feat: HVAC ductwork + DWV plumbing systems (#402)

Adds two new MEP node families (HVAC ductwork, DWV plumbing) built on a shared port-connectivity model. Co-authored by @sudhir9297.

apps/editor/components/build-tab.tsx

@@ -2,6 +2,7 @@
 
 import { nodeRegistry } from '@pascal-app/core'
 import { MaterialPaintPanel, triggerSFX, useEditor } from '@pascal-app/editor'
+import { useLiquidLineToolOptions } from '@pascal-app/nodes'
 import Image from 'next/image'
 import { useCallback, useEffect, useMemo, useRef, useState } from 'react'
 import {
@@ -30,17 +31,40 @@ type BuildToolKind =
   | 'shelf'
   | 'spawn'
 
+/**
+ * MEP (mechanical / plumbing) tool kinds surfaced under the Build tab's "MEP"
+ * group tile — its own sub-grid, like Roof's "Features".
+ */
+type MepToolKind =
+  | 'duct-segment'
+  | 'duct-fitting'
+  | 'duct-terminal'
+  | 'hvac-equipment'
+  | 'lineset'
+  | 'liquid-line'
+  | 'pipe-segment'
+  | 'pipe-fitting'
+
 type BuildType = {
-  /** Selection id — equals `kind` for tool types, `'painting'` for paint mode. */
+  /** Selection id — equals `kind` for tool types, `'painting'` for paint mode, `'mep'` for the MEP group. */
   id: string
   label: string
+  /** Raster asset tile (legacy Build sidebar artwork). */
   iconSrc: string
-  /** Present for structure-tool types (absent for the paint mode). */
+  /** Present for structure-tool types (absent for paint mode and the MEP group). */
   kind?: BuildToolKind
   /** Non-placement special mode. */
   mode?: 'material-paint'
 }
 
+type MepItem = {
+  /** Selection id — equals `kind`. */
+  id: string
+  label: string
+  iconSrc: string
+  kind: MepToolKind
+}
+
 // Same icons + ordering as the community Build sidebar, minus presets.
 const BUILD_TYPES: BuildType[] = [
   { id: 'wall', label: 'Wall', iconSrc: '/icons/wall.png', kind: 'wall' },
@@ -55,14 +79,32 @@ const BUILD_TYPES: BuildType[] = [
   { id: 'column', label: 'Column', iconSrc: '/icons/column.png', kind: 'column' },
   { id: 'shelf', label: 'Shelf', iconSrc: '/icons/shelf.png', kind: 'shelf' },
   { id: 'spawn', label: 'Spawn Point', iconSrc: '/icons/spawn-point.png', kind: 'spawn' },
+  // Group tile — no tool of its own; opens the MEP sub-grid below (like Roof).
+  { id: 'mep', label: 'MEP', iconSrc: '/icons/HVAC.png' },
   { id: 'painting', label: 'Painting', iconSrc: '/icons/paint.png', mode: 'material-paint' },
 ]
 
+// MEP sub-grid surfaced under the "MEP" tile — same icons + ordering the MEP
+// tools had in the community Build sidebar.
+const MEP_ITEMS: MepItem[] = [
+  { id: 'duct-segment', label: 'Duct', iconSrc: '/icons/duct.png', kind: 'duct-segment' },
+  {
+    id: 'duct-terminal',
+    label: 'Register',
+    iconSrc: '/icons/registers.png',
+    kind: 'duct-terminal',
+  },
+  { id: 'hvac-equipment', label: 'HVAC Unit', iconSrc: '/icons/HVAC.png', kind: 'hvac-equipment' },
+  { id: 'lineset', label: 'Lineset', iconSrc: '/icons/lineset.png', kind: 'lineset' },
+  { id: 'liquid-line', label: 'Liquid Line', iconSrc: '/icons/lineset.png', kind: 'liquid-line' },
+  { id: 'pipe-segment', label: 'DWV Pipe', iconSrc: '/icons/dwv-pipes.png', kind: 'pipe-segment' },
+]
+
 /**
  * Activate a raw structure draw/cursor tool. Mirrors the editor's own
  * structure-tool activation (`setPhase`/`setStructureLayer`/`setMode`/`setTool`).
  */
-function activateBuildTool(kind: BuildToolKind): void {
+function activateBuildTool(kind: BuildToolKind | MepToolKind): void {
   const ed = useEditor.getState()
   ed.setPhase('structure')
   ed.setStructureLayer('elements')
@@ -111,10 +153,31 @@ function activateRoofFeatureTool(kind: string): void {
 export function BuildTab() {
   const activeTool = useEditor((s) => s.tool)
   const mode = useEditor((s) => s.mode)
-  // Which build tile's panel is showing. Roof is the only tile with a panel
-  // (its Features group); others arm a tool and show nothing below.
+  const follow = useLiquidLineToolOptions((s) => s.follow)
+  const toggleFollow = useLiquidLineToolOptions((s) => s.toggleFollow)
+  // Which build tile's panel is showing. Roof (Features) and MEP (its tool
+  // sub-grid) are the tiles with a panel; others arm a tool and show nothing
+  // below.
   const [selectedTypeId, setSelectedTypeId] = useState<string | null>(null)
 
+  // The fitting / follow tools are armed from a segment's panel, not a grid
+  // tile — keep the segment tile lit so the panel (and the way back) stays
+  // visible.
+  const ductContext =
+    mode === 'build' && (activeTool === 'duct-segment' || activeTool === 'duct-fitting')
+  const pipeContext =
+    mode === 'build' && (activeTool === 'pipe-segment' || activeTool === 'pipe-fitting')
+  const liquidLineContext = mode === 'build' && activeTool === 'liquid-line'
+
+  const isMepItemActive = (item: MepItem) =>
+    item.kind === 'duct-segment'
+      ? ductContext
+      : item.kind === 'pipe-segment'
+        ? pipeContext
+        : item.kind === 'liquid-line'
+          ? liquidLineContext
+          : mode === 'build' && activeTool === item.kind
+
   // Read at render time (not module scope): the registry is populated by the
   // app bootstrap, so enumerating earlier would race it and see no kinds.
   const roofFeatures = useMemo<RoofFeature[]>(() => {
@@ -141,6 +204,10 @@ export function BuildTab() {
   const handleTypeClick = useCallback((type: BuildType) => {
     if (type.mode === 'material-paint') {
       activatePaintMode()
+    } else if (type.id === 'mep') {
+      // MEP is a group tile: arm its first tool so a usable tool is active
+      // (and we leave any prior paint mode), then reveal the MEP sub-grid.
+      activateBuildTool('duct-segment')
     } else if (type.kind) {
       activateBuildTool(type.kind)
     }
@@ -250,6 +317,137 @@ export function BuildTab() {
             </div>
           </TooltipProvider>
         </div>
+      ) : selectedTypeId === 'mep' ? (
+        <div className="flex min-h-0 flex-1 flex-col gap-2 overflow-y-auto">
+          <div className="px-0.5 pt-1 font-medium text-muted-foreground text-xs">MEP</div>
+          <TooltipProvider delayDuration={0} disableHoverableContent>
+            <div
+              className="grid gap-1.5 px-0.5"
+              style={{ gridTemplateColumns: 'repeat(auto-fill, minmax(56px, 1fr))' }}
+            >
+              {MEP_ITEMS.map((item) => {
+                const active = isMepItemActive(item)
+                return (
+                  <Tooltip key={item.id}>
+                    <TooltipTrigger asChild>
+                      <button
+                        className={cn(
+                          'group relative flex aspect-square items-center justify-center rounded-xl transition-all duration-200',
+                          active
+                            ? 'bg-primary/10 ring-1 ring-primary/50'
+                            : 'bg-muted/40 opacity-70 grayscale hover:bg-muted hover:opacity-100 hover:grayscale-0',
+                        )}
+                        onClick={() => {
+                          triggerSFX('sfx:menu-click')
+                          activateBuildTool(item.kind)
+                        }}
+                        onMouseEnter={() => triggerSFX('sfx:menu-hover')}
+                        type="button"
+                      >
+                        <Image
+                          alt={item.label}
+                          className="size-full object-contain transition-transform duration-200 group-hover:scale-110"
+                          height={48}
+                          src={item.iconSrc}
+                          width={48}
+                        />
+                      </button>
+                    </TooltipTrigger>
+                    <TooltipContent className="pointer-events-none" side="top">
+                      {item.label}
+                    </TooltipContent>
+                  </Tooltip>
+                )
+              })}
+            </div>
+          </TooltipProvider>
+
+          {ductContext ? (
+            <div className="flex flex-col gap-1.5">
+              <span className="text-muted-foreground text-xs">Duct</span>
+              <button
+                className={cn(
+                  'flex items-center gap-2 rounded-lg px-3 py-2 text-sm transition-all duration-200',
+                  activeTool === 'duct-fitting'
+                    ? 'bg-primary/10 ring-1 ring-primary/50'
+                    : 'bg-muted/40 hover:bg-muted',
+                )}
+                onClick={() => {
+                  triggerSFX('sfx:menu-click')
+                  activateBuildTool(activeTool === 'duct-fitting' ? 'duct-segment' : 'duct-fitting')
+                }}
+                onMouseEnter={() => triggerSFX('sfx:menu-hover')}
+                type="button"
+              >
+                <Image
+                  alt=""
+                  aria-hidden
+                  className="size-4 object-contain"
+                  height={16}
+                  src="/icons/duct-fitting.png"
+                  width={16}
+                />
+                Add Fitting
+              </button>
+            </div>
+          ) : null}
+
+          {pipeContext ? (
+            <div className="flex flex-col gap-1.5">
+              <span className="text-muted-foreground text-xs">DWV Pipe</span>
+              <button
+                className={cn(
+                  'flex items-center gap-2 rounded-lg px-3 py-2 text-sm transition-all duration-200',
+                  activeTool === 'pipe-fitting'
+                    ? 'bg-primary/10 ring-1 ring-primary/50'
+                    : 'bg-muted/40 hover:bg-muted',
+                )}
+                onClick={() => {
+                  triggerSFX('sfx:menu-click')
+                  activateBuildTool(activeTool === 'pipe-fitting' ? 'pipe-segment' : 'pipe-fitting')
+                }}
+                onMouseEnter={() => triggerSFX('sfx:menu-hover')}
+                type="button"
+              >
+                <Image
+                  alt=""
+                  aria-hidden
+                  className="size-4 object-contain"
+                  height={16}
+                  src="/icons/duct-fitting.png"
+                  width={16}
+                />
+                Add Fitting
+              </button>
+            </div>
+          ) : null}
+
+          {liquidLineContext ? (
+            <div className="flex flex-col gap-1.5">
+              <span className="text-muted-foreground text-xs">Liquid Line</span>
+              <button
+                className={cn(
+                  'flex items-center justify-between gap-2 rounded-lg px-3 py-2 text-sm transition-all duration-200',
+                  follow ? 'bg-primary/10 ring-1 ring-primary/50' : 'bg-muted/40 hover:bg-muted',
+                )}
+                onClick={() => {
+                  triggerSFX('sfx:menu-click')
+                  toggleFollow()
+                }}
+                onMouseEnter={() => triggerSFX('sfx:menu-hover')}
+                type="button"
+              >
+                <span>Follow lineset</span>
+                <span className="text-muted-foreground text-xs">{follow ? 'On' : 'Off'}</span>
+              </button>
+              <span className="px-1 text-[11px] text-muted-foreground">
+                {follow
+                  ? 'Click a lineset to lay the line beside it.'
+                  : 'Trace a line alongside an existing lineset (F).'}
+              </span>
+            </div>
+          ) : null}
+        </div>
       ) : null}
     </div>
   )

apps/ifc-converter/components/IfcConverter.tsx

@@ -115,6 +115,7 @@ export default function IfcConverter() {
     return results
   }, [pascalData, searchQuery])
 
+  // biome-ignore lint/correctness/useExhaustiveDependencies: runs once on mount to load the initial file from the URL.
   useEffect(() => {
     const params = new URLSearchParams(window.location.search)
     const requested = params.get('file')
@@ -201,6 +202,7 @@ export default function IfcConverter() {
     }
   }
 
+  // biome-ignore lint/correctness/useExhaustiveDependencies: stable drop handler; handleFile only calls setState setters, so a mount-time capture stays correct.
   const handleDrop = useCallback((e: React.DragEvent) => {
     e.preventDefault()
     setIsDragging(false)
@@ -234,7 +236,7 @@ export default function IfcConverter() {
     const url = URL.createObjectURL(blob)
     const a = document.createElement('a')
     a.href = url
-    a.download = fileName.replace('.ifc', '') + '_pascal.json'
+    a.download = `${fileName.replace('.ifc', '')}_pascal.json`
     a.click()
     URL.revokeObjectURL(url)
   }

apps/ifc-converter/next-env.d.ts

@@ -1,6 +1,6 @@
 /// <reference types="next" />
 /// <reference types="next/image-types/global" />
-import "./.next/types/routes.d.ts";
+import "./.next/dev/types/routes.d.ts";
 
 // NOTE: This file should not be edited
 // see https://nextjs.org/docs/app/api-reference/config/typescript for more information.

packages/core/src/events/bus.ts

@@ -11,13 +11,22 @@ import type {
   DoorNode,
   DormerNode,
   DownspoutNode,
+  DuctFittingNode,
+  DuctSegmentNode,
+  DuctTerminalNode,
   ElevatorNode,
   EyebrowVentNode,
   FenceNode,
   GuideNode,
   GutterNode,
+  HvacEquipmentNode,
   ItemNode,
   LevelNode,
+  LinesetNode,
+  LiquidLineNode,
+  PipeFittingNode,
+  PipeSegmentNode,
+  PipeTrapNode,
   RidgeVentNode,
   RoofNode,
   RoofSegmentNode,
@@ -107,6 +116,15 @@ export type SolarPanelEvent = NodeEvent<SolarPanelNode>
 export type SkylightEvent = NodeEvent<SkylightNode>
 export type DormerEvent = NodeEvent<DormerNode>
 export type DownspoutEvent = NodeEvent<DownspoutNode>
+export type DuctSegmentEvent = NodeEvent<DuctSegmentNode>
+export type DuctFittingEvent = NodeEvent<DuctFittingNode>
+export type DuctTerminalEvent = NodeEvent<DuctTerminalNode>
+export type HvacEquipmentEvent = NodeEvent<HvacEquipmentNode>
+export type PipeSegmentEvent = NodeEvent<PipeSegmentNode>
+export type PipeFittingEvent = NodeEvent<PipeFittingNode>
+export type PipeTrapEvent = NodeEvent<PipeTrapNode>
+export type LinesetEvent = NodeEvent<LinesetNode>
+export type LiquidLineEvent = NodeEvent<LiquidLineNode>
 
 // Event suffixes - exported for use in hooks
 export const eventSuffixes = [
@@ -261,6 +279,15 @@ type EditorEvents = GridEvents &
   NodeEvents<'skylight', SkylightEvent> &
   NodeEvents<'dormer', DormerEvent> &
   NodeEvents<'downspout', DownspoutEvent> &
+  NodeEvents<'duct-segment', DuctSegmentEvent> &
+  NodeEvents<'duct-fitting', DuctFittingEvent> &
+  NodeEvents<'duct-terminal', DuctTerminalEvent> &
+  NodeEvents<'hvac-equipment', HvacEquipmentEvent> &
+  NodeEvents<'pipe-segment', PipeSegmentEvent> &
+  NodeEvents<'pipe-fitting', PipeFittingEvent> &
+  NodeEvents<'pipe-trap', PipeTrapEvent> &
+  NodeEvents<'lineset', LinesetEvent> &
+  NodeEvents<'liquid-line', LiquidLineEvent> &
   CameraControlEvents &
   ToolEvents &
   GuideEvents &

packages/core/src/registry/index.ts

@@ -56,6 +56,7 @@ export type {
   Capabilities,
   CapabilityCtx,
   CuttableConfig,
+  DistributionRole,
   DragAction,
   EditorCtx,
   FloorPlacedConfig,
@@ -85,6 +86,7 @@ export type {
   MovableConfig,
   NodeCategory,
   NodeDefinition,
+  NodePort,
   NodeRegistry,
   PaintCapability,
   PaintEffectiveMaterialArgs,

packages/core/src/registry/types.ts

@@ -168,6 +168,40 @@ export type FloorplanStyle = {
   cursor?: string
 }
 
+// ─── NodePort ────────────────────────────────────────────────────────
+//
+// A typed connection point exposed by a node — the open end of a duct
+// run, the collar of a fitting, the supply plenum of an air handler.
+// Ports are what placement tools snap to and what a future system graph
+// walks to decide connectivity.
+//
+// Coordinates are LEVEL-LOCAL meters — the same space duct paths and
+// grid events use. Kinds whose schema stores a node transform
+// (`position` / `rotation`) apply it themselves inside `def.ports` so
+// consumers never need to know how a kind stores its placement.
+
+export type NodePort = {
+  /** Stable identifier within the node, e.g. 'start', 'end', 'branch'. */
+  id: string
+  /** Level-local meters. */
+  position: readonly [number, number, number]
+  /** Unit vector pointing OUT of the port (away from the node body). */
+  direction: readonly [number, number, number]
+  /** Nominal connection diameter in inches. For a rect / oval port this is
+   *  the area-equivalent round size, so a round run still mates sensibly. */
+  diameter: number
+  /** Which distribution loop the port belongs to, e.g. 'supply' | 'return'. */
+  system?: string
+  /** Cross-section of the connection. Omitted = round at `diameter`. A duct
+   *  run joining a rect / oval port adopts this shape and rolls its
+   *  cross-section to line up with the collar. */
+  shape?: 'round' | 'rect' | 'oval'
+  /** Rect / oval cross-section in inches: width is the collar's horizontal
+   *  face at roll 0, height the vertical one. */
+  width?: number
+  height?: number
+}
+
 // ─── ToolHint ────────────────────────────────────────────────────────
 //
 // A single key + label entry in the contextual shortcut hint panel.
@@ -666,12 +700,26 @@ export type SurfaceRole =
   | 'glazing'
   | 'furnishing'
 
+/** Role a kind plays in a duct / pipe / lineset distribution system. */
+export type DistributionRole = 'run' | 'fitting' | 'terminal' | 'equipment'
+
 export type NodeDefinition<S extends ZodObject<any>> = {
   kind: string
   schemaVersion: number
   schema: S
   category: NodeCategory
   surfaceRole?: SurfaceRole
+  /**
+   * Role this kind plays in a distribution system (HVAC duct / DWV pipe /
+   * refrigerant lineset). Lets the system-graph summary classify a
+   * component without branching on `node.type`:
+   *   - `'run'` — a duct / pipe / lineset segment (carries `path`).
+   *   - `'fitting'` — an inline fitting (elbow / tee / reducer / trap).
+   *   - `'terminal'` — a grille / register / diffuser endpoint.
+   *   - `'equipment'` — a furnace / air handler / condenser source.
+   * Kinds outside any distribution system leave this unset.
+   */
+  distributionRole?: DistributionRole
 
   defaults: () => Omit<z.infer<S>, 'id' | 'type'>
   migrate?: Record<number, (old: unknown) => unknown>
@@ -829,6 +877,15 @@ export type NodeDefinition<S extends ZodObject<any>> = {
     nodes: Record<AnyNodeId, AnyNode>
     liveOverrides: Map<string, Record<string, unknown>>
   }) => Record<AnyNodeId, AnyNode>
+  /**
+   * Typed connection points this kind exposes (duct/pipe open ends,
+   * fitting collars, equipment plenums). Pure function of the node —
+   * returns LEVEL-LOCAL positions/directions (the kind applies its own
+   * transform). Consumed by placement tools for port-snapping and, in a
+   * later slice, by the system graph for connectivity. Kinds with no
+   * connectable geometry omit this.
+   */
+  ports?: (node: z.infer<S>) => NodePort[]
   system?: SystemContribution
   tool?: LazyComponent
   /**
@@ -915,6 +972,14 @@ export type KeyboardActions = {
   r?: KeyboardAction
   /** T / Shift+T secondary action. */
   t?: KeyboardAction
+  /**
+   * Set for kinds whose R/T rotation turns around a user-cyclable world
+   * axis (Alt cycles Y → X → Z) — duct / pipe fittings with full 3D
+   * orientation. The floating action menu reads this to surface the
+   * active-axis pill above the selected node; kinds with plain Y-only
+   * rotation omit it.
+   */
+  axisCycling?: boolean
 }
 
 export type KeyboardAction = {
@@ -1279,6 +1344,31 @@ export type CapabilityCtx = { node: AnyNode }
 export type MovableConfig = {
   axes: ReadonlyArray<'x' | 'y' | 'z'>
   gridSnap?: boolean
+  /**
+   * Pin the dragged node to the cursor (absolute placement) instead of the
+   * default offset-preserving drag, where the node moves by the cursor's
+   * delta from where the drag started. Offset preservation suits large
+   * furniture you grab by an edge; small connector-like kinds (duct
+   * fittings) read as "lagging behind the mouse" — they want the cursor.
+   */
+  cursorAttached?: boolean
+  /**
+   * Magnetically snap one of this kind's own ports onto a nearby scene
+   * port while dragging — e.g. a register's collar onto a duct run end.
+   * The dragged node shifts in XZ so its closest matching port lands on
+   * the target port. Alt bypasses the snap. Kinds without `def.ports`
+   * can't use this. Snap takes precedence over grid / alignment snap.
+   */
+  portSnap?: {
+    /**
+     * Distribution loops a target port must belong to (e.g.
+     * `['supply', 'return']`). A target port with no `system` always
+     * matches. Omit to match every port.
+     */
+    systems?: readonly string[]
+    /** Snap radius in meters (XZ). Defaults to 0.5. */
+    radius?: number
+  }
   override?: (ctx: CapabilityCtx) => MovableConfig | null
 }
 
@@ -1411,7 +1501,24 @@ export type Relations = {
 export type ParametricDescriptor<N> = {
   groups: ParamGroup<N>[]
   invariants?: ReadonlyArray<(n: N) => Issue[]>
-  derive?: (n: N) => Partial<N>
+  /**
+   * Co-update hook for fields that must stay consistent when edited
+   * from the inspector. Called with the node AFTER `patch` is merged
+   * plus the patch itself (so the hook can tell which field the user
+   * touched); whatever it returns is folded into the same update.
+   * Direct store/MCP writes bypass it — keep real invariants in
+   * `invariants`.
+   */
+  derive?: (next: N, patch: Partial<N>) => Partial<N>
+  /**
+   * Cross-node companion to `derive`: after an inspector edit lands on
+   * this node, return patches for OTHER nodes that must follow to keep
+   * the scene consistent — e.g. duct runs re-trimmed onto a resized
+   * fitting's collars. `prev` is the node before the edit, `next` after
+   * (with `derive` already folded in). Applied in the same gesture via
+   * `updateNodes`.
+   */
+  reconcile?: (prev: N, next: N) => 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/index.ts

@@ -59,6 +59,9 @@ export {
   getEffectiveDormerSurfaceMaterial,
 } from './nodes/dormer'
 export { DownspoutNode } from './nodes/downspout'
+export { DuctFittingNode } from './nodes/duct-fitting'
+export { DuctSegmentNode } from './nodes/duct-segment'
+export { DuctTerminalNode } from './nodes/duct-terminal'
 export {
   ElevatorDoorPanelStyle,
   ElevatorDoorStyle,
@@ -69,6 +72,7 @@ export { EyebrowVentNode } from './nodes/eyebrow-vent'
 export { FenceBaseStyle, FenceNode, FenceStyle } from './nodes/fence'
 export { GuideNode, GuideScaleReference } from './nodes/guide'
 export { GutterNode, GutterOutlet } from './nodes/gutter'
+export { HvacEquipmentNode } from './nodes/hvac-equipment'
 export type {
   AnimationEffect,
   Asset,
@@ -88,6 +92,11 @@ export {
   LOW_PROFILE_ITEM_SURFACE_MAX_HEIGHT,
 } from './nodes/item'
 export { LevelNode } from './nodes/level'
+export { LinesetNode } from './nodes/lineset'
+export { LiquidLineNode } from './nodes/liquid-line'
+export { PipeFittingNode } from './nodes/pipe-fitting'
+export { PipeSegmentNode } from './nodes/pipe-segment'
+export { PipeTrapNode } from './nodes/pipe-trap'
 // Nodes
 export { RidgeVentNode } from './nodes/ridge-vent'
 export type { RoofSurfaceMaterialRole, RoofSurfaceMaterialSpec } from './nodes/roof'

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

@@ -0,0 +1,94 @@
+import dedent from 'dedent'
+import { z } from 'zod'
+import { BaseNode, nodeType, objectId } from '../base'
+
+/**
+ * Duct fitting — the junction pieces that connect round duct segments:
+ * elbows (direction change), tees (branch takeoff), reducers (diameter
+ * transition).
+ *
+ * Phase 2 of the HVAC node system. Fittings are the first kind to expose
+ * typed ports (`def.ports`) — placement tools snap duct endpoints onto a
+ * fitting's collars, and the future system graph walks ports to decide
+ * connectivity.
+ *
+ * `position` is level-local meters; `rotation` is an XYZ euler in radians
+ * so a fitting can turn a horizontal run vertical (riser elbows).
+ *
+ * Local-frame conventions (before `rotation` is applied):
+ *   - elbow:   inlet faces -X, outlet turned by `angle` degrees in the
+ *              XZ plane (90° → +Z).
+ *   - tee:     run along the X axis (ports face -X and +X), branch
+ *              collar at `branchAngle`° from the +X (outlet) axis in the
+ *              XZ plane — 90° a square straight tee, <90° a lateral
+ *              leaning downstream toward the outlet, >90° leaning upstream
+ *              toward the inlet — sized at `diameter2`.
+ *   - cross:   four-way junction — run along the X axis (ports face -X
+ *              and +X) at the run profile, two opposed branches square to
+ *              the run along ±Z (branch faces +Z, branch2 faces -Z) at the
+ *              branch profile (`shape2` / `diameter2`).
+ *   - reducer: inlet at `diameter` faces -X, outlet at `diameter2`
+ *              faces +X.
+ *   - transition: square-to-round — rect end at `width` × `height` faces
+ *              -X, round end at `diameter2` faces +X. `diameter` carries
+ *              the rect end's area-equivalent round size.
+ */
+export const DuctFittingNode = BaseNode.extend({
+  id: objectId('duct-fitting'),
+  type: nodeType('duct-fitting'),
+  // Level-local meters.
+  position: z.tuple([z.number(), z.number(), z.number()]).default([0, 0, 0]),
+  // XYZ euler radians.
+  rotation: z.tuple([z.number(), z.number(), z.number()]).default([0, 0, 0]),
+  fittingType: z.enum(['elbow', 'tee', 'cross', 'reducer', 'transition']).default('elbow'),
+  // Run-leg cross-section: round collars, or a rect / flat-oval profile
+  // 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'),
+  // 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),
+  // Tee / cross BRANCH cross-section: a round collar at `diameter2` or a
+  // 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'),
+  // 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),
+  // 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
+  // upstream toward the inlet. Ignored by every other fitting type.
+  branchAngle: z.number().min(45).max(135).default(90),
+  // Main (run/inlet) nominal diameter in inches.
+  diameter: z.number().min(2).max(48).default(6),
+  // Secondary diameter in inches — tee branch collar, reducer outlet.
+  // Ignored by elbows.
+  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'),
+}).describe(
+  dedent`
+  Duct fitting - elbow, tee, cross, reducer, or square-to-round transition between duct runs.
+  - position: [x, y, z] level-local meters
+  - rotation: [x, y, z] euler radians
+  - fittingType: elbow | tee | cross | reducer | transition (rect end -X, round end +X)
+  - shape: round | rect | oval run legs (matches the trunk; ignored by reducer / transition)
+  - width / height: rect / oval run-leg profile in inches (transition: the rect end)
+  - shape2: round | rect | oval tee / cross branch (matches the duct drawn off the tap)
+  - width2 / height2: rect / oval branch profile in inches
+  - angle: elbow turn in degrees (45 or 90 typical)
+  - branchAngle: tee branch angle off the outlet axis (90 straight tee, 45 downstream lateral, 135 upstream); cross branches are always square
+  - diameter: main nominal diameter in inches
+  - diameter2: tee / cross branch / reducer outlet / transition round-end diameter in inches
+  - ductMaterial: sheet-metal | flex | duct-board
+  - system: supply | return
+  `,
+)
+export type DuctFittingNode = z.infer<typeof DuctFittingNode>
+export type DuctFittingNodeId = DuctFittingNode['id']

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

@@ -0,0 +1,77 @@
+import dedent from 'dedent'
+import { z } from 'zod'
+import { BaseNode, nodeType, objectId } from '../base'
+
+/**
+ * Round duct segment — a polyline of 3D points connected by cylindrical
+ * duct sections. Forced-air HVAC supply/return runs in US residential.
+ *
+ * Phase 1 of the HVAC node system: just the geometry primitive. Fittings,
+ * terminals, equipment, and typed ports come in later slices.
+ *
+ * Path coordinates are level-local meters: [x, y, z] tuples. y is height
+ * above the level floor. A duct hung at ceiling height through three points
+ * is e.g. `[[0, 2.6, 0], [3, 2.6, 0], [3, 2.6, 4]]`.
+ *
+ * Diameters are nominal US round-duct sizes in inches; the geometry
+ * builder converts to meters for the cylinder radius.
+ */
+export const DuctSegmentNode = BaseNode.extend({
+  id: objectId('duct-segment'),
+  type: nodeType('duct-segment'),
+  // Polyline path in level-local meters. Minimum two points (start, end).
+  path: z.array(z.tuple([z.number(), z.number(), z.number()])).min(2),
+  // Cross-section. Round is the branch default; rect is the trunk /
+  // plenum profile (real US systems: rect trunk, round branches); oval
+  // is the flat-oval profile (two semicircles of the duct height joined
+  // by flat sides) used where round won't fit a joist bay.
+  shape: z.enum(['round', 'rect', 'oval']).default('round'),
+  // Nominal inner diameter in inches (round shape). Common residential
+  // sizes 4"–14"; we accept any positive number so the inspector slider
+  // stays ergonomic and larger commercial sizes load without a schema bump.
+  diameter: z.number().min(2).max(48).default(6),
+  // Rect / oval cross-section in inches: width is the horizontal face,
+  // height the vertical. Typical residential trunks 12×8 – 24×10. For
+  // oval, height is also the end-cap semicircle diameter (width ≥ height).
+  width: z.number().min(4).max(60).default(14),
+  height: z.number().min(3).max(40).default(8),
+  // Cross-section roll (radians) about the run direction. 0 = width
+  // horizontal / height vertical (the natural orientation the geometry
+  // derives from direction). Non-zero only on a rect riser turned out of
+  // the horizontal plane, so its profile stays continuous through the
+  // elbow it left instead of snapping to the world-axis fallback.
+  roll: z.number().default(0),
+  // Construction material. Spiral is round rigid sheet metal with the
+  // helical lock seam drawn on the body (round shape only — rect / oval
+  // runs render it as plain sheet metal).
+  ductMaterial: z.enum(['sheet-metal', 'spiral', 'flex', 'duct-board']).default('flex'),
+  // Whether to draw the construction body detail (spiral lock seam /
+  // flex wire corrugation) on round runs. Off renders a smooth body —
+  // lighter on the eyes and the GPU in dense scenes.
+  seamDetail: z.boolean().default(false),
+  // Whether the run wears its external insulation wrap (drawn as a
+  // translucent shell). Off by default — bare duct.
+  insulated: z.boolean().default(false),
+  // External insulation R-value (used when insulated). Common flex-duct
+  // values are R-4.2, R-6, R-8.
+  insulationR: z.number().min(0).max(12).default(0.5),
+  // 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'),
+}).describe(
+  dedent`
+  Duct segment - polyline of 3D points connected by duct sections.
+  - path: list of [x, y, z] points in level-local meters (min 2)
+  - shape: round (branches) | rect (trunks / plenums) | oval (flat-oval, tight joist bays)
+  - diameter: nominal inner diameter in inches for round (typ. 4-14 residential)
+  - width / height: rect / oval cross-section in inches (typ. 12x8 - 24x10 trunks)
+  - roll: cross-section roll in radians (0 = upright; set on risers to stay continuous through their elbow)
+  - ductMaterial: sheet-metal | spiral (round rigid, helical seam) | flex | duct-board
+  - seamDetail: draw the spiral seam / flex corrugation on round runs (default off)
+  - insulated: whether the run wears its external insulation wrap (default off)
+  - insulationR: external insulation R-value when insulated (4, 6, 8 typical)
+  - system: supply | return (drives visual tint)
+  `,
+)
+export type DuctSegmentNode = z.infer<typeof DuctSegmentNode>
+export type DuctSegmentNodeId = DuctSegmentNode['id']

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

@@ -0,0 +1,56 @@
+import dedent from 'dedent'
+import { z } from 'zod'
+import { BaseNode, nodeType, objectId } from '../base'
+
+/**
+ * Duct terminal — where the air loop meets the room: supply registers,
+ * ceiling diffusers, return grilles.
+ *
+ * Phase 3 of the HVAC node system. Each terminal exposes a single typed
+ * port at its collar (behind/above/below the face depending on mount),
+ * so duct runs end onto it like any other port.
+ *
+ * `position` is the center of the visible face in level-local meters —
+ * floor registers at y≈0, ceiling diffusers at ceiling height, wall
+ * registers at their height on the wall. `rotation` is yaw radians.
+ */
+export const DuctTerminalNode = BaseNode.extend({
+  id: objectId('duct-terminal'),
+  type: nodeType('duct-terminal'),
+  // Level-local meters — center of the face.
+  position: z.tuple([z.number(), z.number(), z.number()]).default([0, 0, 0]),
+  // Yaw in radians.
+  rotation: z.number().default(0),
+  terminalType: z.enum(['supply-register', 'diffuser', 'return-grille']).default('supply-register'),
+  // Which surface the terminal mounts on. Drives face orientation and
+  // which way the collar (and its port) points.
+  mount: z.enum(['floor', 'ceiling', 'wall']).default('floor'),
+  // Face dimensions in meters. Typical floor register ~0.30 × 0.15;
+  // ceiling diffusers are square (0.6 × 0.6); return grilles run large.
+  width: z.number().min(0.1).max(1.5).default(0.3),
+  depth: z.number().min(0.05).max(1.5).default(0.15),
+  // Collar cross-section on the duct side. Round is the default; rect and
+  // oval (flat-oval) match the duct shapes a run might end with.
+  collarShape: z.enum(['round', 'rect', 'oval']).default('round'),
+  // Round collar diameter in inches on the duct side.
+  collarDiameter: z.number().min(4).max(20).default(6),
+  // Rect / oval collar cross-section in inches: width is the horizontal
+  // face, height the vertical. For oval, height is also the end-cap
+  // semicircle diameter (width ≥ height).
+  collarWidth: z.number().min(4).max(20).default(10),
+  collarHeight: z.number().min(3).max(20).default(6),
+}).describe(
+  dedent`
+  Duct terminal - supply register, ceiling diffuser, or return grille.
+  - position: [x, y, z] level-local meters, center of the face
+  - rotation: yaw radians
+  - terminalType: supply-register | diffuser | return-grille (grille = return side)
+  - mount: floor | ceiling | wall - face orientation + collar direction
+  - width / depth: face size in meters
+  - collarShape: round | rect | oval - duct-side collar cross-section
+  - collarDiameter: round collar diameter in inches
+  - collarWidth / collarHeight: rect / oval collar cross-section in inches
+  `,
+)
+export type DuctTerminalNode = z.infer<typeof DuctTerminalNode>
+export type DuctTerminalNodeId = DuctTerminalNode['id']

packages/core/src/schema/nodes/hvac-equipment.ts

@@ -0,0 +1,60 @@
+import dedent from 'dedent'
+import { z } from 'zod'
+import { BaseNode, nodeType, objectId } from '../base'
+
+/**
+ * HVAC equipment — the boxes duct systems start and end at: furnace,
+ * air handler, outdoor condenser.
+ *
+ * Phase 3 of the HVAC node system. Furnaces and air handlers expose
+ * typed duct ports (supply plenum on top, return drop on the side) so
+ * duct runs and fittings snap onto them. Every unit also exposes a
+ * refrigerant service port on its valve face — a condenser, the outdoor
+ * half of a split system, carries no duct ports but pipes to the indoor
+ * coil through a `lineset` run mating onto that port.
+ *
+ * Floor-placed: `position` is level-local meters with y at the base,
+ * `rotation` is yaw radians (the editor's default R-rotate applies).
+ */
+export const HvacEquipmentNode = BaseNode.extend({
+  id: objectId('hvac-equipment'),
+  type: nodeType('hvac-equipment'),
+  // Level-local meters, y at the unit's base.
+  position: z.tuple([z.number(), z.number(), z.number()]).default([0, 0, 0]),
+  // Yaw in radians.
+  rotation: z.number().default(0),
+  equipmentType: z.enum(['furnace', 'air-handler', 'condenser']).default('furnace'),
+  // Cabinet dimensions in meters. Defaults match a typical upflow
+  // furnace cabinet (~22" × 28" footprint, ~43" tall).
+  width: z.number().min(0.3).max(2).default(0.56),
+  depth: z.number().min(0.3).max(2).default(0.71),
+  height: z.number().min(0.4).max(2.5).default(1.1),
+  // Duct collar cross-section on the supply / return connections. Round is
+  // the default; rect and oval (flat-oval) match the duct shapes a run
+  // might mate with. Condensers carry no duct collars (ignored).
+  supplyShape: z.enum(['round', 'rect', 'oval']).default('round'),
+  returnShape: z.enum(['round', 'rect', 'oval']).default('round'),
+  // Round collar diameters in inches.
+  supplyDiameter: z.number().min(6).max(30).default(8),
+  returnDiameter: z.number().min(6).max(30).default(8),
+  // Rect / oval collar cross-section in inches: width is the horizontal
+  // face, height the vertical. For oval, height is also the end-cap
+  // semicircle diameter (width ≥ height).
+  supplyWidth: z.number().min(6).max(30).default(12),
+  supplyHeight: z.number().min(6).max(30).default(8),
+  returnWidth: z.number().min(6).max(30).default(14),
+  returnHeight: z.number().min(6).max(30).default(8),
+}).describe(
+  dedent`
+  HVAC equipment cabinet - furnace, air handler, or outdoor condenser.
+  - position: [x, y, z] level-local meters (y = base)
+  - rotation: yaw radians
+  - equipmentType: furnace | air-handler | condenser
+  - width / depth / height: cabinet size in meters
+  - supplyShape / returnShape: round | rect | oval duct collar cross-section (ignored by condenser)
+  - supplyDiameter / returnDiameter: round collar sizes in inches
+  - supplyWidth / supplyHeight / returnWidth / returnHeight: rect / oval collar cross-section in inches
+  `,
+)
+export type HvacEquipmentNode = z.infer<typeof HvacEquipmentNode>
+export type HvacEquipmentNodeId = HvacEquipmentNode['id']

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

@@ -0,0 +1,43 @@
+import dedent from 'dedent'
+import { z } from 'zod'
+import { BaseNode, nodeType, objectId } from '../base'
+
+/**
+ * Refrigerant lineset — the copper pipe pair that links the outdoor
+ * condenser to the indoor coil (furnace / air handler) of a split system.
+ * It is the refrigerant-side analogue of a duct run: a polyline of points,
+ * but carrying two lines instead of one airway.
+ *
+ * Real linesets run a fat insulated SUCTION line (cool vapour back to the
+ * compressor) beside a thin bare LIQUID line (warm liquid out to the coil).
+ * The geometry builder draws a single copper line on the path centerline
+ * (sized to `suctionDiameter`, wrapped in a foam jacket when `insulated`);
+ * draw the liquid line as a second lineset rather than both off one path.
+ *
+ * Path coordinates are level-local meters: [x, y, z] tuples, same space as
+ * duct paths and grid events. Diameters are nominal copper OD in inches.
+ */
+export const LinesetNode = BaseNode.extend({
+  id: objectId('lineset'),
+  type: nodeType('lineset'),
+  // Polyline path in level-local meters. Minimum two points (start, end).
+  path: z.array(z.tuple([z.number(), z.number(), z.number()])).min(2),
+  // Nominal suction-line copper OD in inches (the large insulated line).
+  // Common residential sizes are 3/4"–1-1/8".
+  suctionDiameter: z.number().min(0.25).max(2).default(0.875),
+  // Nominal liquid-line copper OD in inches (the small bare line).
+  // Common residential sizes are 1/4"–3/8".
+  liquidDiameter: z.number().min(0.125).max(1).default(0.375),
+  // Whether the suction line carries its foam insulation jacket. Bare = false.
+  insulated: z.boolean().default(true),
+}).describe(
+  dedent`
+  Refrigerant lineset - copper suction + liquid pair linking a condenser to an indoor coil.
+  - path: list of [x, y, z] points in level-local meters (min 2)
+  - suctionDiameter: nominal copper OD in inches of the large insulated line (typ. 3/4"-1-1/8")
+  - liquidDiameter: nominal copper OD in inches of the small bare line (typ. 1/4"-3/8")
+  - insulated: whether the suction line wears its foam jacket
+  `,
+)
+export type LinesetNode = z.infer<typeof LinesetNode>
+export type LinesetNodeId = LinesetNode['id']

packages/core/src/schema/nodes/liquid-line.ts

@@ -0,0 +1,29 @@
+import dedent from 'dedent'
+import { z } from 'zod'
+import { BaseNode, nodeType, objectId } from '../base'
+
+/**
+ * Standalone refrigerant liquid line — the thin bare-copper line that carries
+ * warm liquid out to the indoor coil. It is the line that used to be drawn as
+ * the lineset's second rail; broken out here as its own polyline run so it can
+ * be drawn on its own, including traced alongside an existing lineset.
+ *
+ * Path coordinates are level-local meters: [x, y, z] tuples, the same space as
+ * lineset and duct paths. Diameter is nominal copper OD in inches.
+ */
+export const LiquidLineNode = BaseNode.extend({
+  id: objectId('liquid-line'),
+  type: nodeType('liquid-line'),
+  // Polyline path in level-local meters. Minimum two points (start, end).
+  path: z.array(z.tuple([z.number(), z.number(), z.number()])).min(2),
+  // Nominal copper OD in inches. Common residential sizes are 1/4"–3/8".
+  diameter: z.number().min(0.125).max(1).default(0.375),
+}).describe(
+  dedent`
+  Standalone refrigerant liquid line - a thin bare-copper polyline run.
+  - path: list of [x, y, z] points in level-local meters (min 2)
+  - diameter: nominal copper OD in inches (typ. 1/4"-3/8")
+  `,
+)
+export type LiquidLineNode = z.infer<typeof LiquidLineNode>
+export type LiquidLineNodeId = LiquidLineNode['id']

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

@@ -0,0 +1,48 @@
+import dedent from 'dedent'
+import { z } from 'zod'
+import { BaseNode, nodeType, objectId } from '../base'
+
+/**
+ * DWV pipe fitting — the joints drain systems are actually built from:
+ * elbows (bends), wyes (45° branch entries, the code-preferred way to
+ * join horizontal drains), sanitary tees (square branch entries), and
+ * crosses (two opposed branches where a run passes straight through).
+ *
+ * Local-frame conventions (before `rotation`):
+ *   - elbow:        inlet faces -X, outlet turned `angle`° in XZ.
+ *   - wye:          run along X (inlet -X, outlet +X), branch collar at
+ *                   45° between +X and +Z.
+ *   - sanitary-tee: run along X, branch collar faces +Z.
+ *   - cross:        run along X, two opposed branch collars on ±Z.
+ */
+export const PipeFittingNode = BaseNode.extend({
+  id: objectId('pipe-fitting'),
+  type: nodeType('pipe-fitting'),
+  // Level-local meters.
+  position: z.tuple([z.number(), z.number(), z.number()]).default([0, 0, 0]),
+  // XYZ euler radians.
+  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),
+  // Run nominal size in inches.
+  diameter: z.number().min(1.25).max(8).default(2),
+  // Branch collar size (wye / sanitary-tee).
+  diameter2: z.number().min(1.25).max(8).default(2),
+  pipeMaterial: z.enum(['pvc', 'abs', 'cast-iron']).default('pvc'),
+  system: z.enum(['waste', 'vent']).default('waste'),
+}).describe(
+  dedent`
+  DWV pipe fitting - elbow (bend), wye (45° branch), sanitary tee (square branch), or cross (two opposed branches).
+  - position: [x, y, z] level-local meters
+  - rotation: [x, y, z] euler radians
+  - fittingType: elbow | wye | sanitary-tee | cross
+  - angle: elbow turn in degrees (22.5 / 45 / 90 typical)
+  - diameter: run size in inches; diameter2: branch collar size (both branches for a cross)
+  - pipeMaterial: pvc | abs | cast-iron
+  - system: waste | vent
+  `,
+)
+export type PipeFittingNode = z.infer<typeof PipeFittingNode>
+export type PipeFittingNodeId = PipeFittingNode['id']

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

@@ -0,0 +1,41 @@
+import dedent from 'dedent'
+import { z } from 'zod'
+import { BaseNode, nodeType, objectId } from '../base'
+
+/**
+ * DWV pipe segment — drain / waste / vent runs in US residential
+ * plumbing. Phase 2 of the distribution-system effort: the plumbing
+ * sibling of `duct-segment`, sharing the polyline model and the typed
+ * port machinery.
+ *
+ * The defining difference from ducts is SLOPE: drains must fall
+ * (IPC: ¼" per foot for pipes under 3", ⅛" allowed at 3"+). Slope is
+ * stored implicitly in the path's Y coordinates — the draw tool drops
+ * Y as you draw a waste run; vents run level or vertical.
+ *
+ * Path coordinates are level-local meters. Y may be negative (drains
+ * drop below the floor into the joist / crawl space).
+ */
+export const PipeSegmentNode = BaseNode.extend({
+  id: objectId('pipe-segment'),
+  type: nodeType('pipe-segment'),
+  // Polyline path in level-local meters. Minimum two points.
+  path: z.array(z.tuple([z.number(), z.number(), z.number()])).min(2),
+  // Nominal pipe size in inches. Residential DWV: 1¼ (lav tailpiece) to
+  // 4 (building drain); 6 covers oversized mains.
+  diameter: z.number().min(1.25).max(8).default(2),
+  pipeMaterial: z.enum(['pvc', 'abs', 'cast-iron']).default('pvc'),
+  // Which DWV role the run plays. Waste carries water (sloped); vent
+  // carries air (level or vertical, dashed in plan).
+  system: z.enum(['waste', 'vent']).default('waste'),
+}).describe(
+  dedent`
+  DWV pipe segment - drain / waste / vent run as a polyline of 3D points.
+  - path: list of [x, y, z] points in level-local meters (min 2; y may go below the floor)
+  - diameter: nominal size in inches (1.5 / 2 / 3 / 4 typical residential)
+  - pipeMaterial: pvc | abs | cast-iron
+  - system: waste (sloped drains) | vent (level / vertical air pipes)
+  `,
+)
+export type PipeSegmentNode = z.infer<typeof PipeSegmentNode>
+export type PipeSegmentNodeId = PipeSegmentNode['id']

