diff --git a/docs/ISOMETRIC.md b/docs/ISOMETRIC.md
index a682ceee..fbf63c0c 100644
--- a/docs/ISOMETRIC.md
+++ b/docs/ISOMETRIC.md
@@ -244,7 +244,10 @@ may meet wall bodies and each other, and the overlapping pairs are the Flat ones
 exactly where Flat puts them, without a position correction. A device never
 moves because its Home Assistant state changed (#711 holds trivially: nothing
 is laid out). Neither zoom nor a stage resize is a layout event: a placement
-depends only on the anchor, its owner room, the footprint and the rise.
+depends only on the anchor, its owner room, the footprint and the rise. The
+placement and render-scene caches are keyed by the wall geometry of the
+structural scene (#724): a wall, room or opening edit starts them afresh, and
+the fit envelope and the live frame read one snapshot.
 
 History: #651 used to search a place for every marker (rigid same-room
 clusters, a group collision resolver and a nudge of up to 48 CSS px towards the
diff --git a/scripts/mutation-registry.mjs b/scripts/mutation-registry.mjs
index 600ef709..97e4d043 100644
--- a/scripts/mutation-registry.mjs
+++ b/scripts/mutation-registry.mjs
@@ -11085,21 +11085,22 @@ const MUTANT_DEFINITIONS = [
   {
     id: 'iso-placement-cache-survives-silhouette-change',
     guard: 'npx tsc -p tsconfig.test.json && node scripts/fix-test-build.mjs '
-      + '&& node --test --test-name-pattern="#473 W2" test/iso-scene-render.test.mjs',
-    because: 'placements are cached per wall-silhouette array identity; keying the cache by a '
-      + 'constant serves «near the wall» for a plan whose wall is gone (#473)',
+      + '&& node --test --test-name-pattern="#473 W2|#724 AC2" test/iso-scene-render.test.mjs',
+    because: 'placements are cached per structural wall geometry (#724; the wall-silhouette '
+      + 'array the id names was built only to be this key); keying the cache by a constant '
+      + 'serves a placement, and with it the owner room, of a plan whose walls are gone (#473)',
     patches: [{
       file: 'src/iso-scene-render.ts',
-      find: '  let placements = isoOverlayPlacementCache.get(input.wallSilhouettes);',
+      find: '  let placements = isoOverlayPlacementCache.get(input.structure);',
       replace: '  let placements = isoOverlayPlacementCache.get(ISO_PLACEMENT_CACHE_ANY);',
     }, {
       file: 'src/iso-scene-render.ts',
-      find: '    isoOverlayPlacementCache.set(input.wallSilhouettes, placements);',
+      find: '    isoOverlayPlacementCache.set(input.structure, placements);',
       replace: '    isoOverlayPlacementCache.set(ISO_PLACEMENT_CACHE_ANY, placements);',
     }, {
       file: 'src/iso-scene-render.ts',
       find: 'export const ISO_OVERLAY_PLACEMENT_CACHE_LIMIT = 2048;',
-      replace: 'export const ISO_OVERLAY_PLACEMENT_CACHE_LIMIT = 2048;\nconst ISO_PLACEMENT_CACHE_ANY: readonly IsoWallSilhouette[] = [];',
+      replace: 'export const ISO_OVERLAY_PLACEMENT_CACHE_LIMIT = 2048;\nconst ISO_PLACEMENT_CACHE_ANY = {} as IsoWallGeometry;',
     }],
   },
   // #474: designer furniture artwork is a lazy chunk. Each protective contract
@@ -11395,12 +11396,13 @@ const MUTANT_DEFINITIONS = [
   {
