes the piece
- * that hook can't: **Alt cycles the active rotation axis** while a
- * single fitting is selected. The axis lives on `useEditor.rotationAxis`,
- * which the floating action menu reads to show the axis pill — so this
- * component renders nothing.
- */
 const PipeFittingSelectionAffordance = () => {
   const selectedIds = useViewer((s) => s.selection.selectedIds)
-  const hasSelectedFitting = useScene((s) => {
-    if (selectedIds.length !== 1) return false
-    return s.nodes[selectedIds[0] as AnyNodeId]?.type === 'pipe-fitting'
+  const fitting = useScene((s) => {
+    if (selectedIds.length !== 1) return null
+    const node = s.nodes[selectedIds[0] as AnyNodeId]
+    return node?.type === 'pipe-fitting' ? (node as PipeFittingNode) : null
   })
 
+  const hasSelectedFitting = !!fitting
   useEffect(() => {
     if (!hasSelectedFitting) return
     const onKeyDown = (e: KeyboardEvent) => {
@@ -31,13 +263,527 @@ const PipeFittingSelectionAffordance = () => {
       e.preventDefault()
       cycleRotationAxis()
     }
-    // Bubble phase — when the placement tool is active its capture-phase
-    // handler stops propagation, so the two never double-cycle.
     window.addEventListener('keydown', onKeyDown)
     return () => window.removeEventListener('keydown', onKeyDown)
   }, [hasSelectedFitting])
 