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

@@ -0,0 +1,41 @@
+import dedent from 'dedent'
+import { z } from 'zod'
+import { BaseNode, nodeType, objectId } from '../base'
+
+/**
+ * DWV trap — the P-trap between a fixture and the waste system. Holds a
+ * water seal that blocks sewer gas; every drained fixture has exactly
+ * one. Modeled as an explicit fitting (not folded into the fixture) so
+ * the trap-arm rule (IPC 909.1 max developed length to the vent) has a
+ * node to attach to and the inspector can edit size + arm length.
+ *
+ * Local-frame convention (before `rotation`): inlet faces +Y (up, to
+ * the fixture tailpiece), outlet faces +X (the horizontal trap arm
+ * toward the vented waste line).
+ */
+export const PipeTrapNode = BaseNode.extend({
+  id: objectId('pipe-trap'),
+  type: nodeType('pipe-trap'),
+  // Level-local meters.
+  position: z.tuple([z.number(), z.number(), z.number()]).default([0, 0, 0]),
+  // 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),
+  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
+  // inspector. Drives the IPC 909.1 max-trap-arm check.
+  armLengthM: z.number().min(0).default(0),
+}).describe(
+  dedent`
+  DWV trap (P-trap) - the water-seal fitting between a fixture and the waste line.
+  - position: [x, y, z] level-local meters
+  - rotation: yaw radians (trap-arm direction in plan)
+  - diameter: trap size in inches (matches the fixture drain)
+  - pipeMaterial: pvc | abs | cast-iron
+  - armLengthM: developed length from trap to vent in meters (IPC 909.1 limited by size)
+  `,
+)
+export type PipeTrapNode = z.infer<typeof PipeTrapNode>
+export type PipeTrapNodeId = PipeTrapNode['id']

packages/core/src/schema/types.ts

@@ -8,13 +8,22 @@ import { CupolaNode } from './nodes/cupola'
 import { DoorNode } from './nodes/door'
 import { DormerNode } from './nodes/dormer'
 import { DownspoutNode } from './nodes/downspout'
+import { DuctFittingNode } from './nodes/duct-fitting'
+import { DuctSegmentNode } from './nodes/duct-segment'
+import { DuctTerminalNode } from './nodes/duct-terminal'
 import { ElevatorNode } from './nodes/elevator'
 import { EyebrowVentNode } from './nodes/eyebrow-vent'
 import { FenceNode } from './nodes/fence'
 import { GuideNode } from './nodes/guide'
 import { GutterNode } from './nodes/gutter'
+import { HvacEquipmentNode } from './nodes/hvac-equipment'
 import { ItemNode } from './nodes/item'
 import { LevelNode } from './nodes/level'
+import { LinesetNode } from './nodes/lineset'
+import { LiquidLineNode } from './nodes/liquid-line'
+import { PipeFittingNode } from './nodes/pipe-fitting'
+import { PipeSegmentNode } from './nodes/pipe-segment'
+import { PipeTrapNode } from './nodes/pipe-trap'
 import { RidgeVentNode } from './nodes/ridge-vent'
 import { RoofNode } from './nodes/roof'
 import { RoofSegmentNode } from './nodes/roof-segment'
@@ -65,6 +74,15 @@ export const AnyNode = z.discriminatedUnion('type', [
   SkylightNode,
   DormerNode,
   DownspoutNode,
+  DuctSegmentNode,
+  DuctFittingNode,
+  DuctTerminalNode,
+  HvacEquipmentNode,
+  LinesetNode,
+  LiquidLineNode,
+  PipeSegmentNode,
+  PipeFittingNode,
+  PipeTrapNode,
 ])
 
 export type AnyNode = z.infer<typeof AnyNode>

packages/core/src/services/alignment-anchors.ts

@@ -295,8 +295,43 @@ export function nodeAlignmentAnchors(
     const poly = (node as { polygon?: [number, number][] }).polygon
     return poly ? polygonAnchors(node.id, poly) : []
   }
+
+  const anchors: AlignmentAnchor[] = []
+
+  // Box footprint (items, columns, shelves, stairs, …).
   const aabb = alignmentAABB(node, nodes)
-  return aabb ? bboxCornerAnchors(node.id, aabb.minX, aabb.minZ, aabb.maxX, aabb.maxZ) : []
+  if (aabb) {
+    anchors.push(...bboxCornerAnchors(node.id, aabb.minX, aabb.minZ, aabb.maxX, aabb.maxZ))
+  }
+
+  // Polyline kinds (duct / pipe / lineset): every path vertex is an anchor,
+  // so anything dragged snaps to a run's ends and bends.
+  const path = (node as { path?: unknown }).path
+  if (Array.isArray(path)) {
+    for (const p of path as Array<[number, number, number]>) {
+      anchors.push({ nodeId: node.id, kind: 'corner', x: p[0], z: p[2] })
+    }
+  }
+
+  // Typed ports (fittings, equipment, terminals, run ends): connection points
+  // are natural alignment targets — line a new run up with an existing collar.
+  const ports = nodeRegistry.get(node.type)?.ports?.(node)
+  if (ports) {
+    for (const port of ports) {
+      anchors.push({ nodeId: node.id, kind: 'corner', x: port.position[0], z: port.position[2] })
+    }
+  }
+
+  // Position-based kinds with no footprint (e.g. duct fittings): the origin
+  // itself is a useful centre anchor.
+  if (!aabb) {
+    const position = (node as { position?: [number, number, number] }).position
+    if (Array.isArray(position)) {
+      anchors.push({ nodeId: node.id, kind: 'center', x: position[0], z: position[2] })
+    }
+  }
+
+  return anchors
 }
 
 /**

packages/core/src/services/index.ts

@@ -41,6 +41,10 @@ export {
   pickHost,
   type Vec3,
 } from './hosting'
+export {
+  DEFAULT_LEVEL_HEIGHT,
+  getLevelHeight,
+} from './level-height'
 export {
   type AxisLock,
   applyAxisLock,
@@ -69,6 +73,19 @@ export {
   type VerticalFeature,
   type WallExtent,
 } from './opening-guides'
+export {
+  analyzePortConnectivity,
+  type PortConnection,
+  type PortConnectivity,
+  resolveConnectivityUpdates,
+} from './port-connectivity'
+export {
+  buildRiserDiagram,
+  projectIso,
+  type RiserDiagram,
+  type RiserLine,
+  type RiserMarker,
+} from './riser-diagram'
 export {
   DEFAULT_ANGLE_STEP,
   DEFAULT_GRID_STEP,
@@ -82,3 +99,13 @@ export {
   snapVec3ToGrid,
   snapWorldXZToBuildingLocal,
 } from './snap'
+export {
+  buildPortComponents,
+  type SystemSummary,
+  summarizeSystemFor,
+} from './system-graph'
+export {
+  type DwvFinding,
+  type DwvSeverity,
+  validateDwv,
+} from './validate-dwv'

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

@@ -0,0 +1,43 @@
+import { sceneRegistry } from '../hooks/scene-registry/scene-registry'
+import type { CeilingNode, LevelNode, WallNode } from '../schema'
+import type { AnyNode, AnyNodeId } from '../schema/types'
+
+export const DEFAULT_LEVEL_HEIGHT = 2.5
+
+// Cache: levelId → computed height. Invalidated when the nodes reference changes.
+// Zustand produces a new `nodes` object on every mutation, so reference equality
+// is a zero-cost way to detect stale data without any subscription overhead.
+const heightCache = new Map<string, number>()
+let lastNodesRef: object | null = null
+
+export function getLevelHeight(levelId: string, nodes: Record<AnyNodeId, AnyNode>): number {
+  if (nodes !== lastNodesRef) {
+    heightCache.clear()
+    lastNodesRef = nodes
+  }
+
+  if (heightCache.has(levelId)) return heightCache.get(levelId)!
+
+  const level = nodes[levelId as LevelNode['id']] as LevelNode | undefined
+  if (!level) return DEFAULT_LEVEL_HEIGHT
+
+  let maxTop = 0
+
+  for (const childId of level.children) {
+    const child = nodes[childId as keyof typeof nodes]
+    if (!child) continue
+    if (child.type === 'ceiling') {
+      const ch = (child as CeilingNode).height ?? DEFAULT_LEVEL_HEIGHT
+      if (ch > maxTop) maxTop = ch
+    } else if (child.type === 'wall') {
+      let meshY = sceneRegistry.nodes.get(childId as AnyNodeId)?.position.y ?? 0
+      if (meshY < 0) meshY = 0
+      const top = meshY + ((child as WallNode).height ?? DEFAULT_LEVEL_HEIGHT)
+      if (top > maxTop) maxTop = top
+    }
+  }
+
+  const height = maxTop > 0 ? maxTop : DEFAULT_LEVEL_HEIGHT
+  heightCache.set(levelId, height)
+  return height
+}

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

@@ -0,0 +1,189 @@
+import { nodeRegistry } from '../registry'
+import type { AnyNode, AnyNodeId } from '../schema'
+
+/**
+ * Connectivity-aware editing for port-bearing kinds (HVAC ductwork).
+ *
+ * Two nodes are "connected" when a port of one coincides in space with a
+ * port of the other — exactly how the placement tools mate a fitting onto
+ * a duct end (they snap the fitting's collar onto the run's open port).
+ * This service reads that relationship back out so an edit to one node can
+ * carry its neighbours along.
+ *
+ * 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.
+ *
+ * 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.
+ */
+
+type Point = readonly [number, number, number]
+
+/** Distance (meters) under which two ports count as the same joint. Joints
+ *  formed by placement snapping coincide to sub-millimeter; 5 cm leaves
+ *  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. */
+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. */
+      kind: 'rigid-node'
+      nodeId: AnyNodeId
+      movedPortId: string
+      /** Partner node's `position` at edit-start. */
+      startPosition: Point
+    }
+
+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. */
+  startMovedPorts: Record<string, Point>
+  connections: PortConnection[]
+}
+
+function portsOf(node: AnyNode): ReadonlyArray<{ id: string; position: Point }> | undefined {
+  return nodeRegistry.get(node.type)?.ports?.(node) as
+    | ReadonlyArray<{ id: string; position: Point }>
+    | undefined
+}
+
+function distSq(a: Point, b: Point): number {
+  const dx = a[0] - b[0]
+  const dy = a[1] - b[1]
+  const dz = a[2] - b[2]
+  return dx * dx + dy * dy + dz * dz
+}
+
+/**
+ * Snapshot which nodes are connected to `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 duct-segment (endpoint stretch) and duct-fitting (rigid follow)
+ * partners are tracked — terminals and equipment usually mount to a
+ * surface and shouldn't be yanked off it when an adjacent fitting nudges.
+ */
+export function analyzePortConnectivity(
+  movedNode: AnyNode,
+  nodes: Record<string, AnyNode>,
+): PortConnectivity {
+  const movedPorts = portsOf(movedNode) ?? []
+  const startMovedPorts: Record<string, Point> = {}
+  for (const p of movedPorts) startMovedPorts[p.id] = p.position
+
+  const connections: PortConnection[] = []
+  const epsSq = COINCIDENT_EPS_M * COINCIDENT_EPS_M
+
+  for (const other of Object.values(nodes)) {
+    if (!other || other.id === movedNode.id) continue
+    if (other.type !== 'duct-segment' && other.type !== 'duct-fitting') continue
+    const otherPorts = portsOf(other)
+    if (!otherPorts) continue
+
+    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) {
+          matchedId = mp.id
+          break
+        }
+      }
+      if (!matchedId) continue
+
+      if (other.type === 'duct-segment') {
+        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]],
+        })
+      }
+    }
+  }
+
+  return { movedNodeId: movedNode.id as AnyNodeId, connections, startMovedPorts }
+}
+
+/**
+ * Given the moved node in its live (in-drag) transform, produce the patches
+ * 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.
+ */
+export function resolveConnectivityUpdates(
+  connectivity: PortConnectivity,
+  previewNode: AnyNode,
+): { id: AnyNodeId; data: Partial<AnyNode> }[] {
+  const newPorts = portsOf(previewNode) ?? []
+  const newById: Record<string, Point> = {}
+  for (const p of newPorts) newById[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
+
+    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>,
+      })
+    }
+  }
+  return updates
+}

packages/core/src/services/riser-diagram.test.ts

@@ -0,0 +1,75 @@
+import { describe, expect, test } from 'bun:test'
+import type { AnyNode, AnyNodeId } from '../schema'
+import { buildRiserDiagram, projectIso } from './riser-diagram'
+
+type Point = [number, number, number]
+
+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>
+}
+
+describe('projectIso', () => {
+  test('higher elevation maps to smaller screen Y', () => {
+    const [, lowY] = projectIso(0, 0, 0)
+    const [, highY] = projectIso(0, 2, 0)
+    expect(highY).toBeLessThan(lowY)
+  })
+})
+
+describe('buildRiserDiagram', () => {
+  test('null when no DWV nodes', () => {
+    const wall = makeNode('wall', {})
+    expect(buildRiserDiagram(sceneOf(wall))).toBeNull()
+  })
+
+  test('classifies a vertical stack vs a sloped horizontal drain', () => {
+    const stack = makeNode('pipe-segment', {
+      path: [
+        [0, 0, 0],
+        [0, 3, 0],
+      ] as Point[],
+      diameter: 3,
+      system: 'vent',
+    })
+    const drain = makeNode('pipe-segment', {
+      path: [
+        [0, 0, 0],
+        [3, -0.06, 0],
+      ] as Point[],
+      diameter: 2,
+      system: 'waste',
+    })
+    const diagram = buildRiserDiagram(sceneOf(stack, drain))!
+    const stackLine = diagram.lines.find((l) => l.nodeId === stack.id)!
+    const drainLine = diagram.lines.find((l) => l.nodeId === drain.id)!
+    expect(stackLine.vertical).toBe(true)
+    expect(drainLine.vertical).toBe(false)
+  })
+
+  test('emits a vent-termination marker for a vent run', () => {
+    const vent = makeNode('pipe-segment', {
+      path: [
+        [0, 0, 0],
+        [0, 3, 0],
+      ] as Point[],
+      diameter: 2,
+      system: 'vent',
+    })
+    const diagram = buildRiserDiagram(sceneOf(vent))!
+    expect(diagram.markers.some((m) => m.kind === 'vent-termination')).toBe(true)
+  })
+
+  test('labels traps', () => {
+    const trap = makeNode('pipe-trap', {
+      position: [1, 0, 0] as Point,
+      diameter: 1.5,
+    })
+    const diagram = buildRiserDiagram(sceneOf(trap))!
+    expect(diagram.markers.some((m) => m.kind === 'trap')).toBe(true)
+  })
+})

packages/core/src/services/riser-diagram.ts

@@ -0,0 +1,143 @@
+import type { AnyNode, AnyNodeId } from '../schema'
+
+/**
+ * Riser diagram (plumbing isometric) — the conventional way DWV systems
+ * are drawn for permit: the drain/vent tree projected to a 30° iso so
+ * vertical stacks read as vertical and horizontal runs lean off at 30°,
+ * annotated with size + slope and vent terminations.
+ *
+ * This is a pure projector: it turns the scene's DWV nodes into 2D
+ * drawables (level-independent, no rendering). The editor draws the
+ * result as SVG. Air/refrigerant nodes are ignored — riser diagrams are
+ * a plumbing convention.
+ */
+
+const COS30 = Math.cos(Math.PI / 6)
+const SIN30 = Math.sin(Math.PI / 6)
+
+/** A 3D level-local point (meters) projected to 2D iso screen space.
+ *  Screen Y grows DOWNWARD (SVG convention), so higher elevation → lower
+ *  screen Y. */
+export function projectIso(x: number, y: number, z: number): [number, number] {
+  const sx = (x - z) * COS30
+  const sy = (x + z) * SIN30 - y
+  return [sx, sy]
+}
+
+export type RiserLine = {
+  /** Projected endpoints in iso screen space. */
+  from: [number, number]
+  to: [number, number]
+  system: 'waste' | 'vent'
+  /** Nominal size in inches. */
+  diameter: number
+  /** True for a (near-)vertical run — drawn solid/bold as a stack. */
+  vertical: boolean
+  /** Source node, so the editor can link selection. */
+  nodeId: AnyNodeId
+}
+
+export type RiserMarker = {
+  point: [number, number]
+  kind: 'trap' | 'vent-termination' | 'fitting'
+  label: string
+  nodeId: AnyNodeId
+}
+
+export type RiserDiagram = {
+  lines: RiserLine[]
+  markers: RiserMarker[]
+  /** Bounding box of all projected geometry, screen space. */
+  bounds: { minX: number; minY: number; maxX: number; maxY: number }
+}
+
+/** Elevation gain per horizontal meter under which a leg is "vertical". */
+const VERTICAL_EPS = 4 // dy/dxz ratio: steeper than this reads as a stack
+
+type Vec3 = readonly [number, number, number]
+
+function legIsVertical(a: Vec3, b: Vec3): boolean {
+  const horizontal = Math.hypot(b[0] - a[0], b[2] - a[2])
+  const vertical = Math.abs(b[1] - a[1])
+  if (horizontal < 1e-4) return true
+  return vertical / horizontal > VERTICAL_EPS
+}
+
+/**
+ * Build the riser diagram for the whole scene. Returns null when there's
+ * no DWV geometry to draw.
+ */
+export function buildRiserDiagram(
+  nodes: Readonly<Record<AnyNodeId, AnyNode>>,
+): RiserDiagram | null {
+  const lines: RiserLine[] = []
+  const markers: RiserMarker[] = []
+
+  let minX = Infinity
+  let minY = Infinity
+  let maxX = -Infinity
+  let maxY = -Infinity
+  const grow = (p: [number, number]) => {
+    if (p[0] < minX) minX = p[0]
+    if (p[1] < minY) minY = p[1]
+    if (p[0] > maxX) maxX = p[0]
+    if (p[1] > maxY) maxY = p[1]
+  }
+
+  for (const node of Object.values(nodes)) {
+    if (!node) continue
+    if (node.type === 'pipe-segment') {
+      const path = node.path as Vec3[]
+      for (let i = 0; i < path.length - 1; i++) {
+        const a = path[i]!
+        const b = path[i + 1]!
+        const from = projectIso(a[0], a[1], a[2])
+        const to = projectIso(b[0], b[1], b[2])
+        grow(from)
+        grow(to)
+        lines.push({
+          from,
+          to,
+          system: node.system,
+          diameter: node.diameter,
+          vertical: legIsVertical(a, b),
+          nodeId: node.id,
+        })
+      }
+      // Vent runs that end above everything are vent terminations
+      // (through-roof). Tag the highest endpoint of a vent run.
+      if (node.system === 'vent') {
+        const top = path.reduce((hi, p) => (p[1] > hi[1] ? p : hi), path[0]!)
+        const pt = projectIso(top[0], top[1], top[2])
+        markers.push({
+          point: pt,
+          kind: 'vent-termination',
+          label: `${node.diameter}" VTR`,
+          nodeId: node.id,
+        })
+      }
+    } else if (node.type === 'pipe-trap') {
+      const pt = projectIso(node.position[0], node.position[1], node.position[2])
+      grow(pt)
+      markers.push({
+        point: pt,
+        kind: 'trap',
+        label: `${node.diameter}" P-trap`,
+        nodeId: node.id,
+      })
+    } else if (node.type === 'pipe-fitting') {
+      const pt = projectIso(node.position[0], node.position[1], node.position[2])
+      grow(pt)
+      markers.push({
+        point: pt,
+        kind: 'fitting',
+        label: node.fittingType,
+        nodeId: node.id,
+      })
+    }
+  }
+
+  if (lines.length === 0 && markers.length === 0) return null
+
+  return { lines, markers, bounds: { minX, minY, maxX, maxY } }
+}

packages/core/src/services/system-graph.test.ts

@@ -0,0 +1,158 @@
+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 { buildPortComponents, summarizeSystemFor } from './system-graph'
+
+type Point = [number, number, number]
+
+// Stub registrations: the graph consults `def.ports` for the connectivity
+// graph and `def.distributionRole` to classify each node. Mirrors the real
+// kinds' port + role conventions (duct runs expose start/end, equipment a
+// supply collar, terminals one collar) without importing the nodes package.
+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('hvac-equipment', 'equipment', (node) => {
+  const position = (node as unknown as { position: Point }).position
+  return [{ id: 'supply', position, direction: [0, 1, 0], diameter: 12, system: 'supply' }]
+})
+stubDef('duct-terminal', 'terminal', (node) => {
+  const position = (node as unknown as { position: Point }).position
+  return [{ id: 'collar', position, direction: [0, -1, 0], diameter: 6, system: 'supply' }]
+})
+
+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 run(path: Point[], system = 'supply'): AnyNode {
+  return makeNode('duct-segment', { path, system, diameter: 6 })
+}
+
+describe('buildPortComponents', () => {
+  test('chained runs land in one component; a distant run is separate', () => {
+    const a = run([
+      [0, 0, 0],
+      [3, 0, 0],
+    ])
+    const b = run([
+      [3, 0, 0],
+      [3, 0, 4],
+    ]) // shares a's end
+    const c = run([
+      [20, 0, 0],
+      [24, 0, 0],
+    ]) // far away
+    const components = buildPortComponents(sceneOf(a, b, c))
+    expect(components.length).toBe(2)
+    const joined = components.find((g) => g.length === 2)!
+    expect(new Set(joined)).toEqual(new Set([a.id, b.id]))
+  })
+
+  test('joints within tolerance still join; outside do not', () => {
+    const a = run([
+      [0, 0, 0],
+      [3, 0, 0],
+    ])
+    const near = run([
+      [3.03, 0, 0],
+      [6, 0, 0],
+    ]) // 3 cm — joined
+    const far = run([
+      [3.2, 0, 4],
+      [6, 0, 4],
+    ]) // 20 cm in another row — separate
+    const components = buildPortComponents(sceneOf(a, near, far))
+    expect(components.length).toBe(2)
+  })
+
+  test('nodes without ports do not participate', () => {
+    const wall = makeNode('wall', {})
+    const a = run([
+      [0, 0, 0],
+      [3, 0, 0],
+    ])
+    const components = buildPortComponents(sceneOf(wall, a))
+    expect(components.length).toBe(1)
+    expect(components[0]).toEqual([a.id])
+  })
+})
+
+describe('summarizeSystemFor', () => {
+  test('full tree: equipment → run → terminal, stats add up', () => {
+    const furnace = makeNode('hvac-equipment', { position: [0, 0, 0] as Point })
+    const trunk = run([
+      [0, 0, 0],
+      [4, 0, 0],
+    ])
+    const branch = run([
+      [4, 0, 0],
+      [4, 0, 3],
+    ])
+    const register = makeNode('duct-terminal', {
+      position: [4, 0, 3] as Point,
+      terminalType: 'supply-register',
+    })
+    const scene = sceneOf(furnace, trunk, branch, register)
+
+    const summary = summarizeSystemFor(register.id, scene)!
+    expect(summary.nodeIds.length).toBe(4)
+    expect(summary.connectedToEquipment).toBe(true)
+    expect(summary.runCount).toBe(2)
+    expect(summary.runLengthM).toBeCloseTo(7, 6)
+    expect(summary.terminalCount).toBe(1)
+    expect(summary.equipmentCount).toBe(1)
+    expect(summary.systems).toEqual(['supply'])
+  })
+
+  test('orphaned run reports no equipment', () => {
+    const lonely = run([
+      [10, 0, 10],
+      [14, 0, 10],
+    ])
+    const summary = summarizeSystemFor(lonely.id, sceneOf(lonely))!
+    expect(summary.connectedToEquipment).toBe(false)
+    expect(summary.runCount).toBe(1)
+    expect(summary.runLengthM).toBeCloseTo(4, 6)
+  })
+
+  test('port-less node → null', () => {
+    const wall = makeNode('wall', {})
+    expect(summarizeSystemFor(wall.id, sceneOf(wall))).toBeNull()
+  })
+})

packages/core/src/services/system-graph.ts

@@ -0,0 +1,196 @@
+import { nodeRegistry } from '../registry'
+import type { AnyNode, AnyNodeId } from '../schema'
+
+/**
+ * The "System" primitive: connected components over the port graph.
+ *
+ * Two nodes are joined when a port of one coincides in space with a port
+ * of the other — the same mated-joint relationship `port-connectivity`
+ * uses for drag propagation, read here at whole-scene scope. A component
+ * is one distribution system: a furnace, its trunk, the tees, branches,
+ * and registers hanging off it.
+ *
+ * Pure logic (def.ports + arithmetic), no rendering — lives in core so
+ * the editor (badges, schedules) and analyses (sizing, code checks) can
+ * share it.
+ */
+
+/** Distance (meters) under which two ports count as the same joint —
+ *  matches port-connectivity's tolerance for hand-placed joints. */
+const COINCIDENT_EPS_M = 0.05
+
+export type SystemSummary = {
+  /** Every node in this connected component. */
+  nodeIds: AnyNodeId[]
+  /** Distribution loops present, e.g. ['supply'], ['supply','return']. */
+  systems: string[]
+  /** Duct / lineset run statistics. */
+  runCount: number
+  runLengthM: number
+  fittingCount: number
+  terminalCount: number
+  equipmentCount: number
+  /** False = orphaned subtree: air goes nowhere (no furnace / air
+   *  handler / condenser anywhere in the component). */
+  connectedToEquipment: boolean
+}
+
+type PortRecord = {
+  nodeId: AnyNodeId
+  x: number
+  y: number
+  z: number
+  system: string | undefined
+}
+
+function collectPorts(nodes: Readonly<Record<AnyNodeId, AnyNode>>): PortRecord[] {
+  const result: PortRecord[] = []
+  for (const node of Object.values(nodes)) {
+    if (!node) continue
+    const ports = nodeRegistry.get(node.type)?.ports?.(node)
+    if (!ports) continue
+    for (const port of ports) {
+      result.push({
+        nodeId: node.id,
+        x: port.position[0],
+        y: port.position[1],
+        z: port.position[2],
+        system: port.system,
+      })
+    }
+  }
+  return result
+}
+
+/** Union-find over node ids. */
+class Components {
+  private parent = new Map<AnyNodeId, AnyNodeId>()
+
+  find(id: AnyNodeId): AnyNodeId {
+    let root = this.parent.get(id) ?? id
+    if (root !== id) {
+      root = this.find(root)
+      this.parent.set(id, root)
+    }
+    return root
+  }
+
+  union(a: AnyNodeId, b: AnyNodeId): void {
+    const ra = this.find(a)
+    const rb = this.find(b)
+    if (ra !== rb) this.parent.set(rb, ra)
+  }
+}
+
+function pathLength(path: ReadonlyArray<readonly [number, number, number]>): number {
+  let total = 0
+  for (let i = 0; i < path.length - 1; i++) {
+    const a = path[i]!
+    const b = path[i + 1]!
+    total += Math.hypot(b[0] - a[0], b[1] - a[1], b[2] - a[2])
+  }
+  return total
+}
+
+/**
+ * Group every port-bearing node into connected components via coinciding
+ * ports. Nodes with ports but no joints form singleton components; nodes
+ * without `def.ports` don't participate at all.
+ */
+export function buildPortComponents(nodes: Readonly<Record<AnyNodeId, AnyNode>>): AnyNodeId[][] {
+  const ports = collectPorts(nodes)
+  const components = new Components()
+  const epsSq = COINCIDENT_EPS_M * COINCIDENT_EPS_M
+
+  for (let i = 0; i < ports.length; i++) {
+    const a = ports[i]!
+    for (let j = i + 1; j < ports.length; j++) {
+      const b = ports[j]!
+      if (a.nodeId === b.nodeId) continue
+      const dx = a.x - b.x
+      const dy = a.y - b.y
+      const dz = a.z - b.z
+      if (dx * dx + dy * dy + dz * dz <= epsSq) components.union(a.nodeId, b.nodeId)
+    }
+  }
+
+  const grouped = new Map<AnyNodeId, AnyNodeId[]>()
+  const seen = new Set<AnyNodeId>()
+  for (const port of ports) {
+    if (seen.has(port.nodeId)) continue
+    seen.add(port.nodeId)
+    const root = components.find(port.nodeId)
+    const group = grouped.get(root)
+    if (group) group.push(port.nodeId)
+    else grouped.set(root, [port.nodeId])
+  }
+  return [...grouped.values()]
+}
+
+function summarize(
+  nodeIds: AnyNodeId[],
+  nodes: Readonly<Record<AnyNodeId, AnyNode>>,
+): SystemSummary {
+  const systems = new Set<string>()
+  let runCount = 0
+  let runLengthM = 0
+  let fittingCount = 0
+  let terminalCount = 0
+  let equipmentCount = 0
+
+  for (const id of nodeIds) {
+    const node = nodes[id]
+    if (!node) continue
+    const role = nodeRegistry.get(node.type)?.distributionRole
+    const fields = node as {
+      path?: ReadonlyArray<readonly [number, number, number]>
+      system?: string
+      terminalType?: string
+    }
+    if (role === 'run') {
+      runCount += 1
+      if (fields.path) runLengthM += pathLength(fields.path)
+      // Linesets carry refrigerant; duct / pipe runs name their own loop.
+      systems.add(fields.system ?? 'refrigerant')
+    } else if (role === 'fitting') {
+      fittingCount += 1
+      if (fields.system) systems.add(fields.system)
+    } else if (role === 'terminal') {
+      terminalCount += 1
+      systems.add(fields.terminalType === 'return-grille' ? 'return' : 'supply')
+    } else if (role === 'equipment') {
+      equipmentCount += 1
+    }
+  }
+
+  return {
+    nodeIds,
+    systems: [...systems].sort(),
+    runCount,
+    runLengthM,
+    fittingCount,
+    terminalCount,
+    equipmentCount,
+    connectedToEquipment: equipmentCount > 0,
+  }
+}
+
+/**
+ * Summary of the system the given node belongs to, or null when the node
+ * has no ports (not a distribution kind). A node with ports but no
+ * joints yet still gets a (singleton) summary — `connectedToEquipment:
+ * false` is the interesting signal there.
+ */
+export function summarizeSystemFor(
+  nodeId: AnyNodeId,
+  nodes: Readonly<Record<AnyNodeId, AnyNode>>,
+): SystemSummary | null {
+  const node = nodes[nodeId]
+  if (!node) return null
+  const ports = nodeRegistry.get(node.type)?.ports?.(node)
+  if (!ports || ports.length === 0) return null
+  for (const component of buildPortComponents(nodes)) {
+    if (component.includes(nodeId)) return summarize(component, nodes)
+  }
+  return summarize([nodeId], nodes)
+}

packages/core/src/services/validate-dwv.test.ts

@@ -0,0 +1,125 @@
+import { describe, expect, test } from 'bun:test'
+import type { AnyNodeDefinition, NodePort } from '../registry'
+import { registerNode } from '../registry'
+import type { AnyNode, AnyNodeId } from '../schema'
+import { validateDwv } from './validate-dwv'
+
+type Point = [number, number, number]
+
+// The validator reads node fields directly + buildPortComponents (which
+// consults def.ports), so register stub port-providers for the DWV kinds
+// it groups by. Mirrors the system-graph test's approach.
+function stubDef(kind: string, ports: (node: AnyNode) => NodePort[]): void {
+  registerNode({
+    kind,
+    schemaVersion: 1,
+    schema: {},
+    category: 'utility',
+    defaults: () => ({}),
+    capabilities: {},
+    ports,
+  } as unknown as AnyNodeDefinition)
+}
+
+stubDef('pipe-segment', (node) => {
+  const path = (node as unknown as { path: Point[] }).path
+  const diameter = (node as unknown as { diameter: number }).diameter
+  const system = (node as unknown as { system: string }).system
+  return [
+    { id: 'start', position: path[0]!, direction: [-1, 0, 0], diameter, system },
+    {
+      id: 'end',
+      position: path[path.length - 1]!,
+      direction: [1, 0, 0],
+      diameter,
+      system,
+    },
+  ]
+})
+stubDef('pipe-trap', (node) => {
+  const position = (node as unknown as { position: Point }).position
+  return [{ id: 'inlet', position, direction: [0, 1, 0], diameter: 1.5, system: 'waste' }]
+})
+
+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>
+}
+
+/** A waste run from a→b. Drop the end Y to slope it. */
+function waste(path: Point[], diameter = 2): AnyNode {
+  return makeNode('pipe-segment', { path, diameter, system: 'waste' })
+}
+
+const QUARTER_PER_FOOT = 1 / 48
+
+describe('validateDwv — slope', () => {
+  test('flags a flat waste run', () => {
+    const run = waste([
+      [0, 0, 0],
+      [3, 0, 0], // dead level
+    ])
+    const findings = validateDwv(sceneOf(run))
+    expect(findings.some((f) => f.code === 'slope-too-flat')).toBe(true)
+  })
+
+  test('passes a run sloped at quarter-inch per foot', () => {
+    const drop = 3 * QUARTER_PER_FOOT
+    const run = waste([
+      [0, 0, 0],
+      [3, -drop, 0],
+    ])
+    const findings = validateDwv(sceneOf(run))
+    expect(findings.some((f) => f.code === 'slope-too-flat')).toBe(false)
+  })
+
+  test('flags an over-steep run (siphoning risk)', () => {
+    // 2" pipe, max slope = 2/12 ≈ 0.167; drop 2m over 1m horizontal.
+    const run = waste([
+      [0, 0, 0],
+      [1, -2, 0],
+    ])
+    const findings = validateDwv(sceneOf(run))
+    expect(findings.some((f) => f.code === 'slope-too-steep')).toBe(true)
+  })
+
+  test('ignores vents (level is fine)', () => {
+    const vent = makeNode('pipe-segment', {
+      path: [
+        [0, 0, 0],
+        [0, 3, 0],
+      ] as Point[],
+      diameter: 2,
+      system: 'vent',
+    })
+    const findings = validateDwv(sceneOf(vent))
+    expect(findings.length).toBe(0)
+  })
+})
+
+describe('validateDwv — trap arm', () => {
+  test('flags an over-long trap arm', () => {
+    const trap = makeNode('pipe-trap', {
+      position: [0, 0, 0] as Point,
+      diameter: 1.5, // max arm 42in = 1.067m
+      armLengthM: 2, // way over
+    })
+    const findings = validateDwv(sceneOf(trap))
+    expect(findings.some((f) => f.code === 'trap-arm-too-long')).toBe(true)
+  })
+
+  test('passes a trap arm within the limit', () => {
+    const trap = makeNode('pipe-trap', {
+      position: [0, 0, 0] as Point,
+      diameter: 2, // max arm 60in = 1.524m
+      armLengthM: 1,
+    })
+    const findings = validateDwv(sceneOf(trap))
+    expect(findings.some((f) => f.code === 'trap-arm-too-long')).toBe(false)
+  })
+})

packages/core/src/services/validate-dwv.ts

@@ -0,0 +1,161 @@
+import type { AnyNode, AnyNodeId } from '../schema'
+import { buildPortComponents } from './system-graph'
+
+/**
+ * IPC validators for the DWV (drain-waste-vent) system — the "CodeRule"
+ * primitive from the domain brief. The slope, minimum-size, and
+ * trap-arm rules are all geometric and read straight off the node
+ * fields, so they live here in core (pure logic) where the editor can
+ * surface them and analyses can reuse them.
+ *
+ * Scope is residential IPC, simplified:
+ *   - 704.1 drainage slope by pipe size.
+ *   - 909 trap-arm maximum developed length by trap size.
+ *
+ * These are intentionally conservative approximations, not a certified
+ * plan-check — enough to flag the mistakes a drawing tool invites.
+ */
+
+/** Drainage findings, worst-first per consumer's sort. */
+export type DwvSeverity = 'error' | 'warning'
+
+export type DwvFinding = {
+  severity: DwvSeverity
+  /** Stable rule id, e.g. 'slope-too-flat'. */
+  code: string
+  /** Human-readable, already-formatted message. */
+  message: string
+  /** Nodes the finding implicates (usually one). */
+  nodeIds: AnyNodeId[]
+}
+
+/** IPC 704.1 minimum drainage slope (rise/run, dimensionless) by
+ *  nominal pipe size: ¼"/ft (1:48) under 3", ⅛"/ft (1:96) for 3–6",
+ *  1/16"/ft (1:192) at 8"+. */
+function minSlopeFor(diameterIn: number): number {
+  if (diameterIn < 3) return 1 / 48
+  if (diameterIn < 8) return 1 / 96
+  return 1 / 192
+}
+
+/** IPC Table 909.1 maximum trap-arm developed length (meters) by trap
+ *  size: 30" @ 1¼", 42" @ 1½", 60" @ 2", 72" @ 3", 120" @ 4". */
+const TRAP_ARM_MAX_M: ReadonlyArray<readonly [number, number]> = [
+  [1.25, 30 * 0.0254],
+  [1.5, 42 * 0.0254],
+  [2, 60 * 0.0254],
+  [3, 72 * 0.0254],
+  [4, 120 * 0.0254],
+]
+
+function trapArmMaxFor(diameterIn: number): number {
+  let max = Infinity
+  for (const [size, lengthM] of TRAP_ARM_MAX_M) {
+    if (diameterIn <= size) return lengthM
+    max = lengthM
+  }
+  return max
+}
+
+/** Slopes shallower than this fraction of the minimum are flagged
+ *  "too flat" — a small tolerance keeps round-off off the list. */
+const SLOPE_TOLERANCE = 0.9
+/** Horizontal legs shorter than this (meters) are treated as vertical
+ *  stacks and skipped from the slope check. */
+const VERTICAL_LEG_EPS_M = 0.02
+
+type Vec3 = readonly [number, number, number]
+
+function legSlope(a: Vec3, b: Vec3): { horizontalM: number; slope: number } {
+  const horizontalM = Math.hypot(b[0] - a[0], b[2] - a[2])
+  if (horizontalM < VERTICAL_LEG_EPS_M) return { horizontalM, slope: Infinity }
+  return { horizontalM, slope: Math.abs(a[1] - b[1]) / horizontalM }
+}
+
+function inchLabel(value: number): string {
+  return `${value}"`
+}
+
+/** Per-foot slope as a readable fraction, e.g. 0.0208 → '¼"/ft'. */
+function slopePerFootLabel(slope: number): string {
+  const inchesPerFoot = slope * 12
+  return `${inchesPerFoot.toFixed(2)}"/ft`
+}
+
+/**
+ * Run every DWV rule over the scene and return the findings. Empty
+ * array = nothing to flag. Pure: no scene/store access, no rendering.
+ */
+export function validateDwv(nodes: Readonly<Record<AnyNodeId, AnyNode>>): DwvFinding[] {
+  const findings: DwvFinding[] = []
+
+  // ── Per-segment slope (waste only) ──────────────────────────────
+  for (const node of Object.values(nodes)) {
+    if (!node || node.type !== 'pipe-segment' || node.system !== 'waste') continue
+    const path = node.path as Vec3[]
+    const minSlope = minSlopeFor(node.diameter)
+    const maxSlope = node.diameter / 12 // 1 pipe-diameter per foot → siphoning
+    let flaggedFlat = false
+    let flaggedSteep = false
+    for (let i = 0; i < path.length - 1; i++) {
+      const { slope } = legSlope(path[i]!, path[i + 1]!)
+      if (slope === Infinity) continue // vertical stack leg
+      if (!flaggedFlat && slope < minSlope * SLOPE_TOLERANCE) {
+        findings.push({
+          severity: 'error',
+          code: 'slope-too-flat',
+          message: `${inchLabel(node.diameter)} drain slopes ${slopePerFootLabel(
+            slope,
+          )} — IPC 704.1 requires at least ${slopePerFootLabel(minSlope)}.`,
+          nodeIds: [node.id],
+        })
+        flaggedFlat = true
+      }
+      if (!flaggedSteep && slope > maxSlope) {
+        findings.push({
+          severity: 'warning',
+          code: 'slope-too-steep',
+          message: `${inchLabel(node.diameter)} drain slopes ${slopePerFootLabel(
+            slope,
+          )} — over one pipe-diameter per foot risks siphoning the traps.`,
+          nodeIds: [node.id],
+        })
+        flaggedSteep = true
+      }
+    }
+  }
+
+  // ── Component-scoped trap rules ──────────────────────────────────
+  for (const component of buildPortComponents(nodes)) {
+    const traps: AnyNode[] = []
+
+    for (const id of component) {
+      const node = nodes[id]
+      if (!node) continue
+      if (node.type === 'pipe-trap') {
+        traps.push(node)
+      }
+    }
+
+    // Trap-arm developed length: trap outlet → its vent, capped by size.
+    // Independent of waste segments — a trap on its own can already be
+    // over-armed.
+    for (const trap of traps) {
+      const t = trap as { id: AnyNodeId; diameter: number; armLengthM?: number }
+      const armLengthM = t.armLengthM ?? 0
+      const maxArm = trapArmMaxFor(t.diameter)
+      if (armLengthM > maxArm + 1e-6) {
+        findings.push({
+          severity: 'error',
+          code: 'trap-arm-too-long',
+          message: `${inchLabel(t.diameter)} trap arm runs ${(armLengthM / 0.0254).toFixed(
+            0,
+          )}" to its vent — IPC 909.1 caps it at ${(maxArm / 0.0254).toFixed(0)}".`,
+          nodeIds: [t.id],
+        })
+      }
+    }
+  }
+
+  return findings
+}

packages/editor/src/components/editor-2d/floorplan-registry-action-menu.tsx

@@ -48,6 +48,13 @@ export function FloorplanRegistryActionMenu() {
   const selectedId = useViewer((s) => s.selection.selectedIds[0]) as AnyNodeId | undefined
   const movingNode = useEditor((s) => s.movingNode)
   const setMovingNode = useEditor((s) => s.setMovingNode)
+  // Gate on floorplan hover so this 2D menu never coexists with the 3D
+  // FloatingActionMenu in split view — that menu hides while the floorplan
+  // is hovered, so this one must only show then. Mirrors the legacy
+  // FloorplanActionMenuLayer guard. Without it a registry kind (e.g. a
+  // duct) shows two Duplicate buttons whenever the pointer is outside the
+  // 2D panel.
+  const isFloorplanHovered = useEditor((s) => s.isFloorplanHovered)
 
   const [position, setPosition] = useState<{ left: number; top: number } | null>(null)
 
@@ -56,7 +63,7 @@ export function FloorplanRegistryActionMenu() {
   const selectedKind = useScene((s) => (selectedId ? (s.nodes[selectedId]?.type ?? null) : null))
   const def = selectedKind ? nodeRegistry.get(selectedKind) : null
   const isRegistryKind = !!def
-  const isVisible = isRegistryKind && !movingNode
+  const isVisible = isRegistryKind && !movingNode && isFloorplanHovered
   const isWall = selectedKind === 'wall'
 
   useEffect(() => {
@@ -191,6 +198,11 @@ export function FloorplanRegistryActionMenu() {
       cloned.metadata && typeof cloned.metadata === 'object' && !Array.isArray(cloned.metadata)
         ? (cloned.metadata as Record<string, unknown>)
         : {}
+    // Mark fresh + hand to the placement cursor so the copy follows the
+    // pointer and only lands on the next click — same gesture for every
+    // kind. Polyline runs (duct / pipe / lineset) ride the same path:
+    // `FloorplanRegistryMoveOverlay` translates their whole `path`, so they
+    // no longer need the old "offset + drop already-placed" special case.
     cloned.metadata = { ...prevMeta, isNew: true }
     const parsed = def.schema.parse(cloned) as AnyNode
     useScene.getState().createNode(parsed, node.parentId as AnyNodeId)

packages/editor/src/components/editor-2d/floorplan-registry-move-overlay.tsx

@@ -429,11 +429,32 @@ export function FloorplanRegistryMoveOverlay() {
     const entry = scene.querySelector(`[data-node-id="${movingNode.id}"]`) as SVGGElement | null
     if (!entry) return
 
-    const originalPosition = ((
-      movingNode as unknown as {
-        position?: [number, number, number]
-      }
-    ).position ?? [0, 0, 0]) as [number, number, number]
+    // Polyline kinds (duct / pipe / lineset) carry a `path`, not a
+    // `position` — translating a `position` here would write a field their
+    // schema ignores and snap the run back. For those we move every path
+    // point by the cursor delta and commit the translated `path` instead.
+    // The reference origin is the path centre so the SVG `translate` delta
+    // matches the geometry's actual location (which isn't at [0,0,0]).
+    const originalPath =
+      'path' in movingNode && Array.isArray((movingNode as { path?: unknown }).path)
+        ? (movingNode as { path: [number, number, number][] }).path.map(
+            (p) => [...p] as [number, number, number],
+          )
+        : null
+    const originalPosition: [number, number, number] = originalPath
+      ? (() => {
+          let cx = 0
+          let cz = 0
+          for (const p of originalPath) {
+            cx += p[0]
+            cz += p[2]
+          }
+          const n = originalPath.length || 1
+          return [cx / n, originalPath[0]?.[1] ?? 0, cz / n]
+        })()
+      : (((movingNode as unknown as { position?: [number, number, number] }).position ?? [
+          0, 0, 0,
+        ]) as [number, number, number])
     const isFreshPlacement = isFreshPlacementMetadata(
       (movingNode as { metadata?: unknown }).metadata,
     )
@@ -450,13 +471,34 @@ export function FloorplanRegistryMoveOverlay() {
       const otherId = el.getAttribute('data-node-id')
       if (!otherId || otherId === movingNode.id) continue
       const b = (el as SVGGraphicsElement).getBBox()
-      if (b.width <= 0 || b.height <= 0) continue
+      // Skip only fully-degenerate (point) entries. A thin run (duct / pipe /
+      // lineset drawn as a line) has one zero dimension but is still a valid
+      // alignment target — its endpoints become line anchors.
+      if (b.width <= 0 && b.height <= 0) continue
       candidateAnchors.push(...bboxAnchors(otherId, b.x, b.y, b.x + b.width, b.y + b.height))
     }
 
     let lastSnapped: [number, number] | null = null
     let dragAnchor: [number, number] | null = null
 
+    // Footprint bounding box drawn around the dragged entry — the 2D
+    // counterpart of the 3D `DragBoundingBox`, so a moved / duplicated node
+    // reads the same in both views. Green wireframe rect over the entry's
+    // own bbox, translated in lockstep with it. The entry stays visible the
+    // whole drag (no hide-until-move) so it never appears to vanish.
+    const SVG_NS = 'http://www.w3.org/2000/svg'
+    const boxEl = document.createElementNS(SVG_NS, 'rect')
+    boxEl.setAttribute('x', String(movingLocalBBox.x))
+    boxEl.setAttribute('y', String(movingLocalBBox.y))
+    boxEl.setAttribute('width', String(movingLocalBBox.width))
+    boxEl.setAttribute('height', String(movingLocalBBox.height))
+    boxEl.setAttribute('fill', 'none')
+    boxEl.setAttribute('stroke', '#22c55e')
+    boxEl.setAttribute('stroke-width', '1.5')
+    boxEl.setAttribute('vector-effect', 'non-scaling-stroke')
+    boxEl.setAttribute('pointer-events', 'none')
+    scene.appendChild(boxEl)
+
     const onMove = (event: PointerEvent) => {
       // Same target guard as Path 1 — pointer must be over the floor
       // plan scene; otherwise we'd react to 3D-canvas moves with garbage
@@ -527,6 +569,7 @@ export function FloorplanRegistryMoveOverlay() {
       const dx = finalX - originalPosition[0]
       const dz = finalZ - originalPosition[2]
       entry.setAttribute('transform', `translate(${dx} ${dz})`)
+      boxEl.setAttribute('transform', `translate(${dx} ${dz})`)
       lastSnapped = [finalX, finalZ]
     }
 