     id: 'stage3-w5-runtime-nudge-writes-storage',
     guard: 'node demo/smoke_isometric_live_touch.mjs',
-    because: 'W5: runtime nudge is presentation-only and must never write config, layout or '
+    because: 'W5: the 2.5D overlay scene (the wall-top rise of tiles and lock badges; nothing '
+      + 'is nudged since #713) is presentation-only and must never write config, layout or '
       + 'browser storage (#160)',
     patches: [{
       file: 'src/houseplan-card.ts',
       find: '    return runtime.buildIsoOverlayRenderScene({',
-      replace: "    localStorage.setItem('houseplan_stage3_nudge_mutant', space.id);\n"
+      replace: "    localStorage.setItem('houseplan_stage3_overlay_mutant', space.id);\n"
         + '    return runtime.buildIsoOverlayRenderScene({',
     }],
   },
@@ -11415,8 +11417,8 @@ const MUTANT_DEFINITIONS = [
       replace: '    if (!runtime || !layers || (!structural && disp.showBorders)) return null;',
     }, {
       file: 'src/houseplan-card.ts',
-      find: '      wallSilhouettes: structural.wallSilhouettes,',
-      replace: '      wallSilhouettes: structural?.wallSilhouettes ?? [],',
+      find: '      structure: structural.geometry,',
+      replace: "      structure: structural?.geometry ?? { topPath: '', topFaces: [], sides: [], contactPath: '', edgeCount: 0 },",
     }],
   },
   {
diff --git a/src/houseplan-card.ts b/src/houseplan-card.ts
index de26ee54..b7390e7b 100755
--- a/src/houseplan-card.ts
+++ b/src/houseplan-card.ts
@@ -6012,7 +6012,7 @@ export class HouseplanCard extends LitElement {
     const overlays = this._isoOverlayScene(
       space, this._renderDevices.filter((device) => device.space === space.id && !device.hidden),
       disp, runtime.resolveIsoDecorationLayers(disp), scene, iconPct, effectiveDeviceBaseSize(iconPct),
-      disp.showLqi ?? this._config?.show_signal ?? true, false);
+      disp.showLqi ?? this._config?.show_signal ?? true);
     const envelope = overlays && runtime.resolveIsoOverlayFitEnvelope({
       baseBounds: scene.frame, entries: overlays.entries, stageSize, targetView: (bounds) =>
         fitView([bounds.x, bounds.y, bounds.w, bounds.h], aspect) });
@@ -6067,14 +6067,12 @@ export class HouseplanCard extends LitElement {
     iconPct: number,
     deviceBasePct: number,
     showLqi: boolean,
-    resolveCollisions = true,
   ): IsoOverlayRenderScene | null {
     const runtime = this._isoSceneRuntime;
     if (!runtime || !layers?.structural || !structural) return null;
     return runtime.buildIsoOverlayRenderScene({
       space, devices: devs, openings: this._openingsR, display: disp,
-      wallSilhouettes: structural.wallSilhouettes,
-      resolveCollisions,
+      structure: structural.geometry,
       iconPct, deviceBasePct, showLqi, cellCm: this._cellCm,
       kioskIconScale: this._mode === 'view' ? this._kioskScale.icon : 1,
       kioskFontScale: this._mode === 'view' ? this._kioskScale.font : 1,
diff --git a/src/iso-overlays.ts b/src/iso-overlays.ts
index c85a6221..d94c5d09 100644
--- a/src/iso-overlays.ts
+++ b/src/iso-overlays.ts
@@ -19,15 +19,8 @@ export interface IsoOverlayRoom {
   holes?: readonly (readonly PlanPoint[])[];
 }
 