-  return null
+  const fittingId = fitting?.id ?? null
+  const [target, setTarget] = useState<Object3D | null>(null)
+  useEffect(() => {
+    if (!fittingId) {
+      setTarget(null)
+      return
+    }
+    let frameId = 0
+    const resolve = () => {
+      const next = sceneRegistry.nodes.get(fittingId as AnyNodeId) ?? null
+      setTarget((cur) => (cur === next ? cur : next))
+      if (!next) frameId = window.requestAnimationFrame(resolve)
+    }
+    resolve()
+    return () => window.cancelAnimationFrame(frameId)
+  }, [fittingId])
+
+  if (!fitting || !target) return null
+  const mount = target.parent ?? target
+  return createPortal(<FittingHandles fitting={fitting} />, mount, undefined)
+}
+
+const FittingHandles = ({ fitting }: { fitting: PipeFittingNode }) => {
+  const { camera, gl } = useThree()
+  const [frame, setFrame] = useState<Group | null>(null)
+  const [open, setOpen] = useState(false)
+  const [dragging, setDragging] = useState(false)
+  const [sideSign, setSideSign] = useState(1)
+
+  const makeRay = (clientX: number, clientY: number) => {
+    const rect = gl.domElement.getBoundingClientRect()
+    const ndc = new Vector2(
+      ((clientX - rect.left) / rect.width) * 2 - 1,
+      -((clientY - rect.top) / rect.height) * 2 + 1,
+    )
+    const raycaster = new Raycaster()
+    raycaster.setFromCamera(ndc, camera)
+    return raycaster.ray
+  }
+  const intersect = (clientX: number, clientY: number, plane: Plane): Vector3 | null => {
+    const hit = new Vector3()
+    return makeRay(clientX, clientY).intersectPlane(plane, hit) ? hit : null
+  }
+  const sampleAxisParameter = (
+    clientX: number,
+    clientY: number,
+    axisOrigin: Vector3,
+    axisDirection: Vector3,
+  ): number => closestAxisParameterToRay(axisOrigin, axisDirection, makeRay(clientX, clientY))
+  const intersectVerticalY = (
+    clientX: number,
+    clientY: number,
+    anchorWorld: Vector3,
+  ): number | null => {
+    if (!frame) return null
+    const forward = camera.getWorldDirection(new Vector3())
+    forward.y = 0
+    if (forward.lengthSq() < 1e-6) forward.set(0, 0, 1)
+    forward.normalize()
+    const plane = new Plane().setFromNormalAndCoplanarPoint(forward, anchorWorld)
+    const hit = intersect(clientX, clientY, plane)
+    return hit ? frame.worldToLocal(hit.clone()).y : null
+  }
+
+  const toWorld = (p: Point): Vector3 =>
+    frame ? frame.localToWorld(new Vector3(p[0], p[1], p[2])) : new Vector3(p[0], p[1], p[2])
+  const axisToWorld = (origin: Point, axis: Vector3): Vector3 => {
+    const originWorld = toWorld(origin)
+    const tipWorld = frame
+      ? frame.localToWorld(new Vector3(origin[0] + axis.x, origin[1] + axis.y, origin[2] + axis.z))
+      : new Vector3(origin[0] + axis.x, origin[1] + axis.y, origin[2] + axis.z)
+    return tipWorld.sub(originWorld).normalize()
+  }
+
+  const sampleAxis = (
+    axis: RotationAxis,
+    clientX: number,
+    clientY: number,
+    anchorWorld: Vector3,
+  ): number | null => {
+    if (axis === 'y') return intersectVerticalY(clientX, clientY, anchorWorld)
+    const plane = new Plane().setFromNormalAndCoplanarPoint(UP, anchorWorld)
+    const hit = intersect(clientX, clientY, plane)
+    if (!hit || !frame) return null
+    const local = frame.worldToLocal(hit.clone())
+    return axis === 'x' ? local.x : local.z
+  }
+
+  const connectivityUpdates = (
+    connectivity: PortConnectivity | null,
+    transform: FittingTransform,
+  ): { id: AnyNodeId; data: Partial<AnyNode> }[] => {
+    if (!connectivity) return []
+    const preview = { ...(fitting as Record<string, unknown>), ...transform } as AnyNode
+    const nodes = useScene.getState().nodes
+    return resolveConnectivityUpdates(connectivity, preview)
+      .filter((u) => nodes[u.id])
+      .map((u) => {
+        const node = nodes[u.id]
+        if (node?.type !== 'pipe-fitting') return u
+        return {
+          id: u.id,
+          data: preserveFittingParameters(
+            node as PipeFittingNode,
+            u.data as Partial<PipeFittingNode>,
+          ),
+        }
+      })
+  }
+
+  const beginDrag =
+    (
+      cursor: Cursor,
+      makeCompute: (
+        e: ThreeEvent<PointerEvent>,
+      ) => (event: PointerEvent) => FittingTransform | null,
+    ) =>
+    (e: ThreeEvent<PointerEvent>) => {
+      e.stopPropagation()
+      const initialPosition = [...fitting.position] as Point
+      const initialRotation = [...fitting.rotation] as Point
+      const connectivity = analyzePortConnectivity(fitting as AnyNode, useScene.getState().nodes)
+      const compute = makeCompute(e)
+      pauseSceneHistory(useScene)
+      useViewer.getState().setInputDragging(true)
+      setDragging(true)
+      document.body.style.cursor = cursor
+      let current: FittingTransform | null = null
+
+      const buildBatch = (t: FittingTransform): { id: AnyNodeId; data: Partial<AnyNode> }[] => [
+        {
+          id: fitting.id as AnyNodeId,
+          data: preserveFittingParameters(fitting, t as Partial<PipeFittingNode>),
+        },
+        ...connectivityUpdates(connectivity, t),
+      ]
+
+      const onMove = (event: PointerEvent) => {
+        const next = compute(event)
+        if (!next) return
+        current = next
+        useScene.getState().updateNodes(buildBatch(next))
+      }
+
+      const cleanup = () => {
+        window.removeEventListener('pointermove', onMove)
+        window.removeEventListener('pointerup', onUp)
+        window.removeEventListener('pointercancel', onUp)
+        useViewer.getState().setInputDragging(false)
+        setDragging(false)
+        if (document.body.style.cursor === cursor) document.body.style.cursor = ''
+      }
+
+      const onUp = () => {
+        swallowNextClick()
+        cleanup()
+        const reverts: { id: AnyNodeId; data: Partial<AnyNode> }[] = (
+          connectivity?.connections ?? []
+        ).map((conn) => {
+          if (conn.kind !== 'rigid-node') {
+            return { id: conn.nodeId, data: { path: conn.startPath } as Partial<AnyNode> }
+          }
+          const node = useScene.getState().nodes[conn.nodeId]
+          return {
+            id: conn.nodeId,
+            data:
+              node?.type === 'pipe-fitting'
+                ? preserveFittingParameters(node as PipeFittingNode, {
+                    position: conn.startPosition as Point,
+                  })
+                : ({ position: conn.startPosition } as Partial<AnyNode>),
+          }
+        })
+        useScene.getState().updateNodes([
+          {
+            id: fitting.id as AnyNodeId,
+            data: preserveFittingParameters(fitting, {
+              position: initialPosition,
+              rotation: initialRotation,
+            }),
+          },
+          ...reverts.filter((u) => useScene.getState().nodes[u.id]),
+        ])
+        resumeSceneHistory(useScene)
+        if (current) useScene.getState().updateNodes(buildBatch(current))
+      }
+
+      window.addEventListener('pointermove', onMove)
+      window.addEventListener('pointerup', onUp)
+      window.addEventListener('pointercancel', onUp)
+    }
+
+  const moveCompute =
+    (axis: RotationAxis) =>
+    (e: ThreeEvent<PointerEvent>): ((event: PointerEvent) => FittingTransform | null) => {
+      const anchorWorld = toWorld(fitting.position as Point)
+      const start = sampleAxis(axis, e.nativeEvent.clientX, e.nativeEvent.clientY, anchorWorld)
+      const base = [...fitting.position] as Point
+      const axisIndex = axis === 'x' ? 0 : axis === 'y' ? 1 : 2
+      let lastDelta = Number.NaN
+      return (event: PointerEvent): FittingTransform | null => {
+        if (start === null) return null
+        const s = sampleAxis(axis, event.clientX, event.clientY, anchorWorld)
+        if (s === null) return null
+        const step = event.shiftKey ? 0 : useEditor.getState().gridSnapStep
+        const delta = snap(s - start, step)
+        if (delta === lastDelta) return null
+        lastDelta = delta
+        if (step > 0) triggerSFX('sfx:grid-snap')
+        const next = [...base] as Point
+        next[axisIndex] = base[axisIndex] + delta
+        return { position: next }
+      }
+    }
+
+  const rotateCompute =
+    (axis: RotationAxis) =>
+    (e: ThreeEvent<PointerEvent>): ((event: PointerEvent) => FittingTransform | null) => {
+      const normal = AXIS_VECTORS[axis].clone()
+      const center = toWorld(fitting.position as Point)
+      const ref = axis === 'y' ? new Vector3(1, 0, 0) : new Vector3(0, 1, 0)
+      const u = ref
+        .clone()
+        .sub(normal.clone().multiplyScalar(ref.dot(normal)))
+        .normalize()
+      const v = new Vector3().crossVectors(normal, u)
+      const plane = new Plane().setFromNormalAndCoplanarPoint(normal, center)
+      const bearing = (clientX: number, clientY: number): number | null => {
+        const hit = intersect(clientX, clientY, plane)
+        if (!hit) return null
+        const d = hit.sub(center)
+        return Math.atan2(d.dot(v), d.dot(u))
+      }
+      const startBearing = bearing(e.nativeEvent.clientX, e.nativeEvent.clientY)
+      const startQuat = new Quaternion().setFromEuler(
+        new Euler(fitting.rotation[0], fitting.rotation[1], fitting.rotation[2]),
+      )
+      let lastStep = Number.NaN
+      return (event: PointerEvent): FittingTransform | null => {
+        if (startBearing === null) return null
+        const b = bearing(event.clientX, event.clientY)