@@ -540,6 +583,33 @@ export function FloorplanRegistryMoveOverlay() {
       const [, oldY] = originalPosition
       setMovingNodeOrigin('2d')
       let selectedId = movingNode.id as AnyNodeId
+      if (originalPath) {
+        // Polyline kinds: shift every point by the committed delta and
+        // write `path`. Strip the fresh-placement flags on first drop.
+        const dx = sx - originalPosition[0]
+        const dz = sz - originalPosition[2]
+        const nextPath = originalPath.map(
+          ([x, y, z]) => [x + dx, y, z + dz] as [number, number, number],
+        )
+        useScene.getState().updateNode(
+          movingNode.id as AnyNodeId,
+          (isFreshPlacement
+            ? {
+                path: nextPath,
+                metadata: stripPlacementMetadataFlags(
+                  (movingNode as { metadata?: unknown }).metadata,
+                ),
+                visible: true,
+              }
+            : { path: nextPath }) as Partial<AnyNode>,
+        )
+        useViewer.getState().setSelection({ selectedIds: [movingNode.id as AnyNodeId] })
+        entry.removeAttribute('transform')
+        useAlignmentGuides.getState().clear()
+        setMovingNode(null)
+        swallowNextClick()
+        return
+      }
       if (isFreshPlacement) {
         selectedId =
           commitFreshPlacementSubtree(
@@ -592,6 +662,10 @@ export function FloorplanRegistryMoveOverlay() {
       window.removeEventListener('pointerup', onPointerUp)
       window.removeEventListener('keydown', onKey)
       entry.removeAttribute('transform')
+      // Always un-hide on teardown so a committed copy shows and a
+      // never-revealed entry doesn't leak a hidden style onto a reused node.
+      entry.style.visibility = ''
+      boxEl.remove()
       useAlignmentGuides.getState().clear()
     }
   }, [isActive, movingNode, setMovingNode, setMovingNodeOrigin, hasMoveTarget, def])

packages/editor/src/components/editor/floating-action-menu.tsx

@@ -24,6 +24,7 @@ import {
   StairNode,
   StairSegmentNode,
   sceneRegistry,
+  summarizeSystemFor,
   useLiveNodeOverrides,
   useScene,
   WallNode,
@@ -32,7 +33,7 @@ import {
 import { useViewer } from '@pascal-app/viewer'
 import { Html } from '@react-three/drei'
 import { useFrame } from '@react-three/fiber'
-import { useCallback, useRef } from 'react'
+import { useCallback, useMemo, useRef } from 'react'
 import * as THREE from 'three'
 import { duplicateRoofSubtree } from '../../lib/roof-duplication'
 import { emitDeleteSFX, sfxEmitter } from '../../lib/sfx-bus'
@@ -41,6 +42,21 @@ import useEditor from '../../store/use-editor'
 import { formatMeasurement, MeasurementPill } from './measurement-pill'
 import { NodeActionMenu } from './node-action-menu'
 
+/**
+ * A kind shows the system pill when it exposes typed ports — `def.ports`
+ * is exactly what makes a node participate in the supply/return graph the
+ * pill summarizes. Keeps the menu off a hand-maintained kind list.
+ */
+const hasPorts = (type: string) => nodeRegistry.get(type)?.ports != null
+
+/**
+ * A kind shows the rotation-axis pill when its R/T keyboard rotation
+ * turns around a user-cyclable axis (`keyboardActions.axisCycling`) —
+ * duct / pipe fittings with full 3D orientation.
+ */
+const hasAxisCycling = (type: string) =>
+  nodeRegistry.get(type)?.keyboardActions?.axisCycling === true
+
 const ALLOWED_TYPES = [
   'item',
   'door',
@@ -200,6 +216,8 @@ export function FloatingActionMenu() {
   // flips only at drag start / end, so subscribing here is cheap — the live
   // height value is written imperatively in the useFrame below.
   const activeHandleDrag = useEditor((s) => s.activeHandleDrag)
+  // R/T rotation axis for kinds with full 3D orientation (duct fittings).
+  const rotationAxis = useEditor((s) => s.rotationAxis)
 
   const groupRef = useRef<THREE.Group>(null)
   const menuScaleRef = useRef<HTMLDivElement>(null)
@@ -490,10 +508,26 @@ export function FloatingActionMenu() {
           // item without clicking" bug. (Item has its own
           // draft-committing move tool, so it must skip the generic
           // registry auto-create branch below.)
+        } else if (
+          duplicate.type === 'duct-segment' ||
+          duplicate.type === 'duct-fitting' ||
+          duplicate.type === 'pipe-segment' ||
+          duplicate.type === 'lineset' ||
+          duplicate.type === 'liquid-line'
+        ) {
+          // Duct runs & fittings, DWV pipe runs, and refrigerant linesets use
+          // pure drag-to-place: NO node is inserted into the scene until the
+          // commit click. `setMovingNode` below hands the clone (with
+          // `metadata.isNew`) to its ghost tool (`MoveDuctSegmentTool` /
+          // `MoveDuctFittingTool` / `MovePipeSegmentTool` / `MoveLinesetTool`),
+          // which previews a translucent copy inside a footprint bounding box
+          // on the cursor and calls `createNode` on the drop click.
+          // Pre-creating here would drop a copy before any click — the
+          // "auto-places it" bug.
         } else if (nodeRegistry.has(duplicate.type)) {
-          // Registry-driven kinds: offset the position slightly so the
-          // duplicate doesn't overlap exactly, then create + hand to the
-          // move tool. Mirrors the roof-segment / stair-segment behavior.
+          // Registry-driven kinds: offset slightly so the duplicate doesn't
+          // overlap exactly, then create + hand to the move tool. Mirrors the
+          // roof-segment / stair-segment behavior.
           if ('position' in duplicate && Array.isArray((duplicate as any).position)) {
             const pos = (duplicate as { position: [number, number, number] }).position
             ;(duplicate as { position: [number, number, number] }).position = [
@@ -501,6 +535,12 @@ export function FloatingActionMenu() {
               pos[1],
               pos[2] + 1,
             ]
+          } else if ('path' in duplicate && Array.isArray((duplicate as any).path)) {
+            // Other polyline kinds (pipe / lineset) carry a `path`, not a
+            // `position`. Create the copy HIDDEN so nothing is auto-placed:
+            // their shared path mover reveals it as a cursor-following
+            // preview on the first mouse move and commits on the next click.
+            ;(duplicate as { visible?: boolean }).visible = false
           }
           useScene.getState().createNode(duplicate, duplicate.parentId as AnyNodeId)
         }
@@ -643,9 +683,86 @@ export function FloatingActionMenu() {
                 />
               </div>
             ) : null}
+            {/* HVAC chrome above the menu — same slot as the wall height
+                pill. System pill (which tree, run length, equipment reach)
+                for every distribution kind; the rotation-axis pill stacks
+                under it for duct fittings. */}
+            {node && hasPorts(node.type) ? (
+              <div className="-translate-x-1/2 pointer-events-none absolute bottom-full left-1/2 mb-2 flex flex-col items-center gap-1">
+                <SystemSummaryPill nodeId={node.id} unit={unit} />
+                {hasAxisCycling(node.type) ? (
+                  <div className="flex items-center gap-2 whitespace-nowrap rounded-full border border-border/60 bg-background/90 px-4 py-1.5 text-xs tabular-nums shadow-sm backdrop-blur">
+                    <span className="font-medium text-foreground">
+                      Axis {rotationAxis.toUpperCase()}
+                    </span>
+                    <span aria-hidden className="text-muted-foreground">
+                      ·
+                    </span>
+                    <span className="text-muted-foreground">R/T rotate</span>
+                    <span aria-hidden className="text-muted-foreground">
+                      ·
+                    </span>
+                    <span className="text-muted-foreground">⌥ axis</span>
+                  </div>
+                ) : null}
+              </div>
+            ) : null}
           </div>
         </Html>
       </group>
     </group>
   )
 }
+
+/**
+ * System summary pill for a selected distribution kind (HVAC duct / DWV
+ * pipe / refrigerant lineset): which supply/return tree it belongs to, its
+ * run length, and whether it actually reaches a piece of equipment.
+ *
+ * Mounted only while an HVAC node is selected, so the full-`nodes`
+ * subscription it needs (connectivity changes when ANY joint moves) doesn't
+ * re-render the always-mounted parent menu on every unrelated scene tick.
+ */
+function SystemSummaryPill({ nodeId, unit }: { nodeId: AnyNodeId; unit: 'metric' | 'imperial' }) {
+  const allNodes = useScene((s) => s.nodes)
+  const summary = useMemo(() => summarizeSystemFor(nodeId, allNodes), [nodeId, allNodes])
+  if (!summary) return null
+  return (
+    <div className="flex items-center gap-2 whitespace-nowrap rounded-full border border-border/60 bg-background/90 px-4 py-1.5 text-xs tabular-nums shadow-sm backdrop-blur">
+      <span className="font-medium text-foreground">
+        {summary.systems.length > 0
+          ? summary.systems.map((sys) => sys[0]!.toUpperCase() + sys.slice(1)).join(' + ')
+          : 'System'}
+      </span>
+      {summary.runCount > 0 ? (
+        <>
+          <span aria-hidden className="text-muted-foreground">
+            ·
+          </span>
+          <span className="text-muted-foreground">
+            {formatMeasurement(summary.runLengthM, unit)} · {summary.runCount}{' '}
+            {summary.runCount === 1 ? 'run' : 'runs'}
+          </span>
+        </>
+      ) : null}
+      {summary.terminalCount > 0 ? (
+        <>
+          <span aria-hidden className="text-muted-foreground">
+            ·
+          </span>
+          <span className="text-muted-foreground">
+            {summary.terminalCount} {summary.terminalCount === 1 ? 'register' : 'registers'}
+          </span>
+        </>
+      ) : null}
+      {summary.connectedToEquipment ? null : (
+        <>
+          <span aria-hidden className="text-muted-foreground">
+            ·
+          </span>
+          <span className="font-medium text-amber-500">⚠ no equipment</span>
+        </>
+      )}
+    </div>
+  )
+}

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

@@ -5551,15 +5551,7 @@ export function FloorplanPanel({
       } as AnyNode
       usePlacementPreview.getState().set(ghost, wall)
     },
-    [
-      DoorNodeSchema,
-      WallNodeSchema,
-      WindowNodeSchema,
-      floorplanOpeningLocalY,
-      isDoorBuildActive,
-      movingNode,
-      movingOpeningType,
-    ],
+    [floorplanOpeningLocalY, isDoorBuildActive, movingNode, movingOpeningType],
   )
   // Drop the floating opening ghost whenever opening placement ends (commit,
   // tool change, mode switch, cancel) or the active level changes, so a stale
@@ -5567,6 +5559,7 @@ export function FloorplanPanel({
   useEffect(() => {
     if (!isOpeningPlacementActive) usePlacementPreview.getState().clear()
   }, [isOpeningPlacementActive])
+  // biome-ignore lint/correctness/useExhaustiveDependencies: `levelId` is an intentional re-run trigger; the effect drops the placement ghost when the active level changes.
   useEffect(() => {
     usePlacementPreview.getState().clear()
   }, [levelId])
@@ -8813,7 +8806,14 @@ export function FloorplanPanel({
       isFenceBuildActive,
       isFloorplanGridInteractionActive,
       isMarqueeSelectionToolActive,
-      isOpeningPlacementActive,
+      isOpeningBuildActive,
+      isOpeningMoveActive,
+      // The off-wall opening ghost is published through this memoised
+      // callback, whose glyph (door swing-arc vs window panes) is bound to
+      // `isDoorBuildActive`. It must be a dependency or a door→window tool
+      // switch (which changes none of the other listed deps) would keep the
+      // stale closure and float a door symbol while the window tool is armed.
+      showOpeningGhost,
       isPolygonBuildActive,
       isRoofBuildActive,
       isSlabBuildActive,

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

@@ -24,6 +24,7 @@ import useEditor from '../../store/use-editor'
 import { CeilingSelectionAffordanceSystem } from '../systems/ceiling/ceiling-selection-affordance-system'
 import { CeilingSystem } from '../systems/ceiling/ceiling-system'
 import { RoofEditSystem } from '../systems/roof/roof-edit-system'
+import { SelectionAffordanceManager } from '../systems/selection-affordance-manager'
 import { StairEditSystem } from '../systems/stair/stair-edit-system'
 import { ZoneLabelEditorSystem } from '../systems/zone/zone-label-editor-system'
 import { ZoneSystem } from '../systems/zone/zone-system'
@@ -55,6 +56,7 @@ import { Grid } from './grid'
 import { GroupMoveHandle } from './group-move-handle'
 import { GroupRotateHandle } from './group-rotate-handle'
 import { NodeArrowHandles } from './node-arrow-handles'
+import { RiserDiagramPanel } from './riser-diagram-panel'
 import { SelectionManager } from './selection-manager'
 import { SiteEdgeLabels } from './site-edge-labels'
 import { SlabHoleHighlights } from './slab-hole-highlights'
@@ -617,6 +619,7 @@ const ViewerSceneContent = memo(function ViewerSceneContent({
       {isFirstPersonMode ? <ViewerZoneSystem /> : <ZoneSystem />}
       <CeilingSystem />
       <CeilingSelectionAffordanceSystem />
+      {!noEditing && <SelectionAffordanceManager />}
       <RoofEditSystem />
       <StairEditSystem />
       {!(isLoading || isFirstPersonMode) && <SnapAwareGrid />}
@@ -1287,6 +1290,7 @@ export default function Editor({
             <div className="pointer-events-auto">
               <HelperManager />
             </div>
+            <RiserDiagramPanel />
             {isFirstPersonMode && (
               <FirstPersonOverlay onExit={() => useEditor.getState().setFirstPersonMode(false)} />
             )}

packages/editor/src/components/editor/measurement-pill.tsx

@@ -23,11 +23,64 @@ const PART_ORDER: { key: MeasurePart; prefix: string }[] = [
   { key: 'thickness', prefix: 'T' },
 ]
 
+export interface DimensionPillPart {
+  key: string
+  prefix: string
+  value: number
+  /** Render an explicit +/- sign — for deltas rather than absolute sizes. */
+  signed?: boolean
+}
+
+/**
+ * Generic floating dimension pill: a row of `prefix value` readouts with the
+ * active one emphasised. Styled to match the top-center floating info bar
+ * (rounded-full, design-token colours) so it tracks the app theme.
+ *
+ * `primaryRef` points at the primary value's `<span>` so a caller driving a
+ * per-frame drag can rewrite its text imperatively without a React re-render.
+ */
+export function DimensionPill({
+  parts,
+  unit,
+  primary,
+  primaryRef,
+}: {
+  parts: DimensionPillPart[]
+  unit: 'metric' | 'imperial'
+  primary?: string
+  primaryRef?: ForwardedRef<HTMLSpanElement>
+}) {
+  return (
+    <div className="flex items-center gap-2 whitespace-nowrap rounded-full border border-border/60 bg-background/90 px-4 py-1.5 text-xs tabular-nums shadow-sm backdrop-blur">
+      {parts.map((part, index) => {
+        const text = part.signed
+          ? `${part.value < 0 ? '-' : '+'}${formatMeasurement(Math.abs(part.value), unit)}`
+          : formatMeasurement(part.value, unit)
+        return (
+          <Fragment key={part.key}>
+            {index > 0 ? (
+              <span aria-hidden className="text-muted-foreground">
+                ·
+              </span>
+            ) : null}
+            <span
+              className={
+                part.key === primary ? 'font-medium text-foreground' : 'text-muted-foreground'
+              }
+              ref={part.key === primary ? primaryRef : undefined}
+            >
+              {`${part.prefix} ${text}`}
+            </span>
+          </Fragment>
+        )
+      })}
+    </div>
+  )
+}
+
 /**
  * Floating dimension pill shown during wall / fence drags: `H · L · T` with
- * the actively-dragged dimension emphasised. Styled to match the top-center
- * floating info bar (rounded-full, design-token colours) so it tracks the
- * app theme.
+ * the actively-dragged dimension emphasised.
  *
  * The forwarded ref points at the `primary` value's `<span>` so a caller
  * driving a per-frame drag (the height arrow) can rewrite its text
@@ -52,24 +105,11 @@ export const MeasurementPill = forwardRef(function MeasurementPill(
 ) {
   const values: Record<MeasurePart, number> = { height, length, thickness }
   return (
-    <div className="flex items-center gap-2 whitespace-nowrap rounded-full border border-border/60 bg-background/90 px-4 py-1.5 text-xs tabular-nums shadow-sm backdrop-blur">
-      {PART_ORDER.map((part, index) => (
-        <Fragment key={part.key}>
-          {index > 0 ? (
-            <span aria-hidden className="text-muted-foreground">
-              ·
-            </span>
-          ) : null}
-          <span
-            className={
-              part.key === primary ? 'font-medium text-foreground' : 'text-muted-foreground'
-            }
-            ref={part.key === primary ? primaryRef : undefined}
-          >
-            {`${part.prefix} ${formatMeasurement(values[part.key], unit)}`}
-          </span>
-        </Fragment>
-      ))}
-    </div>
+    <DimensionPill
+      parts={PART_ORDER.map((part) => ({ ...part, value: values[part.key] }))}
+      primary={primary}
+      primaryRef={primaryRef}
+      unit={unit}
+    />
   )
 })

packages/editor/src/components/editor/riser-diagram-panel.tsx

@@ -0,0 +1,137 @@
+'use client'
+
+import { type AnyNodeId, buildRiserDiagram, useScene } from '@pascal-app/core'
+import { useViewer } from '@pascal-app/viewer'
+import { X } from 'lucide-react'
+import { useMemo } from 'react'
+import useEditor from '../../store/use-editor'
+
+const WASTE_COLOR = '#0ea5e9'
+const VENT_COLOR = '#a855f7'
+const MARKER_COLOR = '#1e293b'
+const PADDING = 32
+/** Meters → SVG units. The iso projection is in meters; scale up so a
+ *  typical house drain (a few meters) fills the panel. */
+const SCALE = 90
+
+/**
+ * DWV riser diagram — the plumbing isometric drawn from the scene's
+ * drain/waste/vent nodes. Read-only; toggled from the view controls.
+ * Vertical stacks read vertical, sloped drains lean at 30°, with size +
+ * vent-termination annotations, matching the permit-drawing convention.
+ * Clicking a line/marker selects its node in 3D.
+ */
+export function RiserDiagramPanel() {
+  const isOpen = useEditor((s) => s.isRiserOpen)
+  // Only the open flag lives here. The whole-scene subscription that drives
+  // the diagram lives in the child, mounted only while the panel is open —
+  // so a closed panel doesn't re-render on every scene mutation.
+  if (!isOpen) return null
+  return <RiserDiagramContent />
+}
+
+function RiserDiagramContent() {
+  const setRiserOpen = useEditor((s) => s.setRiserOpen)
+  const nodes = useScene((s) => s.nodes)
+  const selectedIds = useViewer((s) => s.selection.selectedIds)
+
+  const diagram = useMemo(() => buildRiserDiagram(nodes), [nodes])
+
+  const select = (nodeId: AnyNodeId) => useViewer.getState().setSelection({ selectedIds: [nodeId] })
+
+  const width = diagram ? (diagram.bounds.maxX - diagram.bounds.minX) * SCALE + PADDING * 2 : 320
+  const height = diagram ? (diagram.bounds.maxY - diagram.bounds.minY) * SCALE + PADDING * 2 : 200
+  const tx = diagram ? -diagram.bounds.minX * SCALE + PADDING : 0
+  const ty = diagram ? -diagram.bounds.minY * SCALE + PADDING : 0
+
+  return (
+    <div className="dark pointer-events-auto absolute top-4 right-4 z-30 flex max-h-[80vh] w-[26rem] flex-col overflow-hidden rounded-2xl border border-border/40 bg-background/95 text-foreground shadow-lg backdrop-blur-xl">
+      <div className="flex items-center justify-between border-border/40 border-b px-4 py-2.5">
+        <div className="flex flex-col">
+          <span className="font-medium text-sm">Riser Diagram</span>
+          <span className="text-muted-foreground text-xs">DWV plumbing isometric</span>
+        </div>
+        <button
+          className="flex h-7 w-7 items-center justify-center rounded-md transition-colors hover:bg-white/10"
+          onClick={() => setRiserOpen(false)}
+        >
+          <X className="h-4 w-4 text-muted-foreground" />
+        </button>
+      </div>
+
+      <div className="flex items-center gap-3 border-border/40 border-b px-4 py-2 text-xs">
+        <span className="flex items-center gap-1.5">
+          <span className="h-0.5 w-4" style={{ background: WASTE_COLOR }} /> Waste
+        </span>
+        <span className="flex items-center gap-1.5">
+          <span className="h-0 w-4 border-t-2 border-dashed" style={{ borderColor: VENT_COLOR }} />{' '}
+          Vent
+        </span>
+      </div>
+
+      <div className="overflow-auto p-2">
+        {diagram ? (
+          <svg
+            height={Math.max(height, 120)}
+            role="img"
+            aria-label="DWV riser diagram"
+            viewBox={`0 0 ${Math.max(width, 200)} ${Math.max(height, 120)}`}
+            width="100%"
+          >
+            <g transform={`translate(${tx}, ${ty})`}>
+              {diagram.lines.map((line, i) => {
+                const isSel = selectedIds.includes(line.nodeId)
+                const color = line.system === 'waste' ? WASTE_COLOR : VENT_COLOR
+                return (
+                  <g key={`${line.nodeId}-${i}`}>
+                    <line
+                      className="cursor-pointer"
+                      onClick={() => select(line.nodeId)}
+                      stroke={color}
+                      strokeDasharray={line.system === 'vent' ? '5 4' : undefined}
+                      strokeLinecap="round"
+                      strokeWidth={(line.vertical ? 3.5 : 2.5) + (isSel ? 2 : 0)}
+                      x1={line.from[0] * SCALE}
+                      x2={line.to[0] * SCALE}
+                      y1={line.from[1] * SCALE}
+                      y2={line.to[1] * SCALE}
+                    />
+                    <text
+                      fill={color}
+                      fontSize={9}
+                      x={((line.from[0] + line.to[0]) / 2) * SCALE + 4}
+                      y={((line.from[1] + line.to[1]) / 2) * SCALE - 3}
+                    >
+                      {line.diameter}"
+                    </text>
+                  </g>
+                )
+              })}
+              {diagram.markers.map((marker, i) => (
+                <g
+                  className="cursor-pointer"
+                  key={`${marker.nodeId}-${i}`}
+                  onClick={() => select(marker.nodeId)}
+                  transform={`translate(${marker.point[0] * SCALE}, ${marker.point[1] * SCALE})`}
+                >
+                  {marker.kind === 'vent-termination' ? (
+                    <path d="M -5 0 L 0 -7 L 5 0" fill="none" stroke={VENT_COLOR} strokeWidth={2} />
+                  ) : (
+                    <circle fill={MARKER_COLOR} r={3} stroke={MARKER_COLOR} strokeWidth={1.5} />
+                  )}
+                  <text fill={MARKER_COLOR} fontSize={9} x={8} y={3}>
+                    {marker.label}
+                  </text>
+                </g>
+              ))}
+            </g>
+          </svg>
+        ) : (
+          <div className="flex h-32 items-center justify-center px-6 text-center text-muted-foreground text-sm">
+            No drain, waste, or vent pipes yet. Draw plumbing to see the riser diagram.
+          </div>
+        )}
+      </div>
+    </div>
+  )
+}

packages/editor/src/components/systems/selection-affordance-manager.tsx

@@ -0,0 +1,38 @@
+'use client'
+
+import { type AnyNodeId, useScene } from '@pascal-app/core'
+import { useViewer } from '@pascal-app/viewer'
+import { type ComponentType, Suspense, useMemo } from 'react'
+import { getRegistryAffordanceTool } from '../tools/shared/affordance-dispatch'
+
+/**
+ * Editor-mounted dispatcher for a kind's selection-time editing UI.
+ *
+ * Some kinds expose drag-to-edit affordances that should appear only
+ * while a single node of that kind is selected — duct / pipe / lineset
+ * path-point handles, fitting Alt-axis-cycling listeners. These read
+ * `useEditor` (grid snap step, rotation axis) and render the editor's
+ * `DimensionPill`, so they must NOT ride in `def.system` (which the
+ * viewer package mounts for the read-only route). The kind declares the
+ * component under `def.affordanceTools.selection` and this manager —
+ * mounted inside the editor only — loads it for the selected kind.
+ */
+export function SelectionAffordanceManager() {
+  const selectedIds = useViewer((s) => s.selection.selectedIds)
+  const selectedKind = useScene((s) => {
+    if (selectedIds.length !== 1) return null
+    return s.nodes[selectedIds[0] as AnyNodeId]?.type ?? null
+  })
+
+  const Component = useMemo<ComponentType | null>(() => {
+    if (!selectedKind) return null
+    return getRegistryAffordanceTool(selectedKind, 'selection')
+  }, [selectedKind])
+
+  if (!Component) return null
+  return (
+    <Suspense fallback={null}>
+      <Component />
+    </Suspense>
+  )
+}

packages/editor/src/components/tools/item/move-tool.tsx

@@ -9,14 +9,17 @@ import { getRegistryAffordanceTool } from '../shared/affordance-dispatch'
 /**
  * MoveTool dispatcher. Routes to (in order):
  *
- *   1. `MoveRegistryNodeTool` — generic translate-on-XZ for kinds that
- *      declare `capabilities.movable` (shelf, spawn, item-with-floor-attach,
- *      …).
- *   2. `def.affordanceTools.move` — kind-owned move component, lazy-loaded
- *      via `getRegistryAffordanceTool`. Covers both generic movers
- *      (slab / ceiling / wall / fence / column / item / door / window) and
- *      the bespoke roof / roof-segment / stair / stair-segment / building
- *      movers ported into `@pascal-app/nodes`.
+ *   1. `def.affordanceTools.move` — kind-owned move component, lazy-loaded
+ *      via `getRegistryAffordanceTool`. Covers generic movers
+ *      (slab / ceiling / wall / fence / column / item / door / window), the
+ *      bespoke roof / roof-segment / stair / stair-segment / building
+ *      movers, and the polyline / fitting ghost-placement movers
+ *      (duct-segment / duct-fitting). A kind that ships its own mover wins
+ *      even if it also declares `capabilities.movable` (duct-fitting keeps
+ *      `movable` for the inspector / hint readers but places via its ghost).
+ *   2. `MoveRegistryNodeTool` — generic translate-on-XZ for kinds that only
+ *      declare `capabilities.movable` (shelf, spawn, duct-terminal,
+ *      hvac-equipment, …).
  *   3. `elevator` is the lone remaining legacy arm — its bespoke cab/shaft
  *      mover hasn't been ported to a kind-owned affordance yet.
  */
@@ -29,9 +32,6 @@ export const MoveTool: React.FC<{
   if (!movingNode) return null
 
   const def = nodeRegistry.get(movingNode.type)
-  if (def?.capabilities?.movable) {
-    return <MoveRegistryNodeTool node={movingNode} />
-  }
 
   const RegistryMove = getRegistryAffordanceTool(movingNode.type, 'move')
   if (RegistryMove) {
@@ -42,6 +42,10 @@ export const MoveTool: React.FC<{
     )
   }
 
+  if (def?.capabilities?.movable) {
+    return <MoveRegistryNodeTool node={movingNode} />
+  }
+
   if (movingNode.type === 'elevator')
     return <MoveElevatorTool node={movingNode as ElevatorNode} onCommitted={onNodeMoved} />
   return null

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

@@ -5,6 +5,7 @@ import '../../../three-types'
 import {
   type AnyNode,
   type AnyNodeId,
+  analyzePortConnectivity,
   collectAlignmentAnchors,
   type EventSuffix,
   emitter,
@@ -12,9 +13,12 @@ import {
   movingFootprintAnchors,
   type NodeEvent,
   nodeRegistry,
+  type PortConnectivity,
   resolveAlignment,
+  resolveConnectivityUpdates,
   sceneRegistry,
   spatialGridManager,
+  useLiveNodeOverrides,
   useLiveTransforms,
   useScene,
 } from '@pascal-app/core'
@@ -44,6 +48,65 @@ const snapToGridStep = (value: number) => {
 /** 45° steps, matching the GLB item placement rotation. */
 const ROTATION_STEP = Math.PI / 4
 
+/** Default magnetic radius (meters, XZ) for `movable.portSnap`. */
+const PORT_SNAP_RADIUS_M = 0.5
+
+/**
+ * Magnetic port snap for a dragged node: if one of the node's own ports
+ * (read live from `def.ports`) lands within `radius` of a matching scene
+ * port at the candidate XZ, return the node XZ that mates them exactly.
+ *
+ * Pure core: ports come through `nodeRegistry` so this stays layer-clean.
+ * Ports are level-local meters — the same frame as the cursor's
+ * `localPosition`, so no extra transform is needed. The dragged node's
+ * ports move rigidly with its position, so a port at candidate `(x,z)`
+ * sits at `portStored + (candidate - nodeStored)`. We pick the closest
+ * (own-port, target-port) pair and shift the node so they coincide in XZ.
+ */
+function resolvePortSnap(
+  node: AnyNode,
+  candidate: [number, number],
+  config: { systems?: readonly string[]; radius?: number },
+): [number, number] | null {
+  const nodePos = (node as { position?: [number, number, number] }).position
+  if (!nodePos) return null
+  const ownPorts = nodeRegistry.get(node.type)?.ports?.(node)
+  if (!ownPorts || ownPorts.length === 0) return null
+
+  const radius = config.radius ?? PORT_SNAP_RADIUS_M
+  const radiusSq = radius * radius
+  const { systems } = config
+  const dragDx = candidate[0] - nodePos[0]
+  const dragDz = candidate[1] - nodePos[2]
+
+  const nodes = useScene.getState().nodes
+  let bestDistSq = radiusSq
+  let snap: [number, number] | null = null
+
+  for (const node2 of Object.values(nodes)) {
+    if (!node2 || node2.id === node.id) continue
+    const targets = nodeRegistry.get(node2.type)?.ports?.(node2)
+    if (!targets) continue
+    for (const target of targets) {
+      if (systems && target.system !== undefined && !systems.includes(target.system)) continue
+      for (const own of ownPorts) {
+        // Own port at the candidate position = stored port + drag delta.
+        const ownX = own.position[0] + dragDx
+        const ownZ = own.position[2] + dragDz
+        const dx = target.position[0] - ownX
+        const dz = target.position[2] - ownZ
+        const distSq = dx * dx + dz * dz
+        if (distSq <= bestDistSq) {
+          bestDistSq = distSq
+          // Shift the node so this own port lands on the target (XZ only).
+          snap = [candidate[0] + dx, candidate[1] + dz]
+        }
+      }
+    }
+  }
+  return snap
+}
+
 /** Figma-style alignment-snap threshold (meters), matching the 2D
  *  floor-plan overlay's `ALIGNMENT_THRESHOLD_M`. 8 cm gives a magnetic pull
  *  without fighting grid snap. Fixed for v1 — no zoom-scaling in 3D. */
@@ -145,6 +208,15 @@ export function MoveRegistryNodeTool({ node }: { node: AnyNode }) {
   // and bumped by R/T. Applied imperatively + mirrored to `useLiveTransforms`,
   // and committed to the scene on drop.
   const rotationRef = useRef(originalRotationY)
+  // Snapshot of which ducts / fittings are mated to this node's ports at
+  // drag-start (duct fittings only). Drives the "connected ductwork follows"
+  // behaviour: connected nodes preview through `useLiveNodeOverrides` during
+  // the drag and commit alongside the moved node on drop. Null for kinds with
+  // no ports, so every other movable kind is unaffected.
+  const connectivityRef = useRef<PortConnectivity | null>(null)
+  // Node ids this drag has pushed live overrides onto — cleared on
+  // commit / cancel / unmount so a follow-on drag starts clean.
+  const overriddenIdsRef = useRef<AnyNodeId[]>([])
 
   // Shelf placement shows the same green/red footprint box GLB items use
   // (instead of the vertical-arrow cursor) and refuses an invalid drop unless
@@ -163,6 +235,15 @@ export function MoveRegistryNodeTool({ node }: { node: AnyNode }) {
   const [cursorRotationY, setCursorRotationY] = useState(originalRotationY)
   const { isFreshPlacement, previewVisible, revealFreshPlacement, useAbsoluteCursorPlacement } =
     useFreshPlacementVisibility({ node })
+  // Kinds that declare `movable.cursorAttached` (duct fittings) pin to the
+  // cursor instead of preserving the grab offset — small connector-like
+  // nodes read an offset drag as "lagging behind the mouse".
+  const cursorAttached = nodeRegistry.get(node.type)?.capabilities?.movable?.cursorAttached === true
+  // Kinds that declare `movable.portSnap` (duct terminals) magnetically
+  // mate one of their own ports onto a nearby scene port while dragging —
+  // a register collar drops onto a duct run end. Reads `def.ports` through
+  // the core registry, so it stays layer-clean (no @pascal-app/nodes import).
+  const portSnapConfig = nodeRegistry.get(node.type)?.capabilities?.movable?.portSnap ?? null
   // Mirrors of `valid` / Shift for the event handlers inside the effect, which
   // can't read React state without stale closures.
   const validRef = useRef(true)
@@ -212,6 +293,45 @@ export function MoveRegistryNodeTool({ node }: { node: AnyNode }) {
       }
     }
 
+    // Connectivity follow (duct fittings): the moved node with its live drag
+    // transform, so `def.ports` recomputes for `resolveConnectivityUpdates`.
+    // Uses the logical (un-stacked) position + Y rotation that commit writes,
+    // not the floor-lifted visual position.
+    const buildPreviewNode = (position: [number, number, number], rotationY: number): AnyNode =>
+      ({
+        ...(node as Record<string, unknown>),
+        position,
+        rotation: toCommitRotation(rotationY),
+      }) as AnyNode
+
+    // Resolve the patches that keep connected ductwork attached and preview
+    // them through `useLiveNodeOverrides` (transient — no history churn;
+    // GeometrySystem merges overrides via getEffectiveNode). Each connected
+    // node is re-dirtied so its geometry rebuilds against the new override.
+    const previewConnectivity = (position: [number, number, number], rotationY: number) => {
+      const connectivity = connectivityRef.current
+      if (!connectivity) return
+      const updates = resolveConnectivityUpdates(
+        connectivity,
+        buildPreviewNode(position, rotationY),
+      )
+      if (updates.length === 0) return
+      useLiveNodeOverrides
+        .getState()
+        .setMany(updates.map((u) => [u.id, u.data as Record<string, unknown>] as const))
+      overriddenIdsRef.current = updates.map((u) => u.id)
+      for (const u of updates) {
+        if (useScene.getState().nodes[u.id]) useScene.getState().markDirty(u.id)
+      }
+    }
+
+    const clearConnectivityOverrides = () => {
+      for (const id of overriddenIdsRef.current) {
+        useLiveNodeOverrides.getState().clear(id)
+        if (useScene.getState().nodes[id]) useScene.getState().markDirty(id)
+      }
+    }
+
     setCursorPosition(getVisualPosition(originalPosition, originalRotationY))
 
     // Re-run the floor-collision check at the live cursor + rotation and push
@@ -277,6 +397,16 @@ export function MoveRegistryNodeTool({ node }: { node: AnyNode }) {
       useViewer.getState().selection.levelId ?? node.parentId,
     )
 
+    // Connectivity snapshot (existing port-bearing nodes only — fresh
+    // placements aren't connected to anything yet). Records which ducts /
+    // fittings are mated to this node's ports so they can follow the drag.
+    connectivityRef.current = null
+    overriddenIdsRef.current = []
+    if (!isNew && nodeRegistry.get(node.type)?.ports) {
+      const snapshot = analyzePortConnectivity(node, useScene.getState().nodes)
+      if (snapshot.connections.length > 0) connectivityRef.current = snapshot
+    }
+
     const onGridMove = (event: GridEvent) => {
       const rawX = event.localPosition[0]
       const rawZ = event.localPosition[2]
@@ -286,7 +416,7 @@ export function MoveRegistryNodeTool({ node }: { node: AnyNode }) {
         cursor: [rawX, rawZ],
         original: [originalPosition[0], originalPosition[2]],
         anchor: dragAnchorRef.current,
-        mode: useAbsoluteCursorPlacement ? 'absolute' : 'relative',
+        mode: useAbsoluteCursorPlacement || cursorAttached ? 'absolute' : 'relative',
         snap: event.nativeEvent?.shiftKey === true ? (value) => value : snapToGridStep,
       })
       dragAnchorRef.current = resolved.anchor
@@ -313,6 +443,18 @@ export function MoveRegistryNodeTool({ node }: { node: AnyNode }) {
         useAlignmentGuides.getState().clear()
       }
 
+      // Magnetic port snap (duct terminals): mate a collar onto a nearby
+      // duct run end. Takes precedence over grid / alignment snap; Alt
+      // bypasses. Only kinds that opted in via `movable.portSnap`.
+      if (!bypass && portSnapConfig) {
+        const mated = resolvePortSnap(node, [x, z], portSnapConfig)
+        if (mated) {
+          x = mated[0]
+          z = mated[1]
+          useAlignmentGuides.getState().clear()
+        }
+      }
+
       const position: [number, number, number] = [x, originalPosition[1], z]
       const visualPosition = getVisualPosition(position)
       hasMovedRef.current = true
@@ -337,6 +479,8 @@ export function MoveRegistryNodeTool({ node }: { node: AnyNode }) {
         rotation: rotationRef.current,
       })
       markMovedNodeDirty()
+      // Carry connected ductwork along (preview only — committed on drop).
+      previewConnectivity(position, rotationRef.current)
 
       const prev = previousSnapRef.current
       if (event.nativeEvent?.shiftKey !== true && (!prev || prev[0] !== x || prev[1] !== z)) {
@@ -403,8 +547,18 @@ export function MoveRegistryNodeTool({ node }: { node: AnyNode }) {
             committedId = finalId
           }
         } else {
+          // Fold the connected-ductwork follow-updates into the SAME
+          // batch as the moved node so the whole thing is one undo step.
+          const connectivityUpdates = connectivityRef.current
+            ? resolveConnectivityUpdates(
+                connectivityRef.current,
+                buildPreviewNode(position, rotationRef.current),
+              ).filter((u) => useScene.getState().nodes[u.id])
+            : []
           useScene.temporal.getState().resume()
-          useScene.getState().updateNode(node.id, data)
+          useScene
+            .getState()
+            .updateNodes([{ id: node.id as AnyNodeId, data }, ...connectivityUpdates])
           useScene.temporal.getState().pause()
           committed = true
         }
@@ -430,6 +584,9 @@ export function MoveRegistryNodeTool({ node }: { node: AnyNode }) {
       // canonical position, then restamp the lifted presentation Y for the
       // current frame.
       useLiveTransforms.getState().clear(node.id)
+      // Connected ductwork is now committed to the store — drop its live
+      // overrides so the renderers read the canonical path/position.
+      clearConnectivityOverrides()
       const mesh = sceneRegistry.nodes.get(node.id)
       if (mesh) {
         mesh.position.set(...visualPosition)
@@ -491,6 +648,8 @@ export function MoveRegistryNodeTool({ node }: { node: AnyNode }) {
         rotation: rotationRef.current,
       })
       markMovedNodeDirty()
+      // Rotating the fitting swings its collars — connected ducts follow.
+      previewConnectivity(position, rotationRef.current)
       // Rotation changes the footprint's collision span — re-check validity.
       recomputeValidity()
     }
@@ -533,6 +692,7 @@ export function MoveRegistryNodeTool({ node }: { node: AnyNode }) {
 
     const onCancel = () => {
       useLiveTransforms.getState().clear(node.id)
+      clearConnectivityOverrides()
       if (isNew) {
         useScene.getState().deleteNode(node.id as AnyNodeId)
       } else {
@@ -570,6 +730,7 @@ export function MoveRegistryNodeTool({ node }: { node: AnyNode }) {
       const finalisedBy2D = useEditor.getState().movingNodeOrigin === '2d'
       if (!(committed || isNew || finalisedBy2D)) {
         useLiveTransforms.getState().clear(node.id)
+        clearConnectivityOverrides()
         sceneRegistry.nodes
           .get(node.id)
           ?.position.set(...getVisualPosition(originalPosition, originalRotationY))
@@ -579,6 +740,8 @@ export function MoveRegistryNodeTool({ node }: { node: AnyNode }) {
     }
   }, [
     boxDimensions,
+    cursorAttached,
+    portSnapConfig,
     exitMoveMode,
     isFreshPlacement,
     node,

packages/editor/src/components/ui/action-menu/structure-tools.tsx

@@ -25,4 +25,12 @@ export const tools: ToolConfig[] = [
   { id: 'zone', iconSrc: '/icons/zone.png', label: 'Zone' },
   { id: 'spawn', iconSrc: '/icons/spawn-point.png', label: 'Spawn Point' },
   { id: 'shelf', iconSrc: '/icons/shelf.png', label: 'Shelf' },
+  { id: 'duct-segment', iconSrc: '/icons/duct.png', label: 'Duct' },
+  { id: 'duct-fitting', iconSrc: '/icons/duct-fitting.png', label: 'Duct Fitting' },
+  { id: 'duct-terminal', iconSrc: '/icons/registers.png', label: 'Register' },
+  { id: 'hvac-equipment', iconSrc: '/icons/HVAC.png', label: 'HVAC Unit' },
+  { id: 'pipe-segment', iconSrc: '/icons/dwv-pipes.png', label: 'DWV Pipe' },
+  { id: 'pipe-fitting', iconSrc: '/icons/duct-fitting.png', label: 'Pipe Fitting' },
+  { id: 'lineset', iconSrc: '/icons/lineset.png', label: 'Lineset' },
+  { id: 'liquid-line', iconSrc: '/icons/lineset.png', label: 'Liquid Line' },
 ]

packages/editor/src/components/ui/action-menu/view-toggles.tsx

@@ -10,7 +10,7 @@ import {
   useScene,
 } from '@pascal-app/core'
 import { useViewer } from '@pascal-app/viewer'
-import { Check, ChevronDown, Eye, EyeOff, Layers2, Plus, Trash2 } from 'lucide-react'
+import { Check, ChevronDown, Eye, EyeOff, Layers2, Plus, Trash2, Waypoints } from 'lucide-react'
 import { useCallback, useRef, useState } from 'react'
 import { useShallow } from 'zustand/react/shallow'
 import { getLevelDisplayName } from '@pascal-app/core'
@@ -989,6 +989,29 @@ function ReferenceFloorControl() {
   )
 }
 
+// ── Riser diagram control ────────────────────────────────────────────────────
+
+function RiserControl() {
+  const isRiserOpen = useEditor((state) => state.isRiserOpen)
+  const toggleRiserOpen = useEditor((state) => state.toggleRiserOpen)
+
+  return (
+    <ActionButton
+      className={cn(
+        isRiserOpen
+          ? 'bg-white/15'
+          : 'opacity-60 grayscale hover:bg-white/5 hover:opacity-100 hover:grayscale-0',
+      )}
+      label="Riser diagram"
+      onClick={toggleRiserOpen}
+      size="icon"
+      variant="ghost"
+    >
+      <Waypoints className="h-4 w-4" />
+    </ActionButton>
+  )
+}
+
 // ── Exports ─────────────────────────────────────────────────────────────────
 
 export { GridSnapControl }
@@ -1008,6 +1031,7 @@ export function ViewToggles() {
       <ScansControl />
       <GuidesControl />
       <ReferenceFloorControl />
+      <RiserControl />
     </div>
   )
 }

packages/editor/src/components/ui/panels/parametric-inspector.tsx

@@ -62,9 +62,22 @@ export function ParametricInspector({
   const handleUpdate = useCallback(
     (patch: Partial<AnyNode>) => {
       if (!selectedId) return
-      useScene.getState().updateNode(selectedId, patch)
+      const scene = useScene.getState()
+      const node = scene.nodes[selectedId]
+      if (parametrics?.derive && node) {
+        const next = { ...node, ...patch } as AnyNode
+        patch = { ...patch, ...parametrics.derive(next, patch) }
+      }
+      // Bundle the edited node + any reconcile follow-ups into ONE
+      // updateNodes call so a single inspector edit is a single undo step.
+      const updates: { id: AnyNodeId; data: Partial<AnyNode> }[] = [{ id: selectedId, data: patch }]
+      if (parametrics?.reconcile && node) {
+        const next = { ...node, ...patch } as AnyNode
+        updates.push(...parametrics.reconcile(node as AnyNode, next))
+      }
+      scene.updateNodes(updates)
     },
-    [selectedId],
+    [selectedId, parametrics],
   )
 
   const clearSelection = useCallback(() => {

packages/editor/src/index.tsx

@@ -12,7 +12,12 @@ export { default as Editor } from './components/editor'
 // surface uses the shorter, shell-friendly names from the unified
 // preset-system spec.
 export { FloatingActionMenu as FloatingMenu } from './components/editor/floating-action-menu'
-export { formatMeasurement, MeasurementPill } from './components/editor/measurement-pill'
+export {
+  DimensionPill,
+  type DimensionPillPart,
+  formatMeasurement,
+  MeasurementPill,
+} from './components/editor/measurement-pill'
 export {
   type SnapshotCameraData,
   ThumbnailGenerator,

packages/editor/src/store/use-editor.tsx

@@ -106,6 +106,14 @@ export type StructureTool =
   | 'dormer'
   | 'gutter'
   | 'downspout'
+  | 'duct-segment'
+  | 'duct-fitting'
+  | 'duct-terminal'
+  | 'hvac-equipment'
+  | 'lineset'
+  | 'liquid-line'
+  | 'pipe-segment'
+  | 'pipe-fitting'
 
 // Furnish mode tools (items and decoration)
 export type FurnishTool = 'item'
@@ -291,6 +299,14 @@ type EditorState = {
    */
   activeHandleDrag: { nodeId: AnyNodeId; label: string } | null
   setActiveHandleDrag: (drag: { nodeId: AnyNodeId; label: string } | null) => void
+  /**
+   * World axis the R/T keyboard rotation turns around, for kinds with
+   * full 3D orientation (duct fittings). Alt cycles it Y → X → Z; the
+   * kind's tool / keyboard actions read it, and the floating action
+   * menu surfaces it in a pill above the selected node.
+   */
+  rotationAxis: 'x' | 'y' | 'z'
+  cycleRotationAxis: () => 'x' | 'y' | 'z'
   curvingWall: WallNode | null
   setCurvingWall: (wall: WallNode | null) => void
   curvingFence: FenceNode | null
@@ -348,6 +364,10 @@ type EditorState = {
   toggleFloorplanOpen: () => void
   isFloorplanHovered: boolean
   setFloorplanHovered: (hovered: boolean) => void
+  // Toggleable DWV riser-diagram (plumbing isometric) overlay.
+  isRiserOpen: boolean
+  setRiserOpen: (open: boolean) => void
+  toggleRiserOpen: () => void
   navigationSyncPose: NavigationSyncPose | null
   publishNavigationSyncPose: (pose: NavigationSyncPoseInput) => void
   floorplanSelectionTool: FloorplanSelectionTool
@@ -808,6 +828,13 @@ const useEditor = create<EditorState>()(
       setMovingFenceEndpoint: (value) => set({ movingFenceEndpoint: value }),
       activeHandleDrag: null,
       setActiveHandleDrag: (drag) => set({ activeHandleDrag: drag }),
+      rotationAxis: 'y',
+      cycleRotationAxis: () => {
+        const order = ['y', 'x', 'z'] as const
+        const next = order[(order.indexOf(get().rotationAxis as 'y' | 'x' | 'z') + 1) % 3]!
+        set({ rotationAxis: next })
+        return next
+      },
       curvingWall: null,
       setCurvingWall: (wall) => set({ curvingWall: wall }),
       curvingFence: null,
@@ -934,6 +961,9 @@ const useEditor = create<EditorState>()(
         }),
       isFloorplanHovered: false,
       setFloorplanHovered: (hovered) => set({ isFloorplanHovered: hovered }),
+      isRiserOpen: false,
+      setRiserOpen: (open) => set({ isRiserOpen: open }),
+      toggleRiserOpen: () => set((state) => ({ isRiserOpen: !state.isRiserOpen })),
       navigationSyncPose: null,
       publishNavigationSyncPose: (pose) =>
         set((state) => ({