-/** A projected, canonical physical-wall surface. No union is done per marker. */
-export interface IsoWallSilhouette {
-  outer: readonly ScenePoint[];
-  holes?: readonly (readonly ScenePoint[])[];
-}
-
 export interface IsoOverlayOwner {
   id: string;
-  area: number;
 }
 
 export interface IsoOverlayOwnerInput {
@@ -45,36 +38,22 @@ export interface IsoOverlayPlacementInput extends IsoOverlayOwnerInput {
   /** Half-size of the invisible floor-parallel footprint in plan units. */
   footprintHalfSize: PlanPoint;
   visualOffset?: number;
-  filtersSupported?: boolean;
-  hovered?: boolean;
-  focused?: boolean;
-  selected?: boolean;
   camera?: IsoCamera;
   /** Internal scene-builder fast path; arbitrary callers still resolve safely. */
   ownerAlreadyResolved?: boolean;
   resolvedOwner?: IsoOverlayOwner | null;
 }
 
-export interface IsoOverlayTetherGeometry {
-  from: ScenePoint;
-  to: ScenePoint;
-  visible: boolean;
-  length: number;
-  angleDeg: number;
-}
-
 export interface IsoOverlayPlacement {
   plane: IsoOverlayPlane;
   owner: IsoOverlayOwner | null;
   /** This is always the input logical point; the raised visual never mutates it. */
   floorAnchor: PlanPoint;
   floorScene: ScenePoint;
-  raisedScene: ScenePoint;
+  /** The screen-facing root: the floor anchor lifted by `visualOffset` (#713). */
   visualScene: ScenePoint;
   /** Invisible fit footprint; never render it as a surface. */
   footprint: readonly ScenePoint[];
-  grounding: { center: ScenePoint; visible: boolean };
-  tether: IsoOverlayTetherGeometry;
 }
 
 const EPS = 1e-9;
@@ -167,7 +146,7 @@ export function resolveIsoOverlayOwner(input: IsoOverlayOwnerInput): IsoOverlayO
     // a saved label may legitimately lie outside that room.
     room = preferred;
   }
-  return room ? { id: room.id, area: roomArea(room) } : null;
+  return room ? { id: room.id } : null;
 }
 
 export function isoOverlayPlane(kind: IsoOverlayKind, showBorders: boolean): IsoOverlayPlane {
@@ -196,13 +175,6 @@ export function buildIsoFootprintPolygon(
   });
 }
 
-function tetherGeometry(
-  from: ScenePoint, to: ScenePoint, visible: boolean,
-): IsoOverlayTetherGeometry {
-  const dx = to[0] - from[0], dy = to[1] - from[1];
-  return { from, to, visible, length: Math.hypot(dx, dy), angleDeg: Math.atan2(dy, dx) * 180 / Math.PI };
-}
-
 /**
  * Resolve one overlay without mutating its saved coordinate. Since #713 a
  * raised root is its floor anchor shifted straight up by `visualOffset`; #714
@@ -220,30 +192,20 @@ export function resolveIsoOverlayPlacement(input: IsoOverlayPlacementInput): Iso
   const floorScene = projectPlanPoint(floorAnchor, 0, camera);
   const plane = isoOverlayPlane(input.kind, input.showBorders);
   if (plane === 'floor') {
-    return {
-      plane, owner: null, floorAnchor, floorScene, raisedScene: floorScene,
-      visualScene: floorScene, footprint: [],
-      grounding: { center: floorScene, visible: false },
-      tether: tetherGeometry(floorScene, floorScene, false),
-    };
+    return { plane, owner: null, floorAnchor, floorScene, visualScene: floorScene, footprint: [] };
   }
 
   // The canonical floor anchor and footprint stay; the screen-facing content
   // stands `visualOffset` above the floor (#713: the wall top for tiles and
   // lock badges, 0 for room names).
-  const raisedScene = projectPlanPoint(floorAnchor, visualOffset, camera);
+  const visualScene = projectPlanPoint(floorAnchor, visualOffset, camera);
   const owner = input.ownerAlreadyResolved
     ? input.resolvedOwner ?? null
     : resolveIsoOverlayOwner(input);
   const footprint = buildIsoFootprintPolygon(floorAnchor, input.footprintHalfSize,
     visualOffset, camera);
   // Ownership remains encoded by the immutable anchor and invisible bounded
-  // footprint. Stage 4 deliberately removes the visible ground dot and long
-  // tether which made the architectural view look like a debug overlay.
-  const tetherVisible = false;
-  return {
-    plane, owner, floorAnchor, floorScene, raisedScene, visualScene: raisedScene, footprint,
-    grounding: { center: floorScene, visible: false },
-    tether: tetherGeometry(floorScene, raisedScene, tetherVisible),
-  };
+  // footprint. Stage 4 removed the visible ground dot and long tether which made
+  // the architectural view look like a debug overlay; #724 removed their data.
+  return { plane, owner, floorAnchor, floorScene, visualScene, footprint };
 }
diff --git a/src/iso-scene-render.ts b/src/iso-scene-render.ts
index e53a87db..f39a368a 100644
--- a/src/iso-scene-render.ts
+++ b/src/iso-scene-render.ts
@@ -13,7 +13,7 @@ import { clampScale, islandsOf, roomPoly, type SpaceDisplay } from './logic';
 import {
   ISO_CAMERA, ISO_FLOOR_EDGE_HEIGHT,
   ISO_RAISED_OVERLAY_HEIGHT, ISO_WALL_HEIGHT,
-  projectPlanPoint, projectedFrame, type PlanPoint, type ScenePoint,
+  projectedFrame, type PlanPoint, type ScenePoint,
 } from './iso-projection';
 import {
   buildIsoFloorGeometry, buildIsoWallGeometry, isoGeometryFingerprint,
@@ -28,7 +28,6 @@ import {
 import {
   resolveIsoOverlayOwner, resolveIsoOverlayPlacement,
   type IsoOverlayPlacement, type IsoOverlayRoom, type IsoRaisedOverlayKind,
-  type IsoWallSilhouette,
 } from './iso-overlays';
 import {
   floorFootprintGeometry, openingInnerFaceOffsetFromIndex,
@@ -376,7 +375,6 @@ export function isoRaisedOverlayHalfSize(input: IsoRaisedFootprintInput): PlanPo
 export type IsoSceneCacheEntry = {
   geometry: IsoWallGeometry;
   floor: IsoFloorGeometry;
-  wallSilhouettes: readonly IsoWallSilhouette[];
   openings: readonly IsoOpeningBasis[];
   openingSurfaces: readonly IsoOpeningRenderSurface[];
 };
@@ -568,27 +566,6 @@ export function createIsoStructuralSource(
   };
 }
 