+        if (b === null) return null
+        const raw = b - startBearing
+        const delta = event.shiftKey ? raw : Math.round(raw / ROTATE_STEP_RAD) * ROTATE_STEP_RAD
+        if (!event.shiftKey) {
+          const step = Math.round(raw / ROTATE_STEP_RAD)
+          if (step !== lastStep) {
+            lastStep = step
+            triggerSFX('sfx:item-rotate')
+          }
+        }
+        const turn = new Quaternion().setFromAxisAngle(normal, delta)
+        const euler = new Euler().setFromQuaternion(turn.multiply(startQuat))
+        return { rotation: [euler.x, euler.y, euler.z] }
+      }
+    }
+
+  const beginDimensionDrag =
+    (dimension: PipeDimension, axisLocal: Vector3, cursor: Cursor) =>
+    (e: ThreeEvent<PointerEvent>) => {
+      e.stopPropagation()
+      const baseValue = fitting[dimension]
+      const initialPatch = dimensionPatch(fitting, dimension, baseValue)
+      const centerWorld = toWorld(fitting.position as Point)
+      const axisWorld = axisToWorld(fitting.position as Point, axisLocal)
+      const start = sampleAxisParameter(
+        e.nativeEvent.clientX,
+        e.nativeEvent.clientY,
+        centerWorld,
+        axisWorld,
+      )
+      pauseSceneHistory(useScene)
+      useViewer.getState().setInputDragging(true)
+      setDragging(true)
+      document.body.style.cursor = cursor
+      let current: Partial<PipeFittingNode> | null = null
+      let lastValue = Number.NaN
+
+      const apply = (patch: Partial<PipeFittingNode>) => {
+        useScene.getState().updateNodes([
+          {
+            id: fitting.id as AnyNodeId,
+            data: preserveFittingParameters(fitting, patch),
+          },
+        ])
+      }
+
+      const onMove = (event: PointerEvent) => {
+        const rawDeltaM =
+          sampleAxisParameter(event.clientX, event.clientY, centerWorld, axisWorld) - start
+        const deltaIn = (rawDeltaM / INCHES_TO_METERS) * 2
+        const nextRaw = baseValue + deltaIn
+        const nextValue = clamp(event.shiftKey ? nextRaw : snap(nextRaw, RESIZE_STEP_IN), 1.25, 8)
+        if (nextValue === lastValue) return
+        lastValue = nextValue
+        current = dimensionPatch(fitting, dimension, nextValue)
+        if (!event.shiftKey) triggerSFX('sfx:grid-snap')
+        apply(current)
+      }
+
+      const cleanup = () => {
+        window.removeEventListener('pointermove', onMove)
+        window.removeEventListener('pointerup', onUp)
+        window.removeEventListener('pointercancel', onUp)
+        useViewer.getState().setInputDragging(false)
+        setDragging(false)
+        if (document.body.style.cursor === cursor) document.body.style.cursor = ''
+      }
+
+      const onUp = () => {
+        swallowNextClick()
+        cleanup()
+        apply(initialPatch)
+        resumeSceneHistory(useScene)
+        if (current) apply(current)
+      }
+
+      window.addEventListener('pointermove', onMove)
+      window.addEventListener('pointerup', onUp)
+      window.addEventListener('pointercancel', onUp)
+    }
+
+  const extent = useMemo(() => fittingExtentM(fitting), [fitting])
+  const p = fitting.position as Point
+  const base = extent + ARROW_GAP
+  const fittingRotation = useMemo(
+    () => new Euler(fitting.rotation[0], fitting.rotation[1], fitting.rotation[2]),
+    [fitting.rotation],
+  )
+  const runDiameterAxis = useMemo(() => {
+    const axis = new Vector3(0, 1, 0).applyEuler(fittingRotation).normalize()
+    return axis.dot(UP) >= 0 ? axis : axis.multiplyScalar(-1)
+  }, [fittingRotation])
+  const baseBranchAxis = useMemo(
+    () => new Vector3(0, 0, 1).applyEuler(fittingRotation).normalize(),
+    [fittingRotation],
+  )
+  const branchAxis = useMemo(
+    () => baseBranchAxis.clone().multiplyScalar(sideSign),
+    [baseBranchAxis, sideSign],
+  )
+  useFrame(() => {
+    if (!frame || fitting.fittingType === 'elbow') return
+    const cameraPosition = camera.getWorldPosition(new Vector3())
+    const cameraLocal = frame.worldToLocal(cameraPosition)
+    const toCamera = cameraLocal.sub(new Vector3(p[0], p[1], p[2]))
+    const nextSign = baseBranchAxis.dot(toCamera) >= 0 ? 1 : -1
+    setSideSign((current) => (current === nextSign ? current : nextSign))
+  })
+
+  const resizeHandleBase = extent + RESIZE_HANDLE_GAP
+  const resizeHandles: {
+    key: PipeDimension
+    axis: Vector3
+    cursor: Cursor
+    guideFrom: Point
+    guideTo: Point
+    position: Point
+  }[] = [
+    {
+      key: 'diameter',
+      axis: runDiameterAxis,
+      cursor: 'ns-resize',
+      guideFrom: [
+        p[0] + runDiameterAxis.x * resizeHandleBase,
+        p[1] + runDiameterAxis.y * resizeHandleBase,
+        p[2] + runDiameterAxis.z * resizeHandleBase,
+      ],
+      guideTo: [
+        p[0] + runDiameterAxis.x * Math.max(extent * 0.18, 0.04),
+        p[1] + runDiameterAxis.y * Math.max(extent * 0.18, 0.04),
+        p[2] + runDiameterAxis.z * Math.max(extent * 0.18, 0.04),
+      ],
+      position: [
+        p[0] + runDiameterAxis.x * resizeHandleBase,
+        p[1] + runDiameterAxis.y * resizeHandleBase,
+        p[2] + runDiameterAxis.z * resizeHandleBase,
+      ],
+    },
+    ...(fitting.fittingType === 'elbow'
+      ? []
+      : [
+          {
+            key: 'diameter2' as const,
+            axis: branchAxis,
+            cursor: 'ew-resize' as Cursor,
+            guideFrom: [
+              p[0] + branchAxis.x * resizeHandleBase,
+              p[1] + branchAxis.y * resizeHandleBase,
+              p[2] + branchAxis.z * resizeHandleBase,
+            ] as Point,
+            guideTo: [
+              p[0] + branchAxis.x * Math.max(extent * 0.18, 0.04),
+              p[1] + branchAxis.y * Math.max(extent * 0.18, 0.04),
+              p[2] + branchAxis.z * Math.max(extent * 0.18, 0.04),
+            ] as Point,
+            position: [
+              p[0] + branchAxis.x * resizeHandleBase,
+              p[1] + branchAxis.y * resizeHandleBase,
+              p[2] + branchAxis.z * resizeHandleBase,
+            ] as Point,
+          },
+        ]),
+  ]
+
+  const moveArrows: {
+    key: string
+    axis: RotationAxis
+    position: Point
+    rotationY: number
+    vertical?: 'up' | 'down'
+    cursor: Cursor
+  }[] = [
+    { key: '+x', axis: 'x', position: [p[0] + base, p[1], p[2]], rotationY: 0, cursor: 'grab' },
+    {
+      key: '-x',
+      axis: 'x',
+      position: [p[0] - base, p[1], p[2]],
+      rotationY: Math.PI,
+      cursor: 'grab',
+    },
+    {
+      key: '+z',
+      axis: 'z',
+      position: [p[0], p[1], p[2] + base],
+      rotationY: -Math.PI / 2,
+      cursor: 'grab',
+    },
+    {
+      key: '-z',
+      axis: 'z',
+      position: [p[0], p[1], p[2] - base],
+      rotationY: Math.PI / 2,
+      cursor: 'grab',
+    },
+    {
+      key: '+y',
+      axis: 'y',
+      position: [p[0], p[1] + base, p[2]],
+      rotationY: 0,
+      vertical: 'up',
+      cursor: 'ns-resize',
+    },
+    {
+      key: '-y',
+      axis: 'y',
+      position: [p[0], p[1] - base, p[2]],
+      rotationY: 0,
+      vertical: 'down',
+      cursor: 'ns-resize',
+    },
+  ]
+
+  const d = base * Math.SQRT1_2
+  const rotateArcs: { key: string; axis: RotationAxis; position: Point; rotation: Point }[] = (
+    ['x', 'y', 'z'] as RotationAxis[]
+  ).map((axis) => {
+    const q = new Quaternion().setFromUnitVectors(UP, AXIS_VECTORS[axis])
+    if (axis === 'z') {
+      q.premultiply(new Quaternion().setFromAxisAngle(AXIS_VECTORS.z, Math.PI / 4))
+    } else if (axis === 'x') {
+      q.premultiply(new Quaternion().setFromAxisAngle(AXIS_VECTORS.x, (-145 * Math.PI) / 180))
+    } else if (axis === 'y') {
+      q.premultiply(new Quaternion().setFromAxisAngle(AXIS_VECTORS.y, (-45 * Math.PI) / 180))
+    }
+    const e = new Euler().setFromQuaternion(q)
+    const position: Point =
+      axis === 'x'
+        ? [p[0], p[1] + d, p[2] + d]
+        : axis === 'y'
+          ? [p[0] + d, p[1], p[2] + d]
+          : [p[0] + d, p[1] + d, p[2]]
+    return { key: `r${axis}`, axis, position, rotation: [e.x, e.y, e.z] }
+  })
+
+  if (dragging) return <group ref={setFrame} />
+  return (
+    <group ref={setFrame}>
+      <HandleCube active={open} onClick={() => setOpen((o) => !o)} position={p} />
+      {!open &&
+        resizeHandles.map((handle) => (
+          <group key={handle.key}>
+            <DashedResizeGuide from={handle.guideFrom} to={handle.guideTo} />
+            <ResizeSphereHandle
+              cursor={handle.cursor}
+              onPointerDown={beginDimensionDrag(handle.key, handle.axis, handle.cursor)}
+              position={handle.position}
+            />
+          </group>
+        ))}
+      {open && (
+        <>
+          {moveArrows.map((a) => (
+            <MoveChevron
+              cursor={a.cursor}
+              key={a.key}
+              onPointerDown={beginDrag(
+                a.axis === 'y' ? 'ns-resize' : 'grabbing',
+                moveCompute(a.axis),
+              )}
+              position={a.position}
+              rotationY={a.rotationY}
+              vertical={a.vertical}
+            />
+          ))}
+          {rotateArcs.map((arc) => (
+            <RotateArc
+              key={arc.key}
+              onPointerDown={beginDrag('grabbing', rotateCompute(arc.axis))}
+              position={arc.position}
+              rotation={arc.rotation}
+            />
+          ))}
+        </>
+      )}
+    </group>
+  )
 }
 