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

@@ -17,6 +17,7 @@ import type { BoxVentNode } from './schema'
  * the cursor ray and starve the placement tool of `roof:move` events.
  */
 const BoxVentPreview = ({ node, invalid }: { node: BoxVentNode; invalid?: boolean }) => {
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const geometry = useMemo(
     () => buildBoxVentGeometry(node),
     [node.width, node.depth, node.height, node.hoodOverhang, node.style],

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

@@ -75,6 +75,7 @@ const BoxVentRenderer = ({ node: storeNode }: { node: BoxVentNode }) => {
   // every parametric field, including the per-style ones. Listing them
   // explicitly keeps the dep array tight (vs. `[node]` which would
   // also fire on `name` / `visible` flips).
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const geometry = useMemo(
     () => buildBoxVentGeometry(node),
     [

packages/nodes/src/chimney/preview.tsx

@@ -48,6 +48,7 @@ const ChimneyPreview = ({
   const material = invalid ? invalidGhostMaterial : ghostMaterial
   const effectiveSegment = segment ?? RoofSegmentSchema.parse({})
 
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const geo = useMemo(
     () => buildChimneyGeometry(node, effectiveSegment),
     [

packages/nodes/src/chimney/renderer.tsx

@@ -77,24 +77,16 @@ const ChimneyRenderer = ({ node: storeNode }: { node: ChimneyNode }) => {
   }, [node, segment])
 
   // Segment brushes for the body trim. Building these is non-trivial
-  // (4 CSG-ready Brush instances per segment), so memoise by the shape
-  // fields that drive their geometry. A chimney slider drag changes
-  // `node.*` but not these, so the cached brushes survive the drag —
-  // previously each frame rebuilt all four.
-  const segmentBrushes = useMemo(
-    () => (segment ? getRoofSegmentBrushes(segment) : null),
-    [
-      segment?.roofType,
-      segment?.width,
-      segment?.depth,
-      segment?.wallHeight,
-      segment?.pitch,
-      segment?.wallThickness,
-      segment?.deckThickness,
-      segment?.overhang,
-      segment?.shingleThickness,
-    ],
-  )
+  // (4 CSG-ready Brush instances per segment). `segment` comes from a
+  // `useScene` selector, so it only re-identifies when the segment's own
+  // data changes — depend on it directly (as the `geo` memo above does)
+  // and the brushes rebuild exactly when the host roof reshapes, incl.
+  // the gambrel / mansard / dutch-hip width-ratio fields that
+  // `getRoofSegmentBrushes` reads. A chimney slider drag changes `node`,
+  // not `segment`, so the cache still survives the drag. Enumerating
+  // individual fields here previously omitted those ratios and left the
+  // trim CSG-ing against a stale roof outline.
+  const segmentBrushes = useMemo(() => (segment ? getRoofSegmentBrushes(segment) : null), [segment])
   useEffect(
     () => () => {
       if (segmentBrushes) {

packages/nodes/src/cupola/preview.tsx

@@ -13,6 +13,7 @@ import type { CupolaNode } from './schema'
  * so the preview doesn't intercept the cursor ray feeding the tool.
  */
 const CupolaPreview = ({ node, invalid }: { node: CupolaNode; invalid?: boolean }) => {
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const geometry = useMemo(
     () => buildCupolaGeometry(node),
     [node.width, node.depth, node.height, node.roofStyle, node.finial],

packages/nodes/src/cupola/renderer.tsx

@@ -53,6 +53,7 @@ const CupolaRenderer = ({ node: storeNode }: { node: CupolaNode }) => {
       : undefined,
   )
 
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const geometry = useMemo(
     () => buildCupolaGeometry(node),
     [node.width, node.depth, node.height, node.roofStyle, node.finial],

packages/nodes/src/dormer/csg-geometry.ts

@@ -325,7 +325,6 @@ export function generateDormerGeometry(
 
   const dormerBrushes = getRoofSegmentBrushes(virtualSegment)
   if (!dormerBrushes) {
-    // biome-ignore lint/suspicious/noConsole: keep diagnostic — fallback path.
     console.warn('[dormer] getRoofSegmentBrushes returned null; using fallback silhouette.')
     return buildDormerFallbackGeometry(dormer)
   }
@@ -472,7 +471,6 @@ export function generateDormerGeometry(
     remapRoofShellFaces(resultGeo, virtualSegment)
     splitDormerGableMaterial(resultGeo, dormer.height, DORMER_GABLE_MATERIAL_INDEX)
   } catch (e) {
-    // biome-ignore lint/suspicious/noConsole: dormer CSG can throw; keep diagnostic.
     console.error('[dormer] CSG failed, falling back to silhouette:', e)
     if (dormerSolid) {
       try {
@@ -492,7 +490,6 @@ export function generateDormerGeometry(
   // dormer is at least visible.
   const triCount = resultGeo.getIndex()?.count ?? resultGeo.getAttribute('position')?.count ?? 0
   if (triCount === 0) {
-    // biome-ignore lint/suspicious/noConsole: keep diagnostic — empty CSG.
     console.warn('[dormer] CSG produced empty geometry; using fallback silhouette.')
     return buildDormerFallbackGeometry(dormer)
   }

packages/nodes/src/dormer/panel-position-section.tsx

@@ -41,6 +41,7 @@ export function DormerPositionSection({
   const segmentId = segment?.id
   const roofChildrenKey = (roof?.children ?? []).join(',')
 
+  // biome-ignore lint/correctness/useExhaustiveDependencies: roofChildrenKey is the stable signature of `roof.children`; intentionally omitting `roof` (object identity) in favor of the joined ids.
   const worldXform = useMemo(() => {
     const dormerObj = sceneRegistry.nodes.get(selectedId)
     let worldX = 0
@@ -79,7 +80,6 @@ export function DormerPositionSection({
       if (Number.isFinite(lo_x)) bounds = { minX: lo_x, maxX: hi_x, minZ: lo_z, maxZ: hi_z }
     }
     return { worldX, worldZ, worldRotation, bounds }
-    // biome-ignore lint/correctness/useExhaustiveDependencies: roofChildrenKey is the stable signature of `roof.children`; intentionally omitting `roof` (object identity) in favor of the joined ids.
   }, [selectedId, px, py, pz, nodeRotation, segmentId, roofChildrenKey])
 
   const worldX_now = worldXform.worldX

packages/nodes/src/dormer/panel.tsx

@@ -107,7 +107,7 @@ export default function DormerPanel() {
   }, [node, selectedId, setMovingNode, setSelection])
 
   const handleDuplicate = useCallback(() => {
-    if (!(node && node.roofSegmentId)) return
+    if (!node?.roofSegmentId) return
     triggerSFX('sfx:item-pick')
     // Deep clone and strip the id so the move tool's onClick branch
     // (`isNew || !node.id`) takes the "create fresh" path. Setting

packages/nodes/src/dormer/preview.tsx

@@ -26,6 +26,7 @@ const invalidGhostMaterial = new THREE.MeshStandardMaterial({
 const DormerPreview = ({ node, invalid }: { node: DormerNode; invalid?: boolean }) => {
   const material = invalid ? invalidGhostMaterial : ghostMaterial
 
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const geo = useMemo(
     () => buildDormerGhostGeometry(node),
     [node.width, node.depth, node.height, node.roofHeight, node.roofType, node.wallSkirtHeight],

packages/nodes/src/dormer/renderer.tsx

@@ -59,6 +59,7 @@ const DormerRenderer = ({ node: storeNode }: { node: DormerNode }) => {
   // shingle, 4=Gable wall. Walls take the 'wall' role, the deck side and
   // shingle take 'roof'. When textures are off, every slot snaps to its
   // role colour regardless of explicit paint (the render-modes invariant).
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const material = useMemo(() => {
     const wallRole = () => createSurfaceRoleMaterial('wall', colorPreset, undefined, sceneTheme)
     const roofRole = () => createSurfaceRoleMaterial('roof', colorPreset, undefined, sceneTheme)
@@ -111,6 +112,7 @@ const DormerRenderer = ({ node: storeNode }: { node: DormerNode }) => {
     [colorPreset, sceneTheme],
   )
 
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const geometry = useMemo(() => {
     if (!segment) return null
     if (isLiveDrag) return buildDormerFallbackGeometry(node)

packages/nodes/src/dormer/window-assembly.tsx

@@ -28,6 +28,7 @@ const DormerWindowAssembly = ({
   frameMaterial: THREE.Material
   glassMaterial: THREE.Material
 }) => {
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const skirtWin = useMemo(
     () => getDormerSkirtWindowDims(node),
     [
@@ -45,6 +46,7 @@ const DormerWindowAssembly = ({
   const winShape: DormerWindowShape = node.windowShape
   const resolvedRadii: [number, number, number, number] = [...node.windowCornerRadii]
 
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const winGeo = useMemo(
     () =>
       buildDormerWindowGeometries(
@@ -101,6 +103,7 @@ const DormerWindowAssembly = ({
   )
   useEffect(() => () => sillGeo?.dispose(), [sillGeo])
 
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const exposed = useMemo(
     () => getDormerExposedFaces(node, segment),
     [
@@ -142,7 +145,6 @@ const DormerWindowAssembly = ({
       {winGeo.glassPanes.map((pane, i) => (
         <mesh
           geometry={pane.geo}
-          // biome-ignore lint/suspicious/noArrayIndexKey: glass panes are derived from grid indices, no stable id.
           key={`${keyPrefix}-glass-${i}`}
           material={glassMaterial}
           name={`dormer-glass-${keyPrefix}-${i}`}
@@ -153,7 +155,6 @@ const DormerWindowAssembly = ({
         <mesh
           castShadow
           geometry={bar.geo}
-          // biome-ignore lint/suspicious/noArrayIndexKey: frame bars are derived from grid indices, no stable id.
           key={`${keyPrefix}-bar-${i}`}
           material={frameMaterial}
           name={`dormer-frame-${keyPrefix}-${i}`}

packages/nodes/src/downspout/preview.tsx

@@ -26,6 +26,7 @@ const DownspoutPreview = ({
   routing?: DownspoutRouting | null
   invalid?: boolean
 }) => {
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const geometry = useMemo(
     () => buildDownspoutGeometry(node, routing),
     [

packages/nodes/src/downspout/renderer.tsx

@@ -101,6 +101,7 @@ const DownspoutRenderer = ({ node: storeNode }: { node: DownspoutNode }) => {
   // that actually move the jog or the collar bore, so the pipe geometry
   // only rebuilds when one of those changes (not on every override-merge
   // render). Resolves to null when the gutter has no outlet.
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const routing = useMemo(
     () =>
       effectiveGutter && effectiveSegment
@@ -117,6 +118,7 @@ const DownspoutRenderer = ({ node: storeNode }: { node: DownspoutNode }) => {
     ],
   )
 
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const geometry = useMemo(
     () => buildDownspoutGeometry(node, routing),
     [

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

@@ -0,0 +1,134 @@
+import type { NodeDefinition } from '@pascal-app/core'
+import { rotateFittingNode } from '../shared/fitting-rotation'
+import { buildDuctFittingFloorplan } from './floorplan'
+import { buildDuctFittingGeometry } from './geometry'
+import { ductFittingParametrics } from './parametrics'
+import { getDuctFittingPorts } from './ports'
+import { DuctFittingNode } from './schema'
+
+/**
+ * Phase 2 of the HVAC node system — duct fittings (elbow / tee / reducer)
+ * and the first kind to expose typed ports (`def.ports`).
+ *
+ * Composition: `def.geometry` only, same as duct-segment. Ports are the
+ * architectural payload: placement tools snap onto them, and a later
+ * slice walks them to build the supply/return system graph.
+ */
+export const ductFittingDefinition: NodeDefinition<typeof DuctFittingNode> = {
+  kind: 'duct-fitting',
+  schemaVersion: 1,
+  schema: DuctFittingNode,
+  category: 'utility',
+  distributionRole: 'fitting',
+
+  defaults: () => ({
+    object: 'node',
+    parentId: null,
+    visible: true,
+    metadata: {},
+    position: [0, 0, 0],
+    rotation: [0, 0, 0],
+    fittingType: 'elbow',
+    shape: 'round',
+    width: 14,
+    height: 8,
+    shape2: 'round',
+    width2: 14,
+    height2: 8,
+    angle: 90,
+    branchAngle: 90,
+    diameter: 6,
+    diameter2: 6,
+    ductMaterial: 'sheet-metal',
+    system: 'supply',
+  }),
+
+  capabilities: {
+    selectable: { hitVolume: 'bbox' },
+    // `cursorAttached`: a fitting is a small connector — an offset-
+    // preserving drag reads as the mesh trailing the mouse, so pin its
+    // origin to the cursor instead.
+    movable: { axes: ['x', 'y', 'z'], gridSnap: true, cursorAttached: true },
+    duplicable: true,
+    deletable: true,
+  },
+
+  parametrics: ductFittingParametrics,
+
+  geometry: buildDuctFittingGeometry,
+  geometryKey: (n) =>
+    JSON.stringify([
+      n.fittingType,
+      // The mitered elbow + flange profiles swap width/height roles based
+      // on where world-up sits in the local frame, so orientation is a
+      // geometry input.
+      n.rotation,
+      n.shape,
+      n.width,
+      n.height,
+      n.shape2,
+      n.width2,
+      n.height2,
+      n.angle,
+      n.branchAngle,
+      n.diameter,
+      n.diameter2,
+      n.ductMaterial,
+      n.system,
+    ]),
+
+  ports: getDuctFittingPorts,
+
+  floorplan: buildDuctFittingFloorplan,
+
+  // R/T rotate a selected fitting ±45° around the shared active axis.
+  // The default editor rotate only knows Y; fittings need X/Z for
+  // risers, so this overrides it. Alt-cycling of the axis + the axis
+  // badge live in `./selection.tsx`.
+  keyboardActions: {
+    r: {
+      appliesTo: (node) => node.type === 'duct-fitting',
+      run: (node) => rotateFittingNode(node, 1),
+    },
+    t: {
+      appliesTo: (node) => node.type === 'duct-fitting',
+      run: (node) => rotateFittingNode(node, -1),
+    },
+    axisCycling: true,
+  },
+
+  // Alt-cycles the active rotation axis while a fitting is selected.
+  // Editor-only (drives `useEditor.rotationAxis`), so it mounts via the
+  // editor's SelectionAffordanceManager rather than `def.system`.
+  affordanceTools: {
+    selection: () => import('./selection'),
+    // Ghost-preview duplicate / move. Duplicate is pure drag-to-place: a
+    // translucent copy of the fitting (built from its real geometry, at its
+    // own rotation, so an elbow / riser stays properly aligned) follows the
+    // cursor and only lands on the commit click. Takes priority over
+    // `capabilities.movable` in the MoveTool dispatcher.
+    move: () => import('./move-tool'),
+  },
+
+  tool: () => import('./tool'),
+  toolHints: [
+    { key: 'Click', label: 'Place fitting' },
+    { key: 'Hover a duct end', label: 'Snap onto the run' },
+    { key: 'R / T', label: 'Rotate ±45°' },
+    { key: 'Alt', label: 'Switch rotation axis (Y → X → Z)' },
+    { key: 'Esc', label: 'Exit' },
+  ],
+
+  presentation: {
+    label: 'Duct Fitting',
+    description: 'Elbow, tee, reducer, or square-to-round transition connecting duct runs.',
+    icon: { kind: 'url', src: '/icons/duct-fitting.png' },
+    paletteSection: 'structure',
+    paletteOrder: 91,
+  },
+
+  mcp: {
+    description:
+      'A duct fitting (elbow, tee, reducer, or square-to-round transition) with typed connection ports. Position is level-local meters; rotation is an XYZ euler in radians.',
+  },
+}

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

@@ -0,0 +1,69 @@
+import type { FloorplanGeometry, GeometryContext } from '@pascal-app/core'
+import { INCHES_TO_METERS } from '../duct-segment/geometry'
+import { getDuctFittingPorts } from './ports'
+import type { DuctFittingNode } from './schema'
+
+const SUPPLY_COLOR = '#d4825a'
+const RETURN_COLOR = '#5a8ad4'
+const BODY_COLOR = '#9ca3af'
+
+/**
+ * Floor-plan symbol for a duct fitting: one stub line per port from the
+ * junction center out to the collar (drawn at each collar's real
+ * diameter), plus a junction circle. Ports are computed in level-local
+ * 3D and projected to plan, so a rotated or riser-turned fitting shows
+ * its true plan footprint; a vertical port collapses onto the junction
+ * circle, which is exactly how it should read from above.
+ */
+export function buildDuctFittingFloorplan(
+  node: DuctFittingNode,
+  ctx: GeometryContext,
+): FloorplanGeometry | null {
+  const [cx, , cz] = node.position
+  const ports = getDuctFittingPorts(node)
+  const view = ctx.viewState
+  const palette = view?.palette
+  const showSelectedChrome = (view?.selected || view?.highlighted) ?? false
+  const accent = node.system === 'supply' ? SUPPLY_COLOR : RETURN_COLOR
+  const bodyStroke = showSelectedChrome && palette ? palette.selectedStroke : BODY_COLOR
+
+  const children: FloorplanGeometry[] = []
+  for (const port of ports) {
+    const px = port.position[0]
+    const pz = port.position[2]
+    // Vertical port — projects onto the junction itself; skip the stub.
+    if (Math.hypot(px - cx, pz - cz) < 1e-4) continue
+    children.push({
+      kind: 'line',
+      x1: cx,
+      y1: cz,
+      x2: px,
+      y2: pz,
+      stroke: bodyStroke,
+      strokeWidth: port.diameter * INCHES_TO_METERS,
+      strokeLinecap: 'round',
+      opacity: showSelectedChrome ? 0.95 : 0.8,
+    })
+  }
+
+  children.push({
+    kind: 'circle',
+    cx,
+    cy: cz,
+    r: (node.diameter * INCHES_TO_METERS) / 2 + 0.015,
+    fill: bodyStroke,
+    stroke: accent,
+    strokeWidth: 1.5,
+    vectorEffect: 'non-scaling-stroke',
+    opacity: 0.95,
+  })
+
+  if (showSelectedChrome) {
+    children.push({
+      kind: 'move-handle',
+      point: [cx, cz],
+    })
+  }
+
+  return { kind: 'group', children }
+}

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

@@ -0,0 +1,463 @@
+import {
+  BufferGeometry,
+  CylinderGeometry,
+  DoubleSide,
+  Euler,
+  Float32BufferAttribute,
+  Group,
+  Mesh,
+  type MeshStandardMaterial,
+  SphereGeometry,
+  TorusGeometry,
+  Vector3,
+} from 'three'
+import {
+  buildOvalSection,
+  buildRectSection,
+  buildSection,
+  createDuctMaterial,
+  INCHES_TO_METERS,
+} from '../duct-segment/geometry'
+import { localFittingPorts } from './ports'
+import type { DuctFittingNode } from './schema'
+
+const RADIAL_SEGMENTS = 24
+const UP = new Vector3(0, 1, 0)
+
+/**
+ * Mitered rectangular elbow as ONE closed solid — the way sheet-metal
+ * square elbows are actually folded. The rect profile sweeps from the
+ * inlet face to the outlet face through a single miter ring lying on
+ * the corner's bisector plane (the classic 2D miter-join offset:
+ * join(u) = (wA + wB) · u / (1 + wA·wB)), so the two legs meet in a
+ * crisp seam instead of interpenetrating boxes.
+ *
+ * Local frame: legs in the XZ plane (ports convention) so the fold hinge
+ * is always local Y. `sweepM` is the profile dimension carried through the
+ * bend (in the XZ bend plane); `cheekM` is the dimension that stays
+ * constant along the hinge. Which physical dimension (width vs height)
+ * plays each role depends on the elbow's world orientation and is decided
+ * by the caller — a floor turn folds about vertical (cheek = height),
+ * a wall riser folds about horizontal (cheek = width).
+ *
+ * Non-indexed triangles → flat face normals for the folded-metal look;
+ * the closed solid renders double-sided so winding never makes a face
+ * vanish.
+ */
+/**
+ * Stadium (flat-oval) outline in profile (u, v) coordinates: u-extent
+ * `uM`, v-extent `vM`, semicircular caps of the smaller dimension. The
+ * caps land on whichever axis is longer, so a riser-rotated profile
+ * (swapped roles) stays a valid stadium.
+ */
+function stadiumOutline(uM: number, vM: number, samplesPerCap = 10): Array<[number, number]> {
+  const pts: Array<[number, number]> = []
+  const r = Math.min(uM, vM) / 2
+  const s = (Math.max(uM, vM) - Math.min(uM, vM)) / 2
+  const cap = (cu: number, cv: number, startA: number) => {
+    for (let i = 0; i <= samplesPerCap; i++) {
+      const a = startA + (Math.PI * i) / samplesPerCap
+      pts.push([cu + r * Math.cos(a), cv + r * Math.sin(a)])
+    }
+  }
+  if (uM >= vM) {
+    cap(s, 0, -Math.PI / 2)
+    cap(-s, 0, Math.PI / 2)
+  } else {
+    cap(0, s, 0)
+    cap(0, -s, Math.PI)
+  }
+  return pts
+}
+
+function buildMiteredElbow(
+  inletPos: Vector3,
+  outletPos: Vector3,
+  sweepM: number,
+  cheekM: number,
+  profileShape: 'rect' | 'oval',
+  material: MeshStandardMaterial,
+): Mesh {
+  const travelIn = inletPos.clone().multiplyScalar(-1).normalize() // inlet → junction
+  const travelOut = outletPos.clone().normalize() // junction → outlet
+  const wA = new Vector3().crossVectors(UP, travelIn).normalize()
+  const wB = new Vector3().crossVectors(UP, travelOut).normalize()
+  // Elbow turns are ≤ 90°, so wA·wB ≥ 0 and the join never degenerates.
+  const miterScale = 1 / (1 + wA.dot(wB))
+  const wJoin = new Vector3().addVectors(wA, wB)
+
+  const hw = sweepM / 2
+  const hh = cheekM / 2
+  const corners: Array<[number, number]> =
+    profileShape === 'oval'
+      ? stadiumOutline(sweepM, cheekM)
+      : [
+          [hw, hh],
+          [-hw, hh],
+          [-hw, -hh],
+          [hw, -hh],
+        ]
+  const n = corners.length
+  const ring = (center: Vector3, uAxis: Vector3, scale = 1): Vector3[] =>
+    corners.map(([u, v]) =>
+      center
+        .clone()
+        .addScaledVector(uAxis, u * scale)
+        .addScaledVector(UP, v),
+    )
+
+  const inletRing = ring(inletPos, wA)
+  const miterRing = ring(new Vector3(0, 0, 0), wJoin, miterScale)
+  const outletRing = ring(outletPos, wB)
+
+  const positions: number[] = []
+  const tri = (a: Vector3, b: Vector3, c: Vector3) =>
+    positions.push(a.x, a.y, a.z, b.x, b.y, b.z, c.x, c.y, c.z)
+  const quad = (a: Vector3, b: Vector3, c: Vector3, d: Vector3) => {
+    tri(a, b, c)
+    tri(a, c, d)
+  }
+  const skin = (from: Vector3[], to: Vector3[]) => {
+    for (let k = 0; k < n; k++) {
+      const k2 = (k + 1) % n
+      quad(from[k]!, to[k]!, to[k2]!, from[k2]!)
+    }
+  }
+  skin(inletRing, miterRing)
+  skin(miterRing, outletRing)
+  // End caps — triangle fans so any convex profile closes.
+  for (let k = 1; k < n - 1; k++) {
+    tri(inletRing[0]!, inletRing[k]!, inletRing[k + 1]!)
+    tri(outletRing[k + 1]!, outletRing[k]!, outletRing[0]!)
+  }
+
+  const geometry = new BufferGeometry()
+  geometry.setAttribute('position', new Float32BufferAttribute(positions, 3))
+  geometry.computeVertexNormals()
+  const solidMaterial = material.clone()
+  solidMaterial.side = DoubleSide
+  const mesh = new Mesh(geometry, solidMaterial)
+  mesh.name = `fitting-elbow-${profileShape}`
+  return mesh
+}
+
+/**
+ * Square-to-round loft between a rect ring at `xRect` and a round ring
+ * at `xRound`, both centered on the local X axis (the straight-through
+ * run). Profiles are sampled at matching polar angles — the rect point
+ * is the ray's intersection with the rectangle boundary — so the skin
+ * twists nowhere. Non-indexed triangles + computed normals give the
+ * faceted gore look of a real shop-made square-to-round.
+ */
+function buildRectToRoundLoft(
+  xRect: number,
+  xRound: number,
+  widthM: number,
+  heightM: number,
+  radius: number,
+  material: MeshStandardMaterial,
+): Mesh {
+  const hw = widthM / 2
+  const hh = heightM / 2
+  const rectRing: Vector3[] = []
+  const roundRing: Vector3[] = []
+  for (let i = 0; i < RADIAL_SEGMENTS; i++) {
+    const theta = (2 * Math.PI * i) / RADIAL_SEGMENTS
+    const cz = Math.cos(theta)
+    const sy = Math.sin(theta)
+    // Scale the unit ray until it hits the rectangle boundary. Width
+    // spans local Z and height local Y — the same axes buildRectSection
+    // gives a +X run.
+    const t = 1 / Math.max(Math.abs(cz) / hw, Math.abs(sy) / hh)
+    rectRing.push(new Vector3(xRect, t * sy, t * cz))
+    roundRing.push(new Vector3(xRound, radius * sy, radius * cz))
+  }
+
+  const positions: number[] = []
+  const tri = (a: Vector3, b: Vector3, c: Vector3) =>
+    positions.push(a.x, a.y, a.z, b.x, b.y, b.z, c.x, c.y, c.z)
+  for (let i = 0; i < RADIAL_SEGMENTS; i++) {
+    const j = (i + 1) % RADIAL_SEGMENTS
+    tri(rectRing[i]!, roundRing[i]!, roundRing[j]!)
+    tri(rectRing[i]!, roundRing[j]!, rectRing[j]!)
+  }
+
+  const geometry = new BufferGeometry()
+  geometry.setAttribute('position', new Float32BufferAttribute(positions, 3))
+  geometry.computeVertexNormals()
+  const solidMaterial = material.clone()
+  solidMaterial.side = DoubleSide
+  const mesh = new Mesh(geometry, solidMaterial)
+  mesh.name = 'fitting-transition-loft'
+  return mesh
+}
+
+/**
+ * Pure geometry builder for a duct fitting, in the fitting's LOCAL frame —
+ * `<ParametricNodeRenderer>` applies `node.position` / `node.rotation`.
+ *
+ * Strategy: one cylinder stub per port from the junction center outward
+ * (reusing the segment builder's `buildSection`), a sphere at the
+ * junction, and a slightly-oversized crimp collar ring at each port
+ * opening so fittings read as sheet-metal junctions rather than bare
+ * tube ends.
+ *
+ * The reducer is special-cased: instead of equal stubs + sphere it draws
+ * a short inlet stub, a tapered cone, and a short outlet stub inline.
+ *
+ * Non-round shapes (elbow / tee): run legs carry the fitting's
+ * width × height profile — rect prisms or flat-oval stadiums — matching
+ * the trunk they join; a tee's branch leg carries its own `shape2`
+ * profile (width2 × height2, or round at `diameter2`). The profile's
+ * height rides local +Y — for the horizontal-plane orientations trunks
+ * are drawn in, that's world-vertical.
+ */
+export function buildDuctFittingGeometry(node: DuctFittingNode): Group {
+  const group = new Group()
+  const material = createDuctMaterial(node)
+  const radiusMain = (node.diameter * INCHES_TO_METERS) / 2
+  const ports = localFittingPorts(node)
+  const widthM = node.width * INCHES_TO_METERS
+  const heightM = node.height * INCHES_TO_METERS
+  // The elbow folds about its local Y. Width spans the XZ bend plane and
+  // height rides the hinge ONLY when local Y is world-vertical (a floor
+  // turn). For a riser the node is rotated so local Y lands horizontal —
+  // then it's width that runs along the hinge, so the roles swap. Pick by
+  // where world-up sits in the fitting's local frame.
+  const hingeWorld = UP.clone().applyEuler(
+    new Euler(node.rotation[0], node.rotation[1], node.rotation[2]),
+  )
+  const hingeIsVertical = Math.abs(hingeWorld.y) >= Math.SQRT1_2
+
+  if (node.fittingType === 'reducer') {
+    const radiusOut = (node.diameter2 * INCHES_TO_METERS) / 2
+    const inlet = ports[0]!
+    const outlet = ports[1]!
+    const taperHalf = Math.abs(inlet.position.x) / 3
+    const stubA = buildSection(
+      inlet.position,
+      new Vector3(-taperHalf, 0, 0),
+      radiusMain,
+      material,
+      'fitting-stub-inlet',
+    )
+    if (stubA) group.add(stubA)
+    const cone = new Mesh(
+      new CylinderGeometry(radiusOut, radiusMain, taperHalf * 2, RADIAL_SEGMENTS, 1, false),
+      material,
+    )
+    cone.name = 'fitting-taper'
+    cone.quaternion.setFromUnitVectors(UP, new Vector3(1, 0, 0))
+    group.add(cone)
+    const stubB = buildSection(
+      new Vector3(taperHalf, 0, 0),
+      outlet.position,
+      radiusOut,
+      material,
+      'fitting-stub-outlet',
+    )
+    if (stubB) group.add(stubB)
+  } else if (node.fittingType === 'transition') {
+    // Square-to-round: rect stub on the inlet, lofted gore body through
+    // the junction, round stub on the outlet. Same inline layout as the
+    // reducer, with the taper replaced by the loft.
+    const radiusOut = (node.diameter2 * INCHES_TO_METERS) / 2
+    const inlet = ports[0]!
+    const outlet = ports[1]!
+    const taperHalf = Math.abs(inlet.position.x) / 3
+    const stubA = buildRectSection(
+      inlet.position,
+      new Vector3(-taperHalf, 0, 0),
+      widthM,
+      heightM,
+      material,
+      'fitting-stub-inlet',
+    )
+    if (stubA) group.add(stubA)
+    group.add(buildRectToRoundLoft(-taperHalf, taperHalf, widthM, heightM, radiusOut, material))
+    const stubB = buildSection(
+      new Vector3(taperHalf, 0, 0),
+      outlet.position,
+      radiusOut,
+      material,
+      'fitting-stub-outlet',
+    )
+    if (stubB) group.add(stubB)
+  } else if (node.shape !== 'round' && node.fittingType === 'elbow') {
+    // One mitered solid — no stubs, no junction blob. Oval profiles
+    // sweep the same way; the ring is a stadium instead of 4 corners.
+    const inlet = ports.find((p) => p.id === 'inlet')!
+    const outlet = ports.find((p) => p.id === 'outlet')!
+    group.add(
+      buildMiteredElbow(
+        inlet.position,
+        outlet.position,
+        hingeIsVertical ? widthM : heightM,
+        hingeIsVertical ? heightM : widthM,
+        node.shape,
+        material,
+      ),
+    )
+  } else if (node.shape !== 'round' && node.fittingType === 'tee') {
+    // Straight rect / oval run inlet→outlet (one prism — nothing to
+    // miter) plus a branch leg tapping its side. The branch carries its
+    // own profile: rect or oval at width2 × height2, round at diameter2.
+    //
+    // Same orientation swap as the elbow: the run prism and branch stub
+    // are built on the `rectSectionAxes` basis, whose height rides local
+    // +Y. That's world-vertical only when the tee's local Y stays vertical
+    // (a flat tap off a horizontal trunk). When the tee is rotated so
+    // local Y lands horizontal, width and height roles swap so the
+    // physical height keeps reading as the vertical face — without this a
+    // tee drawn along the perpendicular axis looks squished.
+    const inlet = ports.find((p) => p.id === 'inlet')!
+    const outlet = ports.find((p) => p.id === 'outlet')!
+    const branch = ports.find((p) => p.id === 'branch')!
+    const width2M = node.width2 * INCHES_TO_METERS
+    const height2M = node.height2 * INCHES_TO_METERS
+    const buildRunSection = node.shape === 'oval' ? buildOvalSection : buildRectSection
+    const run = buildRunSection(
+      inlet.position,
+      outlet.position,
+      hingeIsVertical ? widthM : heightM,
+      hingeIsVertical ? heightM : widthM,
+      material,
+      'fitting-run',
+    )
+    if (run) group.add(run)
+    const buildBranchSection = node.shape2 === 'oval' ? buildOvalSection : buildRectSection
+    const stub =
+      node.shape2 !== 'round'
+        ? buildBranchSection(
+            new Vector3(0, 0, 0),
+            branch.position,
+            hingeIsVertical ? width2M : height2M,
+            hingeIsVertical ? height2M : width2M,
+            material,
+            'fitting-stub-branch',
+          )
+        : buildSection(
+            new Vector3(0, 0, 0),
+            branch.position,
+            (branch.diameter * INCHES_TO_METERS) / 2,
+            material,
+            'fitting-stub-branch',
+          )
+    if (stub) group.add(stub)
+  } else if (node.shape !== 'round' && node.fittingType === 'cross') {
+    // Straight rect / oval run inlet→outlet plus two opposed branch legs
+    // (±Z) carrying the branch profile — both halves of the run that
+    // passed through, same size at `width2 × height2` / `diameter2`. Same
+    // orientation swap as the tee / elbow so the cross stays upright when
+    // rotated so its local Y lands horizontal.
+    const inlet = ports.find((p) => p.id === 'inlet')!
+    const outlet = ports.find((p) => p.id === 'outlet')!
+    const width2M = node.width2 * INCHES_TO_METERS
+    const height2M = node.height2 * INCHES_TO_METERS
+    const buildRunSection = node.shape === 'oval' ? buildOvalSection : buildRectSection
+    const run = buildRunSection(
+      inlet.position,
+      outlet.position,
+      hingeIsVertical ? widthM : heightM,
+      hingeIsVertical ? heightM : widthM,
+      material,
+      'fitting-run',
+    )
+    if (run) group.add(run)
+    const buildBranchSection = node.shape2 === 'oval' ? buildOvalSection : buildRectSection
+    for (const id of ['branch', 'branch2'] as const) {
+      const branch = ports.find((p) => p.id === id)!
+      const stub =
+        node.shape2 !== 'round'
+          ? buildBranchSection(
+              new Vector3(0, 0, 0),
+              branch.position,
+              hingeIsVertical ? width2M : height2M,
+              hingeIsVertical ? height2M : width2M,
+              material,
+              `fitting-stub-${id}`,
+            )
+          : buildSection(
+              new Vector3(0, 0, 0),
+              branch.position,
+              (branch.diameter * INCHES_TO_METERS) / 2,
+              material,
+              `fitting-stub-${id}`,
+            )
+      if (stub) group.add(stub)
+    }
+  } else {
+    for (const port of ports) {
+      const stub = buildSection(
+        new Vector3(0, 0, 0),
+        port.position,
+        (port.diameter * INCHES_TO_METERS) / 2,
+        material,
+        `fitting-stub-${port.id}`,
+      )
+      if (stub) group.add(stub)
+    }
+    const junction = new Mesh(new SphereGeometry(radiusMain * 1.02, RADIAL_SEGMENTS, 12), material)
+    junction.name = 'fitting-junction'
+    group.add(junction)
+  }
+
+  // Joint trim at each opening. Round legs get a crimp-collar torus just
+  // proud of the stub; rect legs get a drive-cleat flange — the thin
+  // raised rim (TDC/S-cleat) real sheet-metal trunk joints wear where a
+  // section meets a fitting. The plate is centered on the collar plane so
+  // the rim reads as the seam between fitting and duct. Run legs
+  // (inlet/outlet) are rect when `shape` is rect; a rect tee's branch is
+  // rect when `shape2` is rect. Reducers ignore shape.
+  // Which profile a leg's opening carries: a transition's inlet is its
+  // rect end regardless of `shape`; reducers are always round; otherwise
+  // the run legs follow `shape` and a tee's branch follows `shape2`
+  // (only meaningful when the run itself is non-round).
+  const legShape = (portId: string): 'round' | 'rect' | 'oval' => {
+    if (node.fittingType === 'transition') return portId === 'inlet' ? 'rect' : 'round'
+    if (node.fittingType === 'reducer' || node.shape === 'round') return 'round'
+    return portId === 'branch' || portId === 'branch2' ? node.shape2 : node.shape
+  }
+  // The flange's profile must match the leg it caps: the branch carries
+  // its own width2 × height2; elbow legs swap width/height roles when the
+  // fold hinge lies horizontal (riser elbows) — same choice as the
+  // mitered solid above.
+  const rectLegProfile = (portId: string): [number, number] => {
+    if (portId === 'branch' || portId === 'branch2') {
+      const width2M = node.width2 * INCHES_TO_METERS
+      const height2M = node.height2 * INCHES_TO_METERS
+      return hingeIsVertical ? [width2M, height2M] : [height2M, width2M]
+    }
+    if (!hingeIsVertical) return [heightM, widthM]
+    return [widthM, heightM]
+  }
+  const FLANGE_LIP_M = 0.02
+  const FLANGE_THICK_M = 0.012
+  for (const port of ports) {
+    const profile = legShape(port.id)
+    if (profile !== 'round') {
+      const [w, h] = rectLegProfile(port.id)
+      const start = port.position.clone().addScaledVector(port.direction, -FLANGE_THICK_M / 2)
+      const end = port.position.clone().addScaledVector(port.direction, FLANGE_THICK_M / 2)
+      const buildFlange = profile === 'oval' ? buildOvalSection : buildRectSection
+      const flange = buildFlange(
+        start,
+        end,
+        w + FLANGE_LIP_M * 2,
+        h + FLANGE_LIP_M * 2,
+        material,
+        `fitting-flange-${port.id}`,
+      )
+      if (flange) group.add(flange)
+      continue
+    }
+    const radius = (port.diameter * INCHES_TO_METERS) / 2
+    const collar = new Mesh(new TorusGeometry(radius, radius * 0.12, 8, RADIAL_SEGMENTS), material)
+    collar.name = `fitting-collar-${port.id}`
+    collar.position.copy(port.position)
+    collar.quaternion.setFromUnitVectors(new Vector3(0, 0, 1), port.direction)
+    group.add(collar)
+  }
+
+  return group
+}

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

@@ -0,0 +1,4 @@
+export { ductFittingDefinition } from './definition'
+export { buildDuctFittingGeometry } from './geometry'
+export { getDuctFittingPorts } from './ports'
+export { DuctFittingNode } from './schema'

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

@@ -0,0 +1,286 @@
+'use client'
+
+import {
+  type AlignmentAnchor,
+  type AnyNode,
+  type AnyNodeId,
+  DuctFittingNode,
+  emitter,
+  type GridEvent,
+  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 { buildDuctFittingGeometry } from './geometry'
+
+type Vec3 = [number, number, number]
+
+const GHOST_COLOR = '#818cf8'
+const GHOST_OPACITY = 0.5
+
+/** 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 duct fittings (elbow / tee /
+ * reducer / transition).
+ *
+ * **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.
+ *
+ * Wired via `def.affordanceTools.move`.
+ */
+export const MoveDuctFittingTool: React.FC<{ node: AnyNode }> = ({ node }) => {
+  const fitting = node as DuctFittingNode
+  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 = buildDuctFittingGeometry(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)
+
+    let lastPos: Vec3 = originalPosition
+
+    const onMove = (event: GridEvent) => {
+      const bypass = event.nativeEvent?.shiftKey === true
+      const snap = bypass ? (v: number) => v : snapToGridStep
+      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()
+      }
+
+      const next: Vec3 = [x, originalPosition[1], z]
+      if (next[0] !== lastPos[0] || next[2] !== lastPos[2]) triggerSFX('sfx:grid-snap')
+      lastPos = next
+      hasMoved = true
+      setCursorPos(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 = DuctFittingNode.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 {
+        useScene.getState().updateNode(nodeId, { position: lastPos } as Partial<AnyNode>)
+        useScene.getState().markDirty(nodeId)
+      }
+      useScene.temporal.getState().pause()
+      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 = () => {
+      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)
+      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 MoveDuctFittingTool

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

@@ -0,0 +1,293 @@
+import {
+  type AnyNode,
+  type AnyNodeId,
+  type DuctSegmentNode,
+  type ParametricDescriptor,
+  useScene,
+} from '@pascal-app/core'
+import { Vector3 } from 'three'
+import {
+  ductPortDiameterIn,
+  equivalentDiameterIn,
+  ovalEquivalentDiameterIn,
+  rollToContinueAcrossElbow,
+} from '../duct-segment/geometry'
+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))
+
+/** A duct endpoint sitting this close to a collar counts as mated. */
+const MATE_TOL_M = 0.03
+
+type DuctMate = { duct: DuctSegmentNode; endIndex: number }
+
+/**
+ * Ducts whose endpoint sits ON one of the fitting's collars, keyed by
+ * 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> {
+  const mates = new Map<string, DuctMate>()
+  const ports = getDuctFittingPorts(fitting)
+  for (const node of Object.values(useScene.getState().nodes)) {
+    if (node.type !== 'duct-segment') continue
+    const duct = node as DuctSegmentNode
+    for (const endIndex of [0, duct.path.length - 1]) {
+      const p = duct.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, { duct, endIndex })
+        }
+      }
+    }
+  }
+  return mates
+}
+
+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
+  // fitting lands flush instead of at schema defaults. The tee branch
+  // follows its own mated duct (or the run shape when nothing is mated);
+  // `shape2` stays editable afterwards for mixed taps. Rect profiles
+  // also write their area-equivalent round size back into `diameter` /
+  // `diameter2`, which drive leg lengths + advertised ports — without
+  // this the legs keep the stale round size.
+  derive: (next, patch) => {
+    const out: Partial<DuctFittingNode> = {}
+    if ('shape' in patch && next.fittingType !== 'reducer') {
+      // `next` still carries the pre-edit diameters, so its ports sit
+      // where the mated ducts end — size off the actual neighbours.
+      const mates = matedDucts(next)
+      const run = (mates.get('inlet') ?? mates.get('outlet'))?.duct
+      if (next.shape !== 'round' && run?.shape === next.shape) {
+        out.width = run.width
+        out.height = run.height
+      } else if (next.shape === 'round' && run && run.shape !== 'rect') {
+        // Oval runs present their area-equivalent round size.
+        out.diameter = clampDiameter(ductPortDiameterIn(run))
+      }
+      if (next.fittingType === 'tee' || next.fittingType === 'cross') {
+        // A cross's two branches share one profile — size off whichever
+        // branch leg has a duct mated (both halves are the same run).
+        const branchDuct = (mates.get('branch') ?? mates.get('branch2'))?.duct
+        out.shape2 = branchDuct?.shape ?? next.shape
+        if (branchDuct && branchDuct.shape !== 'round') {
+          out.width2 = branchDuct.width
+          out.height2 = branchDuct.height
+        } else if (branchDuct) {
+          out.diameter2 = clampDiameter(ductPortDiameterIn(branchDuct))
+        }
+      }
+    }
+    // Non-round legs write their area-equivalent round size back into the
+    // diameters (leg lengths + advertised ports). A transition's inlet is
+    // always the rect end regardless of `shape`.
+    const runShape = next.fittingType === 'transition' ? 'rect' : next.shape
+    if (runShape !== 'round' && next.fittingType !== 'reducer') {
+      const equivalent = runShape === 'oval' ? ovalEquivalentDiameterIn : equivalentDiameterIn
+      out.diameter = clampDiameter(equivalent(out.width ?? next.width, out.height ?? next.height))
+    }
+    const shape2 = out.shape2 ?? next.shape2
+    if ((next.fittingType === 'tee' || next.fittingType === 'cross') && shape2 !== 'round') {
+      const equivalent2 = shape2 === 'oval' ? ovalEquivalentDiameterIn : equivalentDiameterIn
+      out.diameter2 = clampDiameter(
+        equivalent2(out.width2 ?? next.width2, out.height2 ?? next.height2),
+      )
+    }
+    return out
+  },
+
+  // Resizing a fitting moves its collars (leg lengths follow the
+  // diameters) — re-trim each mated duct's endpoint onto the collar's
+  // new position so metal keeps meeting metal instead of overlapping
+  // one neighbour and gapping off another.
+  reconcile: (prev, next) => {
+    const updates: Array<{ id: AnyNodeId; data: Partial<AnyNode> }> = []
+    const newPorts = new Map(getDuctFittingPorts(next).map((p) => [p.id, p]))
+    const mates = matedDucts(prev)
+    for (const [portId, mate] of mates) {
+      const target = newPorts.get(portId)
+      if (!target) continue
+      const end = mate.duct.path[mate.endIndex]
+      if (!end) continue
+      const data: Partial<DuctSegmentNode> = {}
+      const dx = end[0] - target.position[0]
+      const dy = end[1] - target.position[1]
+      const dz = end[2] - target.position[2]
+      if (dx * dx + dy * dy + dz * dz >= 1e-12) {
+        const path = mate.duct.path.map((p) => [...p] as [number, number, number])
+        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
+            }
+          }
+        }
+      }
+      if (Object.keys(data).length > 0) updates.push({ id: mate.duct.id, data })
+    }
+    return updates
+  },
+  groups: [
+    {
+      label: 'Fitting',
+      fields: [
+        {
+          key: 'fittingType',
+          kind: 'enum',
+          options: ['elbow', 'tee', 'cross', 'reducer', 'transition'],
+          display: 'segmented',
+        },
+        {
+          key: 'angle',
+          kind: 'number',
+          unit: '°',
+          min: 15,
+          max: 90,
+          step: 15,
+          visibleIf: (n) => n.fittingType === 'elbow',
+        },
+        {
+          key: 'branchAngle',
+          kind: 'number',
+          unit: '°',
+          min: 45,
+          max: 135,
+          step: 15,
+          visibleIf: (n) => n.fittingType === 'tee',
+        },
+        {
+          key: 'system',
+          kind: 'enum',
+          options: ['supply', 'return'],
+          display: 'segmented',
+        },
+      ],
+    },
+    {
+      label: 'Connections',
+      fields: [
+        {
+          key: 'shape',
+          kind: 'enum',
+          options: ['round', 'rect', 'oval'],
+          display: 'segmented',
+          // Reducers are always round; a transition's ends are fixed
+          // (rect inlet, round outlet) so there's nothing to pick.
+          visibleIf: (n) => n.fittingType !== 'reducer' && n.fittingType !== 'transition',
+        },
+        {
+          key: 'diameter',
+          kind: 'number',
+          unit: 'in',
+          min: 4,
+          max: 24,
+          step: 1,
+          // Hidden when the run legs are rect / oval (transition's inlet
+          // always is) — `diameter` is then derived as the area equivalent.
+          visibleIf: (n) =>
+            n.fittingType === 'reducer' || (n.fittingType !== 'transition' && n.shape === 'round'),
+        },
+        {
+          key: 'width',
+          kind: 'number',
+          unit: 'in',
+          min: 4,
+          max: 60,
+          step: 1,
+          visibleIf: (n) =>
+            n.fittingType === 'transition' || (n.shape !== 'round' && n.fittingType !== 'reducer'),
+        },
+        {
+          key: 'height',
+          kind: 'number',
+          unit: 'in',
+          min: 3,
+          max: 40,
+          step: 1,
+          visibleIf: (n) =>
+            n.fittingType === 'transition' || (n.shape !== 'round' && n.fittingType !== 'reducer'),
+        },
+        {
+          key: 'shape2',
+          kind: 'enum',
+          options: ['round', 'rect', 'oval'],
+          display: 'segmented',
+          visibleIf: (n) => n.fittingType === 'tee' || n.fittingType === 'cross',
+        },
+        {
+          key: 'diameter2',
+          kind: 'number',
+          unit: 'in',
+          min: 4,
+          max: 24,
+          step: 1,
+          visibleIf: (n) =>
+            n.fittingType !== 'elbow' &&
+            (n.fittingType !== 'tee' || n.shape2 === 'round') &&
+            (n.fittingType !== 'cross' || n.shape2 === 'round'),
+        },
+        {
+          key: 'width2',
+          kind: 'number',
+          unit: 'in',
+          min: 4,
+          max: 60,
+          step: 1,
+          visibleIf: (n) =>
+            (n.fittingType === 'tee' || n.fittingType === 'cross') && n.shape2 !== 'round',
+        },
+        {
+          key: 'height2',
+          kind: 'number',
+          unit: 'in',
+          min: 3,
+          max: 40,
+          step: 1,
+          visibleIf: (n) =>
+            (n.fittingType === 'tee' || n.fittingType === 'cross') && n.shape2 !== 'round',
+        },
+        {
+          key: 'ductMaterial',
+          kind: 'enum',
+          options: ['sheet-metal', 'flex', 'duct-board'],
+        },
+      ],
+    },
+    {
+      label: 'Placement',
+      fields: [
+        { key: 'position', kind: 'vec3' },
+        { key: 'rotation', kind: 'vec3' },
+      ],
+    },
+  ],
+}