-const unknownArray = (value: unknown): readonly unknown[] => Array.isArray(value) ? value : [];
-
-/**
- * Project a cached physical wall union once. Since #714 no overlay is tested
- * against it; the frozen array is the structural identity the overlay caches key on.
- */
-export function isoWallSilhouettesOf(geometry: unknown, height: number): IsoWallSilhouette[] {
-  const projectRing = (raw: unknown): ScenePoint[] => unknownArray(raw).flatMap((point) => {
-    if (!Array.isArray(point) || !Number.isFinite(point[0]) || !Number.isFinite(point[1])) return [];
-    return [projectPlanPoint([Number(point[0]), Number(point[1])], height)];
-  });
-  return unknownArray(geometry).flatMap((rawPolygon) => {
-    const polygon = unknownArray(rawPolygon);
-    if (!polygon.length) return [];
-    const outer = projectRing(polygon[0]);
-    if (outer.length < 3) return [];
-    const holes = polygon.slice(1).map(projectRing).filter((ring) => ring.length >= 3);
-    return [{ outer, holes } satisfies IsoWallSilhouette];
-  });
-}
-
 export interface ResolveIsoSceneInput {
   source: IsoStructuralSource;
   cache: Map<string, IsoSceneCacheEntry>;
@@ -604,15 +581,9 @@ export function resolveIsoScene(input: ResolveIsoSceneInput): IsoRenderScene {
   let value = cached.hit ? cached.value : undefined;
   if (!value) {
     const structural = input.source.build();
-    const geometry = buildIsoWallGeometry(structural.walls, ISO_CAMERA, wallHeight);
-    const wallTops = isoWallSilhouettesOf(structural.walls, wallHeight);
     value = {
-      geometry,
+      geometry: buildIsoWallGeometry(structural.walls, ISO_CAMERA, wallHeight),
       floor: buildIsoFloorGeometry(structural.floor, floorEdgeHeight),
-      wallSilhouettes: Object.freeze([
-        ...wallTops,
-        ...geometry.sides.map((face) => ({ outer: face.points })),
-      ]),
       openings: structural.openings,
       openingSurfaces: structural.openingSurfaces,
     };
@@ -706,13 +677,14 @@ export interface IsoOverlaySceneInput {
   devices: readonly DevItem[];
   openings: readonly RenderOpening[];
   display: SpaceDisplay;
-  /** Identity of the structural scene; the placement caches are keyed by it. */
-  wallSilhouettes: readonly IsoWallSilhouette[];
   /**
-   * `false` for fit-envelope probes, which keep their own cache slot. Since
-   * #713 there is no collision search, so both slots hold equal placements.
+   * The wall geometry of the structural scene the overlays stand in (#724). The
+   * overlay caches are keyed by its identity: the structural LRU hands out the
+   * same object while only zoom, stage size or HA state change, and a new one
+   * after any wall, room or opening edit — so an edit never serves a placement,
+   * and with it an owner room, of a plan that is gone.
    */
-  resolveCollisions?: boolean;
+  structure: IsoWallGeometry;
   iconPct: number;
   deviceBasePct: number;
   showLqi: boolean;
@@ -733,14 +705,13 @@ type IsoOverlayPlacementCacheEntry = { signature: string; placement: IsoOverlayP
 type IsoOverlayOwnerCacheEntry = { signature: string; owner: IsoOverlayPlacement['owner'] };
 export const ISO_OVERLAY_PLACEMENT_CACHE_LIMIT = 2048;
 const isoOverlayPlacementCache = new WeakMap<
-  readonly IsoWallSilhouette[], Map<string, IsoOverlayPlacementCacheEntry>
+  IsoWallGeometry, Map<string, IsoOverlayPlacementCacheEntry>
 >();
 const isoOverlayOwnerCache = new WeakMap<
   readonly IsoOverlayRoomRow[], Map<string, IsoOverlayOwnerCacheEntry>
 >();
-const isoOverlayRenderSceneCache = new WeakMap<
-  readonly IsoWallSilhouette[], Map<'fit' | 'live', IsoOverlayRenderScene>
->();
+/** One snapshot per structure: fit and the live frame share it (#724). */
+const isoOverlayRenderSceneCache = new WeakMap<IsoWallGeometry, IsoOverlayRenderScene>();
 