 export default PipeFittingSelectionAffordance

packages/nodes/src/pipe-segment/move-tool.tsx

@@ -27,6 +27,7 @@ import {
   collectGhostAlignmentCandidates,
   resolveGhostAlignment,
 } from '../shared/ghost-alignment'
+import { type RunMoveConnectivity, startRunMoveConnectivity } from '../shared/run-move-connectivity'
 
 type Vec3 = [number, number, number]
 
@@ -135,6 +136,12 @@ export const MovePipeSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
     }
     if (existedAtStart) setMeshHidden(true)
 
+    // Carry connected fittings (+ their other runs) as the whole run slides.
+    // Snapshot once at drag start; only existing runs are mated to anything.
+    const connectivity: RunMoveConnectivity | null = existedAtStart
+      ? startRunMoveConnectivity(node)
+      : null
+
     const setPreview = (path: Vec3[]) => {
       previewPathRef.current = path
       setPreviewPath(path)
@@ -174,7 +181,9 @@ export const MovePipeSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
       }
       prevSnapRef.current = cur
       hasMovedRef.current = true
-      setPreview(originalPath.map(([x, y, z]) => [x + dx, y, z + dz] as Vec3))
+      const nextPath = originalPath.map(([x, y, z]) => [x + dx, y, z + dz] as Vec3)
+      setPreview(nextPath)
+      connectivity?.preview({ path: nextPath })
     }
 
     const commit = (event: GridEvent) => {
@@ -202,10 +211,21 @@ export const MovePipeSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
         useScene.getState().createNode(created as AnyNode, node.parentId as AnyNodeId)
         selectId = created.id as AnyNodeId
       } else {
-        useScene.getState().updateNode(nodeId, { path: finalPath } as Partial<AnyNode>)
+        // Fold connected-fitting / sibling-run follow-updates into the SAME
+        // batch as the moved run so the whole joint is one undo step.
+        const followUpdates = connectivity?.commitUpdates({ path: finalPath }) ?? []
+        useScene
+          .getState()
+          .updateNodes([
+            { id: nodeId, data: { path: finalPath } as Partial<AnyNode> },
+            ...followUpdates,
+          ])
         useScene.getState().markDirty(nodeId)
       }
       useScene.temporal.getState().pause()
+      // Followers are committed to the store — drop their live overrides so
+      // renderers read the canonical path/position.
+      connectivity?.clear()
       setMeshHidden(false)
 
       useAlignmentGuides.getState().clear()
@@ -217,6 +237,7 @@ export const MovePipeSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
     }
 
     const onCancel = () => {
+      connectivity?.clear()
       if (existedAtStart) {
         setMeshHidden(false)
         useViewer.getState().setSelection({ selectedIds: [nodeId] })
@@ -236,6 +257,7 @@ export const MovePipeSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
       emitter.off('grid:move', onMove)
       emitter.off('grid:click', commit)
       emitter.off('tool:cancel', onCancel)
+      connectivity?.clear()
       useAlignmentGuides.getState().clear()
       if (existedAtStart) setMeshHidden(false)
       useScene.temporal.getState().resume()

packages/nodes/src/pipe-segment/tool.tsx

@@ -55,6 +55,11 @@ import { pipeSegmentDefinition } from './definition'
  *   - Esc clears an anchored start point.
  */
 const PREVIEW_OPACITY = 0.55
+/** green-500 — the project's snap accent. The cursor ring + vertical line
+ *  recolour to this while the point is snapped onto an existing run / port,
+ *  so the coincidence reads with the familiar snap green (matches the duct
+ *  tool). */
+const SNAP_CURSOR_COLOR = '#22c55e'
 /** Nominal residential DWV sizes (inches). */
 const PIPE_DIAMETERS_IN = [1.25, 1.5, 2, 3, 4, 6] as const
 /** IPC default drain slope — ¼" per foot (1:48). */
@@ -88,6 +93,28 @@ function findNearbyPort(point: [number, number, number]): ScenePort | null {
   )
 }
 
+function pipeEndPort(pipe: PipeSegmentNode, id: 'start' | 'end'): ScenePort | null {
+  if (pipe.path.length < 2) return null
+  const index = id === 'start' ? 0 : pipe.path.length - 1
+  const neighborIndex = id === 'start' ? 1 : pipe.path.length - 2
+  const position = pipe.path[index]!
+  const neighbor = pipe.path[neighborIndex]!
+  const dx = position[0] - neighbor[0]
+  const dy = position[1] - neighbor[1]
+  const dz = position[2] - neighbor[2]
+  const len = Math.hypot(dx, dy, dz)
+  const direction: [number, number, number] =
+    len < 1e-9 ? [1, 0, 0] : [dx / len, dy / len, dz / len]
+  return {
+    id,
+    nodeId: pipe.id,
+    position,
+    direction,
+    diameter: pipe.diameter,
+    system: pipe.system,
+  }
+}
+
 function projectToAngleLock(
   from: [number, number, number],
   raw: [number, number, number],
@@ -305,11 +332,14 @@ const PipeSegmentTool = () => {
           ...(cross ? [cross.runUpdate as { id: AnyNode['id']; data: Partial<AnyNode> }] : []),
         ],
       })
+      const nextPipe = pipes.at(-1)
+      const nextStart = nextPipe ? nextPipe.path[nextPipe.path.length - 1]! : end
+      const nextPort = nextPipe ? pipeEndPort(nextPipe, 'end') : endPort
       triggerSFX('sfx:item-place')
-      setDraftStart(null)
+      setDraftStart(nextStart)
       setSnapTarget(null)
-      startPortRef.current = null
-      startBodyRef.current = null
+      startPortRef.current = nextPort
+      startBodyRef.current = nextPort ? null : endBody
       altAnchorRef.current = null
       setAltActive(false)
     }
@@ -478,6 +508,14 @@ const PipeSegmentTool = () => {
         triggerSFX('sfx:grid-snap')
         startPortRef.current = port
         startBodyRef.current = port ? null : body
+        // Continue an existing run at its true size: adopt the snapped
+        // pipe's diameter so the new segment carries on at the same gauge
+        // instead of whatever size the tool last drew.
+        const ownerId = port?.nodeId ?? (port ? null : body?.nodeId)
+        const owner = ownerId ? useScene.getState().nodes[ownerId] : null
+        if (owner?.type === 'pipe-segment' && owner.diameter !== diameterRef.current) {
+          setDiameter(owner.diameter)
+        }
         setDraftStart(point)
         return
       }
@@ -612,7 +650,7 @@ const PipeSegmentTool = () => {
           dimension pill rides just above the cursor. */}
       {cursorPos && (
         <>
-          <CursorSphere position={cursorPos} />
+          <CursorSphere color={snapTarget ? SNAP_CURSOR_COLOR : undefined} position={cursorPos} />
           {pillParts && (
             <group position={cursorPos}>
               <Html

packages/nodes/src/pipe-trap/definition.ts

@@ -26,7 +26,7 @@ export const pipeTrapDefinition: NodeDefinition<typeof PipeTrapNode> = {
     metadata: {},
     position: [0, 0, 0],
     rotation: 0,
-    diameter: 1.5,
+    diameter: 2,
     pipeMaterial: 'pvc',
     armLengthM: 0,
   }),

packages/nodes/src/pipe-trap/geometry.ts

@@ -1,9 +1,14 @@
-import { Group, Mesh, TorusGeometry, Vector3 } from 'three'
+import { DoubleSide, Group, Mesh, SphereGeometry, TorusGeometry, Vector3 } from 'three'
 import { buildSection, INCHES_TO_METERS } from '../duct-segment/geometry'
 import { createPipeMaterial } from '../pipe-segment/geometry'
 import type { PipeTrapNode } from './schema'
 
 const BEND_SEGMENTS = 24
+const RADIAL_SEGMENTS = 20
+/** Sphere hubs filling the U-bend → stub joints read as a coupling and,
+ *  more importantly, hide the wedge gap left where the horizontal arm's
+ *  flat end cap meets the bend's upward-facing opening at 90°. */
+const HUB_RADIUS_FACTOR = 1.12
 