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

@@ -0,0 +1,147 @@
+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'
+
+/**
+ * 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
+ * proportionally longer collars, with a floor so 4" fittings stay
+ * grabbable.
+ */
+export function fittingLegLength(diameterInches: number): number {
+  const radius = (diameterInches * INCHES_TO_METERS) / 2
+  return Math.max(0.14, radius * 2.5)
+}
+
+type LocalPort = { id: string; position: Vector3; direction: Vector3; diameter: number }
+
+/**
+ * Ports in the fitting's LOCAL frame (origin at the junction center,
+ * before `position`/`rotation`). Shared by `def.ports` (which transforms
+ * them to level-local) and the geometry builder (which draws a stub per
+ * port).
+ *
+ * Conventions documented on the schema: elbow inlet -X / outlet turned
+ * `angle`° in XZ; tee run along X with the branch at `branchAngle`° off
+ * the +X outlet axis (90° → +Z square tee, 45° → downstream lateral,
+ * 135° → upstream lateral); reducer -X → +X.
+ */
+export function localFittingPorts(node: DuctFittingNode): LocalPort[] {
+  const main = fittingLegLength(node.diameter)
+  if (node.fittingType === 'elbow') {
+    const theta = (node.angle * Math.PI) / 180
+    const outDir = new Vector3(Math.cos(theta), 0, Math.sin(theta))
+    return [
+      {
+        id: 'inlet',
+        position: new Vector3(-main, 0, 0),
+        direction: new Vector3(-1, 0, 0),
+        diameter: node.diameter,
+      },
+      {
+        id: 'outlet',
+        position: outDir.clone().multiplyScalar(main),
+        direction: outDir,
+        diameter: node.diameter,
+      },
+    ]
+  }
+  if (node.fittingType === 'tee') {
+    const branch = fittingLegLength(node.diameter2)
+    // Branch leans `branchAngle`° off the +X outlet axis in XZ: 90° is a
+    // square tap (+Z), shallower angles sweep the branch downstream
+    // toward the outlet so the lateral merges with the run's flow, and
+    // angles past 90° lean it upstream toward the inlet (cos goes
+    // negative, swinging the collar to -X).
+    const phi = (node.branchAngle * Math.PI) / 180
+    const branchDir = new Vector3(Math.cos(phi), 0, Math.sin(phi))
+    return [
+      {
+        id: 'inlet',
+        position: new Vector3(-main, 0, 0),
+        direction: new Vector3(-1, 0, 0),
+        diameter: node.diameter,
+      },
+      {
+        id: 'outlet',
+        position: new Vector3(main, 0, 0),
+        direction: new Vector3(1, 0, 0),
+        diameter: node.diameter,
+      },
+      {
+        id: 'branch',
+        position: branchDir.clone().multiplyScalar(branch),
+        direction: branchDir,
+        diameter: node.diameter2,
+      },
+    ]
+  }
+  if (node.fittingType === 'cross') {
+    // Four-way junction: run inlet -X / outlet +X at the run profile,
+    // two opposed branches square to the run along ±Z at the branch
+    // profile. Both branches share `diameter2` (one drawn run passes
+    // straight through, so its two halves are the same size).
+    const branch = fittingLegLength(node.diameter2)
+    return [
+      {
+        id: 'inlet',
+        position: new Vector3(-main, 0, 0),
+        direction: new Vector3(-1, 0, 0),
+        diameter: node.diameter,
+      },
+      {
+        id: 'outlet',
+        position: new Vector3(main, 0, 0),
+        direction: new Vector3(1, 0, 0),
+        diameter: node.diameter,
+      },
+      {
+        id: 'branch',
+        position: new Vector3(0, 0, branch),
+        direction: new Vector3(0, 0, 1),
+        diameter: node.diameter2,
+      },
+      {
+        id: 'branch2',
+        position: new Vector3(0, 0, -branch),
+        direction: new Vector3(0, 0, -1),
+        diameter: node.diameter2,
+      },
+    ]
+  }
+  // reducer / transition: straight-through, inlet at `diameter` (the
+  // transition's rect end advertises its area-equivalent round size),
+  // outlet at `diameter2`.
+  return [
+    {
+      id: 'inlet',
+      position: new Vector3(-main, 0, 0),
+      direction: new Vector3(-1, 0, 0),
+      diameter: node.diameter,
+    },
+    {
+      id: 'outlet',
+      position: new Vector3(main, 0, 0),
+      direction: new Vector3(1, 0, 0),
+      diameter: node.diameter2,
+    },
+  ]
+}
+
+/** `def.ports` — local ports transformed into level-local space. */
+export function getDuctFittingPorts(node: DuctFittingNode): NodePort[] {
+  const euler = new Euler(node.rotation[0], node.rotation[1], node.rotation[2])
+  const offset = new Vector3(node.position[0], node.position[1], node.position[2])
+  return localFittingPorts(node).map((port) => {
+    const position = port.position.clone().applyEuler(euler).add(offset)
+    const direction = port.direction.clone().applyEuler(euler).normalize()
+    return {
+      id: port.id,
+      position: [position.x, position.y, position.z] as const,
+      direction: [direction.x, direction.y, direction.z] as const,
+      diameter: port.diameter,
+      system: node.system,
+    }
+  })
+}

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

@@ -0,0 +1 @@
+export { DuctFittingNode } from '@pascal-app/core'

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

@@ -0,0 +1,43 @@
+'use client'
+
+import { type AnyNodeId, useScene } from '@pascal-app/core'
+import { useViewer } from '@pascal-app/viewer'
+import { useEffect } from 'react'
+import { cycleRotationAxis } from '../shared/fitting-rotation'
+
+/**
+ * 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.
+ */
+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'
+  })
+
+  useEffect(() => {
+    if (!hasSelectedFitting) return
+    const onKeyDown = (e: KeyboardEvent) => {
+      if (e.key !== 'Alt' || e.repeat) return
+      const tag = (e.target as HTMLElement | null)?.tagName
+      if (tag === 'INPUT' || tag === 'TEXTAREA') return
+      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
+}
+
+export default DuctFittingSelectionAffordance

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

@@ -0,0 +1,253 @@
+'use client'
+
+import { DuctFittingNode, emitter, type GridEvent, useScene } from '@pascal-app/core'
+import { CursorSphere, EDITOR_LAYER, triggerSFX, useEditor } from '@pascal-app/editor'
+import { useViewer } from '@pascal-app/viewer'
+import { Html } from '@react-three/drei'
+import { useEffect, useMemo, useRef, useState } from 'react'
+import { Euler, Quaternion, Vector3 } from 'three'
+import {
+  AXIS_VECTORS,
+  cycleRotationAxis,
+  getRotationAxis,
+  ROTATE_STEP_RAD,
+} from '../shared/fitting-rotation'
+import { LevelOffsetGroup } from '../shared/level-offset-group'
+import {
+  collectScenePorts,
+  DUCT_PORT_SYSTEMS,
+  findNearestPortXZ,
+  type ScenePort,
+} from '../shared/ports'
+import { ductFittingDefinition } from './definition'
+import { buildDuctFittingGeometry } from './geometry'
+import { localFittingPorts } from './ports'
+
+/** Snap radius (meters, XZ) for mating onto an existing port. */
+const PORT_SNAP_RADIUS_M = 0.5
+const PREVIEW_OPACITY = 0.55
+
+function snap(value: number, step: number): number {
+  if (step <= 0) return value
+  return Math.round(value / step) * step
+}
+
+type Placement = {
+  position: [number, number, number]
+  rotation: [number, number, number]
+  snapPort: ScenePort | null
+}
+
+/**
+ * Resolve where the fitting would land for a cursor at `raw`:
+ *   - Near an existing port → mate: orientation aligns the inlet onto
+ *     the port (plus the user's manual R/T rotation, pivoting around
+ *     the inlet collar so it stays on the port while the body sweeps).
+ *   - Otherwise → grid-snapped free placement on the floor, manual
+ *     rotation only.
+ */
+function resolvePlacement(
+  raw: [number, number, number],
+  previewNode: DuctFittingNode,
+  gridStep: number,
+  manualQuat: Quaternion,
+): Placement {
+  const port = findNearestPortXZ(
+    raw,
+    collectScenePorts({ systems: DUCT_PORT_SYSTEMS }),
+    PORT_SNAP_RADIUS_M,
+  )
+  if (port) {
+    const direction = new Vector3(...port.direction).normalize()
+    // Local +X must map onto the port's outward direction so the inlet
+    // (local -X) faces back into the run it's joining. Manual rotation
+    // composes in the world frame on top of the mate orientation.
+    const mate = new Quaternion().setFromUnitVectors(new Vector3(1, 0, 0), direction)
+    const final = manualQuat.clone().multiply(mate)
+    const inlet = localFittingPorts(previewNode)[0]!
+    const inletWorldOffset = inlet.position.clone().applyQuaternion(final)
+    const position = new Vector3(...port.position).sub(inletWorldOffset)
+    const euler = new Euler().setFromQuaternion(final)
+    return {
+      position: [position.x, position.y, position.z],
+      rotation: [euler.x, euler.y, euler.z],
+      snapPort: port,
+    }
+  }
+  const euler = new Euler().setFromQuaternion(manualQuat)
+  return {
+    position: [snap(raw[0], gridStep), 0, snap(raw[2], gridStep)],
+    rotation: [euler.x, euler.y, euler.z],
+    snapPort: null,
+  }
+}
+
+/**
+ * Click-place tool for duct fittings (elbow / tee / reducer).
+ *
+ * A translucent ghost of the fitting follows the cursor. Within snap
+ * range of any scene port (duct run ends, other fittings' collars) the
+ * ghost jumps onto the port — position AND orientation — so one click
+ * mates the fitting onto the run.
+ *
+ * Rotation while placing: **R / T** turn the ghost ±45° around the
+ * active world axis; **Alt** cycles the axis (Y → X → Z). The HUD badge
+ * above the ghost shows the current axis. When snapped to a port the
+ * rotation pivots around the inlet collar so the joint stays mated.
+ * Handlers run in the capture phase so R doesn't also spin whatever
+ * node happens to be selected.
+ */
+const DuctFittingTool = () => {
+  const activeLevelId = useViewer((s) => s.selection.levelId)
+  const [placement, setPlacement] = useState<Placement | null>(null)
+  const axis = useEditor((s) => s.rotationAxis)
+  // Accumulated manual rotation from R/T presses. Ref (not state) so the
+  // emitter callbacks always read the latest without re-subscribing; a
+  // placement recompute is triggered explicitly after each change.
+  const manualQuatRef = useRef(new Quaternion())
+  // Last raw cursor position so a key press can recompute the placement
+  // without waiting for the next mouse move.
+  const lastRawRef = useRef<[number, number, number] | null>(null)
+
+  // Ghost matches exactly what a click creates (the kind's defaults).
+  const previewNode = useMemo(
+    () => DuctFittingNode.parse({ ...ductFittingDefinition.defaults(), name: 'Duct fitting' }),
+    [],
+  )
+  const ghost = useMemo(() => {
+    const group = buildDuctFittingGeometry(previewNode)
+    group.traverse((child) => {
+      // Overlay layer keeps the placement ghost out of the ink / SSGI
+      // buffers and the thumbnail export, like every other tool preview.
+      child.layers.set(EDITOR_LAYER)
+      const mesh = child as { material?: { transparent: boolean; opacity: number } }
+      if (mesh.material) {
+        mesh.material.transparent = true
+        mesh.material.opacity = PREVIEW_OPACITY
+      }
+    })
+    return group
+  }, [previewNode])
+
+  useEffect(() => {
+    if (!activeLevelId) return
+
+    const recompute = () => {
+      const raw = lastRawRef.current
+      if (!raw) return
+      setPlacement(
+        resolvePlacement(
+          raw,
+          previewNode,
+          useEditor.getState().gridSnapStep,
+          manualQuatRef.current,
+        ),
+      )
+    }
+
+    const onMove = (event: GridEvent) => {
+      lastRawRef.current = [event.localPosition[0], 0, event.localPosition[2]]
+      recompute()
+    }
+
+    const onClick = (event: GridEvent) => {
+      lastRawRef.current = [event.localPosition[0], 0, event.localPosition[2]]
+      const { position, rotation } = resolvePlacement(
+        lastRawRef.current,
+        previewNode,
+        useEditor.getState().gridSnapStep,
+        manualQuatRef.current,
+      )
+      const fitting = DuctFittingNode.parse({
+        ...ductFittingDefinition.defaults(),
+        name: 'Duct fitting',
+        position,
+        rotation,
+      })
+      useScene.getState().createNode(fitting, activeLevelId)
+      useViewer.getState().setSelection({ selectedIds: [fitting.id] })
+      triggerSFX('sfx:item-place')
+    }
+
+    const onKeyDown = (e: KeyboardEvent) => {
+      const tag = (e.target as HTMLElement | null)?.tagName
+      if (tag === 'INPUT' || tag === 'TEXTAREA') return
+      const key = e.key
+      if (key === 'r' || key === 'R' || key === 't' || key === 'T') {
+        // Capture-phase + stopPropagation so the editor's selection-rotate
+        // R handler doesn't also fire while the placement tool owns R.
+        e.preventDefault()
+        e.stopPropagation()
+        const steps = key === 't' || key === 'T' || e.shiftKey ? -1 : 1
+        const turn = new Quaternion().setFromAxisAngle(
+          AXIS_VECTORS[getRotationAxis()],
+          steps * ROTATE_STEP_RAD,
+        )
+        manualQuatRef.current = turn.multiply(manualQuatRef.current)
+        triggerSFX('sfx:item-rotate')
+        recompute()
+      } else if (key === 'Alt' && !e.repeat) {
+        e.preventDefault()
+        e.stopPropagation()
+        cycleRotationAxis()
+      }
+    }
+
+    emitter.on('grid:move', onMove)
+    emitter.on('grid:click', onClick)
+    window.addEventListener('keydown', onKeyDown, true)
+    return () => {
+      emitter.off('grid:move', onMove)
+      emitter.off('grid:click', onClick)
+      window.removeEventListener('keydown', onKeyDown, true)
+    }
+  }, [activeLevelId, previewNode])
+
+  if (!activeLevelId || !placement) return null
+
+  return (
+    <LevelOffsetGroup>
+      {/* Same ground ring + vertical line + tool-icon badge the duct draw
+          tool shows in 3D (icon resolved from the active `duct-fitting`
+          structure-tools entry). In 2D the floorplan overlay draws this for
+          every tool; in 3D each tool renders its own. */}
+      <CursorSphere position={placement.position} />
+      <group position={placement.position} rotation={placement.rotation}>
+        <primitive object={ghost} />
+      </group>
+      {/* Rotation HUD — active axis + key hints, pinned above the ghost. */}
+      <Html
+        center
+        position={[placement.position[0], placement.position[1] + 0.5, placement.position[2]]}
+        style={{ pointerEvents: 'none', userSelect: 'none' }}
+        zIndexRange={[100, 0]}
+      >
+        {/* Same pill shell as DimensionPill so the placement HUD matches
+            the drawing / dragging readouts. */}
+        <div className="flex items-center gap-2 whitespace-nowrap rounded-full border border-border/60 bg-background/90 px-4 py-1.5 text-xs tabular-nums shadow-sm backdrop-blur">
+          <span className="font-medium text-foreground">Axis {axis.toUpperCase()}</span>
+          <span aria-hidden className="text-muted-foreground">
+            ·
+          </span>
+          <span className="text-muted-foreground">R/T rotate</span>
+          <span aria-hidden className="text-muted-foreground">
+            ·
+          </span>
+          <span className="text-muted-foreground">⌥ axis</span>
+        </div>
+      </Html>
+      {/* Port-snap halo so the user sees the click will mate, not free-place. */}
+      {placement.snapPort && (
+        <mesh
+          layers={EDITOR_LAYER}
+          position={placement.snapPort.position as [number, number, number]}
+        >
+          <sphereGeometry args={[0.18, 24, 16]} />
+          <meshBasicMaterial color="#818cf8" depthTest={false} opacity={0.35} transparent />
+        </mesh>
+      )}
+    </LevelOffsetGroup>
+  )
+}
+
+export default DuctFittingTool

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

@@ -0,0 +1,188 @@
+import { type AnyNode, type NodeDefinition, useScene } from '@pascal-app/core'
+import { createPathPointMoveAffordance } from '../shared/path-point-affordance'
+import { buildDuctSegmentFloorplan } from './floorplan'
+import { buildDuctSegmentGeometry, ductPortDiameterIn } from './geometry'
+import { ductSegmentParametrics } from './parametrics'
+import { DuctSegmentNode } from './schema'
+
+/**
+ * Phase 1 of the HVAC node system — round duct segment as a polyline.
+ *
+ * Composition: `def.geometry` only. No custom renderer, no per-frame
+ * system. The framework's `<ParametricNodeRenderer>` mounts an empty
+ * group; `<GeometrySystem>` calls `buildDuctSegmentGeometry` whenever
+ * the node is dirty and swaps in the cylinder+sphere meshes.
+ *
+ * Deferred to later slices:
+ *   - Placement tool (polyline draw UX).
+ *   - Fittings (elbow / tee / reducer) — needs typed ports first.
+ *   - Terminals (registers / diffusers) — needs surface-snapping.
+ *   - Equipment (furnace / air-handler / condenser).
+ *   - Floor-plan rendering.
+ *   - Move / endpoint handles.
+ *
+ * The node can be created programmatically today via
+ * `DuctSegmentNode.parse({ path: [...] })` + `useScene.createNode(...)`.
+ */
+/** R / T roll step (radians) — 45°, matching the fitting rotate. */
+const ROLL_STEP_RAD = Math.PI / 4
+
+/**
+ * R / T roll a selected rect / oval run's cross-section ±45° around its
+ * drawn line, so a rectangular trunk can be turned on its side after
+ * placement. Round runs look identical at any roll, so the action gates
+ * itself off for them (`appliesTo`) and the editor's default rotation —
+ * a no-op for a node with no `rotation` field — takes over harmlessly.
+ */
+function rollDuctSegment(node: AnyNode, steps: 1 | -1): void {
+  const duct = node as DuctSegmentNode
+  useScene.getState().updateNode(duct.id, { roll: duct.roll + steps * ROLL_STEP_RAD })
+}
+
+export const ductSegmentDefinition: NodeDefinition<typeof DuctSegmentNode> = {
+  kind: 'duct-segment',
+  schemaVersion: 1,
+  schema: DuctSegmentNode,
+  category: 'utility',
+  distributionRole: 'run',
+
+  defaults: () => ({
+    object: 'node',
+    parentId: null,
+    visible: true,
+    metadata: {},
+    path: [
+      [0, 0, 0],
+      [3, 0, 0],
+    ],
+    shape: 'rect',
+    diameter: 6,
+    width: 14,
+    height: 8,
+    ductMaterial: 'flex',
+    seamDetail: false,
+    insulated: false,
+    insulationR: 0.5,
+    system: 'supply',
+    roll: 0,
+  }),
+
+  capabilities: {
+    selectable: { hitVolume: 'bbox' },
+    duplicable: true,
+    deletable: true,
+  },
+
+  parametrics: ductSegmentParametrics,
+
+  // R / T roll a selected rect / oval run ±45° around its drawn line.
+  // `appliesTo` lets round runs fall through to the editor's default
+  // (harmless — duct-segment has no `rotation` field).
+  keyboardActions: {
+    r: {
+      appliesTo: (node) => node.type === 'duct-segment' && node.shape !== 'round',
+      run: (node) => rollDuctSegment(node, 1),
+    },
+    t: {
+      appliesTo: (node) => node.type === 'duct-segment' && node.shape !== 'round',
+      run: (node) => rollDuctSegment(node, -1),
+    },
+  },
+
+  geometry: buildDuctSegmentGeometry,
+  geometryKey: (n) =>
+    JSON.stringify([
+      n.path,
+      n.shape,
+      n.diameter,
+      n.width,
+      n.height,
+      n.roll,
+      n.ductMaterial,
+      n.seamDetail,
+      n.insulated,
+      n.insulationR,
+      n.system,
+    ]),
+
+  // Open run ends as typed ports — directions point outward along the
+  // path tangent so fittings mate flush. Path coords are already
+  // level-local, so no transform is needed.
+  ports: (n) => {
+    if (n.path.length < 2) return []
+    const unit = (
+      a: readonly [number, number, number],
+      b: readonly [number, number, number],
+    ): [number, number, number] => {
+      const d: [number, number, number] = [a[0] - b[0], a[1] - b[1], a[2] - b[2]]
+      const len = Math.hypot(d[0], d[1], d[2])
+      return len < 1e-9 ? [1, 0, 0] : [d[0] / len, d[1] / len, d[2] / len]
+    }
+    const first = n.path[0]!
+    const second = n.path[1]!
+    const last = n.path[n.path.length - 1]!
+    const prev = n.path[n.path.length - 2]!
+    return [
+      {
+        id: 'start',
+        position: first,
+        direction: unit(first, second),
+        diameter: ductPortDiameterIn(n),
+        system: n.system,
+      },
+      {
+        id: 'end',
+        position: last,
+        direction: unit(last, prev),
+        diameter: ductPortDiameterIn(n),
+        system: n.system,
+      },
+    ]
+  },
+
+  floorplan: buildDuctSegmentFloorplan,
+
+  // 2D selection-time path-point handles — the floor-plan twin of the 3D
+  // `affordanceTools.selection` handles. The builder emits an
+  // `endpoint-handle` per path vertex; this drags the matching point.
+  floorplanAffordances: {
+    'move-path-point': createPathPointMoveAffordance('duct-segment'),
+  },
+
+  // Selection-time path-point handles (drag to edit a committed run).
+  // Editor-only UI (reads gridSnapStep, renders DimensionPill), so it
+  // mounts via the editor's SelectionAffordanceManager — not `def.system`,
+  // which the viewer package mounts for the read-only route.
+  affordanceTools: {
+    selection: () => import('./selection'),
+    // Ghost-preview duplicate / move. Duplicate is pure drag-to-place: a
+    // translucent copy of the run follows the cursor and only lands on the
+    // commit click — nothing is inserted into the scene before that.
+    move: () => import('./move-tool'),
+  },
+
+  tool: () => import('./tool'),
+  toolHints: [
+    { key: 'Click', label: 'Start segment' },
+    { key: 'Click again', label: 'Place it (locked to 45°)' },
+    { key: 'Shift', label: 'Free angle' },
+    { key: 'Alt + drag', label: 'Go vertical ↕, click to place' },
+    { key: '[ / ]', label: 'Duct diameter down / up' },
+    { key: 'Q', label: 'Round / rect trunk' },
+    { key: 'C', label: 'Ceiling / floor height' },
+    { key: 'Esc', label: 'Cancel start point' },
+  ],
+
+  presentation: {
+    label: 'Duct',
+    description: 'HVAC duct run — polyline of round, rect, or flat-oval sections.',
+    icon: { kind: 'url', src: '/icons/duct.png' },
+    paletteSection: 'structure',
+    paletteOrder: 90,
+  },
+
+  mcp: {
+    description:
+      'An HVAC duct run defined as a polyline — round (branches), rect (trunks/plenums), or flat-oval (tight joist bays). Supply or return, with configurable size, material (incl. spiral seam), and external insulation.',
+  },
+}

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

@@ -0,0 +1,102 @@
+import type { FloorplanGeometry, FloorplanPoint, GeometryContext } from '@pascal-app/core'
+import { INCHES_TO_METERS } from './geometry'
+import type { DuctSegmentNode } from './schema'
+
+const SUPPLY_CENTERLINE = '#d4825a'
+const RETURN_CENTERLINE = '#5a8ad4'
+const BODY_COLOR = '#9ca3af'
+
+/**
+ * Floor-plan representation of a duct run: the path drawn at the duct's
+ * real width (plan-unit stroke so it scales with zoom), with a dashed
+ * centerline tinted by system — orange for supply, blue for return, the
+ * same hues the 3D tint uses. Vertical risers collapse to a point in
+ * plan; consecutive duplicate plan points are dropped so they don't
+ * render zero-length artifacts.
+ */
+export function buildDuctSegmentFloorplan(
+  node: DuctSegmentNode,
+  ctx: GeometryContext,
+): FloorplanGeometry | null {
+  if (node.path.length < 2) return null
+
+  // Project to plan, dropping consecutive duplicates (risers). `indexMap[k]`
+  // is the original path index plan point k came from, so the drag handle
+  // edits the right vertex.
+  const points: FloorplanPoint[] = []
+  const indexMap: number[] = []
+  for (let i = 0; i < node.path.length; i++) {
+    const [x, , z] = node.path[i]!
+    const prev = points[points.length - 1]
+    if (prev && Math.abs(prev[0] - x) < 1e-6 && Math.abs(prev[1] - z) < 1e-6) continue
+    points.push([x, z])
+    indexMap.push(i)
+  }
+
+  // Plan width: rect / oval runs draw at their actual width; round at diameter.
+  const diameterM = (node.shape === 'round' ? node.diameter : node.width) * INCHES_TO_METERS
+  const view = ctx.viewState
+  const palette = view?.palette
+  const showSelectedChrome = (view?.selected || view?.highlighted) ?? false
+  const centerline = node.system === 'supply' ? SUPPLY_CENTERLINE : RETURN_CENTERLINE
+
+  // A pure riser (single plan point) still gets a marker: a circle at
+  // the duct's diameter so the vertical run is visible in plan.
+  if (points.length < 2) {
+    const p = points[0] ?? [node.path[0]![0], node.path[0]![2]]
+    return {
+      kind: 'group',
+      children: [
+        {
+          kind: 'circle',
+          cx: p[0],
+          cy: p[1],
+          r: diameterM / 2,
+          fill: BODY_COLOR,
+          stroke: showSelectedChrome && palette ? palette.selectedStroke : centerline,
+          strokeWidth: 0.02,
+          opacity: 0.9,
+        },
+      ],
+    }
+  }
+
+  const children: FloorplanGeometry[] = [
+    {
+      kind: 'polyline',
+      points,
+      stroke: showSelectedChrome && palette ? palette.selectedStroke : BODY_COLOR,
+      strokeWidth: diameterM,
+      strokeLinecap: 'round',
+      strokeLinejoin: 'round',
+      opacity: showSelectedChrome ? 0.95 : 0.8,
+    },
+    {
+      kind: 'polyline',
+      points,
+      stroke: centerline,
+      strokeWidth: 1.5,
+      vectorEffect: 'non-scaling-stroke',
+      strokeDasharray: '5 4',
+      strokeLinecap: 'round',
+      strokeLinejoin: 'round',
+      opacity: 0.9,
+    },
+  ]
+
+  // Selection chrome: one draggable handle per path vertex (2D twin of the
+  // 3D selection handles). Routes to the shared `move-path-point` affordance.
+  if (view?.selected) {
+    for (let k = 0; k < points.length; k++) {
+      children.push({
+        kind: 'endpoint-handle',
+        point: points[k]!,
+        state: 'idle',
+        affordance: 'move-path-point',
+        payload: { pointIndex: indexMap[k]! },
+      })
+    }
+  }
+
+  return { kind: 'group', children }
+}

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

@@ -0,0 +1,466 @@
+import {
+  BoxGeometry,
+  CatmullRomCurve3,
+  CylinderGeometry,
+  ExtrudeGeometry,
+  Group,
+  Matrix4,
+  Mesh,
+  MeshStandardMaterial,
+  Quaternion,
+  Shape,
+  SphereGeometry,
+  TubeGeometry,
+  Vector3,
+} from 'three'
+import type { DuctSegmentNode } from './schema'
+
+export const INCHES_TO_METERS = 0.0254
+// Insulation wraps the duct in a roughly uniform shell. A strictly physical
+// mapping (fiberglass ≈ R-3.2 per inch) makes low R-values nearly invisible
+// at screen scale — R-1 would add only ~8 mm over a 15 cm duct. So the shell
+// uses a perceptual mapping: a visible base jacket as soon as insulation is
+// non-zero, plus a clear per-R increment. Anchored so R-8 still lands near
+// the real-world ~3" jacket.
+const INSULATION_BASE_IN = 0.5
+const INSULATION_INCHES_PER_R = 0.3125
+function pickInsulationThickness(r: number): number {
+  if (r <= 0) return 0
+  return (INSULATION_BASE_IN + r * INSULATION_INCHES_PER_R) * INCHES_TO_METERS
+}
+
+// Supply/return tint — kept only for the spiral seam ridge accent; the duct
+// body itself is plain white (see createDuctMaterial).
+const SUPPLY_COLOR = '#d4825a'
+const RETURN_COLOR = '#5a8ad4'
+
+const RADIAL_SEGMENTS = 24
+
+const UP = new Vector3(0, 1, 0)
+
+/**
+ * Area-equivalent round diameter (inches) for a rect cross-section —
+ * what a rect trunk advertises on its ports so round fittings / branches
+ * mate at a sensible size.
+ */
+export function equivalentDiameterIn(widthIn: number, heightIn: number): number {
+  return 2 * Math.sqrt((widthIn * heightIn) / Math.PI)
+}
+
+/**
+ * Area-equivalent round diameter (inches) for a flat-oval cross-section:
+ * a rectangle of (width − height) × height plus the two semicircular caps.
+ */
+export function 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)
+}
+
+/** The diameter (inches) a duct segment presents at its ports. */
+export function ductPortDiameterIn(node: {
+  shape?: 'round' | 'rect' | 'oval'
+  diameter: number
+  width?: number
+  height?: number
+}): 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
+}
+
+/**
+ * Cross-section axes for a rect run along `dir`, rolled `roll` radians
+ * about the run direction. At roll 0: width is the horizontal axis
+ * (UP × dir) and height the vertical one — vertical runs, where that
+ * cross product degenerates, fall back to world X/Z. `roll` rotates the
+ * pair in the plane perpendicular to `dir`, letting a riser carry the
+ * orientation of the run it turned off instead of the bare fallback.
+ */
+export function rectSectionAxes(dir: Vector3, roll = 0): { width: Vector3; height: Vector3 } {
+  const d = dir.clone().normalize()
+  const xBase = new Vector3().crossVectors(UP, d)
+  if (xBase.lengthSq() < 1e-8) xBase.set(1, 0, 0)
+  xBase.normalize()
+  const zBase = new Vector3().crossVectors(xBase, d)
+  const c = Math.cos(roll)
+  const s = Math.sin(roll)
+  const width = xBase.clone().multiplyScalar(c).addScaledVector(zBase, s)
+  const height = xBase.clone().multiplyScalar(-s).addScaledVector(zBase, c)
+  return { width, height }
+}
+
+/**
+ * Roll (radians) that keeps a rect cross-section continuous across an
+ * elbow: the dimension lying along the joint's hinge — the bend-plane
+ * normal `portDir × newDir`, perpendicular to both legs — must stay on
+ * the same physical face on the new run as on the source run. Returns 0
+ * for an in-plane (degenerate-normal) joint, so horizontal turns keep
+ * the natural width-horizontal orientation.
+ */
+export function rollToContinueAcrossElbow(
+  sourceDir: Vector3,
+  sourceRoll: number,
+  portDir: Vector3,
+  newDir: Vector3,
+): number {
+  const n = new Vector3().crossVectors(portDir, newDir)
+  if (n.lengthSq() < 1e-8) return 0
+  n.normalize()
+  const src = rectSectionAxes(sourceDir, sourceRoll)
+  const carriesWidth = Math.abs(src.width.dot(n)) >= Math.abs(src.height.dot(n))
+  const d = newDir.clone().normalize()
+  const xBase = new Vector3().crossVectors(UP, d)
+  if (xBase.lengthSq() < 1e-8) xBase.set(1, 0, 0)
+  xBase.normalize()
+  const zBase = new Vector3().crossVectors(xBase, d)
+  // Place the hinge-aligned face on the same axis the source carries it.
+  return carriesWidth
+    ? Math.atan2(n.dot(zBase), n.dot(xBase))
+    : Math.atan2(-n.dot(xBase), n.dot(zBase))
+}
+
+/**
+ * Rect box spanning `start`→`end`. Orientation comes from `rectSectionAxes`
+ * (width horizontal, height vertical by default; `roll` reorients a riser
+ * to stay continuous through its elbow). Quaternion from an explicit basis
+ * — the minimal-rotation `setFromUnitVectors` used for cylinders would roll
+ * the cross-section on axis-aligned runs.
+ */
+export function buildRectSection(
+  start: Vector3,
+  end: Vector3,
+  widthM: number,
+  heightM: number,
+  material: MeshStandardMaterial,
+  name: string,
+  roll = 0,
+): Mesh | null {
+  const dir = new Vector3().subVectors(end, start)
+  const length = dir.length()
+  if (length < 1e-6) return null
+  dir.normalize()
+
+  const { width: x, height: z } = rectSectionAxes(dir, roll)
+
+  const geom = new BoxGeometry(widthM, length, heightM)
+  const mesh = new Mesh(geom, material)
+  mesh.name = name
+  mesh.position.copy(start).addScaledVector(dir, length / 2)
+  mesh.quaternion.copy(new Quaternion().setFromRotationMatrix(new Matrix4().makeBasis(x, dir, z)))
+  return mesh
+}
+
+/**
+ * Flat-oval (stadium) profile in the XY plane: width along X, height
+ * along Y, flat top/bottom joined by semicircular end caps of the height.
+ * Degenerates to a circle when width ≤ height.
+ */
+function stadiumShape(widthM: number, heightM: number): Shape {
+  const r = Math.min(widthM, heightM) / 2
+  const straight = Math.max(0, widthM - heightM) / 2
+  const shape = new Shape()
+  shape.absarc(straight, 0, r, -Math.PI / 2, Math.PI / 2, false)
+  shape.absarc(-straight, 0, r, Math.PI / 2, (3 * Math.PI) / 2, false)
+  shape.closePath()
+  return shape
+}
+
+/**
+ * Centered flat-oval prism with the same local axes as the rect box
+ * (X = width, Y = run length, Z = height), so sections and previews
+ * orient it with the `rectSectionAxes` basis.
+ */
+export function createOvalSectionGeometry(
+  widthM: number,
+  heightM: number,
+  lengthM: number,
+): ExtrudeGeometry {
+  const geom = new ExtrudeGeometry(stadiumShape(widthM, heightM), {
+    depth: lengthM,
+    bevelEnabled: false,
+    curveSegments: RADIAL_SEGMENTS / 2,
+  })
+  geom.translate(0, 0, -lengthM / 2)
+  geom.rotateX(-Math.PI / 2)
+  return geom
+}
+
+/**
+ * Flat-oval section spanning `start`→`end` — the oval counterpart of
+ * `buildRectSection`, sharing its orientation basis and roll semantics.
+ */
+export function buildOvalSection(
+  start: Vector3,
+  end: Vector3,
+  widthM: number,
+  heightM: number,
+  material: MeshStandardMaterial,
+  name: string,
+  roll = 0,
+): Mesh | null {
+  const dir = new Vector3().subVectors(end, start)
+  const length = dir.length()
+  if (length < 1e-6) return null
+  dir.normalize()
+
+  const { width: x, height: z } = rectSectionAxes(dir, roll)
+
+  const mesh = new Mesh(createOvalSectionGeometry(widthM, heightM, length), material)
+  mesh.name = name
+  mesh.position.copy(start).addScaledVector(dir, length / 2)
+  mesh.quaternion.copy(new Quaternion().setFromRotationMatrix(new Matrix4().makeBasis(x, dir, z)))
+  return mesh
+}
+
+/**
+ * Cylinder spanning `start`→`end` at `radius`. Shared by the segment and
+ * fitting builders — fittings are just short sections + a junction.
+ */
+export function buildSection(
+  start: Vector3,
+  end: Vector3,
+  radius: number,
+  material: MeshStandardMaterial,
+  name: string,
+): Mesh | null {
+  const dir = new Vector3().subVectors(end, start)
+  const length = dir.length()
+  if (length < 1e-6) return null
+  dir.normalize()
+
+  // Capped, front-side-only — ducts should read as solid metal tubes,
+  // not hollow open-ended shells.
+  const geom = new CylinderGeometry(radius, radius, length, RADIAL_SEGMENTS, 1, false)
+  const mesh = new Mesh(geom, material)
+  mesh.name = name
+  mesh.position.copy(start).addScaledVector(dir, length / 2)
+  mesh.quaternion.setFromUnitVectors(UP, dir)
+  return mesh
+}
+
+/**
+ * Helical ridge wound around the cylinder spanning `start`→`end` at the
+ * given `pitch` (meters of run per turn) and `ridge` tube radius. The
+ * ridge sits centered on the body surface, so half its thickness reads
+ * as raised. Two construction details share this: the spiral duct's
+ * lock seam (long pitch, thin ridge) and the flex duct's wire helix
+ * (tight pitch, fat ridge → corrugated look).
+ */
+function buildHelixRidge(
+  start: Vector3,
+  end: Vector3,
+  radius: number,
+  pitch: number,
+  ridge: number,
+  material: MeshStandardMaterial,
+  name: string,
+): Mesh | null {
+  const dir = new Vector3().subVectors(end, start)
+  const length = dir.length()
+  if (length < 1e-6) return null
+  dir.normalize()
+
+  const turns = length / pitch
+  const { width: u, height: v } = rectSectionAxes(dir)
+  const samples = Math.min(4096, Math.max(8, Math.ceil(turns * 12)))
+  const pts: Vector3[] = []
+  for (let i = 0; i <= samples; i++) {
+    const t = i / samples
+    const theta = 2 * Math.PI * turns * t
+    pts.push(
+      start
+        .clone()
+        .addScaledVector(dir, t * length)
+        .addScaledVector(u, radius * Math.cos(theta))
+        .addScaledVector(v, radius * Math.sin(theta)),
+    )
+  }
+  const geom = new TubeGeometry(new CatmullRomCurve3(pts), samples, ridge, 6, false)
+  const mesh = new Mesh(geom, material)
+  mesh.name = name
+  return mesh
+}
+
+/**
+ * Helix parameters for a construction material's body detail, or null
+ * for materials with a smooth body. Spiral: the machine seam keeps a
+ * roughly constant helix angle, so pitch scales with the diameter.
+ * Flex: the wire helix is tight and reads as corrugation; its pitch
+ * also follows the diameter but is clamped much lower.
+ */
+function helixRidgeFor(
+  ductMaterial: DuctAppearance['ductMaterial'],
+  radius: number,
+): { pitch: number; ridge: number; color: string } | null {
+  if (ductMaterial === 'spiral') {
+    return {
+      pitch: Math.min(0.3, Math.max(0.08, radius * 1.2)),
+      ridge: Math.min(0.006, Math.max(0.002, radius * 0.06)),
+      color: '#9b9b9b',
+    }
+  }
+  if (ductMaterial === 'flex') {
+    return {
+      pitch: Math.min(0.06, Math.max(0.025, radius * 0.5)),
+      ridge: Math.min(0.009, Math.max(0.004, radius * 0.12)),
+      color: '#737373',
+    }
+  }
+  return null
+}
+
+type DuctAppearance = {
+  ductMaterial: 'sheet-metal' | 'spiral' | 'flex' | 'duct-board'
+  system: 'supply' | 'return'
+}
+
+function getSystemTint(node: DuctAppearance): string {
+  return node.system === 'supply' ? SUPPLY_COLOR : RETURN_COLOR
+}
+
+/**
+ * Standard duct body material — a plain white matte finish so runs and
+ * fittings read like walls / other building elements rather than tinted
+ * 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,
+  })
+}
+
+/**
+ * Pure geometry builder for a round duct segment polyline.
+ *
+ * Strategy:
+ *   - For every consecutive pair of path points, build a cylinder of the
+ *     duct's inner diameter.
+ *   - Drop a sphere of the same radius at every interior joint to cap the
+ *     corner smoothly (no mitering yet — fittings come in a later slice).
+ *   - When insulation is non-zero, repeat the same pattern at a larger
+ *     radius using a translucent shell material.
+ *
+ * All children are returned in level-local meters; the framework's
+ * `<ParametricNodeRenderer>` handles the node-level transform (currently
+ * identity since the schema has no position field — the path itself is
+ * absolute within the level).
+ */
+export function buildDuctSegmentGeometry(node: DuctSegmentNode): Group {
+  const group = new Group()
+  if (node.path.length < 2) return group
+
+  const isRect = node.shape === 'rect'
+  const isOval = node.shape === 'oval'
+  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 points = node.path.map(([x, y, z]) => new Vector3(x, y, z))
+
+  const addRun = (
+    half: number,
+    rectW: number,
+    rectH: number,
+    material: MeshStandardMaterial,
+    namePrefix: string,
+    endInsetM = 0,
+  ) => {
+    for (let i = 0; i < points.length - 1; i++) {
+      // Loop bounds + min(2) on the schema guarantee both points exist.
+      let a = points[i] as Vector3
+      let b = points[i + 1] as Vector3
+      // Pull the run's open ends in so this shell's end faces never sit
+      // coplanar with the duct's own end caps (z-fighting). Clamped so
+      // a short section can't invert.
+      if (endInsetM > 0) {
+        const dir = new Vector3().subVectors(b, a)
+        const length = dir.length()
+        if (length < 1e-6) continue
+        dir.divideScalar(length)
+        const inset = Math.min(endInsetM, length * 0.25)
+        if (i === 0) a = a.clone().addScaledVector(dir, inset)
+        if (i === points.length - 2) b = b.clone().addScaledVector(dir, -inset)
+      }
+      const mesh = isRect
+        ? buildRectSection(a, b, rectW, rectH, material, `${namePrefix}-section-${i}`, node.roll)
+        : 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)
+    }
+    // Joint caps at interior points only (skip first and last — they're
+    // open ends; equipment / terminal / fitting collars cap them). Rect
+    // joints are cubes spanning the cross-section (oval joints the same
+    // prism in stadium profile); round joints spheres.
+    for (let i = 1; i < points.length - 1; i++) {
+      const joint = isRect
+        ? new Mesh(new BoxGeometry(rectW, rectH, rectW), material)
+        : isOval
+          ? new Mesh(createOvalSectionGeometry(rectW, rectH, rectW), material)
+          : new Mesh(new SphereGeometry(half, RADIAL_SEGMENTS, 12), material)
+      joint.name = `${namePrefix}-joint-${i}`
+      joint.position.copy(points[i] as Vector3)
+      group.add(joint)
+    }
+  }
+
+  addRun(radius, widthM, heightM, ductMaterial, 'duct')
+
+  // Construction body detail: spiral winds its lock seam, flex its wire
+  // helix (tight pitch — reads as corrugation) over each round section.
+  // These are round-body details, so rect / oval runs render smooth.
+  const helix =
+    node.shape === 'round' && node.seamDetail ? helixRidgeFor(node.ductMaterial, radius) : null
+  if (helix) {
+    const ridgeMaterial = new MeshStandardMaterial({
+      color: helix.color,
+      metalness: node.ductMaterial === 'flex' ? 0.1 : 0.7,
+      roughness: node.ductMaterial === 'flex' ? 0.85 : 0.35,
+      emissive: getSystemTint(node),
+      emissiveIntensity: 0.08,
+    })
+    for (let i = 0; i < points.length - 1; i++) {
+      const seam = buildHelixRidge(
+        points[i] as Vector3,
+        points[i + 1] as Vector3,
+        radius,
+        helix.pitch,
+        helix.ridge,
+        ridgeMaterial,
+        `duct-seam-${i}`,
+      )
+      if (seam) group.add(seam)
+    }
+  }
+
+  const insulationThickness = node.insulated ? pickInsulationThickness(node.insulationR) : 0
+  if (insulationThickness > 0) {
+    const insulationMaterial = new MeshStandardMaterial({
+      color: '#f0e4c8',
+      roughness: 1,
+      metalness: 0,
+      transparent: true,
+      opacity: 0.25,
+    })
+    addRun(
+      radius + insulationThickness,
+      widthM + insulationThickness * 2,
+      heightM + insulationThickness * 2,
+      insulationMaterial,
+      'duct-insulation',
+      0.01,
+    )
+  }
+
+  return group
+}

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

@@ -0,0 +1,3 @@
+export { ductSegmentDefinition } from './definition'
+export { buildDuctSegmentGeometry } from './geometry'
+export { DuctSegmentNode } from './schema'