 function samePlacementMap<K>(
   previous: ReadonlyMap<K, IsoOverlayPlacement>, next: ReadonlyMap<K, IsoOverlayPlacement>,
@@ -795,10 +766,10 @@ export function buildIsoOverlayRenderScene(input: IsoOverlaySceneInput): IsoOver
   const roomPlacements = new Map<RoomCfg, IsoOverlayPlacement>();
   const locks = new Map<string, IsoOverlayPlacement>();
   const entries: IsoOverlayRenderEntry[] = [];
-  let placements = isoOverlayPlacementCache.get(input.wallSilhouettes);
+  let placements = isoOverlayPlacementCache.get(input.structure);
   if (!placements) {
     placements = new Map();
-    isoOverlayPlacementCache.set(input.wallSilhouettes, placements);
+    isoOverlayPlacementCache.set(input.structure, placements);
   }
   let owners = isoOverlayOwnerCache.get(roomRows);
   if (!owners) {
@@ -815,8 +786,7 @@ export function buildIsoOverlayRenderScene(input: IsoOverlaySceneInput): IsoOver
     preferredRoomId?: string | null,
   ): IsoOverlayPlacement => {
     const visualOffset = kind === 'room-label' ? 0 : wallHeight;
-    const collisionMode = input.resolveCollisions === false ? 'fit' : 'live';
-    const cacheKey = `${collisionMode}\u0000${kind}\u0000${id}`;
+    const cacheKey = `${kind}\u0000${id}`;
     // Nothing here depends on zoom or stage size, so a pinch, wheel or resize
     // reuses the immutable placement and Lit keeps the raised SVG subtree.
     const signature = [floorAnchor[0], floorAnchor[1],
@@ -825,16 +795,15 @@ export function buildIsoOverlayRenderScene(input: IsoOverlaySceneInput): IsoOver
     ].join('|');
     const cached = lruRead(placements!, cacheKey);
     if (cached.hit && cached.value.signature === signature) return cached.value.placement;
-    const ownerKey = `${kind}\u0000${id}`;
     const ownerSignature = [floorAnchor[0], floorAnchor[1], preferredRoomId || ''].join('|');
-    const cachedOwner = lruRead(owners!, ownerKey);
+    const cachedOwner = lruRead(owners!, cacheKey);
     const owner = cachedOwner.hit && cachedOwner.value.signature === ownerSignature
       ? cachedOwner.value.owner
       : resolveIsoOverlayOwner({
         kind, floorAnchor, rooms, roomsValidated: true, preferredRoomId,
       });
     if (!cachedOwner.hit || cachedOwner.value.signature !== ownerSignature) {
-      lruWrite(owners!, ownerKey, { signature: ownerSignature, owner },
+      lruWrite(owners!, cacheKey, { signature: ownerSignature, owner },
         ISO_OVERLAY_PLACEMENT_CACHE_LIMIT);
     }
     const placement = resolveIsoOverlayPlacement({
@@ -927,17 +896,11 @@ export function buildIsoOverlayRenderScene(input: IsoOverlaySceneInput): IsoOver
       });
     }
   }
-  const mode = input.resolveCollisions === false ? 'fit' : 'live';
-  let renderScenes = isoOverlayRenderSceneCache.get(input.wallSilhouettes);
-  if (!renderScenes) {
-    renderScenes = new Map();
-    isoOverlayRenderSceneCache.set(input.wallSilhouettes, renderScenes);
-  }
-  const previous = renderScenes.get(mode);
+  const previous = isoOverlayRenderSceneCache.get(input.structure);
   const layoutSignature = entries.map((entry) => {
     const placement = entry.placement;
     return [entry.kind, entry.id, placement.floorAnchor[0], placement.floorAnchor[1],
-      placement.raisedScene[0], placement.raisedScene[1], placement.owner?.id || '',
+      placement.visualScene[0], placement.visualScene[1], placement.owner?.id || '',
       layoutHalfSizeOf(entry)[0], layoutHalfSizeOf(entry)[1]].join('|');
   }).sort().join('\u0001');
   if (previous?.layoutSignature === layoutSignature
@@ -960,7 +923,7 @@ export function buildIsoOverlayRenderScene(input: IsoOverlaySceneInput): IsoOver
           ? { ...entry, screenHalfSize: next } : entry;
       })),
     };
-    renderScenes.set(mode, refreshed);
+    isoOverlayRenderSceneCache.set(input.structure, refreshed);
     return refreshed;
   }
 