 /** Inlet drop and arm reach in pipe radii — keeps the trap proportional
  *  to its size without per-size tuning. */
@@ -19,8 +24,12 @@ const ARM_REACH_RADII = 3.2
 export function buildPipeTrapGeometry(node: PipeTrapNode): Group {
   const group = new Group()
   const material = createPipeMaterial({ pipeMaterial: node.pipeMaterial, system: 'waste' })
+  // Double-sided so the thin pipe walls don't drop out at grazing angles,
+  // which read as cuts/holes on the bend and stub ends.
+  material.side = DoubleSide
   const radius = (node.diameter * INCHES_TO_METERS) / 2
   const bendR = radius * 1.6
+  const hubRadius = radius * HUB_RADIUS_FACTOR
 
   // U-bend: half torus in the XY plane, opening upward. Sits so its two
   // tops are at y = bendR (the inlet riser and the arm rise).
@@ -49,6 +58,19 @@ export function buildPipeTrapGeometry(node: PipeTrapNode): Group {
   const arm = buildSection(armStart, armEnd, radius, material, 'pipe-trap-arm')
   if (arm) group.add(arm)
 
+  // Coupling hubs at the two U-bend tops where the straight stubs meet the
+  // torus. They fill the 90° miter wedge (the visible "cut") and read as
+  // the trap's slip-joint nuts.
+  for (const [i, center] of [
+    new Vector3(0, bendR, 0),
+    new Vector3(bendR * 2, bendR, 0),
+  ].entries()) {
+    const hub = new Mesh(new SphereGeometry(hubRadius, RADIAL_SEGMENTS, 12), material)
+    hub.name = `pipe-trap-hub-${i}`
+    hub.position.copy(center)
+    group.add(hub)
+  }
+
   return group
 }
 

packages/nodes/src/pipe-trap/tool.tsx

@@ -26,7 +26,7 @@ const PipeTrapTool = () => {
   const activeLevelId = useViewer((s) => s.selection.levelId)
   const [cursor, setCursor] = useState<[number, number, number] | null>(null)
   const [yaw, setYaw] = useState(0)
-  const [diameter] = useState(1.5)
+  const [diameter] = useState(pipeTrapDefinition.defaults().diameter)
   const yawRef = useRef(0)
   const diameterRef = useRef(diameter)
   diameterRef.current = diameter

packages/nodes/src/ridge-vent/move-tool.tsx

@@ -5,6 +5,7 @@ import {
   emitter,
   type RidgeVentNode,
   type RoofEvent,
+  type RoofNode,
   type RoofSegmentNode,
   sceneRegistry,
   useScene,
@@ -20,8 +21,13 @@ import {
   createRelativeRoofDrag,
   type RelativeRoofDragTarget,
   roofSegmentLocalToBuildingLocal,
+  snapRelativeRoofDragTarget,
 } from '../shared/relative-roof-drag'
 import { getSurfaceY } from '../shared/roof-surface'
+import {
+  clearRoofSurfacePlacementGuides,
+  publishRoofSurfaceNodePlacementGuides,
+} from '../shared/roof-surface-placement-guides'
 import RidgeVentPreview from './preview'
 
 type RidgeVentDragTarget = Pick<RelativeRoofDragTarget, 'segment' | 'localX'> & {
@@ -72,11 +78,13 @@ export default function MoveRidgeVentTool({ node }: { node: RidgeVentNode }) {
       lastTarget = null
       lastSnap = null
       setPreviewPos(null)
+      clearRoofSurfacePlacementGuides()
     }
 
     const resolveTarget = (event: RoofEvent): RidgeVentDragTarget | null => {
-      const target = roofDrag.resolve(event)
-      if (!target) return null
+      const rawTarget = roofDrag.resolve(event)
+      if (!rawTarget) return null
+      const target = snapRelativeRoofDragTarget(rawTarget, event.nativeEvent?.shiftKey === true)
       return {
         segment: target.segment,
         localX: target.localX,
@@ -111,6 +119,13 @@ export default function MoveRidgeVentTool({ node }: { node: RidgeVentNode }) {
           target.localZ,
         ]),
       )
+      publishRoofSurfaceNodePlacementGuides({
+        roof: event.node as RoofNode,
+        segment: target.segment,
+        center: [target.localX, target.localY, target.localZ],
+        node,
+        mode: 'linear-edge',
+      })
       event.stopPropagation()
     }
 
@@ -157,6 +172,7 @@ export default function MoveRidgeVentTool({ node }: { node: RidgeVentNode }) {
       if (obj) obj.visible = true
 
       triggerSFX('sfx:item-place')
+      clearRoofSurfacePlacementGuides()
       exitMoveMode()
       event.stopPropagation()
     }
@@ -175,6 +191,7 @@ export default function MoveRidgeVentTool({ node }: { node: RidgeVentNode }) {
         useScene.getState().deleteNode(node.id as AnyNodeId)
         useScene.temporal.getState().resume()
         markToolCancelConsumed()
+        clearRoofSurfacePlacementGuides()
         exitMoveMode()
         return
       }
@@ -194,6 +211,7 @@ export default function MoveRidgeVentTool({ node }: { node: RidgeVentNode }) {
 
       useScene.temporal.getState().resume()
       markToolCancelConsumed()
+      clearRoofSurfacePlacementGuides()
       exitMoveMode()
     }
 
@@ -223,6 +241,7 @@ export default function MoveRidgeVentTool({ node }: { node: RidgeVentNode }) {
 
       const obj = sceneRegistry.nodes.get(node.id)
       if (obj) obj.visible = true
+      clearRoofSurfacePlacementGuides()
       useScene.temporal.getState().resume()
     }
   }, [exitMoveMode, node])

packages/nodes/src/ridge-vent/tool.tsx

@@ -16,6 +16,11 @@ import * as THREE from 'three'
 import { resolveRidgeSnap } from '../shared/ridge-snap'
 import { RoofAttachmentFallbackPreview } from '../shared/roof-attachment-fallback-preview'
 import { resolveRoofSegmentHit } from '../shared/roof-segment-hit'
+import {
+  clearRoofSurfacePlacementGuides,
+  publishRoofSurfacePlacementGuides,
+  roofSurfaceFootprintFromNode,
+} from '../shared/roof-surface-placement-guides'
 import { ridgeVentDefinition } from './definition'
 import RidgeVentPreview from './preview'
 
@@ -73,6 +78,7 @@ const RidgeVentTool = () => {
       const snap = resolveRidgeSnap(hit.segment, hit.localX, hit.localZ)
       if (!snap) {
         setPreviewPos(null)
+        clearRoofSurfacePlacementGuides()
         return
       }
       const segObj = sceneRegistry.nodes.get(hit.segment.id)
@@ -96,6 +102,13 @@ const RidgeVentTool = () => {
 
       setPreviewYaw((event.node.rotation ?? 0) + (hit.segment.rotation ?? 0))
       setPreviewPos(worldToBuildingLocal(ridgeWorld[0], ridgeWorld[1], ridgeWorld[2]))
+      publishRoofSurfacePlacementGuides({
+        roof: event.node as RoofNode,
+        segment: hit.segment,
+        center: [snap.localX, hit.localY, snap.localZ],
+        footprint: roofSurfaceFootprintFromNode(previewNode),
+        mode: 'linear-edge',
+      })
       event.stopPropagation()
     }
 
@@ -122,6 +135,7 @@ const RidgeVentTool = () => {
       state.dirtyNodes.add(hit.segment.id as AnyNodeId)
       setSelection({ selectedIds: [vent.id] })
       triggerSFX('sfx:item-place')
+      clearRoofSurfacePlacementGuides()
       event.stopPropagation()
     }
 