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

@@ -0,0 +1,330 @@
+'use client'
+
+import {
+  type AlignmentAnchor,
+  type AnyNode,
+  type AnyNodeId,
+  DuctSegmentNode,
+  emitter,
+  type GridEvent,
+  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, useRef, useState } from 'react'
+import { Matrix4, Vector3 } from 'three'
+import {
+  type Aabb2D,
+  collectGhostAlignmentCandidates,
+  resolveGhostAlignment,
+} from '../shared/ghost-alignment'
+import { rectSectionAxes } from './geometry'
+
+type Vec3 = [number, number, number]
+
+const GHOST_COLOR = '#818cf8'
+const GHOST_OPACITY = 0.5
+const IN_TO_M = 0.0254
+
+/** 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
+}
+
+function pathCenterXZ(path: readonly Vec3[]): [number, number] {
+  let x = 0
+  let z = 0
+  for (const p of path) {
+    x += p[0]
+    z += p[2]
+  }
+  const n = path.length || 1
+  return [x / n, z / n]
+}
+
+/** Half the run's cross-section (meters) — the box / footprint padding. */
+function runRadiusM(duct: DuctSegmentNode): number {
+  if (duct.shape === 'round') return (duct.diameter * IN_TO_M) / 2
+  return (Math.max(duct.width, duct.height) * IN_TO_M) / 2
+}
+
+/** The run's vertical box extent (meters). */
+function runHeightM(duct: DuctSegmentNode): number {
+  return (duct.shape === 'round' ? duct.diameter : duct.height) * IN_TO_M
+}
+
+/** XZ bounds of a path padded by the run's radius. */
+function pathAabb(path: readonly Vec3[], r: number): Aabb2D {
+  let minX = Number.POSITIVE_INFINITY
+  let maxX = Number.NEGATIVE_INFINITY
+  let minZ = Number.POSITIVE_INFINITY
+  let maxZ = Number.NEGATIVE_INFINITY
+  for (const p of path) {
+    if (p[0] < minX) minX = p[0]
+    if (p[0] > maxX) maxX = p[0]
+    if (p[2] < minZ) minZ = p[2]
+    if (p[2] > maxZ) maxZ = p[2]
+  }
+  return { minX: minX - r, maxX: maxX + r, minZ: minZ - r, maxZ: maxZ + r }
+}
+
+/**
+ * Ghost-preview duplicate / move tool for duct runs.
+ *
+ * **Duplicate** (`metadata.isNew`): pure drag-to-place — NOTHING is
+ * inserted into the scene until the commit click. A translucent ghost of
+ * the run (cylinders / boxes matching its profile) rides the cursor inside
+ * a footprint bounding box — the same affordance other items get — and
+ * Figma-style alignment guides snap the box's edges to nearby geometry. The
+ * next grid click calls `createNode`; Esc discards.
+ *
+ * **Move** (existing run): the real node is hidden while the same ghost +
+ * box tracks the cursor; the commit click writes the translated `path` and
+ * reveals it, Esc reveals it unchanged.
+ *
+ * Wired via `def.affordanceTools.move`.
+ */
+export const MoveDuctSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
+  const duct = node as DuctSegmentNode
+  const originalPathRef = useRef<Vec3[]>(duct.path.map((p) => [...p] as Vec3))
+
+  const isNew =
+    typeof node.metadata === 'object' &&
+    node.metadata !== null &&
+    !Array.isArray(node.metadata) &&
+    (node.metadata as Record<string, unknown>).isNew === true
+
+  const [previewPath, setPreviewPath] = useState<Vec3[]>(originalPathRef.current)
+  const previewPathRef = useRef<Vec3[]>(originalPathRef.current)
+  const hasMovedRef = useRef(false)
+  const activatedAtRef = useRef<number>(Date.now())
+  const prevSnapRef = useRef<[number, number] | null>(null)
+
+  useEffect(() => {
+    const nodeId = node.id as AnyNodeId
+    const originalPath = originalPathRef.current
+    const [centerX, centerZ] = pathCenterXZ(originalPath)
+    const r = runRadiusM(duct)
+    const baseAabb = pathAabb(originalPath, r)
+
+    useScene.temporal.getState().pause()
+    let committed = false
+
+    const candidates: AlignmentAnchor[] = collectGhostAlignmentCandidates(
+      useScene.getState().nodes,
+      nodeId,
+      useViewer.getState().selection.levelId ?? node.parentId,
+    )
+
+    // Moving an existing run: hide its 3D MESH imperatively (NOT the store
+    // `visible` flag — the 2D floor plan skips `visible:false` nodes, so a
+    // store hide makes the run 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)
+
+    const setPreview = (path: Vec3[]) => {
+      previewPathRef.current = path
+      setPreviewPath(path)
+    }
+
+    const onMove = (event: GridEvent) => {
+      const bypass = event.nativeEvent?.shiftKey === true
+      const snap = bypass ? (v: number) => v : snapToGridStep
+      let dx = snap(event.localPosition[0] - centerX)
+      let dz = snap(event.localPosition[2] - centerZ)
+
+      // Figma-style alignment: snap the run's footprint box edges onto
+      // nearby geometry and publish the guides (Alt / Shift bypass).
+      if (!bypass) {
+        const proposed: Aabb2D = {
+          minX: baseAabb.minX + dx,
+          maxX: baseAabb.maxX + dx,
+          minZ: baseAabb.minZ + dz,
+          maxZ: baseAabb.maxZ + dz,
+        }
+        const { dx: sdx, dz: sdz, guides } = resolveGhostAlignment(nodeId, proposed, candidates)
+        dx += sdx
+        dz += sdz
+        useAlignmentGuides.getState().set(guides)
+      } else {
+        useAlignmentGuides.getState().clear()
+      }
+
+      const cur: [number, number] = [centerX + dx, centerZ + dz]
+      if (
+        !bypass &&
+        (!prevSnapRef.current ||
+          prevSnapRef.current[0] !== cur[0] ||
+          prevSnapRef.current[1] !== cur[1])
+      ) {
+        triggerSFX('sfx:grid-snap')
+      }
+      prevSnapRef.current = cur
+      hasMovedRef.current = true
+      setPreview(originalPath.map(([x, y, z]) => [x + dx, y, z + dz] as Vec3))
+    }
+
+    const commit = (event: GridEvent) => {
+      if (committed) return
+      if (Date.now() - activatedAtRef.current < 150) {
+        event.nativeEvent?.stopPropagation?.()
+        return
+      }
+      if (!hasMovedRef.current) {
+        event.nativeEvent?.stopPropagation?.()
+        return
+      }
+      committed = true
+      const finalPath = previewPathRef.current
+
+      useScene.temporal.getState().resume()
+      let selectId = nodeId
+      if (isNew && !useScene.getState().nodes[nodeId]) {
+        const created = DuctSegmentNode.parse({
+          ...(node as Record<string, unknown>),
+          path: finalPath,
+          metadata: stripPlacementMetadataFlags(node.metadata),
+          visible: true,
+        })
+        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>)
+        useScene.getState().markDirty(nodeId)
+      }
+      useScene.temporal.getState().pause()
+      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 = () => {
+      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)
+      useAlignmentGuides.getState().clear()
+      if (existedAtStart) setMeshHidden(false)
+      useScene.temporal.getState().resume()
+    }
+  }, [duct, isNew, node])
+
+  const segments: Array<{ a: Vec3; b: Vec3 }> = []
+  for (let i = 0; i < previewPath.length - 1; i++) {
+    segments.push({ a: previewPath[i]!, b: previewPath[i + 1]! })
+  }
+
+  // Footprint box spanning the whole run (axis-aligned), drawn around the
+  // ghost the same way items get one. Recomputed from the live preview path.
+  const r = runRadiusM(duct)
+  const box = pathAabb(previewPath, r)
+  const boxY = previewPath[0]?.[1] ?? 0
+
+  return (
+    <group>
+      {segments.map((seg, i) => (
+        <GhostSegment a={seg.a} b={seg.b} duct={duct} key={`ghost-${i}`} />
+      ))}
+      <DragBoundingBox
+        centerY={0}
+        nodeId={node.id}
+        position={[(box.minX + box.maxX) / 2, boxY, (box.minZ + box.maxZ) / 2]}
+        size={[box.maxX - box.minX, runHeightM(duct), box.maxZ - box.minZ]}
+      />
+    </group>
+  )
+}
+
+/** Translucent stand-in for one duct section — mirrors the draw tool's
+ *  `PreviewSegment` so the ghost matches what actually lands. */
+function GhostSegment({ a, b, duct }: { a: Vec3; b: Vec3; duct: DuctSegmentNode }) {
+  const start = new Vector3(...a)
+  const end = new Vector3(...b)
+  const dir = new Vector3().subVectors(end, start)
+  const length = dir.length()
+  if (length < 1e-4) return null
+  dir.normalize()
+  const mid = new Vector3().addVectors(start, end).multiplyScalar(0.5)
+
+  if (duct.shape !== 'round') {
+    const w = duct.width * IN_TO_M
+    const h = duct.height * IN_TO_M
+    return (
+      <mesh
+        layers={EDITOR_LAYER}
+        position={mid.toArray()}
+        ref={(m) => {
+          if (!m) return
+          const { width: x, height: z } = rectSectionAxes(dir, duct.roll)
+          m.quaternion.setFromRotationMatrix(new Matrix4().makeBasis(x, dir, z))
+        }}
+      >
+        <boxGeometry args={[w, length, h]} />
+        <meshBasicMaterial
+          color={GHOST_COLOR}
+          depthTest={false}
+          opacity={GHOST_OPACITY}
+          transparent
+        />
+      </mesh>
+    )
+  }
+
+  const radius = (duct.diameter * IN_TO_M) / 2
+  return (
+    <mesh
+      layers={EDITOR_LAYER}
+      position={mid.toArray()}
+      ref={(m) => {
+        if (!m) return
+        m.quaternion.setFromUnitVectors(new Vector3(0, 1, 0), dir)
+      }}
+    >
+      <cylinderGeometry args={[radius, radius, length, 24, 1, false]} />
+      <meshBasicMaterial
+        color={GHOST_COLOR}
+        depthTest={false}
+        opacity={GHOST_OPACITY}
+        transparent
+      />
+    </mesh>
+  )
+}
+
+export default MoveDuctSegmentTool

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

@@ -0,0 +1,173 @@
+import { type DuctFittingNode, type ParametricDescriptor, useScene } from '@pascal-app/core'
+import { Vector3 } from 'three'
+import { getDuctFittingPorts } from '../duct-fitting/ports'
+import { rollToContinueAcrossElbow } from './geometry'
+import type { DuctSegmentNode } from './schema'
+
+/** A run endpoint sitting this close to a collar counts as mated. */
+const MATE_TOL_M = 0.03
+
+function dist2(a: readonly [number, number, number], b: readonly [number, number, number]): number {
+  const dx = a[0] - b[0]
+  const dy = a[1] - b[1]
+  const dz = a[2] - b[2]
+  return dx * dx + dy * dy + dz * dz
+}
+
+/**
+ * Cross-section roll that keeps this run continuous through a fitting
+ * mated at either endpoint — the same continuity the draw tool computes
+ * for freshly drawn risers (`rollToContinueAcrossElbow`), recovered here
+ * for runs whose shape is flipped to rect AFTER they were drawn. Without
+ * it a riser falls back to the world-axis orientation and its profile
+ * lands 90° off the elbow it rises from. Returns null when no fitting is
+ * mated (roll 0 — the natural horizontal orientation — is correct).
+ */
+function rollFromMatedFitting(duct: DuctSegmentNode): number | null {
+  if (duct.path.length < 2) return null
+  const first = duct.path[0]!
+  const last = duct.path[duct.path.length - 1]!
+  const ends = [
+    { point: first, away: duct.path[1]! },
+    { point: last, away: duct.path[duct.path.length - 2]! },
+  ]
+  const tol2 = MATE_TOL_M * MATE_TOL_M
+  for (const node of Object.values(useScene.getState().nodes)) {
+    if (node.type !== 'duct-fitting') continue
+    const fitting = node as DuctFittingNode
+    if (fitting.fittingType === 'reducer') continue
+    const ports = getDuctFittingPorts(fitting)
+    for (const end of ends) {
+      const mated = ports.find((p) => dist2(end.point, p.position) <= tol2)
+      if (!mated) continue
+      // The leg on the far side of the junction is the source the
+      // profile must stay continuous with: an elbow's other run leg, or
+      // the tee's run when this duct is the branch.
+      const source = ports.find((p) => p.id !== mated.id && p.id !== 'branch')
+      if (!source) continue
+      const srcDuct = Object.values(useScene.getState().nodes).find(
+        (n) =>
+          n.type === 'duct-segment' &&
+          n.id !== duct.id &&
+          ((n as DuctSegmentNode).path.length >= 2
+            ? dist2((n as DuctSegmentNode).path[0]!, source.position) <= tol2 ||
+              dist2(
+                (n as DuctSegmentNode).path[(n as DuctSegmentNode).path.length - 1]!,
+                source.position,
+              ) <= tol2
+            : false),
+      ) as DuctSegmentNode | undefined
+      const newDir = new Vector3(
+        end.away[0] - end.point[0],
+        end.away[1] - end.point[1],
+        end.away[2] - end.point[2],
+      )
+      if (newDir.lengthSq() < 1e-10) continue
+      newDir.normalize()
+      // Only steep runs are ambiguous (world-axis fallback); a
+      // horizontal run's roll-0 orientation is already canonical, and
+      // re-deriving it from a possibly-stale riser roll would corrupt it.
+      if (Math.abs(newDir.y) < Math.SQRT1_2) continue
+      const srcRoll = srcDuct && srcDuct.shape !== 'round' ? srcDuct.roll : 0
+      const srcDir = new Vector3(...source.direction)
+      return rollToContinueAcrossElbow(srcDir, srcRoll, srcDir, newDir)
+    }
+  }
+  return null
+}
+
+export const ductSegmentParametrics: ParametricDescriptor<DuctSegmentNode> = {
+  // Flipping a drawn run to rect / oval recovers the cross-section roll
+  // the draw tool would have computed — risers re-orient to stay
+  // continuous through the elbow they turn off instead of snapping to
+  // the world-axis fallback. Spiral is a round-only construction, so a
+  // non-round run can never hold it: leaving round (or picking spiral on
+  // a rect / oval run) falls back to plain sheet metal.
+  derive: (next, patch) => {
+    const out: Partial<DuctSegmentNode> = {}
+    if (next.ductMaterial === 'spiral' && next.shape !== 'round') {
+      out.ductMaterial = 'sheet-metal'
+    }
+    if ('shape' in patch && next.shape !== 'round') {
+      const roll = rollFromMatedFitting(next)
+      if (roll !== null) out.roll = roll
+    }
+    return out
+  },
+  groups: [
+    {
+      label: 'Air',
+      fields: [
+        {
+          key: 'system',
+          kind: 'enum',
+          options: ['supply', 'return'],
+          display: 'segmented',
+        },
+        {
+          key: 'shape',
+          kind: 'enum',
+          options: ['round', 'rect', 'oval'],
+          display: 'segmented',
+        },
+        {
+          key: 'diameter',
+          kind: 'number',
+          unit: 'in',
+          min: 4,
+          max: 24,
+          step: 1,
+          visibleIf: (n) => n.shape === 'round',
+        },
+        {
+          key: 'width',
+          kind: 'number',
+          unit: 'in',
+          min: 4,
+          max: 60,
+          step: 1,
+          visibleIf: (n) => n.shape !== 'round',
+        },
+        {
+          key: 'height',
+          kind: 'number',
+          unit: 'in',
+          min: 3,
+          max: 40,
+          step: 1,
+          visibleIf: (n) => n.shape !== 'round',
+        },
+      ],
+    },
+    {
+      label: 'Construction',
+      fields: [
+        {
+          key: 'ductMaterial',
+          kind: 'enum',
+          options: ['sheet-metal', 'spiral', 'flex', 'duct-board'],
+        },
+        {
+          key: 'seamDetail',
+          kind: 'boolean',
+          // Only meaningful where a body detail exists: round spiral
+          // (lock seam) and round flex (wire corrugation).
+          visibleIf: (n) =>
+            n.shape === 'round' && (n.ductMaterial === 'spiral' || n.ductMaterial === 'flex'),
+        },
+        {
+          key: 'insulated',
+          kind: 'boolean',
+        },
+        {
+          key: 'insulationR',
+          kind: 'number',
+          min: 0,
+          max: 8,
+          step: 0.5,
+          visibleIf: (n) => n.insulated,
+        },
+      ],
+    },
+  ],
+}

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

@@ -0,0 +1 @@
+export { DuctSegmentNode } from '@pascal-app/core'

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

@@ -0,0 +1,371 @@
+'use client'
+
+import {
+  type AnyNode,
+  type AnyNodeId,
+  analyzePortConnectivity,
+  type DuctSegmentNode,
+  type PortConnectivity,
+  pauseSceneHistory,
+  resolveConnectivityUpdates,
+  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, DUCT_PORT_SYSTEMS, findNearestPortXZ } from '../shared/ports'
+
+/** Handle pip radius (meters). */
+const HANDLE_RADIUS = 0.09
+/** Port-snap radius for dragged run endpoints (meters, XZ). */
+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 duct runs: one draggable handle
+ * per path point.
+ *
+ * Handles are PORTALED into the duct's registered scene group so they
+ * share its exact frame — path coords are node-local, and the level /
+ * building transform above the group applies to the handles for free.
+ * Drag raycasts run in world space and convert hits back into the
+ * group's local frame before writing the path.
+ *
+ * Drag model: by default the point is CONSTRAINED to the axis the
+ * segment was drawn along — a horizontal duct's endpoint slides along
+ * its own length, a riser's endpoint slides vertically. Holding **Alt**
+ * releases the constraint into free horizontal-plane movement (at the
+ * point's height); in free mode dragged run endpoints (first / last
+ * point) also snap onto nearby typed ports so a loose run can be mated
+ * onto a fitting after the fact. Holding **Shift** bypasses grid
+ * snapping in either mode for a perfectly smooth precision drag.
+ *
+ * History does the single-undo dance: paused during the drag (the live
+ * `updateNode` ticks are untracked), then on release the path is
+ * reverted, history resumed, and the final path applied as one tracked
+ * change.
+ */
+const DuctSegmentSelectionAffordance = () => {
+  const selectedIds = useViewer((s) => s.selection.selectedIds)
+  const duct = useScene((s) => {
+    if (selectedIds.length !== 1) return null
+    const node = s.nodes[selectedIds[0] as AnyNodeId]
+    return node?.type === 'duct-segment' ? (node as DuctSegmentNode) : null
+  })
+
+  // Portal target: the duct's registered group. Resolved with a rAF
+  // retry because registration happens on the renderer's mount, which
+  // can land a frame after selection.
+  const ductId = duct?.id ?? null
+  const [target, setTarget] = useState<Object3D | null>(null)
+  useEffect(() => {
+    if (!ductId) {
+      setTarget(null)
+      return
+    }
+    let frameId = 0
+    const resolve = () => {
+      const next = sceneRegistry.nodes.get(ductId as AnyNodeId) ?? null
+      setTarget((cur) => (cur === next ? cur : next))
+      if (!next) frameId = window.requestAnimationFrame(resolve)
+    }
+    resolve()
+    return () => window.cancelAnimationFrame(frameId)
+  }, [ductId])
+
+  if (!duct || !target) return null
+  return createPortal(<DuctPointHandles duct={duct} target={target} />, target, undefined)
+}
+
+const DuctPointHandles = ({ duct, target }: { duct: DuctSegmentNode; 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)
+  // Set while a drag is live; null otherwise. Holds everything the window
+  // pointer handlers need so they never read stale React state.
+  const dragRef = useRef<{
+    index: number
+    initialPath: Point[]
+    current: Point
+    cleanup: () => void
+    // Connectivity snapshot taken at pointer-down: which fittings / ducts are
+    // mated to this run's endpoints, so they follow as the endpoint moves.
+    connectivity: PortConnectivity | null
+  } | 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
+  }
+
+  /**
+   * Signed distance along `axisWorld` (unit, through `anchorWorld`) of the
+   * point on that line closest to the cursor ray. Null when the ray runs
+   * (near-)parallel to the axis and the projection is unstable.
+   */
+  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
+  }
+
+  /** World-space position of a local path point. */
+  const toWorld = (p: Point): Vector3 => target.localToWorld(new Vector3(p[0], p[1], p[2]))
+  /** Convert a world-space hit back into the duct group's local frame. */
+  const toLocal = (world: Vector3): Point => {
+    const local = target.worldToLocal(world.clone())
+    return [local.x, local.y, local.z]
+  }
+
+  // Follow-updates for fittings / ducts mated to this run's endpoints, given
+  // the run's live path. Endpoints whose position didn't change resolve to a
+  // zero delta, so only the dragged endpoint's partner actually moves.
+  const connectivityUpdatesForPath = (
+    connectivity: PortConnectivity | null,
+    path: Point[],
+  ): { id: AnyNodeId; data: Partial<AnyNode> }[] => {
+    if (!connectivity) return []
+    const preview = { ...(duct as Record<string, unknown>), path } as AnyNode
+    return resolveConnectivityUpdates(connectivity, preview).filter(
+      (u) => useScene.getState().nodes[u.id],
+    )
+  }
+
+  const onHandleDown = (index: number) => (e: ThreeEvent<PointerEvent>) => {
+    e.stopPropagation()
+    const initialPath = duct.path.map((p) => [...p] as Point)
+    const startPoint = initialPath[index]!
+    const connectivity = analyzePortConnectivity(duct as AnyNode, useScene.getState().nodes)
+    pauseSceneHistory(useScene)
+    useViewer.getState().setInputDragging(true)
+    document.body.style.cursor = 'grabbing'
+    setDraggingIndex(index)
+
+    const isEndpoint = index === 0 || index === initialPath.length - 1
+
+    // Axis the segment was drawn along, at this point: from the
+    // neighbouring path point toward the dragged one. The default drag
+    // is constrained to this line.
+    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()
+    // World-space anchor + axis, derived once — the constraint line is
+    // fixed for the whole drag regardless of where the point currently is.
+    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
+      // Shift = precision: bypass grid snapping for a perfectly smooth
+      // drag (snap() is a no-op at step 0).
+      const step = event.shiftKey ? 0 : useEditor.getState().gridSnapStep
+      let next: Point | null = null
+      if (event.altKey) {
+        // Alt = freedom: slide on the horizontal plane at the point's
+        // height. Endpoints can port-snap here to mate onto a fitting.
+        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: duct.id, systems: DUCT_PORT_SYSTEMS }),
+              PORT_SNAP_RADIUS_M,
+            )
+            if (port) next = [port.position[0], port.position[1], port.position[2]]
+          }
+        }
+      } else {
+        // Default: constrained to the axis the segment was drawn along —
+        // slide the point closer / further along its own line.
+        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 = duct.path.map((p, i) => (i === drag.index ? next! : p)) as Point[]
+      // Drag the run + any fittings mated to the moved endpoint as one batch.
+      useScene
+        .getState()
+        .updateNodes([
+          { id: duct.id as AnyNodeId, data: { path } },
+          ...connectivityUpdatesForPath(drag.connectivity, path),
+        ])
+    }
+
+    const onUp = () => {
+      const drag = dragRef.current
+      if (!drag) return
+      drag.cleanup()
+      dragRef.current = null
+      setDraggingIndex(null)
+      // Single-undo dance: revert (still paused), resume, re-apply the
+      // final path — plus any connected fitting moves — as one tracked batch.
+      const finalPath = drag.initialPath.map((p, i) =>
+        i === drag.index ? drag.current : p,
+      ) as Point[]
+      const finalUpdates = connectivityUpdatesForPath(drag.connectivity, finalPath)
+      // Revert the run AND the followers to their pre-drag state while paused
+      // so history captures a clean before→after delta.
+      const revertUpdates = (drag.connectivity?.connections ?? []).flatMap((conn) =>
+        conn.kind === 'rigid-node'
+          ? [{ id: conn.nodeId, data: { position: conn.startPosition } as Partial<AnyNode> }]
+          : [{ id: conn.nodeId, data: { path: conn.startPath } as Partial<AnyNode> }],
+      )
+      useScene
+        .getState()
+        .updateNodes([
+          { id: duct.id as AnyNodeId, data: { path: drag.initialPath } },
+          ...revertUpdates.filter((u) => useScene.getState().nodes[u.id]),
+        ])
+      resumeSceneHistory(useScene)
+      const moved = finalPath[drag.index]!.some(
+        (v, axis) => v !== drag.initialPath[drag.index]![axis],
+      )
+      if (moved) {
+        useScene
+          .getState()
+          .updateNodes([{ id: duct.id as AnyNodeId, data: { path: finalPath } }, ...finalUpdates])
+      }
+    }
+
+    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, connectivity }
+    window.addEventListener('pointermove', onMove)
+    window.addEventListener('pointerup', onUp)
+    window.addEventListener('pointercancel', onUp)
+  }
+
+  return (
+    <group>
+      {duct.path.map((p, i) => {
+        const active = draggingIndex === i
+        const hovered = hoverIndex === i
+        return (
+          <mesh
+            key={`duct-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 &&
+        duct.path[draggingIndex] &&
+        (() => {
+          // Same pill as the draw tool: signed per-axis deltas from the
+          // drag-start position, dominant axis emphasised.
+          const point = duct.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 DuctSegmentSelectionAffordance

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

@@ -0,0 +1,989 @@
+'use client'
+
+import {
+  type AnyNode,
+  DuctSegmentNode,
+  emitter,
+  type GridEvent,
+  getLevelHeight,
+  useScene,
+} from '@pascal-app/core'
+import {
+  CursorSphere,
+  DimensionPill,
+  EDITOR_LAYER,
+  markToolCancelConsumed,
+  triggerSFX,
+  useEditor,
+} 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 { getDuctFittingPorts } from '../duct-fitting/ports'
+import {
+  planCrossAtRunBody,
+  planElbowAtPort,
+  planElbowRealign,
+  planTeeAtRunBody,
+} from '../shared/auto-fitting'
+import { alignDrawPoint, clearDrawAlignment } from '../shared/draw-alignment'
+import { LevelOffsetGroup } from '../shared/level-offset-group'
+import {
+  collectScenePorts,
+  DUCT_PORT_SYSTEMS,
+  findNearestPortXZ,
+  findNearestRunBodyXZ,
+  findRunBodyCrossingXZ,
+  type RunBodyHit,
+  type ScenePort,
+} from '../shared/ports'
+import { ductSegmentDefinition } from './definition'
+import { rectSectionAxes, rollToContinueAcrossElbow } from './geometry'
+
+/**
+ * One-segment-at-a-time placement tool for round 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).
+ *   - **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
+ *     outlet collar — corners get real fittings instead of butt joints.
+ *   - **Tee tap**: starting OR ending on the SIDE of an existing run
+ *     (centerline snap) splits the trunk, mints a tee at the tap point,
+ *     and the branch leaves square from its collar.
+ *   - **Cross tap**: drawing a run straight THROUGH the side of an
+ *     existing run (interior crossing) splits the trunk, mints a 4-way
+ *     cross at the crossing, and the drawn run continues out the far
+ *     branch — both fittings inherit the trunk's / branch's profile.
+ *   - 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 the lock.
+ *   - Hold **Alt** → vertical mode. Cursor XZ locks to the start;
+ *     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.
+ *   - Esc clears an anchored start point.
+ */
+const PREVIEW_OPACITY = 0.55
+/**
+ * Nominal US round-duct sizes (inches): 4"–10" in 1" steps, 12"+ in 2"
+ * steps — matches what flex and rigid round actually ship in.
+ */
+const DUCT_DIAMETERS_IN = [4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20] as const
+/** Snap radius (meters) for joining onto an existing duct's start/end. */
+const ENDPOINT_SNAP_RADIUS_M = 0.5
+/** Snap radius (meters) for tapping the SIDE of an existing run — a tee
+ *  is minted there. Tighter than the port radius so run ends keep
+ *  priority near their last stretch. */
+const BODY_SNAP_RADIUS_M = 0.35
+/** Angle step (radians) for the XZ angle lock — 45°. */
+const ANGLE_STEP_RAD = Math.PI / 4
+/** Mouse pixels → meters mapping for Alt-vertical drag. 100 px ≈ 1 m. */
+const ALT_PIXELS_PER_METER = 100
+/** Bounds on Alt-driven Y so a wild fling doesn't fly off. */
+const ALT_Y_MIN_M = -3
+const ALT_Y_MAX_M = 10
+
+function snap(value: number, step: number): number {
+  if (step <= 0) return value
+  return Math.round(value / step) * step
+}
+
+function dist2(a: readonly [number, number, number], b: readonly [number, number, number]): number {
+  const dx = a[0] - b[0]
+  const dy = a[1] - b[1]
+  const dz = a[2] - b[2]
+  return dx * dx + dy * dy + dz * dz
+}
+
+/**
+ * Cross-section roll for a new rect run leaving `port` along `newDir`,
+ * so its profile stays continuous with whatever it joined: a turn
+ * re-derives the roll through the (future) elbow, a straight
+ * continuation inherits the source's roll as-is. Sources: a rect run's
+ * open end, or a rect fitting's open collar (continuity then comes from
+ * the leg on the far side of the junction and the rect run mated
+ * there). Null when the port doesn't carry a rect orientation. Shared
+ * by the ghost preview and the commit so what you see is what lands.
+ */
+function continuityRollFrom(port: ScenePort | null, newDir: Vector3): number | null {
+  if (!port) return null
+  const nodes = useScene.getState().nodes
+  const owner = nodes[port.nodeId]
+  let srcDir: Vector3 | null = null
+  let srcRoll = 0
+  if (
+    (owner?.type === 'hvac-equipment' || owner?.type === 'duct-terminal') &&
+    port.shape &&
+    port.shape !== 'round'
+  ) {
+    // The collar mesh is built at the canonical `rectSectionAxes(dir, 0)`
+    // basis, so it reads as a source run pointing out along the port with
+    // roll 0 — the new leg rolls to continue that across its turn.
+    srcDir = new Vector3(...port.direction)
+    srcRoll = 0
+  } else if (owner?.type === 'duct-segment' && owner.shape !== 'round') {
+    srcDir = new Vector3(...port.direction)
+    srcRoll = owner.roll
+  } else if (
+    owner?.type === 'duct-fitting' &&
+    owner.shape !== 'round' &&
+    owner.fittingType !== 'reducer' &&
+    owner.fittingType !== 'transition'
+  ) {
+    const source = getDuctFittingPorts(owner).find(
+      (p) => p.id !== port.id && p.id !== 'branch' && p.id !== 'branch2',
+    )
+    if (source) {
+      srcDir = new Vector3(...source.direction)
+      const tol2 = 0.03 * 0.03
+      for (const n of Object.values(nodes)) {
+        if (n.type !== 'duct-segment' || n.shape === 'round' || n.path.length < 2) continue
+        const ends = [n.path[0]!, n.path[n.path.length - 1]!]
+        if (ends.some((e) => dist2(e, source.position) <= tol2)) {
+          srcRoll = n.roll
+          break
+        }
+      }
+    }
+  }
+  if (!srcDir) return null
+  const cross = new Vector3().crossVectors(srcDir, newDir)
+  if (cross.lengthSq() < 1e-8) return srcRoll
+  return rollToContinueAcrossElbow(srcDir, srcRoll, srcDir, newDir)
+}
+
+/**
+ * Nearest typed port — duct run ends, fitting collars, anything whose
+ * kind registers `def.ports` — within snap range of `point` on the XZ
+ * plane. Y is ignored for the distance check (grid events ride the floor
+ * while ports hang at duct height); the snap adopts the port's full 3D
+ * position. The full port is returned so the commit knows what it joined
+ * (auto-elbow insertion needs the port's direction and owner).
+ */
+function findNearbyPort(point: [number, number, number]): ScenePort | null {
+  return findNearestPortXZ(
+    point,
+    collectScenePorts({ systems: DUCT_PORT_SYSTEMS }),
+    ENDPOINT_SNAP_RADIUS_M,
+  )
+}
+
+function portPoint(port: ScenePort): [number, number, number] {
+  return [port.position[0], port.position[1], port.position[2]]
+}
+
+/** Cross-section the tool draws with (and commits onto the node). Oval
+ *  never comes from the Q toggle (round ↔ rect) — it enters by joining
+ *  an existing oval run / fitting collar and continuing its profile. */
+type DraftProfile = {
+  shape: 'round' | 'rect' | 'oval'
+  diameter: number
+  width: number
+  height: number
+}
+
+/**
+ * Profile to inherit when the segment start snaps onto `port` — joining
+ * means continuing that thing: a rect trunk end keeps its W×H, a round
+ * run / fitting collar keeps its diameter. Equipment and terminal
+ * collars are round at the port's advertised size.
+ */
+function inheritProfile(port: ScenePort): DraftProfile | null {
+  const owner = useScene.getState().nodes[port.nodeId]
+  if (!owner) return null
+  if (owner.type === 'duct-segment' || owner.type === 'duct-fitting') {
+    return {
+      shape: owner.shape,
+      diameter: Math.min(
+        48,
+        Math.max(2, owner.type === 'duct-segment' ? owner.diameter : port.diameter),
+      ),
+      width: owner.width,
+      height: owner.height,
+    }
+  }
+  if (owner.type === 'hvac-equipment' || owner.type === 'duct-terminal') {
+    const defaults = ductSegmentDefinition.defaults() as DraftProfile
+    // Adopt the collar's cross-section so the run leaves a rect / oval
+    // plenum as rect / oval (rolled to match in `continuityRollFrom`),
+    // falling back to round at the advertised diameter.
+    if (port.shape && port.shape !== 'round') {
+      return {
+        shape: port.shape,
+        diameter: Math.min(48, Math.max(2, port.diameter)),
+        width: port.width ?? defaults.width,
+        height: port.height ?? defaults.height,
+      }
+    }
+    return {
+      shape: 'round',
+      diameter: Math.min(48, Math.max(2, port.diameter)),
+      width: defaults.width,
+      height: defaults.height,
+    }
+  }
+  return null
+}
+
+/**
+ * Project `raw` onto the nearest of the eight 45° rays emanating from
+ * `from` in the XZ plane. Y is preserved from `from`. The projection
+ * keeps the cursor's *distance* along the chosen ray so the user feels
+ * the segment grow with their mouse motion rather than snap to a fixed
+ * length.
+ */
+function projectToAngleLock(
+  from: [number, number, number],
+  raw: [number, number, number],
+): [number, number, number] {
+  const dx = raw[0] - from[0]
+  const dz = raw[2] - from[2]
+  const len = Math.hypot(dx, dz)
+  if (len < 1e-4) return [from[0], from[1], from[2]]
+  const theta = Math.atan2(dz, dx)
+  const snapped = Math.round(theta / ANGLE_STEP_RAD) * ANGLE_STEP_RAD
+  // Distance along the chosen ray = projection of raw onto that direction.
+  const proj = dx * Math.cos(snapped) + dz * Math.sin(snapped)
+  const d = Math.max(0, proj)
+  return [from[0] + Math.cos(snapped) * d, from[1], from[2] + Math.sin(snapped) * d]
+}
+
+const DuctSegmentTool = () => {
+  const activeLevelId = useViewer((s) => s.selection.levelId)
+  const unit = useViewer((s) => s.unit)
+  const cursorRef = useRef<Group>(null)
+  // Cross-section profile for the next committed segment. Q toggles
+  // round/rect, [ / ] steps the round diameter, and snapping the start
+  // onto an existing run / fitting INHERITS that node's profile — so
+  // continuing a 14×8 trunk keeps drawing 14×8, and branching off a
+  // round collar keeps its diameter. Seeded from `toolDefaults`.
+  const [profile, setProfile] = useState<DraftProfile>(() => {
+    const defaults = ductSegmentDefinition.defaults() as DraftProfile
+    const seeded = useEditor.getState().toolDefaults['duct-segment'] as
+      | Partial<DraftProfile>
+      | undefined
+    return {
+      shape: seeded?.shape ?? defaults.shape,
+      diameter: seeded?.diameter ?? defaults.diameter,
+      width: seeded?.width ?? defaults.width,
+      height: seeded?.height ?? defaults.height,
+    }
+  })
+  const [draftPoints, setDraftPoints] = useState<Array<[number, number, number]>>([])
+  const [cursorPos, setCursorPos] = useState<[number, number, number] | null>(null)
+  // 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.
+  const [snapTarget, setSnapTarget] = useState<[number, number, number] | 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)
+  // Mirror into refs so emitter callbacks (closing over the first render's
+  // setState) read the latest values without re-subscribing.
+  const draftRef = useRef(draftPoints)
+  draftRef.current = draftPoints
+  const cursorPosRef = useRef(cursorPos)
+  cursorPosRef.current = cursorPos
+  const profileRef = useRef(profile)
+  profileRef.current = profile
+  const ceilingModeRef = useRef(ceilingMode)
+  ceilingModeRef.current = ceilingMode
+  // Port the anchored START point snapped onto (null = free placement).
+  // Read at commit so a turn off an existing run mints an elbow there.
+  const startPortRef = useRef<ScenePort | null>(null)
+  // Centerline hit the anchored START point snapped onto (null = none).
+  // Read at commit so a branch off a trunk's side mints a tee there.
+  const startBodyRef = useRef<RunBodyHit | null>(null)
+  // Anchor captured when Alt is pressed: screen Y at that moment and the
+  // base elevation (= last point's Y). Cleared on Alt release.
+  const altAnchorRef = useRef<{ clientY: number; baseY: number } | null>(null)
+  // Latest mouse clientY from grid:move; used so the Alt anchor knows where
+  // the cursor was at key-press time.
+  const lastClientYRef = useRef<number | null>(null)
+
+  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).
+    //
+    // 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.
+    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],
+      )
+      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)]
+      // 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> }),
+        ],
+      })
+      triggerSFX('sfx:item-place')
+      setDraftPoints([])
+      setSnapTarget(null)
+      startPortRef.current = null
+      startBodyRef.current = null
+      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 => {
+      if (!ceilingModeRef.current) return 0
+      const ceiling = getLevelHeight(activeLevelId, useScene.getState().nodes)
+      const p = profileRef.current
+      const verticalIn = p.shape === 'round' ? p.diameter : p.height
+      return Math.max(0, ceiling - (verticalIn * 0.0254) / 2)
+    }
+
+    const resolveSnappedPoint = (
+      event: GridEvent,
+    ): {
+      point: [number, number, number]
+      snapped: [number, number, number] | null
+      port: ScenePort | null
+      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.
+      if (!last) {
+        const baseY = resolveBaseY()
+        const raw: [number, number, number] = [
+          event.localPosition[0],
+          baseY,
+          event.localPosition[2],
+        ]
+        const step = useEditor.getState().gridSnapStep
+        const shift = event.nativeEvent?.shiftKey === true
+        if (event.nativeEvent?.altKey !== true) {
+          const target = findNearbyPort(raw)
+          if (target)
+            return {
+              point: portPoint(target),
+              snapped: portPoint(target),
+              port: target,
+              body: null,
+            }
+          // No open end nearby — try the side of a run (tee tap). Probe
+          // with a grid-snapped cursor so the tap steps along the duct
+          // like every other placement; Shift frees it to ride smoothly.
+          const probe: [number, number, number] = shift
+            ? raw
+            : [snap(raw[0], step), baseY, snap(raw[2], step)]
+          const body = findNearestRunBodyXZ(probe, BODY_SNAP_RADIUS_M)
+          if (body) return { point: body.point, snapped: body.point, port: null, body }
+        }
+        return {
+          point: [snap(raw[0], step), baseY, snap(raw[2], step)],
+          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.
+      const rawXZ: [number, number, number] = [
+        event.localPosition[0],
+        last[1],
+        event.localPosition[2],
+      ]
+      const shift = event.nativeEvent?.shiftKey === true
+      const angled = shift ? rawXZ : projectToAngleLock(last, rawXZ)
+      const step = useEditor.getState().gridSnapStep
+      // Port snap (Alt bypass) — checked against the RAW cursor, not the
+      // angle-locked projection, so a port slightly off the 45° ray can
+      // still capture the cursor. Joining beats the lock.
+      if (event.nativeEvent?.altKey !== true && !shift) {
+        const target = findNearbyPort(rawXZ)
+        if (target)
+          return { point: portPoint(target), snapped: portPoint(target), port: target, body: null }
+        // No open end nearby — landing on the side of a run taps a tee
+        // there (mirror of the first-point tee tap). Probe with a
+        // grid-snapped cursor so the tap steps along the duct instead of
+        // sliding smoothly (Shift above frees it). Checked against the
+        // cursor, not the 45° projection, so a slightly-off trunk captures.
+        const probe: [number, number, number] = [
+          snap(rawXZ[0], step),
+          rawXZ[1],
+          snap(rawXZ[2], step),
+        ]
+        const body = findNearestRunBodyXZ(probe, BODY_SNAP_RADIUS_M)
+        if (body) return { point: body.point, snapped: body.point, port: null, body }
+      }
+      return {
+        point: [snap(angled[0], step), angled[1], snap(angled[2], step)],
+        snapped: null,
+        port: null,
+        body: null,
+      }
+    }
+
+    /**
+     * Compute the Alt-mode cursor position: XZ locked to the last point,
+     * Y driven by how far the mouse has moved vertically on screen since
+     * Alt was pressed. Returns null if there's no anchor (Alt not active).
+     */
+    const resolveAltVerticalPoint = (clientY: number): [number, number, number] | null => {
+      const anchor = altAnchorRef.current
+      const last = draftRef.current.at(-1)
+      if (!anchor || !last) return null
+      const step = useEditor.getState().gridSnapStep
+      // Screen +Y points down, so subtract to map "drag up = raise Y".
+      const dy = (anchor.clientY - clientY) / ALT_PIXELS_PER_METER
+      const snappedDy = snap(dy, step)
+      const y = Math.min(ALT_Y_MAX_M, Math.max(ALT_Y_MIN_M, anchor.baseY + snappedDy))
+      return [last[0], y, last[2]]
+    }
+
+    // Resolve the cursor point (port / body / grid / angle snap) and then
+    // layer Figma-style alignment on top so a run lines up with other runs,
+    // fittings, and items as it's drawn. Snap is applied for a free point
+    // (first vertex, or Shift free-angle); an angle-locked continuation shows
+    // the guide passively without leaving its 45° ray. A port / body snap or
+    // Alt bypasses alignment entirely.
+    const resolveAlignedPoint = (event: GridEvent) => {
+      const r = resolveSnappedPoint(event)
+      const hasStart = draftRef.current.length > 0
+      const shift = event.nativeEvent?.shiftKey === true
+      const alt = event.nativeEvent?.altKey === true
+      const point = alignDrawPoint(r.point, {
+        applySnap: !hasStart || shift,
+        bypass: alt || r.snapped !== null,
+      })
+      return { ...r, point }
+    }
+
+    const onMove = (event: GridEvent) => {
+      const clientY = (event.nativeEvent as { clientY?: number } | undefined)?.clientY
+      if (typeof clientY === 'number') lastClientYRef.current = clientY
+      // Alt vertical mode wins over the XZ logic.
+      if (altAnchorRef.current && typeof clientY === 'number') {
+        const point = resolveAltVerticalPoint(clientY)
+        if (point) {
+          clearDrawAlignment()
+          setCursorPos(point)
+          setSnapTarget(null)
+          return
+        }
+      }
+      const { point, snapped } = resolveAlignedPoint(event)
+      setCursorPos(point)
+      setSnapTarget(snapped)
+    }
+
+    const onClick = (event: GridEvent) => {
+      const start = draftRef.current.at(-1)
+      // Vertical mode with a start anchored: the click commits the riser
+      // segment right there. Never falls through to the XZ logic — a
+      // no-op Alt click (height unchanged) must not place anything.
+      if (altAnchorRef.current && start) {
+        const clientY =
+          (event.nativeEvent as { clientY?: number } | undefined)?.clientY ?? lastClientYRef.current
+        if (typeof clientY === 'number') {
+          const point = resolveAltVerticalPoint(clientY)
+          if (point && Math.abs(point[1] - start[1]) >= 1e-4) {
+            commitSegment(start, point)
+          }
+        }
+        return
+      }
+      const { point, port, body } = resolveAlignedPoint(event)
+      if (!start) {
+        // First click: anchor the segment start, remembering the port or
+        // run body it snapped to so the commit can mint an elbow / tee.
+        // Joining a port INHERITS the source's cross-section — continuing
+        // a rect trunk keeps drawing rect at its W×H, a round collar its
+        // diameter. Body taps (tee branches) keep the tool's own profile.
+        triggerSFX('sfx:grid-snap')
+        startPortRef.current = port
+        startBodyRef.current = port ? null : body
+        if (port) {
+          const inherited = inheritProfile(port)
+          if (inherited) setProfile(inherited)
+        }
+        setDraftPoints([point])
+        return
+      }
+      // Second click: commit the segment and re-arm. A body hit on the end
+      // (no end port) taps a tee into that run's side.
+      commitSegment(start, point, port, port ? null : body)
+    }
+
+    const enterAltMode = () => {
+      const last = draftRef.current.at(-1)
+      if (!last || lastClientYRef.current === null) return
+      if (altAnchorRef.current) return
+      altAnchorRef.current = { clientY: lastClientYRef.current, baseY: last[1] }
+      setAltActive(true)
+    }
+
+    const exitAltMode = () => {
+      if (!altAnchorRef.current) return
+      altAnchorRef.current = null
+      setAltActive(false)
+    }
+
+    const stepDiameter = (step: 1 | -1) => {
+      const sizes = DUCT_DIAMETERS_IN
+      const current = profileRef.current.diameter
+      // Nearest catalogue index, then step — handles seeded off-catalogue
+      // values (e.g. a preset's 7.5") gracefully.
+      let nearest = 0
+      for (let i = 1; i < sizes.length; i++) {
+        if (Math.abs(sizes[i]! - current) < Math.abs(sizes[nearest]! - current)) nearest = i
+      }
+      const next = sizes[Math.min(sizes.length - 1, Math.max(0, nearest + step))]!
+      if (next === current) return
+      setProfile((p) => ({ ...p, diameter: next }))
+      triggerSFX('sfx:grid-snap')
+    }
+
+    const onKeyDown = (e: KeyboardEvent) => {
+      const tag = (e.target as HTMLElement | null)?.tagName
+      if (tag === 'INPUT' || tag === 'TEXTAREA') return
+      if (e.key === 'Alt') {
+        e.preventDefault()
+        enterAltMode()
+      } else if (e.key === '[') {
+        e.preventDefault()
+        stepDiameter(-1)
+      } else if (e.key === ']') {
+        e.preventDefault()
+        stepDiameter(1)
+      } else if (e.key === 'q' || e.key === 'Q') {
+        e.preventDefault()
+        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.
+        if (draftRef.current.length > 0) return
+        e.preventDefault()
+        setCeilingMode((m) => !m)
+        triggerSFX('sfx:grid-snap')
+      }
+    }
+
+    const onKeyUp = (e: KeyboardEvent) => {
+      if (e.key === 'Alt') {
+        e.preventDefault()
+        exitAltMode()
+      }
+    }
+
+    const onCancel = () => {
+      clearDrawAlignment()
+      if (draftRef.current.length === 0) return
+      markToolCancelConsumed()
+      setDraftPoints([])
+      setCursorPos(null)
+      setSnapTarget(null)
+      startPortRef.current = null
+      startBodyRef.current = null
+    }
+
+    emitter.on('grid:move', onMove)
+    emitter.on('grid:click', onClick)
+    emitter.on('tool:cancel', onCancel)
+    window.addEventListener('keydown', onKeyDown)
+    window.addEventListener('keyup', onKeyUp)
+    return () => {
+      emitter.off('grid:move', onMove)
+      emitter.off('grid:click', onClick)
+      emitter.off('tool:cancel', onCancel)
+      window.removeEventListener('keydown', onKeyDown)
+      window.removeEventListener('keyup', onKeyUp)
+      altAnchorRef.current = null
+      clearDrawAlignment()
+    }
+  }, [activeLevelId])
+
+  if (!activeLevelId) return null
+
+  const previewSegments: Array<{ a: [number, number, number]; b: [number, number, number] }> = []
+  for (let i = 0; i < draftPoints.length - 1; i++) {
+    previewSegments.push({ a: draftPoints[i]!, b: draftPoints[i + 1]! })
+  }
+  const last = draftPoints.at(-1)
+  if (last && cursorPos) {
+    previewSegments.push({ a: last, b: cursorPos })
+  }
+
+  // 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
+  // Alt-vertical mode, otherwise whichever horizontal axis dominates. A
+  // trailing Ø readout shows the diameter the next click commits ([ / ]).
+  const pillParts = cursorPos
+    ? [
+        ...(['x', 'y', 'z'] as const).map((axis, i) => ({
+          key: axis,
+          prefix: axis.toUpperCase(),
+          value: last ? cursorPos[i]! - last[i]! : cursorPos[i]!,
+          signed: !!last,
+        })),
+        ...(profile.shape === 'round'
+          ? [{ key: 'diameter', prefix: 'Ø', value: profile.diameter * 0.0254, signed: false }]
+          : [
+              { key: 'trunk-w', prefix: 'W', value: profile.width * 0.0254, signed: false },
+              { key: 'trunk-h', prefix: 'H', value: profile.height * 0.0254, signed: false },
+            ]),
+      ]
+    : null
+  const pillPrimary =
+    last && cursorPos
+      ? altActive
+        ? 'y'
+        : Math.abs(cursorPos[0] - last[0]) >= Math.abs(cursorPos[2] - last[2])
+          ? 'x'
+          : 'z'
+      : undefined
+
+  return (
+    <LevelOffsetGroup>
+      {/* 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 && (
+        <>
+          <CursorSphere position={cursorPos} ref={cursorRef} />
+          {pillParts && (
+            <group position={cursorPos}>
+              <Html
+                center
+                position={[0, 0.35, 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} />
+                  {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>
+                  )}
+                </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-${i}`} layers={EDITOR_LAYER} position={p}>
+          <sphereGeometry args={[0.07, 16, 12]} />
+          <meshBasicMaterial color="#818cf8" depthTest={false} />
+        </mesh>
+      ))}
+      {/* Preview sections */}
+      {previewSegments.map((seg, i) => (
+        <PreviewSegment
+          a={seg.a}
+          b={seg.b}
+          key={`seg-${i}`}
+          profile={profile}
+          startPort={startPortRef.current}
+        />
+      ))}
+    </LevelOffsetGroup>
+  )
+}
+
+function PreviewSegment({
+  a,
+  b,
+  profile,
+  startPort,
+}: {
+  a: [number, number, number]
+  b: [number, number, number]
+  profile: DraftProfile
+  startPort: ScenePort | null
+}) {
+  const start = new Vector3(...a)
+  const end = new Vector3(...b)
+  const dir = new Vector3().subVectors(end, start)
+  const length = dir.length()
+  if (length < 1e-4) return null
+  dir.normalize()
+  const mid = new Vector3().addVectors(start, end).multiplyScalar(0.5)
+
+  // Rect AND oval ghost as a box — close enough for a translucent guide.
+  if (profile.shape !== 'round') {
+    const w = profile.width * 0.0254
+    const h = profile.height * 0.0254
+    return (
+      <mesh
+        layers={EDITOR_LAYER}
+        position={mid.toArray()}
+        ref={(m) => {
+          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 { width: x, height: z } = rectSectionAxes(dir, roll)
+          m.quaternion.setFromRotationMatrix(new Matrix4().makeBasis(x, dir, z))
+        }}
+      >
+        <boxGeometry args={[w, length, h]} />
+        <meshBasicMaterial
+          color="#818cf8"
+          depthTest={false}
+          opacity={PREVIEW_OPACITY}
+          transparent
+        />
+      </mesh>
+    )
+  }
+
+  const radius = (profile.diameter * 0.0254) / 2
+  return (
+    <mesh
+      layers={EDITOR_LAYER}
+      position={mid.toArray()}
+      ref={(m) => {
+        if (!m) return
+        m.quaternion.setFromUnitVectors(new Vector3(0, 1, 0), dir)
+      }}
+    >
+      <cylinderGeometry args={[radius, radius, length, 24, 1, false]} />
+      <meshBasicMaterial color="#818cf8" depthTest={false} opacity={PREVIEW_OPACITY} transparent />
+    </mesh>
+  )
+}
+
+export default DuctSegmentTool