@@ -983,7 +946,7 @@ export function buildIsoOverlayRenderScene(input: IsoOverlaySceneInput): IsoOver
       && samePlacementMap(previous.devices, scene.devices)
       && samePlacementMap(previous.rooms, scene.rooms)
       && samePlacementMap(previous.locks, scene.locks)) return previous;
-  renderScenes.set(mode, scene);
+  isoOverlayRenderSceneCache.set(input.structure, scene);
   return scene;
 }
 
diff --git a/test/iso-overlays.test.mjs b/test/iso-overlays.test.mjs
index 9851e782..7a852a91 100644
--- a/test/iso-overlays.test.mjs
+++ b/test/iso-overlays.test.mjs
@@ -88,8 +88,8 @@ test('a degenerate or missing owner room still raises the overlay straight up',
     const result = placement(overrides);
     assert.equal(result.owner, null, name);
     assert.equal(result.plane, 'raised', name);
-    assert.deepEqual(result.visualScene, result.raisedScene, `${name}: no move without an owner`);
-    assert.equal(result.tether.visible, false, name);
+    assert.deepEqual(result.visualScene,
+      projectPlanPoint(result.floorAnchor, ISO_RAISED_OVERLAY_HEIGHT), `${name}: no move without an owner`);
   }
 });
 
@@ -106,31 +106,29 @@ test('footprint corners use the same affine camera on the raised plane', () => {
     'zero yaw keeps the screen-facing footprint aligned with the plan axes');
 });
 
+// #724: what a placement carries is what someone reads — no invisible tether or
+// grounding, no second raised point equal to the visual one, no owner area.
+const PLACEMENT_FIELDS = ['floorAnchor', 'floorScene', 'footprint', 'owner', 'plane', 'visualScene'];
+
 test('free low overlay separates the immutable floor anchor from its invisible footprint', () => {
   const normal = placement();
+  assert.deepEqual(Object.keys(normal).sort(), PLACEMENT_FIELDS);
   assert.equal(normal.plane, 'raised');
+  assert.deepEqual(normal.owner, { id: 'room' });
   assert.deepEqual(normal.floorAnchor, [50, 50]);
   assert.deepEqual(normal.floorScene, projectPlanPoint([50, 50], 0));
-  assert.deepEqual(normal.raisedScene, projectPlanPoint([50, 50], ISO_RAISED_OVERLAY_HEIGHT));
-  assert.deepEqual(normal.visualScene, normal.raisedScene);
+  assert.deepEqual(normal.visualScene, projectPlanPoint([50, 50], ISO_RAISED_OVERLAY_HEIGHT));
   assert.deepEqual(normal.footprint,
     buildIsoFootprintPolygon([50, 50], [4, 4], ISO_RAISED_OVERLAY_HEIGHT));
-  assert.equal(normal.grounding.visible, false);
-  assert.equal(normal.tether.visible, false);
-
-  for (const state of ['hovered', 'focused', 'selected'])
-    assert.equal(placement({ [state]: true }).tether.visible, false, state);
-  assert.equal(placement({ filtersSupported: false }).grounding.visible, false,
-    'unsupported filters remove the soft grounding shadow only');
   assert.deepEqual(placement({ visualOffset: 0 }).visualScene, normal.floorScene,
     'a zero offset keeps the root on its floor point (#713 room names)');
 });
 