@@ -133,8 +147,9 @@ const RidgeVentTool = () => {
       emitter.off('roof:move', updatePreview)
       emitter.off('roof:enter', updatePreview)
       emitter.off('roof:click', onClick)
+      clearRoofSurfacePlacementGuides()
     }
-  }, [activeBuildingId, setSelection])
+  }, [activeBuildingId, setSelection, previewNode])
 
   return (
     <>
@@ -150,7 +165,10 @@ const RidgeVentTool = () => {
           )
           return !!hit && !!resolveRidgeSnap(hit.segment, hit.localX, hit.localZ)
         }}
-        onInvalidTarget={() => setPreviewPos(null)}
+        onInvalidTarget={() => {
+          setPreviewPos(null)
+          clearRoofSurfacePlacementGuides()
+        }}
       />
       {activeBuildingId && previewPos && (
         <group position={previewPos}>

packages/nodes/src/shared/auto-fitting.test.ts

@@ -179,16 +179,20 @@ describe('planTeeAtRunBody', () => {
     expect(plan!.fitting.diameter2).toBe(6)
   })
 
-  test('45° drawn branch leaves square (projected perpendicular)', () => {
+  test('45° drawn branch builds a 45° lateral that follows the drawn run', () => {
     const run = trunk([
       [0, 0, 0],
       [6, 0, 0],
     ])
     const d = Math.SQRT1_2
+    // Drawn 45° downstream off the +X trunk. The tee becomes a lateral whose
+    // branch points along the drawn direction, so the new duct continues
+    // straight out of the collar instead of kinking square.
     const plan = planTeeAtRunBody(run, bodyHit(run, 0, [3, 0, 0]), [d, 0, d], ROUND_6)
     expect(plan).not.toBeNull()
+    expect(plan!.fitting.branchAngle).toBeCloseTo(45, 6)
     const branch = getDuctFittingPorts(plan!.fitting).find((p) => p.id === 'branch')!
-    expect(dot(branch.direction, [0, 0, 1])).toBeCloseTo(1, 6)
+    expect(dot(branch.direction, [d, 0, d])).toBeCloseTo(1, 6)
   })
 
   test('tap too close to a run end → null (use the end port instead)', () => {
@@ -502,10 +506,29 @@ describe('planElbowRealign', () => {
     expect(dot(outlet.direction, [0, 0, 1])).toBeCloseTo(1, 6)
   })
 
-  test('arrival needing a turn outside 15–90° → null', () => {
+  test('shallow arrival flattens the elbow toward a straight coupling', () => {
+    const elbow = existingElbow()
+    // Away nearly opposite the fixed inlet direction → turn < 15°. Unlike
+    // fresh-fitting creation, an existing elbow flattens to this small angle
+    // instead of bailing, so the run can be dragged dead straight.
+    const plan = planElbowRealign(elbow, 'outlet', [0.99, 0, 0.14])
+    expect(plan).not.toBeNull()
+    expect(plan!.update.data.angle).toBeLessThan(15)
+    expect(plan!.update.data.angle).toBeGreaterThanOrEqual(0)
+  })
+
+  test('run dragged into line flattens the elbow to a straight 0° coupling', () => {
+    const elbow = existingElbow()
+    // The free outlet pulled exactly opposite the mated inlet → no turn left.
+    const inlet = getDuctFittingPorts(elbow).find((p) => p.id === 'inlet')!
+    const away: Point = [-inlet.direction[0], -inlet.direction[1], -inlet.direction[2]]
+    const plan = planElbowRealign(elbow, 'outlet', away)
+    expect(plan).not.toBeNull()
+    expect(plan!.update.data.angle).toBeCloseTo(0, 5)
+  })
+
+  test('a back-turn sharper than 90° still bails', () => {
     const elbow = existingElbow()
-    // Away nearly opposite the fixed inlet direction → turn < 15°.
-    expect(planElbowRealign(elbow, 'outlet', [0.99, 0, 0.14])).toBeNull()
     // Away aligned WITH the fixed collar direction → turn > 90°.
     expect(planElbowRealign(elbow, 'outlet', [-0.99, 0, 0.14])).toBeNull()
   })

packages/nodes/src/shared/auto-fitting.ts

@@ -202,9 +202,10 @@ export type TeeTapPlan = {
  * upstream half (trimmed one leg short), a new duct-segment node carries
  * the downstream half (starting one leg after), and the tee's run legs
  * bridge the gap with its junction exactly on the centerline hit. The
- * branch collar points along `awayDir` projected perpendicular to the
- * trunk axis — a tee's branch is square to its run, so a 45° drawn
- * branch leaves square and the drawn duct continues from the collar.
+ * branch collar follows `awayDir`: the tee becomes a lateral whose
+ * `branchAngle` (clamped to the buildable 45–135° range) matches the turn
+ * the drawn run makes off the trunk, so the new duct continues straight
+ * out of the collar instead of kinking square.
  *
  * Returns null when the tap can't be built: too close to the segment's
  * ends (no room for the run legs — join the end port instead), or the
@@ -223,13 +224,38 @@ export function planTeeAtRunBody(
   if (axis.lengthSq() < 1e-10) return null
   axis.normalize()
 
-  // Branch leaves square to the run: project the drawn direction onto
-  // the plane perpendicular to the trunk axis.
-  const away = new Vector3(...awayDir)
+  // The branch FOLLOWS the drawn run's angle: the tee becomes a lateral
+  // whose `branchAngle` matches the actual turn the new run makes off the
+  // trunk, instead of forcing a square tap and kinking the drawn duct.
+  // `branchDir` is the drawn direction's component square to the trunk —
+  // it sets the PLANE the branch leans in; the lean amount comes from how
+  // much of `away` runs along the trunk vs. across it.
+  const away = new Vector3(...awayDir).normalize()
+  if (away.lengthSq() < 1e-10) return null
   const branchDir = away.clone().addScaledVector(axis, -away.dot(axis))
   if (branchDir.lengthSq() < 1e-6) return null
   branchDir.normalize()
 
+  // `branchAngle` is measured off the +X (outlet / downstream) axis in the
+  // tee's local XZ plane, where +Z is the branch's square direction. So
+  // the angle is atan2(across-trunk component, along-trunk component) of
+  // the drawn run — 90° when square, <90° leaning downstream, >90° leaning
+  // upstream. Clamped to the schema's buildable 45–135° lateral range.
+  const acrossLen = Math.sqrt(Math.max(0, 1 - away.dot(axis) ** 2))
+  const branchAngleDeg = Math.min(
+    135,
+    Math.max(45, (Math.atan2(acrossLen, away.dot(axis)) * 180) / Math.PI),
+  )
+  const phi = (branchAngleDeg * Math.PI) / 180
+  // Actual branch outward direction at the (possibly clamped) angle — the
+  // new run starts at its collar. When unclamped this equals `away`, so
+  // the drawn duct continues straight out of the tee.
+  const branchOutDir = axis
+    .clone()
+    .multiplyScalar(Math.cos(phi))
+    .addScaledVector(branchDir, Math.sin(phi))
+    .normalize()
+
   // Room check: both run legs must fit inside the hit segment with a
   // margin of real duct on each side.
   // Rect trunks present their area-equivalent round size at joints
@@ -244,8 +270,9 @@ export function planTeeAtRunBody(
   const MIN_STUB = 0.08
   if (upstream < legRun + MIN_STUB || downstream < legRun + MIN_STUB) return null
 