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

@@ -0,0 +1,101 @@
+import type { NodeDefinition } from '@pascal-app/core'
+import { buildDuctTerminalFloorplan } from './floorplan'
+import { buildDuctTerminalGeometry } from './geometry'
+import { ductTerminalParametrics } from './parametrics'
+import { getDuctTerminalPorts } from './ports'
+import { DuctTerminalNode } from './schema'
+
+/**
+ * Phase 3 of the HVAC node system — duct terminals: supply registers,
+ * ceiling diffusers, return grilles. The end of the air loop. One typed
+ * port at the collar (mount-aware direction) so duct runs end onto a
+ * terminal like any other port.
+ *
+ * Composition: `def.geometry` only. Yaw-only rotation — the editor's
+ * default R-rotate works on a selected terminal.
+ */
+export const ductTerminalDefinition: NodeDefinition<typeof DuctTerminalNode> = {
+  kind: 'duct-terminal',
+  schemaVersion: 1,
+  schema: DuctTerminalNode,
+  category: 'utility',
+  distributionRole: 'terminal',
+
+  defaults: () => ({
+    object: 'node',
+    parentId: null,
+    visible: true,
+    metadata: {},
+    position: [0, 0, 0],
+    rotation: 0,
+    terminalType: 'supply-register',
+    mount: 'floor',
+    width: 0.3,
+    depth: 0.15,
+    collarShape: 'round',
+    collarDiameter: 6,
+    collarWidth: 10,
+    collarHeight: 6,
+  }),
+
+  capabilities: {
+    selectable: { hitVolume: 'bbox' },
+    movable: { axes: ['x', 'z'], gridSnap: true, portSnap: { systems: ['supply', 'return'] } },
+    rotatable: { axes: ['y'], snapAngles: [Math.PI / 4] },
+    duplicable: true,
+    deletable: true,
+    // A floor register rests on top of whatever slab is under it — the
+    // generic FloorElevationSystem lifts its mesh Y by the slab's elevation
+    // so the face sits on the slab surface instead of sinking into it.
+    // Ceiling / wall mounts derive their Y elsewhere, so `applies` skips them.
+    floorPlaced: {
+      footprint: (node) => {
+        const t = node as DuctTerminalNode
+        return { dimensions: [t.width, 0, t.depth], rotation: [0, t.rotation, 0] }
+      },
+      applies: (node) => (node as DuctTerminalNode).mount === 'floor',
+    },
+  },
+
+  parametrics: ductTerminalParametrics,
+
+  geometry: buildDuctTerminalGeometry,
+  geometryKey: (n) =>
+    JSON.stringify([
+      n.terminalType,
+      n.mount,
+      n.width,
+      n.depth,
+      n.collarShape,
+      n.collarDiameter,
+      n.collarWidth,
+      n.collarHeight,
+    ]),
+
+  ports: getDuctTerminalPorts,
+
+  floorplan: buildDuctTerminalFloorplan,
+
+  tool: () => import('./tool'),
+  toolHints: [
+    { key: 'Click', label: 'Place register' },
+    { key: 'M', label: 'Mount: floor / ceiling / wall' },
+    { key: 'R / T', label: 'Rotate ±45° (floor / ceiling)' },
+    { key: 'Shift', label: 'Smooth (no grid snap)' },
+    { key: 'Esc', label: 'Exit' },
+  ],
+
+  presentation: {
+    label: 'Register',
+    description:
+      'Duct terminal — supply register, ceiling diffuser, or return grille. Duct runs end at its collar.',
+    icon: { kind: 'url', src: '/icons/registers.png' },
+    paletteSection: 'structure',
+    paletteOrder: 93,
+  },
+
+  mcp: {
+    description:
+      'A duct terminal (supply register, ceiling diffuser, or return grille) with a single collar port. Mount (floor/ceiling/wall) drives the face orientation and collar direction.',
+  },
+}

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

@@ -0,0 +1,73 @@
+import type { FloorplanGeometry, FloorplanPoint, GeometryContext } from '@pascal-app/core'
+import { terminalSystem } from './ports'
+import type { DuctTerminalNode } from './schema'
+
+const SUPPLY_COLOR = '#d4825a'
+const RETURN_COLOR = '#5a8ad4'
+const FRAME_STROKE = '#6b7280'
+const FACE_FILL = '#e5e7eb'
+
+/**
+ * Floor-plan symbol for a duct terminal: the face rectangle (rotated by
+ * yaw) with the conventional register cross-slats hinted as a single
+ * mid-line, tinted by system. Wall mounts render the same footprint —
+ * the face projects to a thin strip, which is close enough for plan
+ * reading at this stage.
+ */
+export function buildDuctTerminalFloorplan(
+  node: DuctTerminalNode,
+  ctx: GeometryContext,
+): FloorplanGeometry | null {
+  const [cx, , cz] = node.position
+  const cos = Math.cos(node.rotation)
+  const sin = Math.sin(node.rotation)
+  const hw = node.width / 2
+  const hd = (node.mount === 'wall' ? 0.06 : node.depth) / 2
+  const corner = (lx: number, lz: number): FloorplanPoint => [
+    cx + lx * cos + lz * sin,
+    cz - lx * sin + lz * cos,
+  ]
+  const points: FloorplanPoint[] = [
+    corner(-hw, -hd),
+    corner(hw, -hd),
+    corner(hw, hd),
+    corner(-hw, hd),
+  ]
+
+  const view = ctx.viewState
+  const palette = view?.palette
+  const showSelectedChrome = (view?.selected || view?.highlighted) ?? false
+  const accent = terminalSystem(node) === 'supply' ? SUPPLY_COLOR : RETURN_COLOR
+  const stroke = showSelectedChrome && palette ? palette.selectedStroke : FRAME_STROKE
+
+  const mid1 = corner(-hw * 0.8, 0)
+  const mid2 = corner(hw * 0.8, 0)
+
+  const children: FloorplanGeometry[] = [
+    {
+      kind: 'polygon',
+      points,
+      fill: FACE_FILL,
+      stroke,
+      strokeWidth: showSelectedChrome ? 0.025 : 0.015,
+      opacity: 0.92,
+    },
+    {
+      kind: 'line',
+      x1: mid1[0],
+      y1: mid1[1],
+      x2: mid2[0],
+      y2: mid2[1],
+      stroke: accent,
+      strokeWidth: 1.5,
+      vectorEffect: 'non-scaling-stroke',
+      opacity: 0.9,
+    },
+  ]
+
+  if (showSelectedChrome) {
+    children.push({ kind: 'move-handle', point: [cx, cz] })
+  }
+
+  return { kind: 'group', children }
+}

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

@@ -0,0 +1,105 @@
+import {
+  BoxGeometry,
+  type BufferGeometry,
+  CylinderGeometry,
+  Group,
+  Mesh,
+  MeshStandardMaterial,
+  Vector3,
+} from 'three'
+import { createOvalSectionGeometry, INCHES_TO_METERS } from '../duct-segment/geometry'
+import { COLLAR_LENGTH, mountQuaternion, terminalSystem } from './ports'
+import type { DuctTerminalNode } from './schema'
+
+const RADIAL_SEGMENTS = 20
+
+/** Radial clearance (meters) the collar sleeve carries over the duct's
+ *  nominal cross-section, so a run leaving at the advertised size nests
+ *  inside the sleeve instead of z-fighting its faces. ~5 mm ≈ a slip joint. */
+const COLLAR_CLEARANCE_M = 0.005
+
+const FRAME_COLOR = '#e3e5e8'
+const SLAT_SUPPLY_COLOR = '#cdd1d6'
+const SLAT_RETURN_COLOR = '#aeb4bb'
+const COLLAR_COLOR = '#c2c2c2'
+
+/**
+ * Pure geometry builder for a duct terminal, in the node's LOCAL frame —
+ * `<ParametricNodeRenderer>` applies `position` + yaw, and the builder
+ * applies the mount orientation itself.
+ *
+ * Canonical (floor) frame before the mount rotation: face plate lying
+ * in XZ at y=0 with its normal +Y, louver slats just above it, collar
+ * cylinder going -Y toward the duct side. Ceiling mounts flip it; wall
+ * mounts stand it up facing +Z.
+ */
+export function buildDuctTerminalGeometry(node: DuctTerminalNode): Group {
+  const group = new Group()
+  const oriented = new Group()
+  oriented.quaternion.copy(mountQuaternion(node.mount))
+  group.add(oriented)
+
+  const frameMaterial = new MeshStandardMaterial({
+    color: FRAME_COLOR,
+    metalness: 0.4,
+    roughness: 0.5,
+  })
+  const slatMaterial = new MeshStandardMaterial({
+    color: terminalSystem(node) === 'return' ? SLAT_RETURN_COLOR : SLAT_SUPPLY_COLOR,
+    metalness: 0.45,
+    roughness: 0.55,
+  })
+
+  const frameThickness = 0.018
+  const frame = new Mesh(new BoxGeometry(node.width, frameThickness, node.depth), frameMaterial)
+  frame.name = 'terminal-frame'
+  frame.position.set(0, frameThickness / 2, 0)
+  oriented.add(frame)
+
+  // Louver slats across the face. Return grilles read denser; diffusers
+  // get concentric-ish wide slats via the same simple pattern.
+  const slatCount = node.terminalType === 'return-grille' ? 7 : 4
+  const innerDepth = node.depth * 0.82
+  const slatDepth = (innerDepth / slatCount) * 0.55
+  for (let i = 0; i < slatCount; i++) {
+    const slat = new Mesh(new BoxGeometry(node.width * 0.86, 0.006, slatDepth), slatMaterial)
+    slat.name = `terminal-slat-${i}`
+    const z = -innerDepth / 2 + (innerDepth / slatCount) * (i + 0.5)
+    slat.position.set(0, frameThickness + 0.002, z)
+    slat.rotation.x = node.terminalType === 'diffuser' ? 0 : -0.5
+    oriented.add(slat)
+  }
+
+  // Collar runs along -Y from the face toward the duct. Round is a
+  // cylinder; rect a box; oval the flat-oval prism (its extrude basis
+  // already puts the run length on Y, matching the collar axis). The
+  // sleeve is grown one clearance on every side so a duct run leaving at
+  // the advertised size nests inside it instead of z-fighting its faces.
+  const grow = 2 * COLLAR_CLEARANCE_M
+  let collarGeom: BufferGeometry
+  if (node.collarShape === 'rect') {
+    collarGeom = new BoxGeometry(
+      node.collarWidth * INCHES_TO_METERS + grow,
+      COLLAR_LENGTH,
+      node.collarHeight * INCHES_TO_METERS + grow,
+    )
+  } else if (node.collarShape === 'oval') {
+    collarGeom = createOvalSectionGeometry(
+      node.collarWidth * INCHES_TO_METERS + grow,
+      node.collarHeight * INCHES_TO_METERS + grow,
+      COLLAR_LENGTH,
+    )
+  } else {
+    const radius = (node.collarDiameter * INCHES_TO_METERS + grow) / 2
+    collarGeom = new CylinderGeometry(radius, radius, COLLAR_LENGTH, RADIAL_SEGMENTS, 1, false)
+  }
+  const collar = new Mesh(
+    collarGeom,
+    new MeshStandardMaterial({ color: COLLAR_COLOR, metalness: 0.6, roughness: 0.4 }),
+  )
+  collar.name = 'terminal-collar'
+  collar.position.copy(new Vector3(0, -COLLAR_LENGTH / 2, 0))
+  oriented.add(collar)
+
+  return group
+}

packages/nodes/src/duct-terminal/index.ts

@@ -0,0 +1,4 @@
+export { ductTerminalDefinition } from './definition'
+export { buildDuctTerminalGeometry } from './geometry'
+export { getDuctTerminalPorts } from './ports'
+export { DuctTerminalNode } from './schema'

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

@@ -0,0 +1,72 @@
+import type { ParametricDescriptor } from '@pascal-app/core'
+import type { DuctTerminalNode } from './schema'
+
+export const ductTerminalParametrics: ParametricDescriptor<DuctTerminalNode> = {
+  groups: [
+    {
+      label: 'Terminal',
+      fields: [
+        {
+          key: 'terminalType',
+          kind: 'enum',
+          options: ['supply-register', 'diffuser', 'return-grille'],
+        },
+        {
+          key: 'mount',
+          kind: 'enum',
+          options: ['floor', 'ceiling', 'wall'],
+          display: 'segmented',
+        },
+      ],
+    },
+    {
+      label: 'Face',
+      fields: [
+        { key: 'width', kind: 'number', unit: 'm', min: 0.1, max: 1.5, step: 0.05 },
+        { key: 'depth', kind: 'number', unit: 'm', min: 0.05, max: 1.5, step: 0.05 },
+      ],
+    },
+    {
+      label: 'Collar',
+      fields: [
+        {
+          key: 'collarShape',
+          kind: 'enum',
+          options: ['round', 'rect', 'oval'],
+          display: 'segmented',
+        },
+        {
+          key: 'collarDiameter',
+          kind: 'number',
+          unit: 'in',
+          min: 4,
+          max: 20,
+          step: 1,
+          visibleIf: (n) => n.collarShape === 'round',
+        },
+        {
+          key: 'collarWidth',
+          kind: 'number',
+          unit: 'in',
+          min: 4,
+          max: 20,
+          step: 1,
+          visibleIf: (n) => n.collarShape !== 'round',
+        },
+        {
+          key: 'collarHeight',
+          kind: 'number',
+          unit: 'in',
+          min: 3,
+          max: 20,
+          step: 1,
+          visibleIf: (n) => n.collarShape !== 'round',
+        },
+      ],
+    },
+    {
+      label: 'Placement',
+      fields: [{ key: 'position', kind: 'vec3' }],
+    },
+  ],
+}

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

@@ -0,0 +1,64 @@
+import type { NodePort } from '@pascal-app/core'
+import { Euler, Quaternion, Vector3 } from 'three'
+import { equivalentDiameterIn, ovalEquivalentDiameterIn } from '../duct-segment/geometry'
+import type { DuctTerminalNode } from './schema'
+
+/** Collar stub length in meters behind the face. */
+export const COLLAR_LENGTH = 0.12
+
+/**
+ * Mount orientation: rotation applied to the canonical floor frame
+ * (face normal +Y, collar pointing -Y). Ceiling flips it; wall stands
+ * it up so the face looks along +Z and the collar points -Z (into the
+ * wall). Yaw is applied on top by the renderer / port transform.
+ */
+export function mountQuaternion(mount: DuctTerminalNode['mount']): Quaternion {
+  if (mount === 'ceiling') return new Quaternion().setFromEuler(new Euler(Math.PI, 0, 0))
+  if (mount === 'wall') return new Quaternion().setFromEuler(new Euler(Math.PI / 2, 0, 0))
+  return new Quaternion()
+}
+
+export function terminalSystem(node: DuctTerminalNode): 'supply' | 'return' {
+  return node.terminalType === 'return-grille' ? 'return' : 'supply'
+}
+
+/**
+ * Diameter (inches) the collar advertises at its port. Rect / oval
+ * collars report the area-equivalent round diameter so round runs mate
+ * at a sensible size — the same convention duct segments use.
+ */
+export function collarPortDiameterIn(node: DuctTerminalNode): number {
+  if (node.collarShape === 'rect') return equivalentDiameterIn(node.collarWidth, node.collarHeight)
+  if (node.collarShape === 'oval') {
+    return ovalEquivalentDiameterIn(node.collarWidth, node.collarHeight)
+  }
+  return node.collarDiameter
+}
+
+/**
+ * `def.ports` — the single collar port in level-local space. Canonical
+ * frame: collar tip at (0, -COLLAR_LENGTH, 0) pointing -Y (away from the
+ * face); mount + yaw + position transform it. Direction points OUT of
+ * the terminal — i.e. toward the duct that should connect.
+ */
+export function getDuctTerminalPorts(node: DuctTerminalNode): NodePort[] {
+  const transform = new Quaternion()
+    .setFromEuler(new Euler(0, node.rotation, 0))
+    .multiply(mountQuaternion(node.mount))
+  const position = new Vector3(0, -COLLAR_LENGTH, 0)
+    .applyQuaternion(transform)
+    .add(new Vector3(node.position[0], node.position[1], node.position[2]))
+  const direction = new Vector3(0, -1, 0).applyQuaternion(transform).normalize()
+  return [
+    {
+      id: 'collar',
+      position: [position.x, position.y, position.z] as const,
+      direction: [direction.x, direction.y, direction.z] as const,
+      diameter: collarPortDiameterIn(node),
+      system: terminalSystem(node),
+      shape: node.collarShape,
+      width: node.collarWidth,
+      height: node.collarHeight,
+    },
+  ]
+}

packages/nodes/src/duct-terminal/schema.ts

@@ -0,0 +1 @@
+export { DuctTerminalNode } from '@pascal-app/core'

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

@@ -0,0 +1,443 @@
+'use client'
+
+import {
+  type AnyNodeId,
+  DuctTerminalNode,
+  emitter,
+  pointInPolygon,
+  resolveLevelId,
+  sceneRegistry,
+  useScene,
+  type WallEvent,
+} from '@pascal-app/core'
+import {
+  CursorSphere,
+  getFloorStackPreviewPosition,
+  triggerSFX,
+  useEditor,
+} from '@pascal-app/editor'
+import { useViewer } from '@pascal-app/viewer'
+import { Html } from '@react-three/drei'
+import { useThree } from '@react-three/fiber'
+import { useEffect, useMemo, useRef, useState } from 'react'
+import { Euler, Matrix3, Matrix4, Plane, Quaternion, Raycaster, Vector2, Vector3 } from 'three'
+import { alignDrawPoint, clearDrawAlignment } from '../shared/draw-alignment'
+import { LevelOffsetGroup } from '../shared/level-offset-group'
+import { collectScenePorts, DUCT_PORT_SYSTEMS, findNearestPortXZ } from '../shared/ports'
+import { ductTerminalDefinition } from './definition'
+import { buildDuctTerminalGeometry } from './geometry'
+import { COLLAR_LENGTH, mountQuaternion } from './ports'
+
+const PREVIEW_OPACITY = 0.55
+/** R/T yaw step — 45°. */
+const ROTATE_STEP_RAD = Math.PI / 4
+/** Fallback height (meters) for a ceiling node that carries no `height`. */
+const DEFAULT_CEILING_HEIGHT = 2.5
+/** Snap radius (meters) for mating the collar onto a nearby duct port. */
+const PORT_SNAP_RADIUS_M = 0.5
+
+type Mount = DuctTerminalNode['mount']
+const MOUNT_CYCLE: Mount[] = ['floor', 'ceiling', 'wall']
+
+function snap(value: number, step: number): number {
+  if (step <= 0) return value
+  return Math.round(value / step) * step
+}
+
+/**
+ * Collar-port offset from the node origin for a given mount + yaw, in
+ * level-local meters — the same transform `def.ports` applies, so the
+ * placement tool can predict where the collar lands and shift the whole
+ * terminal to mate it onto a duct port.
+ */
+function collarOffset(mount: Mount, yaw: number): Vector3 {
+  const transform = new Quaternion()
+    .setFromEuler(new Euler(0, yaw, 0))
+    .multiply(mountQuaternion(mount))
+  return new Vector3(0, -COLLAR_LENGTH, 0).applyQuaternion(transform)
+}
+
+/** The active level's mesh, or null. Carries the building transform plus the
+ *  level's stacked elevation — the frame terminals are stored and parented in,
+ *  so cursor hits resolve to true level-local coords on every floor. */
+function activeLevelMesh() {
+  const levelId = useViewer.getState().selection.levelId
+  return levelId ? (sceneRegistry.nodes.get(levelId as AnyNodeId) ?? null) : null
+}
+
+type Placement = {
+  position: [number, number, number]
+  /** Yaw radians applied to the ghost / committed node. */
+  yaw: number
+  /** Mount the ghost / committed node uses — inferred from the mated port
+   *  when snapped, else the user's manual M selection. */
+  mount: Mount
+  /** True when the collar mated onto a nearby duct port (magnetic snap). */
+  snapped?: boolean
+}
+
+/** Direction is "vertical" when its Y component dominates this much. */
+const VERTICAL_DOT = 0.7
+
+/**
+ * Pick the mount that makes a collar mate onto a duct port pointing
+ * `dir` (the port's outward direction). The collar leaves the face along
+ * −Y in the canonical frame, so the mount rotation must turn −Y to face
+ * *into* the port (i.e. opposite `dir`):
+ *   - port pointing up (a riser top) → collar must point down → **floor**
+ *   - port pointing down (a ceiling drop) → collar points up → **ceiling**
+ *   - port horizontal (a wall stub) → **wall**, yawed so the collar runs
+ *     back along the port. `lockYaw` is set only for wall (floor / ceiling
+ *     yaw is free — the user keeps spinning the face with R/T).
+ */
+function inferMountFromPort(dir: readonly [number, number, number]): {
+  mount: Mount
+  lockYaw: number | null
+} {
+  const v = new Vector3(dir[0], dir[1], dir[2])
+  if (v.lengthSq() < 1e-8) return { mount: 'floor', lockYaw: null }
+  v.normalize()
+  if (v.y > VERTICAL_DOT) return { mount: 'floor', lockYaw: null }
+  if (v.y < -VERTICAL_DOT) return { mount: 'ceiling', lockYaw: null }
+  // Wall collar dir after mount + yaw is (−sin yaw, 0, −cos yaw); set it
+  // opposite the port so the collar runs back into the wall stub.
+  return { mount: 'wall', lockYaw: Math.atan2(v.x, v.z) }
+}
+
+/**
+ * If a duct port is within snap range of `position` (XZ — ports hang at
+ * duct height, the grid hit rides the floor), mate the register onto it:
+ * the port's direction *picks the mount* (floor / ceiling / wall) and, for
+ * walls, the yaw; the whole terminal then hops so its collar lands exactly
+ * on the port. Null when nothing is in range. `fallbackYaw` keeps the
+ * user's R/T face orientation for floor / ceiling mounts.
+ */
+function resolvePortSnap(
+  position: [number, number, number],
+  fallbackYaw: number,
+): { position: [number, number, number]; mount: Mount; yaw: number } | null {
+  const port = findNearestPortXZ(
+    position,
+    collectScenePorts({ systems: DUCT_PORT_SYSTEMS }),
+    PORT_SNAP_RADIUS_M,
+  )
+  if (!port) return null
+  const { mount, lockYaw } = inferMountFromPort(port.direction)
+  const yaw = lockYaw ?? fallbackYaw
+  const offset = collarOffset(mount, yaw)
+  return {
+    position: [
+      port.position[0] - offset.x,
+      port.position[1] - offset.y,
+      port.position[2] - offset.z,
+    ],
+    mount,
+    yaw,
+  }
+}
+
+/**
+ * Click-place tool for duct terminals (registers / diffusers / grilles).
+ *
+ * **Mount drives the target surface** (cycle with **M**): a floor register
+ * snaps to the floor grid, a ceiling diffuser snaps to a horizontal plane at
+ * ceiling height (derived from the level's ceilings/walls), and a wall
+ * register snaps flush onto whichever wall the cursor is over, its face
+ * oriented along the wall's outward normal. **R / T** rotate the floor/ceiling
+ * yaw ±45°; wall yaw is fixed by the wall it mates to.
+ */
+const DuctTerminalTool = () => {
+  const { camera, gl } = useThree()
+  const activeLevelId = useViewer((s) => s.selection.levelId)
+  const [mount, setMount] = useState<Mount>('floor')
+  const [placement, setPlacement] = useState<Placement | null>(null)
+
+  const mountRef = useRef<Mount>('floor')
+  const yawRef = useRef(0)
+  const raycaster = useRef(new Raycaster())
+  const pointer = useRef(new Vector2())
+
+  // The ghost mirrors whatever mount will actually be committed: a snap can
+  // override the manual M selection (port direction picks floor / ceiling /
+  // wall), so the preview must show the inferred mount, not the toolbar one.
+  const effectiveMount = placement?.mount ?? mount
+  const previewNode = useMemo(
+    () =>
+      DuctTerminalNode.parse({
+        ...ductTerminalDefinition.defaults(),
+        name: 'Register',
+        mount: effectiveMount,
+      }),
+    [effectiveMount],
+  )
+  const ghost = useMemo(() => {
+    const group = buildDuctTerminalGeometry(previewNode)
+    group.traverse((child) => {
+      const mesh = child as { material?: { transparent: boolean; opacity: number } }
+      if (mesh.material) {
+        mesh.material.transparent = true
+        mesh.material.opacity = PREVIEW_OPACITY
+      }
+    })
+    return group
+  }, [previewNode])
+
+  useEffect(() => {
+    if (!activeLevelId) return
+    const canvas = gl.domElement
+
+    /**
+     * Intersect the cursor ray with a level-local horizontal plane at `y`.
+     * The ray is transformed into level-local space first (building transform
+     * plus the floor's stacked elevation), so the hit is already in the frame
+     * terminals are stored and parented in — accurate on every floor.
+     */
+    const hitLocalPlane = (nativeEvent: PointerEvent | MouseEvent, y: number): Vector3 | null => {
+      const rect = canvas.getBoundingClientRect()
+      pointer.current.x = ((nativeEvent.clientX - rect.left) / rect.width) * 2 - 1
+      pointer.current.y = -((nativeEvent.clientY - rect.top) / rect.height) * 2 + 1
+      raycaster.current.setFromCamera(pointer.current, camera)
+
+      const level = activeLevelMesh()
+      const ray = raycaster.current.ray.clone()
+      if (level) {
+        const inv = new Matrix4().copy(level.matrixWorld).invert()
+        ray.applyMatrix4(inv)
+      }
+      const plane = new Plane(new Vector3(0, 1, 0), -y)
+      const hit = new Vector3()
+      return ray.intersectPlane(plane, hit) ? hit : null
+    }
+
+    /**
+     * Ceiling mount only lands where the cursor ray actually hits a real
+     * ceiling. Walk the active level's ceiling nodes, raycast each against a
+     * plane at its own height, and keep the lowest one whose polygon (minus
+     * holes) contains the hit — the surface you'd see looking up. Null when
+     * the ray misses every ceiling, so a ceiling register never drops onto a
+     * fixed virtual plane; the height comes from the ceiling itself.
+     */
+    const resolveCeilingHit = (
+      nativeEvent: PointerEvent | MouseEvent,
+    ): { hit: Vector3; height: number } | null => {
+      const nodes = useScene.getState().nodes
+      let best: { hit: Vector3; height: number } | null = null
+      for (const node of Object.values(nodes)) {
+        if (!node || node.type !== 'ceiling') continue
+        if (resolveLevelId(node, nodes) !== activeLevelId) continue
+        const ceiling = node as {
+          height?: number
+          polygon: Array<[number, number]>
+          holes?: Array<Array<[number, number]>>
+        }
+        const height = ceiling.height ?? DEFAULT_CEILING_HEIGHT
+        const hit = hitLocalPlane(nativeEvent, height)
+        if (!hit) continue
+        if (!pointInPolygon(hit.x, hit.z, ceiling.polygon)) continue
+        if (ceiling.holes?.some((h) => h.length >= 3 && pointInPolygon(hit.x, hit.z, h))) continue
+        if (!best || height < best.height) best = { hit, height }
+      }
+      return best
+    }
+
+    const resolvePlanar = (nativeEvent: PointerEvent | MouseEvent): Placement | null => {
+      // Floor sits on the grid (y=0; the slab lift is applied to the committed
+      // mesh by FloorElevationSystem). Ceiling resolves the real ceiling the
+      // ray hits and takes that surface's height — no fixed fallback plane.
+      let hit: Vector3 | null
+      let y: number
+      if (mountRef.current === 'ceiling') {
+        const ceiling = resolveCeilingHit(nativeEvent)
+        if (!ceiling) return null
+        hit = ceiling.hit
+        y = ceiling.height
+      } else {
+        y = 0
+        hit = hitLocalPlane(nativeEvent, y)
+      }
+      if (!hit) return null
+      const step = nativeEvent.shiftKey ? 0 : useEditor.getState().gridSnapStep
+      // Grid-snap, then layer Figma-style alignment so a floor / ceiling
+      // register lines up with ducts, equipment, and items (Shift = free).
+      const position = alignDrawPoint([snap(hit.x, step), y, snap(hit.z, step)], {
+        applySnap: true,
+        bypass: nativeEvent.shiftKey === true,
+      })
+      // Magnetic port snap: if a duct run end / fitting collar is in range,
+      // the port's direction picks the mount (floor / ceiling / wall) and
+      // hops the whole register so its collar mates exactly onto it. Takes
+      // precedence over grid / alignment and the manual M mount; Shift
+      // bypasses.
+      if (!nativeEvent.shiftKey) {
+        const mated = resolvePortSnap(position, yawRef.current)
+        if (mated) {
+          return { position: mated.position, yaw: mated.yaw, mount: mated.mount, snapped: true }
+        }
+      }
+      return { position, yaw: yawRef.current, mount: mountRef.current }
+    }
+
+    const commit = (p: Placement) => {
+      const terminal = DuctTerminalNode.parse({
+        ...ductTerminalDefinition.defaults(),
+        name: 'Register',
+        mount: p.mount,
+        position: p.position,
+        rotation: p.yaw,
+      })
+      useScene.getState().createNode(terminal, activeLevelId)
+      useViewer.getState().setSelection({ selectedIds: [terminal.id] })
+      triggerSFX('sfx:item-place')
+    }
+
+    // ---- Floor / ceiling: own raycast against a horizontal plane ----
+    const onPointerMove = (e: PointerEvent) => {
+      if (mountRef.current === 'wall') return
+      setPlacement(resolvePlanar(e))
+    }
+
+    const onCanvasClick = (e: MouseEvent) => {
+      if (mountRef.current === 'wall') return
+      if (useViewer.getState().cameraDragging) return
+      if ((e as PointerEvent).button !== undefined && (e as PointerEvent).button !== 0) return
+      const p = resolvePlanar(e)
+      if (p) commit(p)
+    }
+
+    // ---- Wall: consume wall hover/click events, orient to the wall ----
+    const resolveWall = (event: WallEvent): Placement | null => {
+      if (!event.normal) return null
+      // Wall faces are the ±Z faces in wall-local space; skip the thin
+      // top / end caps so the terminal only mounts onto a real face.
+      if (Math.abs(event.normal[2]) <= 0.7) return null
+      const worldNormal = new Vector3(event.normal[0], event.normal[1], event.normal[2])
+        .applyNormalMatrix(new Matrix3().getNormalMatrix(event.object.matrixWorld))
+        .normalize()
+      // Face normal after the wall mount + yaw is (sin yaw, 0, cos yaw);
+      // align it with the wall's outward world normal.
+      const yaw = Math.atan2(worldNormal.x, worldNormal.z)
+
+      const world = new Vector3(event.position[0], event.position[1], event.position[2])
+      const level = activeLevelMesh()
+      const local = level ? level.worldToLocal(world.clone()) : world
+      return { position: [local.x, local.y, local.z], yaw, mount: 'wall' }
+    }
+
+    const onWallMove = (event: WallEvent) => {
+      if (mountRef.current !== 'wall') return
+      // Wall-mounted terminals snap flush to the wall — no plan alignment.
+      clearDrawAlignment()
+      const p = resolveWall(event)
+      if (p) setPlacement(p)
+    }
+
+    const onWallClick = (event: WallEvent) => {
+      if (mountRef.current !== 'wall') return
+      if (useViewer.getState().cameraDragging) return
+      const p = resolveWall(event)
+      if (p) commit(p)
+    }
+
+    const onKeyDown = (e: KeyboardEvent) => {
+      const tag = (e.target as HTMLElement | null)?.tagName
+      if (tag === 'INPUT' || tag === 'TEXTAREA') return
+      const key = e.key
+      if (key === 'm' || key === 'M') {
+        e.preventDefault()
+        e.stopPropagation()
+        const next = MOUNT_CYCLE[(MOUNT_CYCLE.indexOf(mountRef.current) + 1) % MOUNT_CYCLE.length]!
+        mountRef.current = next
+        setMount(next)
+        // Wall placement only resolves over a wall; clear the stale ghost.
+        if (next === 'wall') setPlacement(null)
+        triggerSFX('sfx:item-rotate')
+        return
+      }
+      if (key !== 'r' && key !== 'R' && key !== 't' && key !== 'T') return
+      // Wall yaw is dictated by the wall, so R/T only apply to planar mounts.
+      if (mountRef.current === 'wall') return
+      e.preventDefault()
+      e.stopPropagation()
+      const steps = key === 't' || key === 'T' || e.shiftKey ? -1 : 1
+      yawRef.current += steps * ROTATE_STEP_RAD
+      setPlacement((prev) => (prev ? { ...prev, yaw: yawRef.current } : prev))
+      triggerSFX('sfx:item-rotate')
+    }
+
+    canvas.addEventListener('pointermove', onPointerMove)
+    canvas.addEventListener('click', onCanvasClick)
+    emitter.on('wall:move', onWallMove)
+    emitter.on('wall:click', onWallClick)
+    window.addEventListener('keydown', onKeyDown, true)
+    return () => {
+      canvas.removeEventListener('pointermove', onPointerMove)
+      canvas.removeEventListener('click', onCanvasClick)
+      emitter.off('wall:move', onWallMove)
+      emitter.off('wall:click', onWallClick)
+      window.removeEventListener('keydown', onKeyDown, true)
+      clearDrawAlignment()
+    }
+  }, [activeLevelId, camera, gl])
+
+  if (!activeLevelId || !placement) return null
+
+  const mountLabel = effectiveMount.charAt(0).toUpperCase() + effectiveMount.slice(1)
+
+  // The committed mesh's slab lift is applied by FloorElevationSystem, but the
+  // ghost renders here directly — preview it on the slab top too so a floor
+  // register doesn't appear to sink in before the click.
+  const previewPosition =
+    effectiveMount === 'floor'
+      ? getFloorStackPreviewPosition({
+          node: previewNode,
+          position: placement.position,
+          rotation: placement.yaw,
+          levelId: activeLevelId,
+        })
+      : placement.position
+
+  return (
+    <LevelOffsetGroup>
+      {/* Same ground ring + vertical line + tool-icon badge the duct draw
+          tool shows in 3D (icon resolved from the active `duct-terminal`
+          structure-tools entry). In 2D the floorplan overlay draws this for
+          every tool; in 3D each tool renders its own. */}
+      <CursorSphere position={previewPosition} />
+      <group position={previewPosition} rotation={[0, placement.yaw, 0]}>
+        <primitive object={ghost} />
+      </group>
+      <Html
+        center
+        position={[previewPosition[0], previewPosition[1] + 0.45, previewPosition[2]]}
+        style={{ pointerEvents: 'none', userSelect: 'none' }}
+        zIndexRange={[100, 0]}
+      >
+        <div className="flex items-center gap-2 whitespace-nowrap rounded-full border border-border/60 bg-background/90 px-4 py-1.5 text-xs tabular-nums shadow-sm backdrop-blur">
+          {placement.snapped && (
+            <>
+              <span className="font-medium text-primary">Snapped to duct</span>
+              <span aria-hidden className="text-muted-foreground">
+                ·
+              </span>
+            </>
+          )}
+          <span className="font-medium text-foreground">Mount {mountLabel}</span>
+          <span aria-hidden className="text-muted-foreground">
+            ·
+          </span>
+          <span className="text-muted-foreground">M surface</span>
+          {effectiveMount !== 'wall' && (
+            <>
+              <span aria-hidden className="text-muted-foreground">
+                ·
+              </span>
+              <span className="text-muted-foreground">R/T rotate</span>
+            </>
+          )}
+        </div>
+      </Html>
+    </LevelOffsetGroup>
+  )
+}
+
+export default DuctTerminalTool

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

@@ -13,6 +13,7 @@ import type { EyebrowVentNode } from './schema'
  * the preview doesn't intercept the cursor ray feeding the tool.
  */
 const EyebrowVentPreview = ({ node, invalid }: { node: EyebrowVentNode; invalid?: boolean }) => {
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const geometry = useMemo(
     () => buildEyebrowVentGeometry(node),
     [node.width, node.depth, node.height, node.style, node.louverCount, node.backRatio],

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

@@ -55,6 +55,7 @@ const EyebrowVentRenderer = ({ node: storeNode }: { node: EyebrowVentNode }) =>
       : undefined,
   )
 
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const geometry = useMemo(
     () => buildEyebrowVentGeometry(node),
     [node.width, node.depth, node.height, node.style, node.louverCount, node.backRatio],

packages/nodes/src/gutter/preview.tsx

@@ -22,6 +22,7 @@ import type { GutterNode } from './schema'
  * placed gutter.
  */
 const GutterPreview = ({ node, invalid }: { node: GutterNode; invalid?: boolean }) => {
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const geometry = useMemo(
     () => buildGutterGeometry(node),
     [

packages/nodes/src/gutter/renderer.tsx

@@ -117,6 +117,7 @@ const GutterRenderer = ({ node: storeNode }: { node: GutterNode }) => {
   // the FULL host segment (the alignment needs wallHeight / overhang /
   // pitch / roofType to derive each eave Y), which is a superset of what
   // the mitre detector reads — so one list feeds both.
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const { mitres, sharedEaveY } = useMemo(() => {
     if (!effectiveSegment) return { mitres: NO_MITRES, sharedEaveY: undefined }
     const segById = new Map<string, RoofSegmentNode>()
@@ -158,6 +159,7 @@ const GutterRenderer = ({ node: storeNode }: { node: GutterNode }) => {
     mitreNodes,
   ])
 