-  // Local +X (the run) → axis, local +Z (the branch) → branchDir. Both
-  // pairs are perpendicular, so the basis transfer is exact.
+  // Local +X (the run) → axis, local +Z (the branch plane) → branchDir.
+  // Both pairs are perpendicular, so the basis transfer is exact and the
+  // local branch leg (cos φ, sin φ) lands on `branchOutDir` in world.
   const localFrame = frame(new Vector3(1, 0, 0), new Vector3(0, 0, 1))
   const worldFrame = frame(axis, branchDir)
   if (!localFrame || !worldFrame) return null
@@ -256,7 +283,7 @@ export function planTeeAtRunBody(
 
   const inletTrim = P.clone().addScaledVector(axis, -legRun)
   const outletTrim = P.clone().addScaledVector(axis, legRun)
-  const collar = P.clone().addScaledVector(branchDir, legBranch)
+  const collar = P.clone().addScaledVector(branchOutDir, legBranch)
 
   const fitting = DuctFittingNode.parse({
     object: 'node',
@@ -273,6 +300,7 @@ export function planTeeAtRunBody(
     width2: branch.width,
     height2: branch.height,
     diameter2: branchDiameterIn,
+    branchAngle: branchAngleDeg,
     ductMaterial: 'sheet-metal',
     system: trunk.system,
     position: [P.x, P.y, P.z],
@@ -462,24 +490,30 @@ export type ElbowRealignPlan = {
   collarPoint: Point
 }
 
+export type PipeElbowRealignPlan = {
+  update: { id: PipeFittingNode['id']; data: { angle: number; rotation: Point } }
+  collarPoint: Point
+}
+
 /**
- * Re-aim an existing elbow whose open collar a new run just snapped
- * onto. The junction stays put and the OTHER collar keeps its exact
- * position + direction (it's mated to something), while the snapped
- * collar swings to face the incoming run — the elbow's `angle` adjusts
- * to whatever turn that requires.
+ * Shared elbow re-aim geometry for duct AND pipe elbows — both share the
+ * exact same local convention (inlet -X, outlet turned `angle`° in XZ,
+ * 15–90° buildable range), so only the collar leg length differs.
  *
- * Geometry: with the fixed collar's outward direction f and the desired
- * free direction `awayDir`, the elbow's local inlet/outlet pair subtends
- * 180° − angle, so the new turn is θ = 180° − ∠(f, away). Buildable only
- * while θ stays in the elbow's 15–90° range — otherwise null and the
- * caller leaves the joint as a plain butt joint.
+ * The junction stays put and the OTHER collar keeps its exact position +
+ * direction (it's mated to something), while the snapped collar swings to
+ * face `awayDir` — the elbow's `angle` adjusts to whatever turn that
+ * requires. Geometry: with the fixed collar's outward direction f and the
+ * desired free direction `awayDir`, the elbow's local inlet/outlet pair
+ * subtends 180° − angle, so the new turn is θ = 180° − ∠(f, away).
+ * Buildable only while θ stays in 15–90° — otherwise null.
  */
-export function planElbowRealign(
-  elbow: DuctFittingNode,
+function planElbowRealignCore(
+  elbow: { fittingType: string; rotation: Point; angle: number; position: Point },
   snappedPortId: string,
   awayDir: Point,
-): ElbowRealignPlan | null {
+  leg: number,
+): { angle: number; rotation: Point; collarPoint: Point } | null {
   if (elbow.fittingType !== 'elbow') return null
   if (snappedPortId !== 'inlet' && snappedPortId !== 'outlet') return null
 
@@ -498,10 +532,14 @@ export function planElbowRealign(
   )
   const fixedWorld = snappedPortId === 'inlet' ? outletWorld : inletWorld
 
-  // New turn from the fixed collar / free collar pair.
+  // New turn from the fixed collar / free collar pair. Unlike fresh-fitting
+  // creation (which butt-joins near-straight runs rather than minting a flat
+  // elbow), an EXISTING elbow may flatten all the way to 0° — a straight
+  // coupling — when its run is dragged into line, so only the upper bound
+  // guards here.
   const spread = fixedWorld.angleTo(away)
   const turnNew = Math.PI - spread
-  if (turnNew < MIN_TURN_RAD || turnNew > MAX_TURN_RAD) return null
+  if (turnNew > MAX_TURN_RAD) return null
 
   // Local outward pair at the new angle, ordered (fixed, free) to match
   // the world pair.
@@ -512,23 +550,115 @@ export function planElbowRealign(
 
   const localFrame = frame(fixedLocal, freeLocal)
   const worldFrame = frame(fixedWorld, away)
-  if (!localFrame || !worldFrame) return null
-  const rotation = new Quaternion().setFromRotationMatrix(
-    worldFrame.multiply(localFrame.transpose()),
-  )
+  // At (near-)straight the two collars are collinear, so the bend plane is
+  // undefined and `frame()` returns null. Map the fixed collar's local axis
+  // onto its world direction instead; the free collar (antiparallel) lands
+  // on `away` for free, and a straight coupling's roll is arbitrary.
+  const rotation =
+    localFrame && worldFrame
+      ? new Quaternion().setFromRotationMatrix(worldFrame.multiply(localFrame.transpose()))
+      : new Quaternion().setFromUnitVectors(fixedLocal, fixedWorld)
   const euler = new Euler().setFromQuaternion(rotation)
 
-  const leg = fittingLegLength(elbow.diameter)
   const collar = new Vector3(...elbow.position).addScaledVector(away, leg)
 
   return {
-    update: {
-      id: elbow.id,
-      data: {
-        angle: Math.min(90, (turnNew * 180) / Math.PI),
-        rotation: [euler.x, euler.y, euler.z],
-      },
-    },
+    angle: Math.max(0, Math.min(90, (turnNew * 180) / Math.PI)),
+    rotation: [euler.x, euler.y, euler.z],
+    collarPoint: [collar.x, collar.y, collar.z],
+  }
+}
+
+/** Re-aim a DUCT elbow whose open collar a new run just snapped onto. */
+export function planElbowRealign(
+  elbow: DuctFittingNode,
+  snappedPortId: string,
+  awayDir: Point,
+): ElbowRealignPlan | null {
+  const core = planElbowRealignCore(elbow, snappedPortId, awayDir, fittingLegLength(elbow.diameter))
+  if (!core) return null
+  return {
+    update: { id: elbow.id, data: { angle: core.angle, rotation: core.rotation } },
+    collarPoint: core.collarPoint,
+  }
+}
+
+/** Re-aim a DWV PIPE elbow — same geometry, pipe collar leg length. */
+export function planPipeElbowRealign(
+  elbow: PipeFittingNode,
+  snappedPortId: string,
+  awayDir: Point,
+): PipeElbowRealignPlan | null {
+  const core = planElbowRealignCore(
+    elbow,
+    snappedPortId,
+    awayDir,
+    pipeFittingLegLength(elbow.diameter),
+  )
+  if (!core) return null
+  return {
+    update: { id: elbow.id, data: { angle: core.angle, rotation: core.rotation } },
+    collarPoint: core.collarPoint,
+  }
+}
+
+// ─── Tee branch re-aim (run dragged off an existing tee's branch) ────
+
+export type TeeBranchRealignPlan = {
+  /** Patch for the existing tee: new branch lean angle. The run axis and
+   *  the tee's orientation stay fixed (inlet / outlet stay mated to the
+   *  trunk) — only `branchAngle` changes. */
+  update: { id: DuctFittingNode['id']; data: { branchAngle: number } }
+  /** Where the branch collar lands at the new angle — the dragged run's
+   *  mated end rides here. */
+  collarPoint: Point
+}
+
+/**
+ * Re-aim a duct TEE's branch to follow a run dragged off its branch collar.
+ *
+ * Unlike the elbow (which re-orients its whole body), a tee's run legs stay
+ * mated to the trunk, so the body orientation is FIXED: the branch can only
+ * swing within the tee's local XZ plane (local +X = run axis, +Z = the
+ * square branch direction). `awayDir` (junction → dragged end) is projected
+ * onto that plane and read as the lean angle off +X — 90° square, <90°
+ * leaning downstream toward the outlet, >90° upstream toward the inlet —
+ * clamped to the schema's buildable 45–135° lateral range.
+ */
+export function planTeeBranchRealign(
+  tee: DuctFittingNode,
+  awayDir: Point,
+): TeeBranchRealignPlan | null {
+  if (tee.fittingType !== 'tee') return null
+  const away = new Vector3(...awayDir)
+  if (away.lengthSq() < 1e-10) return null
+  away.normalize()
+
+  const rot = new Quaternion().setFromEuler(
+    new Euler(tee.rotation[0], tee.rotation[1], tee.rotation[2]),
+  )
+  const runAxis = new Vector3(1, 0, 0).applyQuaternion(rot)
+  const squareDir = new Vector3(0, 0, 1).applyQuaternion(rot)
+  const ax = away.dot(runAxis)
+  const az = away.dot(squareDir)
+  // Drag straight along the run axis (no square component) leaves the lean
+  // undefined — hold the frame.
+  if (Math.abs(ax) < 1e-9 && Math.abs(az) < 1e-9) return null
+
+  const branchAngleDeg = Math.min(135, Math.max(45, (Math.atan2(az, ax) * 180) / Math.PI))
+  const phi = (branchAngleDeg * Math.PI) / 180
+  const branchDir = runAxis
+    .clone()
+    .multiplyScalar(Math.cos(phi))
+    .addScaledVector(squareDir, Math.sin(phi))
+    .normalize()
+  const collar = new Vector3(...tee.position).addScaledVector(
+    branchDir,
+    fittingLegLength(tee.diameter2),
+  )
+
+  return {
+    update: { id: tee.id, data: { branchAngle: branchAngleDeg } },
     collarPoint: [collar.x, collar.y, collar.z],
   }
 }

packages/nodes/src/shared/auto-offset-tag.test.ts

@@ -0,0 +1,155 @@
+import { describe, expect, it } from 'bun:test'
+import type { AnyNode, AnyNodeId } from '@pascal-app/core'
+import {
+  AUTO_OFFSET_KEY,
+  type AutoOffsetTag,
+  autoOffsetInvalidationUpdates,
+  newAutoOffsetGroupId,
+  readAutoOffsetTag,
+  translateAutoOffsetBase,
+  withAutoOffsetTag,
+  withoutAutoOffsetTag,
+} from './auto-offset-tag'
+
+const sampleTag = (): AutoOffsetTag => ({
+  group: 'aoff_test',
+  dy: 0.6,
+  minted: ['duct-fitting_a' as AnyNodeId, 'duct-segment_r' as AnyNodeId],
+  base: [{ id: 'duct-segment_run' as AnyNodeId, data: { path: [[0, 2, 0]] } }],
+})
+
+describe('auto-offset tag round-trip', () => {
+  it('writes then reads back an identical tag', () => {
+    const tag = sampleTag()
+    const meta = withAutoOffsetTag({ existing: 1 }, tag)
+    expect(meta.existing).toBe(1)
+    expect(readAutoOffsetTag({ metadata: meta })).toEqual(tag)
+  })
+
+  it('replaces a prior tag rather than nesting it', () => {
+    const first = sampleTag()
+    const second: AutoOffsetTag = { ...first, dy: 1.2, group: 'aoff_two' }
+    const meta = withAutoOffsetTag(withAutoOffsetTag({}, first), second)
+    expect(readAutoOffsetTag({ metadata: meta })).toEqual(second)
+  })
+
+  it('removes the tag while preserving other metadata keys', () => {
+    const meta = withAutoOffsetTag({ keep: 'me' }, sampleTag())
+    const stripped = withoutAutoOffsetTag(meta)
+    expect(stripped).toEqual({ keep: 'me' })
+    expect(stripped[AUTO_OFFSET_KEY]).toBeUndefined()
+    expect(readAutoOffsetTag({ metadata: stripped })).toBeNull()
+  })
+})
+
+describe('translateAutoOffsetBase', () => {
+  it('moves path and position patches with a rigid offset translation', () => {
+    const tag: AutoOffsetTag = {
+      ...sampleTag(),
+      base: [
+        {
+          id: 'duct-segment_run' as AnyNodeId,
+          data: {
+            path: [
+              [0, 0, 0],
+              [2, 0, 0],
+            ],
+          },
+        },
+        {
+          id: 'duct-fitting_elbow' as AnyNodeId,
+          data: { position: [4, 1, 5], angle: 90 },
+        },
+      ],
+    }
+
+    const moved = translateAutoOffsetBase(tag, [1, 0, -2])
+
+    expect(moved.base[0]?.data.path).toEqual([
+      [1, 0, -2],
+      [3, 0, -2],
+    ])
+    expect(moved.base[1]?.data.position).toEqual([5, 1, 3])
+    expect(moved.base[1]?.data.angle).toBe(90)
+  })
+})
+
+describe('autoOffsetInvalidationUpdates', () => {
+  it('clears owner tags when a generated offset part is edited manually', () => {
+    const owner = {
+      id: 'duct-segment_owner' as AnyNodeId,
+      metadata: withAutoOffsetTag({}, sampleTag()),
+    } as AnyNode
+    const other = {
+      id: 'duct-segment_other' as AnyNodeId,
+      metadata: withAutoOffsetTag({}, { ...sampleTag(), minted: ['duct-fitting_other'] }),
+    } as AnyNode
+
+    const updates = autoOffsetInvalidationUpdates(
+      {
+        [owner.id]: owner,
+        [other.id]: other,
+      },
+      'duct-fitting_a' as AnyNodeId,
+    )
+
+    expect(updates).toHaveLength(1)
+    expect(updates[0]?.id).toBe(owner.id)
+    expect(readAutoOffsetTag({ metadata: updates[0]?.data.metadata })).toBeNull()
+  })
+
+  it('clears owner tags when a stored base participant is edited manually', () => {
+    const owner = {
+      id: 'duct-segment_owner' as AnyNodeId,
+      metadata: withAutoOffsetTag(
+        {},
+        {
+          ...sampleTag(),
+          base: [
+            { id: 'duct-segment_owner' as AnyNodeId, data: { path: [[0, 0, 0]] } },
+            { id: 'duct-fitting_corner' as AnyNodeId, data: { position: [1, 0, 0] } },
+          ],
+        },
+      ),
+    } as AnyNode
+
+    const updates = autoOffsetInvalidationUpdates(
+      { [owner.id]: owner },
+      'duct-fitting_corner' as AnyNodeId,
+    )
+
+    expect(updates).toHaveLength(1)
+    expect(updates[0]?.id).toBe(owner.id)
+    expect(readAutoOffsetTag({ metadata: updates[0]?.data.metadata })).toBeNull()
+  })
+})
+
+describe('readAutoOffsetTag guards', () => {
+  it('returns null for missing / empty metadata', () => {
+    expect(readAutoOffsetTag(null)).toBeNull()
+    expect(readAutoOffsetTag(undefined)).toBeNull()
+    expect(readAutoOffsetTag({})).toBeNull()
+    expect(readAutoOffsetTag({ metadata: {} })).toBeNull()
+  })
+
+  it('returns null for a malformed tag (wrong field shapes)', () => {
+    const bad = [
+      { group: 1, dy: 0, minted: [], base: [] },
+      { group: 'g', dy: 'x', minted: [], base: [] },
+      { group: 'g', dy: 0, minted: 'nope', base: [] },
+      { group: 'g', dy: 0, minted: [], base: {} },
+    ]
+    for (const tag of bad) {
+      expect(readAutoOffsetTag({ metadata: { [AUTO_OFFSET_KEY]: tag } })).toBeNull()
+    }
+  })
+})
+
+describe('newAutoOffsetGroupId', () => {
+  it('produces a prefixed, unique-ish id', () => {
+    const a = newAutoOffsetGroupId()
+    const b = newAutoOffsetGroupId()
+    expect(a.startsWith('aoff_')).toBe(true)
+    expect(a).not.toBe(b)
+  })
+})