+  // biome-ignore lint/correctness/useExhaustiveDependencies: deps deliberately list the build inputs; depending on the whole object would rebuild on unrelated field changes.
   const geometry = useMemo(
     () => buildGutterGeometry(node, mitres),
     [

packages/nodes/src/hvac-equipment/definition.ts

@@ -0,0 +1,106 @@
+import type { NodeDefinition } from '@pascal-app/core'
+import { buildHvacEquipmentFloorplan } from './floorplan'
+import { buildHvacEquipmentGeometry } from './geometry'
+import { hvacEquipmentParametrics } from './parametrics'
+import { getHvacEquipmentPorts } from './ports'
+import { HvacEquipmentNode } from './schema'
+
+/**
+ * Phase 3 of the HVAC node system — equipment cabinets (furnace /
+ * air handler / condenser). Furnaces and air handlers expose supply +
+ * return ports, giving duct runs a real origin: the duct and fitting
+ * tools snap onto these collars like any other port.
+ *
+ * Composition: `def.geometry` only. Yaw-only rotation, so the editor's
+ * default R-rotate works on a selected unit without custom actions.
+ */
+export const hvacEquipmentDefinition: NodeDefinition<typeof HvacEquipmentNode> = {
+  kind: 'hvac-equipment',
+  schemaVersion: 1,
+  schema: HvacEquipmentNode,
+  category: 'utility',
+  distributionRole: 'equipment',
+
+  defaults: () => ({
+    object: 'node',
+    parentId: null,
+    visible: true,
+    metadata: {},
+    position: [0, 0, 0],
+    rotation: 0,
+    equipmentType: 'furnace',
+    width: 0.56,
+    depth: 0.71,
+    height: 1.1,
+    supplyShape: 'round',
+    returnShape: 'round',
+    supplyDiameter: 8,
+    returnDiameter: 8,
+    supplyWidth: 12,
+    supplyHeight: 8,
+    returnWidth: 14,
+    returnHeight: 8,
+  }),
+
+  capabilities: {
+    selectable: { hitVolume: 'bbox' },
+    movable: { axes: ['x', 'z'], gridSnap: true },
+    rotatable: { axes: ['y'], snapAngles: [Math.PI / 4] },
+    duplicable: true,
+    deletable: true,
+    floorPlaced: {
+      footprint: (node) => {
+        const n = node as HvacEquipmentNode
+        return {
+          dimensions: [n.width, n.height, n.depth],
+          rotation: [0, n.rotation, 0],
+        }
+      },
+    },
+  },
+
+  parametrics: hvacEquipmentParametrics,
+
+  geometry: buildHvacEquipmentGeometry,
+  geometryKey: (n) =>
+    JSON.stringify([
+      n.equipmentType,
+      n.width,
+      n.depth,
+      n.height,
+      n.supplyShape,
+      n.returnShape,
+      n.supplyDiameter,
+      n.returnDiameter,
+      n.supplyWidth,
+      n.supplyHeight,
+      n.returnWidth,
+      n.returnHeight,
+    ]),
+
+  ports: getHvacEquipmentPorts,
+
+  floorplan: buildHvacEquipmentFloorplan,
+
+  tool: () => import('./tool'),
+  toolHints: [
+    { key: 'Click', label: 'Place unit' },
+    { key: 'R / T', label: 'Rotate ±45°' },
+    { key: 'Shift', label: 'Smooth (no grid snap)' },
+    { key: 'Esc', label: 'Exit' },
+  ],
+
+  presentation: {
+    label: 'HVAC Unit',
+    description:
+      'Furnace, air handler, or condenser — duct runs connect to its supply/return collars.',
+    icon: { kind: 'url', src: '/icons/HVAC.png' },
+    paletteSection: 'structure',
+    paletteOrder: 92,
+  },
+
+  mcp: {
+    description:
+      'HVAC equipment cabinet (furnace, air handler, or condenser). Furnaces and air handlers have supply/return duct ports; every unit also has a refrigerant service port that a lineset run connects to. Position is level-local meters; rotation is yaw radians.',
+  },
+}

packages/nodes/src/hvac-equipment/floorplan.ts

@@ -0,0 +1,83 @@
+import type { FloorplanGeometry, FloorplanPoint, GeometryContext } from '@pascal-app/core'
+import { INCHES_TO_METERS } from '../duct-segment/geometry'
+import { getHvacEquipmentPorts } from './ports'
+import type { HvacEquipmentNode } from './schema'
+
+const BODY_FILL = '#c7cbd1'
+const BODY_STROKE = '#6b7280'
+const SUPPLY_COLOR = '#d4825a'
+const RETURN_COLOR = '#5a8ad4'
+
+/**
+ * Floor-plan footprint for HVAC equipment: the cabinet rectangle
+ * (rotated by yaw) with a diagonal so it reads as an equipment symbol,
+ * plus a supply/return collar dot per duct port. Selected → themed
+ * stroke + move handle.
+ */
+export function buildHvacEquipmentFloorplan(
+  node: HvacEquipmentNode,
+  ctx: GeometryContext,
+): FloorplanGeometry | null {
+  const [cx, , cz] = node.position
+  const cos = Math.cos(node.rotation)
+  const sin = Math.sin(node.rotation)
+  const hw = node.width / 2
+  const hd = node.depth / 2
+  // Local corner → plan, applying yaw. Plan x = world x, plan y = world z;
+  // a +yaw about world Y maps local (x, z) to (x cos + z sin, -x sin + z cos).
+  const corner = (lx: number, lz: number): FloorplanPoint => [
+    cx + lx * cos + lz * sin,
+    cz - lx * sin + lz * cos,
+  ]
+  const points: FloorplanPoint[] = [
+    corner(-hw, -hd),
+    corner(hw, -hd),
+    corner(hw, hd),
+    corner(-hw, hd),
+  ]
+
+  const view = ctx.viewState
+  const palette = view?.palette
+  const showSelectedChrome = (view?.selected || view?.highlighted) ?? false
+  const stroke = showSelectedChrome && palette ? palette.selectedStroke : BODY_STROKE
+
+  const children: FloorplanGeometry[] = [
+    {
+      kind: 'polygon',
+      points,
+      fill: BODY_FILL,
+      stroke,
+      strokeWidth: showSelectedChrome ? 0.03 : 0.02,
+      opacity: 0.92,
+    },
+    // Diagonal — the conventional "mechanical equipment" plan mark.
+    {
+      kind: 'line',
+      x1: points[0]![0],
+      y1: points[0]![1],
+      x2: points[2]![0],
+      y2: points[2]![1],
+      stroke,
+      strokeWidth: 1,
+      vectorEffect: 'non-scaling-stroke',
+      opacity: 0.7,
+    },
+  ]
+
+  for (const port of getHvacEquipmentPorts(node)) {
+    children.push({
+      kind: 'circle',
+      cx: port.position[0],
+      cy: port.position[2],
+      r: (port.diameter * INCHES_TO_METERS) / 2,
+      fill: port.system === 'supply' ? SUPPLY_COLOR : RETURN_COLOR,
+      opacity: 0.85,
+    })
+  }
+
+  if (showSelectedChrome) {
+    children.push({ kind: 'move-handle', point: [cx, cz] })
+  }
+
+  return { kind: 'group', children }
+}

packages/nodes/src/hvac-equipment/geometry.ts

@@ -0,0 +1,862 @@
+import {
+  BoxGeometry,
+  type BufferGeometry,
+  CylinderGeometry,
+  ExtrudeGeometry,
+  Group,
+  Matrix4,
+  Mesh,
+  MeshStandardMaterial,
+  Path,
+  Shape,
+  TorusGeometry,
+  Vector3,
+} from 'three'
+import {
+  createOvalSectionGeometry,
+  INCHES_TO_METERS,
+  rectSectionAxes,
+} from '../duct-segment/geometry'
+import { localEquipmentPorts, localRefrigerantPorts } from './ports'
+import type { HvacEquipmentNode } from './schema'
+
+const RADIAL_SEGMENTS = 24
+const SMALL_SEGMENTS = 16
+
+// Shared cabinet white used by every equipment body (furnace, air handler,
+// condenser) so the units read as one product family.
+const EQUIPMENT_WHITE = '#eef0f2'
+const EQUIPMENT_TRIM = '#cfd3d8'
+
+const CABINET_COLOR = EQUIPMENT_WHITE
+const INTERIOR_COLOR = '#9aa1a8'
+const PANEL_COLOR = EQUIPMENT_TRIM
+const CONTROL_COLOR = '#3f4549'
+const CONDENSER_COLOR = EQUIPMENT_WHITE
+const CONDENSER_FRAME_COLOR = EQUIPMENT_TRIM
+const CONDENSER_FIN_COLOR = '#9aa1a8'
+const FAN_COLOR = '#3f4549'
+const BLOWER_COLOR = '#2f6fb0'
+const BLOWER_BLADE_COLOR = '#274f7d'
+const BURNER_COLOR = '#d9772e'
+const GAS_PIPE_COLOR = '#d2691e'
+const AIR_HANDLER_COLOR = EQUIPMENT_WHITE
+const AIR_HANDLER_TRIM = EQUIPMENT_TRIM
+const FAN_GRILLE_COLOR = '#3a3f44'
+const FAN_BLADE_COLOR = '#d7dade'
+const COIL_FIN_COLOR = '#9aa1a8'
+const COPPER_COLOR = '#b06b3f'
+const SERVICE_VALVE_COLOR = '#7a8086'
+
+const UP = new Vector3(0, 1, 0)
+
+/**
+ * Pure geometry builder for an HVAC equipment cabinet, in the node's
+ * LOCAL frame (origin at base center, +Z front, +X right) —
+ * `<ParametricNodeRenderer>` applies `position` + yaw.
+ *
+ * Furnace / air handler: the cabinet is built from individual sheet-metal
+ * walls (not a solid box) so the lower front can be left OPEN — a real
+ * cut that exposes the squirrel-cage circulating fan and, on a furnace,
+ * the orange burner manifold and gas valve. Furnaces also get the
+ * combustion train from the reference drawing: a draft hood + vent
+ * connector elbow on top and a gas pipe with drip leg down the front-left.
+ *
+ * Air handler: tall white cabinet with two stacked guarded axial fans on
+ * the front and finned coil bands down the sides (vertical fan-coil look).
+ * Condenser: squat cabinet with a fan ring and hub on top.
+ */
+export function buildHvacEquipmentGeometry(node: HvacEquipmentNode): Group {
+  const group = new Group()
+  if (node.equipmentType === 'condenser') return buildCondenser(node, group)
+  if (node.equipmentType === 'air-handler') return buildAirHandler(node, group)
+
+  const W = node.width
+  const H = node.height
+  const D = node.depth
+  const hw = W / 2
+  const hd = D / 2
+  const t = Math.min(0.02, W * 0.04, D * 0.04)
+
+  // Single-sided. Each wall is a thin slab whose interior-facing face is an
+  // outward face of its own box, so the cut still shows metal inside — and
+  // single-sided culling means coplanar butt joints can't z-fight.
+  const cabinet = new MeshStandardMaterial({
+    color: CABINET_COLOR,
+    metalness: 0.55,
+    roughness: 0.45,
+  })
+  const interior = new MeshStandardMaterial({
+    color: INTERIOR_COLOR,
+    metalness: 0.4,
+    roughness: 0.6,
+  })
+
+  const addBox = (
+    w: number,
+    h: number,
+    dd: number,
+    mat: MeshStandardMaterial,
+    x: number,
+    y: number,
+    z: number,
+    name: string,
+  ) => {
+    const mesh = new Mesh(new BoxGeometry(w, h, dd), mat)
+    mesh.name = name
+    mesh.position.set(x, y, z)
+    group.add(mesh)
+    return mesh
+  }
+
+  const ports = localEquipmentPorts(node)
+  const supplyPort = ports.find((p) => p.id === 'supply')
+  const returnPort = ports.find((p) => p.id === 'return')
+
+  // ── Cabinet shell as butt-jointed sheet-metal plates. Top + bottom span
+  // the full footprint; the four walls sit *between* them (height innerH),
+  // and back / front pieces sit *between* the side walls (width W - 2t). No
+  // two same-facing surfaces are ever coplanar, which is what was z-fighting
+  // when these were full-size overlapping boxes; single-sided materials
+  // (above) finish the job. Left wall carries the return hole, top the supply.
+  const innerH = H - 2 * t
+  const midY = H / 2
+  const frontZ = hd - t / 2
+
+  addBox(W, t, D, cabinet, 0, t / 2, 0, 'equipment-bottom')
+  addBox(t, innerH, D, interior, hw - t / 2, midY, 0, 'equipment-right')
+  addBox(W - 2 * t, innerH, t, interior, 0, midY, -hd + t / 2, 'equipment-back')
+
+  // Top plate, flat, with the supply hole at the cabinet center. Built
+  // centered in its own XY plane (x→W, y→D); rotate.x = -90° lays it flat.
+  const top = buildHolePlate(W, D, t, supplyPort, 0, 0, cabinet)
+  top.name = 'equipment-top'
+  top.rotation.x = -Math.PI / 2
+  top.position.set(0, H - t / 2, 0)
+  group.add(top)
+
+  // Left wall with the return hole. After rotate.y = -90° the plate's x→world
+  // -z and y→world height; centered at midY with the return port at world
+  // y = H*0.35, so the hole sits at plate-y (H*0.35 - midY).
+  const left = buildHolePlate(D, innerH, t, returnPort, 0, H * 0.35 - midY, interior)
+  left.name = 'equipment-left'
+  left.rotation.y = -Math.PI / 2
+  left.position.set(-hw + t / 2, midY, 0)
+  group.add(left)
+
+  // Front opening: framed sill, jambs and an upper control panel, all inset
+  // to (W - 2t) so they tuck between the side walls. The gap between sill
+  // and panel (and inside the jambs) is the visible cut.
+  const openBottom = H * 0.1
+  const openTop = H * 0.58
+  const jamb = W * 0.08
+  const frontW = W - 2 * t
+  const frontHalf = frontW / 2
+  const panelMat = new MeshStandardMaterial({
+    color: PANEL_COLOR,
+    metalness: 0.5,
+    roughness: 0.5,
+  })
+  addBox(frontW, openBottom - t, t, cabinet, 0, (t + openBottom) / 2, frontZ, 'equipment-sill')
+  addBox(frontW, H - t - openTop, t, panelMat, 0, (openTop + H - t) / 2, frontZ, 'equipment-panel')
+  addBox(
+    jamb,
+    openTop - openBottom,
+    t,
+    cabinet,
+    -frontHalf + jamb / 2,
+    (openBottom + openTop) / 2,
+    frontZ,
+    'equipment-jamb-l',
+  )
+  addBox(
+    jamb,
+    openTop - openBottom,
+    t,
+    cabinet,
+    frontHalf - jamb / 2,
+    (openBottom + openTop) / 2,
+    frontZ,
+    'equipment-jamb-r',
+  )
+
+  // ── Control area on the upper front panel (fan-limit switch + cover).
+  const ctrlMat = new MeshStandardMaterial({
+    color: CONTROL_COLOR,
+    metalness: 0.4,
+    roughness: 0.6,
+  })
+  addBox(
+    W * 0.34,
+    (H - openTop) * 0.5,
+    0.012,
+    ctrlMat,
+    W * 0.18,
+    (openTop + H) / 2,
+    frontZ + 0.008,
+    'equipment-control',
+  )
+  addBox(
+    W * 0.1,
+    (H - openTop) * 0.3,
+    0.02,
+    ctrlMat,
+    -W * 0.22,
+    (openTop + H) / 2,
+    frontZ + 0.012,
+    'equipment-switch',
+  )
+
+  // ── Squirrel-cage circulating fan, seated in the open lower cavity. The
+  // round scroll housing faces front (+Z) so it shows through the cut.
+  const rB = Math.min(W * 0.34, (openTop - openBottom) * 0.42)
+  const housingD = D * 0.42
+  const cy = openBottom + rB + 0.01
+  const zc = hd - t - housingD / 2 - 0.01
+  const blowerMat = new MeshStandardMaterial({
+    color: BLOWER_COLOR,
+    metalness: 0.3,
+    roughness: 0.6,
+  })
+  const bladeMat = new MeshStandardMaterial({
+    color: BLOWER_BLADE_COLOR,
+    metalness: 0.2,
+    roughness: 0.75,
+  })
+  const housing = new Mesh(new CylinderGeometry(rB, rB, housingD, RADIAL_SEGMENTS), blowerMat)
+  housing.name = 'blower-housing'
+  housing.rotation.x = Math.PI / 2 // axis Y → axis Z (round face toward front)
+  housing.position.set(0, cy, zc)
+  group.add(housing)
+  const intake = new Mesh(new TorusGeometry(rB * 0.7, rB * 0.12, 10, RADIAL_SEGMENTS), blowerMat)
+  intake.name = 'blower-intake'
+  intake.position.set(0, cy, hd - t - 0.005)
+  group.add(intake)
+  const hub = new Mesh(
+    new CylinderGeometry(rB * 0.18, rB * 0.18, housingD * 0.9, SMALL_SEGMENTS),
+    bladeMat,
+  )
+  hub.name = 'blower-hub'
+  hub.rotation.x = Math.PI / 2
+  hub.position.set(0, cy, zc)
+  group.add(hub)
+  // Radial cage blades around the hub axis (Z).
+  const BLADES = 14
+  for (let i = 0; i < BLADES; i++) {
+    const a = (i / BLADES) * Math.PI * 2
+    const blade = new Mesh(new BoxGeometry(0.006, rB * 0.62, housingD * 0.82), bladeMat)
+    blade.name = `blower-blade-${i}`
+    blade.position.set(Math.cos(a) * rB * 0.5, cy + Math.sin(a) * rB * 0.5, zc)
+    blade.rotation.z = a
+    group.add(blade)
+  }
+
+  buildCombustionTrain(node, group, { hw, hd, H, openTop, frontZ })
+  buildGasLine(node, group, { hw, hd, H })
+
+  buildCollars(node, group)
+  buildServiceValves(node, group)
+  return group
+}
+
+/** Orange burner manifold + gas valve above the blower (furnace only). */
+function buildCombustionTrain(
+  node: HvacEquipmentNode,
+  group: Group,
+  dims: { hw: number; hd: number; H: number; openTop: number; frontZ: number },
+): void {
+  const { hw, hd, H, openTop } = dims
+  const burnerMat = new MeshStandardMaterial({
+    color: BURNER_COLOR,
+    metalness: 0.35,
+    roughness: 0.55,
+    emissive: BURNER_COLOR,
+    emissiveIntensity: 0.12,
+  })
+  const y = openTop - 0.12
+  const z = hd - node.depth * 0.32
+
+  // Manifold pipe running across the unit (axis X), feeding the burners.
+  const manifold = new Mesh(
+    new CylinderGeometry(0.018, 0.018, node.width * 0.66, SMALL_SEGMENTS),
+    burnerMat,
+  )
+  manifold.name = 'burner-manifold'
+  manifold.rotation.z = Math.PI / 2
+  manifold.position.set(-node.width * 0.05, y, z)
+  group.add(manifold)
+
+  // 4 burner tubes shooting back into the heat exchanger (axis Z).
+  const tubes = 4
+  for (let i = 0; i < tubes; i++) {
+    const x = (-(tubes - 1) / 2 + i) * (node.width * 0.16)
+    const tube = new Mesh(
+      new CylinderGeometry(0.022, 0.022, node.depth * 0.34, SMALL_SEGMENTS),
+      burnerMat,
+    )
+    tube.name = `burner-tube-${i}`
+    tube.rotation.x = Math.PI / 2
+    tube.position.set(x, y, z - node.depth * 0.17)
+    group.add(tube)
+  }
+
+  // Gas valve block at the right end of the manifold.
+  const valve = new Mesh(new BoxGeometry(0.08, 0.07, 0.09), burnerMat)
+  valve.name = 'gas-valve'
+  valve.position.set(hw - 0.07, y, z + 0.02)
+  group.add(valve)
+}
+
+/** Gas supply pipe with a capped drip leg, down the front-left (furnace). */
+function buildGasLine(
+  node: HvacEquipmentNode,
+  group: Group,
+  dims: { hw: number; hd: number; H: number },
+): void {
+  const { hw, hd, H } = dims
+  const gasMat = new MeshStandardMaterial({
+    color: GAS_PIPE_COLOR,
+    metalness: 0.4,
+    roughness: 0.5,
+  })
+  const r = 0.014
+  const x = -hw + 0.06
+  const z = hd + 0.03
+  const teeY = H * 0.34
+
+  // Vertical main running down the front-left face.
+  const mainTop = H * 0.92
+  const mainLen = mainTop - teeY
+  const main = new Mesh(new CylinderGeometry(r, r, mainLen, SMALL_SEGMENTS), gasMat)
+  main.name = 'gas-main'
+  main.position.set(x, teeY + mainLen / 2, z)
+  group.add(main)
+
+  // Tee into the cabinet toward the gas valve (axis X, +).
+  const tee = new Mesh(new CylinderGeometry(r, r, 0.12, SMALL_SEGMENTS), gasMat)
+  tee.name = 'gas-tee'
+  tee.rotation.z = Math.PI / 2
+  tee.position.set(x + 0.06, teeY, z)
+  group.add(tee)
+
+  // Drip leg: short capped vertical pipe below the tee to catch sediment.
+  const legLen = H * 0.14
+  const leg = new Mesh(new CylinderGeometry(r, r, legLen, SMALL_SEGMENTS), gasMat)
+  leg.name = 'gas-drip-leg'
+  leg.position.set(x, teeY - legLen / 2, z)
+  group.add(leg)
+  const cap = new Mesh(new CylinderGeometry(r * 1.4, r * 1.4, 0.02, SMALL_SEGMENTS), gasMat)
+  cap.name = 'gas-drip-cap'
+  cap.position.set(x, teeY - legLen, z)
+  group.add(cap)
+}
+
+type LocalPort = ReturnType<typeof localEquipmentPorts>[number]
+
+type CollarSection = { shape: 'round' | 'rect' | 'oval'; widthM: number; heightM: number }
+
+/**
+ * Radial clearance (meters) the collar sleeve carries over the duct's
+ * nominal cross-section. A duct run leaves the port at the advertised size;
+ * the collar is built one clearance larger on every side so it reads as a
+ * sheet-metal sleeve wrapping the duct — and so their faces never coincide
+ * (no z-fighting where the run overlaps the stub). ~5 mm ≈ a real slip joint.
+ */
+const COLLAR_CLEARANCE_M = 0.005
+
+/**
+ * Collar cross-section in meters, already grown by `COLLAR_CLEARANCE_M` so
+ * the sleeve sits over the duct. Round collapses to a single diameter on
+ * both axes; rect / oval carry the explicit width × height (width is the
+ * horizontal face, height the vertical). For round the port's `diameter`
+ * is the true round size; for rect / oval it is the area-equivalent value
+ * the port advertises, so the mesh uses width / height instead.
+ */
+function collarSection(port: LocalPort): CollarSection {
+  const shape = port.shape ?? 'round'
+  const grow = 2 * COLLAR_CLEARANCE_M
+  if (shape === 'round') {
+    const d = port.diameter * INCHES_TO_METERS + grow
+    return { shape, widthM: d, heightM: d }
+  }
+  return {
+    shape,
+    widthM: (port.width ?? port.diameter) * INCHES_TO_METERS + grow,
+    heightM: (port.height ?? port.diameter) * INCHES_TO_METERS + grow,
+  }
+}
+
+/** Collar sleeve geometry with the run length on local Y and the
+ * cross-section on local X (width) × Z (height) — the basis the caller
+ * orients with `rectSectionAxes`. Round stays open-ended so you can see
+ * straight through into the hole. */
+function collarGeometry(section: CollarSection, length: number): BufferGeometry {
+  if (section.shape === 'rect') return new BoxGeometry(section.widthM, length, section.heightM)
+  if (section.shape === 'oval') {
+    return createOvalSectionGeometry(section.widthM, section.heightM, length)
+  }
+  const r = section.widthM / 2
+  return new CylinderGeometry(r, r, length, RADIAL_SEGMENTS, 1, true)
+}
+
+/**
+ * Hole `Path` in the plate's local XY (width → X, height → Y), centered at
+ * (`hx`, `hy`) and clamped to keep it inside the plate. Three.js corrects
+ * hole winding when extruding, so the path direction here is irrelevant.
+ */
+function collarHolePath(
+  section: CollarSection,
+  hx: number,
+  hy: number,
+  maxHalfW: number,
+  maxHalfH: number,
+): Path | null {
+  if (section.shape === 'rect') {
+    const hw = Math.min(section.widthM / 2, maxHalfW)
+    const hh = Math.min(section.heightM / 2, maxHalfH)
+    if (hw <= 0 || hh <= 0) return null
+    return new Path()
+      .moveTo(hx - hw, hy - hh)
+      .lineTo(hx + hw, hy - hh)
+      .lineTo(hx + hw, hy + hh)
+      .lineTo(hx - hw, hy + hh)
+      .closePath()
+  }
+  if (section.shape === 'oval') {
+    const w = Math.min(section.widthM, maxHalfW * 2)
+    const h = Math.min(section.heightM, maxHalfH * 2)
+    const r = Math.min(w, h) / 2
+    const straight = Math.max(0, w - h) / 2
+    if (r <= 0) return null
+    const path = new Path()
+    path.absarc(hx + straight, hy, r, -Math.PI / 2, Math.PI / 2, false)
+    path.absarc(hx - straight, hy, r, Math.PI / 2, (3 * Math.PI) / 2, false)
+    path.closePath()
+    return path
+  }
+  const r = Math.min(section.widthM / 2, maxHalfW, maxHalfH)
+  if (r <= 0) return null
+  const path = new Path()
+  path.absarc(hx, hy, r, 0, Math.PI * 2, true)
+  return path
+}
+
+/**
+ * Flat rectangular plate of `thickness`, centered on the origin in its own
+ * XY plane (width → X, height → Y) and centered through the thickness on Z,
+ * with the duct opening for `port` punched at (`hx`, `hy`). Callers rotate /
+ * position it into a wall; the hole takes the collar's round / rect / oval
+ * cross-section.
+ */
+function buildHolePlate(
+  width: number,
+  height: number,
+  thickness: number,
+  port: LocalPort | undefined,
+  hx: number,
+  hy: number,
+  material: MeshStandardMaterial,
+): Mesh {
+  const hw = width / 2
+  const hh = height / 2
+  const shape = new Shape()
+    .moveTo(-hw, -hh)
+    .lineTo(hw, -hh)
+    .lineTo(hw, hh)
+    .lineTo(-hw, hh)
+    .lineTo(-hw, -hh)
+
+  const hole = port ? collarHolePath(collarSection(port), hx, hy, hw * 0.95, hh * 0.95) : null
+  if (hole) shape.holes.push(hole)
+
+  const geom = new ExtrudeGeometry(shape, { depth: thickness, bevelEnabled: false })
+  geom.translate(0, 0, -thickness / 2)
+  geom.computeVertexNormals()
+  return new Mesh(geom, material)
+}
+
+/**
+ * Sheet-metal sleeves at the supply/return ports. Each collar straddles the
+ * wall hole — part inside the cabinet, part outside — so a duct run slides
+ * through the opening instead of dead-ending on a panel. The collar takes
+ * the port's round / rect / oval cross-section, oriented with the same
+ * width-horizontal / height-vertical basis as the hole it sits in.
+ */
+function buildCollars(node: HvacEquipmentNode, group: Group): void {
+  const collarMaterial = new MeshStandardMaterial({
+    color: '#c2c2c2',
+    metalness: 0.6,
+    roughness: 0.4,
+    side: 2,
+  })
+  const OUT = 0.12 // sleeve length outside the cabinet
+  const IN = 0.05 // sleeve length reaching inside past the hole
+  const length = OUT + IN
+  for (const port of localEquipmentPorts(node)) {
+    const dir = port.direction.clone().normalize()
+    const sleeve = new Mesh(collarGeometry(collarSection(port), length), collarMaterial)
+    sleeve.name = `equipment-collar-${port.id}`
+    const { width: wAxis, height: hAxis } = rectSectionAxes(dir)
+    sleeve.quaternion.setFromRotationMatrix(new Matrix4().makeBasis(wAxis, dir, hAxis))
+    sleeve.position.copy(port.position).addScaledVector(dir, (OUT - IN) / 2)
+    group.add(sleeve)
+  }
+}
+
+// Default lineset line radii (meters) — must mirror the lineset kind's
+// defaults so the two service stubs sit exactly where its suction/liquid
+// pipes run. See `lineset/geometry.ts` (suction 7/8", liquid 3/8", 3/8"
+// foam jacket) and its symmetric ±offset about the path centerline.
+const LINESET_SUCTION_R = (0.875 * INCHES_TO_METERS) / 2
+const LINESET_LIQUID_R = (0.375 * INCHES_TO_METERS) / 2
+const LINESET_JACKET_R = LINESET_SUCTION_R + 0.01
+const LINESET_PAIR_OFFSET = LINESET_JACKET_R + LINESET_LIQUID_R
+
+/**
+ * Refrigerant service valves at the lineset port — a brass-grey valve body
+ * with two copper stubs the lineset run mates onto. Built on every
+ * equipment type so a split system can be piped from condenser to coil.
+ *
+ * A lineset is a parallel pair (insulated suction + bare liquid) offset
+ * symmetrically about its path centerline. The snap point is that
+ * centerline, so a single stub would sit in the empty gap between the two
+ * pipes. Instead we emit two stubs at exactly the lineset's ±offset along
+ * the port's horizontal perpendicular: the suction pipe lands on the wide
+ * stub, the liquid pipe on the narrow one, when the run leaves the face.
+ */
+function buildServiceValves(node: HvacEquipmentNode, group: Group): void {
+  const valveMat = new MeshStandardMaterial({
+    color: SERVICE_VALVE_COLOR,
+    metalness: 0.7,
+    roughness: 0.35,
+  })
+  const copperMat = new MeshStandardMaterial({
+    color: COPPER_COLOR,
+    metalness: 0.8,
+    roughness: 0.3,
+  })
+  for (const port of localRefrigerantPorts(node)) {
+    const dir = port.direction.clone().normalize()
+    // Horizontal perpendicular to the port — matches the lineset geometry's
+    // `horizontal.cross(UP)`, so the stub offsets track its pipe offsets.
+    const perp = dir.clone().cross(UP).normalize()
+
+    // Brass-grey valve body bolted to the cabinet face, spanning the pair.
+    const bodyWidth = 2 * LINESET_PAIR_OFFSET + 2 * LINESET_JACKET_R
+    const body = new Mesh(new BoxGeometry(0.05, 0.08, bodyWidth), valveMat)
+    body.name = 'service-valve-body'
+    body.position.copy(port.position).addScaledVector(dir, 0.025)
+    body.quaternion.setFromUnitVectors(UP, dir)
+    group.add(body)
+
+    const stubLen = 0.07
+    const addStub = (sign: number, radius: number, id: string) => {
+      const stub = new Mesh(
+        new CylinderGeometry(radius, radius, stubLen, SMALL_SEGMENTS),
+        copperMat,
+      )
+      stub.name = `service-valve-stub-${id}`
+      stub.position
+        .copy(port.position)
+        .addScaledVector(perp, sign * LINESET_PAIR_OFFSET)
+        .addScaledVector(dir, 0.05 + stubLen / 2)
+      stub.quaternion.setFromUnitVectors(UP, dir)
+      group.add(stub)
+    }
+    // Suction pipe is the lineset's -offset line; liquid is +offset.
+    addStub(-1, LINESET_SUCTION_R, 'suction')
+    addStub(1, LINESET_LIQUID_R, 'liquid')
+  }
+}
+
+/**
+ * Residential split-system condenser, matching the reference photos: a
+ * greenish-grey body wrapped in vertical louvered coil fins on all four
+ * sides, a dark base and dark top frame, and a top-mounted fan with a
+ * radial wire guard (concentric rings + spokes) over a recessed throat.
+ */
+function buildCondenser(node: HvacEquipmentNode, group: Group): Group {
+  const W = node.width
+  const H = node.height
+  const D = node.depth
+  const hw = W / 2
+  const hd = D / 2
+
+  const bodyMat = new MeshStandardMaterial({
+    color: CONDENSER_COLOR,
+    metalness: 0.5,
+    roughness: 0.5,
+  })
+  const frameMat = new MeshStandardMaterial({
+    color: CONDENSER_FRAME_COLOR,
+    metalness: 0.4,
+    roughness: 0.6,
+  })
+  const finMat = new MeshStandardMaterial({
+    color: CONDENSER_FIN_COLOR,
+    metalness: 0.65,
+    roughness: 0.4,
+  })
+
+  const frameH = Math.min(0.07, H * 0.09)
+  const post = Math.min(0.04, W * 0.07)
+
+  // Inner body the fins wrap around (inset so corner posts read proud).
+  const body = new Mesh(new BoxGeometry(W - post, H - 2 * frameH, D - post), bodyMat)
+  body.name = 'equipment-body'
+  body.position.set(0, H / 2, 0)
+  group.add(body)
+
+  // Dark base + top frame rings.
+  const base = new Mesh(new BoxGeometry(W, frameH, D), frameMat)
+  base.name = 'condenser-base'
+  base.position.set(0, frameH / 2, 0)
+  group.add(base)
+  const topFrame = new Mesh(new BoxGeometry(W, frameH, D), frameMat)
+  topFrame.name = 'condenser-top-frame'
+  topFrame.position.set(0, H - frameH / 2, 0)
+  group.add(topFrame)
+
+  // Corner posts.
+  for (const sx of [-1, 1]) {
+    for (const sz of [-1, 1]) {
+      const p = new Mesh(new BoxGeometry(post, H, post), frameMat)
+      p.name = `condenser-post-${sx > 0 ? 'r' : 'l'}${sz > 0 ? 'f' : 'b'}`
+      p.position.set(sx * (hw - post / 2), H / 2, sz * (hd - post / 2))
+      group.add(p)
+    }
+  }
+
+  // Vertical louvered coil fins on all four faces. Each fin is a thin
+  // vertical slat standing slightly proud of the body; the gaps between
+  // them read as the coil louvers.
+  const finY = H / 2
+  const finH = H - 2 * frameH
+  const addFins = (count: number, span: number, fixed: number, axis: 'x' | 'z', sign: number) => {
+    for (let i = 0; i < count; i++) {
+      const t = (i + 0.5) / count
+      const c = -span / 2 + t * span
+      const fin =
+        axis === 'x'
+          ? new Mesh(new BoxGeometry(0.006, finH, 0.018), finMat)
+          : new Mesh(new BoxGeometry(0.018, finH, 0.006), finMat)
+      fin.name = `condenser-fin-${axis}${sign > 0 ? '+' : '-'}-${i}`
+      if (axis === 'x') fin.position.set(c, finY, sign * fixed)
+      else fin.position.set(sign * fixed, finY, c)
+      group.add(fin)
+    }
+  }
+  const finsAlongW = Math.max(10, Math.round(W / 0.025))
+  const finsAlongD = Math.max(10, Math.round(D / 0.025))
+  addFins(finsAlongW, W - post, hd - post / 2 + 0.004, 'x', 1) // front
+  addFins(finsAlongW, W - post, hd - post / 2 + 0.004, 'x', -1) // back
+  addFins(finsAlongD, D - post, hw - post / 2 + 0.004, 'z', 1) // right
+  addFins(finsAlongD, D - post, hw - post / 2 + 0.004, 'z', -1) // left
+
+  buildCondenserFanGuard(group, W, H, D)
+  buildServiceValves(node, group)
+  return group
+}
+
+/** Top fan: recessed throat + hub/blades under a radial wire guard. */
+function buildCondenserFanGuard(group: Group, W: number, H: number, D: number): void {
+  const fanMat = new MeshStandardMaterial({
+    color: FAN_COLOR,
+    metalness: 0.3,
+    roughness: 0.7,
+  })
+  const guardMat = new MeshStandardMaterial({
+    color: CONDENSER_FRAME_COLOR,
+    metalness: 0.4,
+    roughness: 0.6,
+  })
+  const r = Math.min(W, D) * 0.4
+  const deckY = H
+
+  // Recessed throat dropping below the top deck so the fan reads as an
+  // opening, not a disc sitting on the lid.
+  const throat = new Mesh(new CylinderGeometry(r, r, H * 0.12, RADIAL_SEGMENTS, 1, true), fanMat)
+  throat.name = 'condenser-fan-throat'
+  throat.position.set(0, deckY - H * 0.06, 0)
+  group.add(throat)
+
+  // Hub + swept blades just below the deck.
+  const bladeMat = new MeshStandardMaterial({
+    color: '#5a6066',
+    metalness: 0.3,
+    roughness: 0.6,
+  })
+  const hub = new Mesh(new CylinderGeometry(r * 0.16, r * 0.16, 0.04, SMALL_SEGMENTS), bladeMat)
+  hub.name = 'condenser-fan-hub'
+  hub.position.set(0, deckY - 0.02, 0)
+  group.add(hub)
+  const BLADES = 6
+  for (let i = 0; i < BLADES; i++) {
+    const a = (i / BLADES) * Math.PI * 2
+    const blade = new Mesh(new BoxGeometry(r * 0.7, 0.006, r * 0.28), bladeMat)
+    blade.name = `condenser-fan-blade-${i}`
+    blade.position.set(Math.cos(a) * r * 0.45, deckY - 0.02, Math.sin(a) * r * 0.45)
+    blade.rotation.y = a
+    blade.rotation.x = 0.35
+    group.add(blade)
+  }
+
+  // Radial wire guard: concentric rings + spokes, slightly domed above deck.
+  const guardY = deckY + 0.012
+  for (let k = 1; k <= 5; k++) {
+    const rr = (r * k) / 5
+    const ring = new Mesh(new TorusGeometry(rr, 0.004, 6, RADIAL_SEGMENTS), guardMat)
+    ring.name = `condenser-guard-ring-${k}`
+    ring.rotation.x = Math.PI / 2
+    ring.position.set(0, guardY, 0)
+    group.add(ring)
+  }
+  const SPOKES = 8
+  for (let i = 0; i < SPOKES; i++) {
+    const a = (i / SPOKES) * Math.PI
+    const spoke = new Mesh(new BoxGeometry(r * 2, 0.004, 0.004), guardMat)
+    spoke.name = `condenser-guard-spoke-${i}`
+    spoke.position.set(0, guardY, 0)
+    spoke.rotation.y = a
+    group.add(spoke)
+  }
+}
+
+/**
+ * Guarded axial fan on the front (+Z) face: a recessed dark throat, a
+ * spider hub with swept blades, and a concentric wire grille — the look of
+ * the units in the air-handler reference. Centered at (`x`, `y`) on the
+ * cabinet front at `frontZ`, radius `r`.
+ */
+function buildAxialFan(
+  group: Group,
+  x: number,
+  y: number,
+  frontZ: number,
+  r: number,
+  index: number,
+): void {
+  const grilleMat = new MeshStandardMaterial({
+    color: FAN_GRILLE_COLOR,
+    metalness: 0.4,
+    roughness: 0.6,
+  })
+  const bladeMat = new MeshStandardMaterial({
+    color: FAN_BLADE_COLOR,
+    metalness: 0.3,
+    roughness: 0.5,
+  })
+
+  // Recessed throat behind the blades so the fan reads as an opening.
+  const throat = new Mesh(new CylinderGeometry(r, r, 0.04, RADIAL_SEGMENTS), grilleMat)
+  throat.name = `fan-${index}-throat`
+  throat.rotation.x = Math.PI / 2
+  throat.position.set(x, y, frontZ - 0.02)
+  group.add(throat)
+
+  // Hub + swept blades, sitting just proud of the throat.
+  const hub = new Mesh(new CylinderGeometry(r * 0.18, r * 0.18, 0.03, SMALL_SEGMENTS), bladeMat)
+  hub.name = `fan-${index}-hub`
+  hub.rotation.x = Math.PI / 2
+  hub.position.set(x, y, frontZ + 0.005)
+  group.add(hub)
+
+  const BLADES = 5
+  for (let i = 0; i < BLADES; i++) {
+    const a = (i / BLADES) * Math.PI * 2
+    const blade = new Mesh(new BoxGeometry(r * 0.34, 0.006, r * 0.78), bladeMat)
+    blade.name = `fan-${index}-blade-${i}`
+    // Position blade outward from hub, then tilt for an airfoil sweep.
+    const br = r * 0.5
+    blade.position.set(x + Math.cos(a) * br, y + Math.sin(a) * br, frontZ + 0.005)
+    blade.rotation.z = a
+    blade.rotation.y = 0.5
+    group.add(blade)
+  }
+
+  // Concentric wire grille (rings) over the front of the fan.
+  const ringMat = new MeshStandardMaterial({
+    color: AIR_HANDLER_TRIM,
+    metalness: 0.5,
+    roughness: 0.4,
+  })
+  for (let k = 1; k <= 3; k++) {
+    const rr = (r * k) / 3
+    const ring = new Mesh(new TorusGeometry(rr, 0.004, 6, RADIAL_SEGMENTS), ringMat)
+    ring.name = `fan-${index}-grille-${k}`
+    ring.position.set(x, y, frontZ + 0.02)
+    group.add(ring)
+  }
+}
+
+/**
+ * Air handler / vertical fan-coil: a tall white cabinet with two stacked
+ * guarded axial fans on the front and finned coil bands down both sides —
+ * the unit in the reference photo. Keeps the supply/return collars (built
+ * by the shared `buildCollars`) so duct runs still connect.
+ */
+function buildAirHandler(node: HvacEquipmentNode, group: Group): Group {
+  const W = node.width
+  const H = node.height
+  const D = node.depth
+  const hw = W / 2
+  const hd = D / 2
+
+  const cabinetMat = new MeshStandardMaterial({
+    color: AIR_HANDLER_COLOR,
+    metalness: 0.3,
+    roughness: 0.55,
+  })
+  const trimMat = new MeshStandardMaterial({
+    color: AIR_HANDLER_TRIM,
+    metalness: 0.4,
+    roughness: 0.5,
+  })
+  const finMat = new MeshStandardMaterial({
+    color: COIL_FIN_COLOR,
+    metalness: 0.6,
+    roughness: 0.45,
+  })
+
+  // Cabinet body + top/bottom trim caps.
+  const body = new Mesh(new BoxGeometry(W, H, D), cabinetMat)
+  body.name = 'equipment-body'
+  body.position.set(0, H / 2, 0)
+  group.add(body)
+  // Trim caps straddle the cabinet's top / bottom edges (centered on
+  // y = H and y = 0) so the body's end faces fall inside the cap volume.
+  // Sitting them flush instead (top face at y = H) leaves two coplanar
+  // full-footprint faces that z-fight.
+  const capH = Math.min(0.05, H * 0.06)
+  const topCap = new Mesh(new BoxGeometry(W * 1.04, capH, D * 1.04), trimMat)
+  topCap.name = 'air-handler-top-cap'
+  topCap.position.set(0, H, 0)
+  group.add(topCap)
+  const botCap = new Mesh(new BoxGeometry(W * 1.04, capH, D * 1.04), trimMat)
+  botCap.name = 'air-handler-bottom-cap'
+  botCap.position.set(0, 0, 0)
+  group.add(botCap)
+
+  // Two stacked axial fans on the front face, sized to the cabinet width.
+  const frontZ = hd + 0.001
+  const fanR = Math.min(W * 0.4, H * 0.22)
+  const margin = capH + fanR + H * 0.04
+  buildAxialFan(group, 0, H - margin, frontZ, fanR, 0)
+  buildAxialFan(group, 0, margin, frontZ, fanR, 1)
+
+  // Finned coil bands down both sides (horizontal slats = condenser fins).
+  const fins = Math.max(6, Math.floor(H / 0.06))
+  for (let side = -1; side <= 1; side += 2) {
+    for (let i = 0; i < fins; i++) {
+      const fy = capH + ((i + 0.5) / fins) * (H - 2 * capH)
+      const fin = new Mesh(new BoxGeometry(0.004, 0.012, D * 0.82), finMat)
+      fin.name = `coil-fin-${side > 0 ? 'r' : 'l'}-${i}`
+      fin.position.set(side * (hw + 0.002), fy, 0)
+      group.add(fin)
+    }
+  }
+
+  buildCollars(node, group)
+  buildServiceValves(node, group)
+  return group
+}

packages/nodes/src/hvac-equipment/index.ts

@@ -0,0 +1,4 @@
+export { hvacEquipmentDefinition } from './definition'
+export { buildHvacEquipmentGeometry } from './geometry'
+export { getHvacEquipmentPorts } from './ports'
+export { HvacEquipmentNode } from './schema'

packages/nodes/src/hvac-equipment/parametrics.ts

@@ -0,0 +1,104 @@
+import type { ParametricDescriptor } from '@pascal-app/core'
+import type { HvacEquipmentNode } from './schema'
+
+export const hvacEquipmentParametrics: ParametricDescriptor<HvacEquipmentNode> = {
+  groups: [
+    {
+      label: 'Equipment',
+      fields: [
+        {
+          key: 'equipmentType',
+          kind: 'enum',
+          options: ['furnace', 'air-handler', 'condenser'],
+          display: 'segmented',
+        },
+      ],
+    },
+    {
+      label: 'Cabinet',
+      fields: [
+        { key: 'width', kind: 'number', unit: 'm', min: 0.3, max: 2, step: 0.05 },
+        { key: 'depth', kind: 'number', unit: 'm', min: 0.3, max: 2, step: 0.05 },
+        { key: 'height', kind: 'number', unit: 'm', min: 0.4, max: 2.5, step: 0.05 },
+      ],
+    },
+    {
+      label: 'Supply',
+      fields: [
+        {
+          key: 'supplyShape',
+          kind: 'enum',
+          options: ['round', 'rect', 'oval'],
+          display: 'segmented',
+          visibleIf: (n) => n.equipmentType !== 'condenser',
+        },
+        {
+          key: 'supplyDiameter',
+          kind: 'number',
+          unit: 'in',
+          min: 6,
+          max: 30,
+          step: 1,
+          visibleIf: (n) => n.equipmentType !== 'condenser' && n.supplyShape === 'round',
+        },
+        {
+          key: 'supplyWidth',
+          kind: 'number',
+          unit: 'in',
+          min: 6,
+          max: 30,
+          step: 1,
+          visibleIf: (n) => n.equipmentType !== 'condenser' && n.supplyShape !== 'round',
+        },
+        {
+          key: 'supplyHeight',
+          kind: 'number',
+          unit: 'in',
+          min: 6,
+          max: 30,
+          step: 1,
+          visibleIf: (n) => n.equipmentType !== 'condenser' && n.supplyShape !== 'round',
+        },
+      ],
+    },
+    {
+      label: 'Return',
+      fields: [
+        {
+          key: 'returnShape',
+          kind: 'enum',
+          options: ['round', 'rect', 'oval'],
+          display: 'segmented',
+          visibleIf: (n) => n.equipmentType !== 'condenser',
+        },
+        {
+          key: 'returnDiameter',
+          kind: 'number',
+          unit: 'in',
+          min: 6,
+          max: 30,
+          step: 1,
+          visibleIf: (n) => n.equipmentType !== 'condenser' && n.returnShape === 'round',
+        },
+        {
+          key: 'returnWidth',
+          kind: 'number',
+          unit: 'in',
+          min: 6,
+          max: 30,
+          step: 1,
+          visibleIf: (n) => n.equipmentType !== 'condenser' && n.returnShape !== 'round',
+        },
+        {
+          key: 'returnHeight',
+          kind: 'number',
+          unit: 'in',
+          min: 6,
+          max: 30,
+          step: 1,
+          visibleIf: (n) => n.equipmentType !== 'condenser' && n.returnShape !== 'round',
+        },
+      ],
+    },
+  ],
+}

packages/nodes/src/hvac-equipment/ports.ts

@@ -0,0 +1,122 @@
+import type { NodePort } from '@pascal-app/core'
+import { Vector3 } from 'three'
+import { equivalentDiameterIn, ovalEquivalentDiameterIn } from '../duct-segment/geometry'
+import type { HvacEquipmentNode } from './schema'
+
+type CollarShape = 'round' | 'rect' | 'oval'
+
+type LocalPort = {
+  id: string
+  position: Vector3
+  direction: Vector3
+  diameter: number
+  system: 'supply' | 'return' | 'refrigerant'
+  // Duct collars only — the cross-section the collar mesh and wall hole
+  // take. `diameter` above is the area-equivalent round size the port
+  // advertises so round runs mate at a sensible size. Refrigerant ports
+  // are always round and omit these.
+  shape?: CollarShape
+  width?: number
+  height?: number
+}
+
+/** Area-equivalent round diameter (inches) a shaped collar advertises. */
+function collarDiameterIn(shape: CollarShape, diameter: number, width: number, height: number) {
+  if (shape === 'rect') return equivalentDiameterIn(width, height)
+  if (shape === 'oval') return ovalEquivalentDiameterIn(width, height)
+  return diameter
+}
+
+/** Nominal suction-line OD (inches) the refrigerant service connection
+ * advertises — matches the lineset kind's default suction diameter so a
+ * lineset run mates cleanly onto the valve. */
+const REFRIGERANT_PORT_DIAMETER_IN = 0.875
+
+/**
+ * Duct ports in the cabinet's LOCAL frame (origin at the base center,
+ * before yaw / position). Matches a typical upflow furnace / vertical air
+ * handler: supply plenum collar on top, return drop on the -X side near
+ * the bottom third. Condensers carry no duct ports — their connection is
+ * the refrigerant lineset (see `localRefrigerantPorts`).
+ */
+export function localEquipmentPorts(node: HvacEquipmentNode): LocalPort[] {
+  if (node.equipmentType === 'condenser') return []
+  return [
+    {
+      id: 'supply',
+      position: new Vector3(0, node.height, 0),
+      direction: new Vector3(0, 1, 0),
+      diameter: collarDiameterIn(
+        node.supplyShape,
+        node.supplyDiameter,
+        node.supplyWidth,
+        node.supplyHeight,
+      ),
+      system: 'supply',
+      shape: node.supplyShape,
+      width: node.supplyWidth,
+      height: node.supplyHeight,
+    },
+    {
+      id: 'return',
+      position: new Vector3(-node.width / 2, node.height * 0.35, 0),
+      direction: new Vector3(-1, 0, 0),
+      diameter: collarDiameterIn(
+        node.returnShape,
+        node.returnDiameter,
+        node.returnWidth,
+        node.returnHeight,
+      ),
+      system: 'return',
+      shape: node.returnShape,
+      width: node.returnWidth,
+      height: node.returnHeight,
+    },
+  ]
+}
+
+/**
+ * Refrigerant service connection in the cabinet's LOCAL frame — the point
+ * a lineset run leaves from (condenser) or arrives at (indoor coil on a
+ * furnace / air handler). Every equipment type exposes exactly one, on the
+ * +X service-valve face: a condenser/air-handler near the bottom third, a
+ * furnace near the top where the cased A-coil sits above the heat
+ * exchanger.
+ */
+export function localRefrigerantPorts(node: HvacEquipmentNode): LocalPort[] {
+  const y = node.equipmentType === 'furnace' ? node.height * 0.8 : node.height * 0.3
+  return [
+    {
+      id: 'lineset',
+      position: new Vector3(node.width / 2, y, 0),
+      direction: new Vector3(1, 0, 0),
+      diameter: REFRIGERANT_PORT_DIAMETER_IN,
+      system: 'refrigerant',
+    },
+  ]
+}
+
+/** `def.ports` — duct + refrigerant ports transformed into level-local
+ * space (yaw + position). */
+export function getHvacEquipmentPorts(node: HvacEquipmentNode): NodePort[] {
+  const offset = new Vector3(node.position[0], node.position[1], node.position[2])
+  const local = [...localEquipmentPorts(node), ...localRefrigerantPorts(node)]
+  return local.map((port) => {
+    const position = port.position.clone().applyAxisAngle(new Vector3(0, 1, 0), node.rotation)
+    position.add(offset)
+    const direction = port.direction
+      .clone()
+      .applyAxisAngle(new Vector3(0, 1, 0), node.rotation)
+      .normalize()
+    return {
+      id: port.id,
+      position: [position.x, position.y, position.z] as const,
+      direction: [direction.x, direction.y, direction.z] as const,
+      diameter: port.diameter,
+      system: port.system,
+      shape: port.shape,
+      width: port.width,
+      height: port.height,
+    }
+  })
+}

packages/nodes/src/hvac-equipment/schema.ts

@@ -0,0 +1 @@
+export { HvacEquipmentNode } from '@pascal-app/core'