 test('show_borders:false is exact no-volume: floor anchor, no footprint/cues', () => {
-  const result = placement({ showBorders: false, hovered: true });
+  const result = placement({ showBorders: false });
+  assert.deepEqual(Object.keys(result).sort(), PLACEMENT_FIELDS);
   assert.equal(result.plane, 'floor');
+  assert.equal(result.owner, null);
   assert.deepEqual(result.visualScene, result.floorScene);
   assert.deepEqual(result.footprint, []);
-  assert.equal(result.grounding.visible, false);
-  assert.equal(result.tether.visible, false);
 });
diff --git a/test/iso-scene-render.test.mjs b/test/iso-scene-render.test.mjs
index d886006c..30029480 100644
--- a/test/iso-scene-render.test.mjs
+++ b/test/iso-scene-render.test.mjs
@@ -36,6 +36,13 @@ import {
   projectPlanPoint,
 } from '../test-build/iso-projection.js';
 
+/**
+ * #724: the overlay caches are keyed by the structural wall geometry. Every
+ * fixture gets its own object, as a structural scene of its own would.
+ */
+const structureOf = (walls = []) => buildIsoWallGeometry(walls);
+const wallRect = (x0, y0, x1, y1) => [[[[x0, y0], [x1, y0], [x1, y1], [x0, y1]]]];
+
 const room = (id, x0, y0, x1, y1) => ({
   id,
   poly: [[x0, y0], [x1, y0], [x1, y1], [x0, y1]],
@@ -121,7 +128,7 @@ test('room footprint treats wide ASCII glyphs conservatively', () => {
 test('overlay bounds use final screen footprint and canonical owner filtering', () => {
   const placement = (owner, center) => ({
     owner: { id: owner }, floorScene: [center[0] - 5, center[1]],
-    raisedScene: center, visualScene: center,
+    visualScene: center,
     footprint: [[center[0] - 2, center[1] - 1], [center[0] + 2, center[1] - 1],
       [center[0] + 2, center[1] + 1], [center[0] - 2, center[1] + 1]],
   });
@@ -139,7 +146,7 @@ test('#713 K8: overlay fit is the structure plus visible tiles, no #651 nudge re
   const entry = {
     id: 'edge', kind: 'device', groundRadius: 1, screenHalfSize: [10, 8],
     placement: {
-      owner: { id: 'room' }, floorScene: [95, 50], raisedScene: [95, 50],
+      owner: { id: 'room' }, floorScene: [95, 50],
       visualScene: [95, 50],
       footprint: [[90, 46], [100, 46], [100, 54], [90, 54]],
     },
@@ -324,7 +331,7 @@ test('opening-lock scene keeps physical host ownership when spatial fallback poi
     view: { x: 0, y: 0, w: 100, h: 100 },
     display: { showNames: false, cardFontScale: 1 },
     layers: { shadows: true },
-    wallSilhouettes: [],
+    structure: structureOf(),
     iconPct: 100,
     deviceBasePct: 100,
     showLqi: false,
@@ -365,7 +372,7 @@ test('opening lock without a canonical host owner never guesses from point conta
     view: { x: 0, y: 0, w: 100, h: 100 },
     display: { showNames: false, cardFontScale: 1 },
     layers: { shadows: true },
-    wallSilhouettes: [{ outer: [[0, 45], [100, 45], [100, 55], [0, 55]] }],
+    structure: structureOf(wallRect(0, 45, 100, 55)),
     iconPct: 100,
     deviceBasePct: 100,
     showLqi: false,
@@ -386,18 +393,15 @@ test('opening lock without a canonical host owner never guesses from point conta
   // the badge simply stands on the wall-top plane above its anchor.
   assert.equal(placement?.plane, 'raised');
   assert.deepEqual(placement?.visualScene, projectPlanPoint(placement.floorAnchor, ISO_WALL_HEIGHT));
-  assert.equal(placement?.tether.visible, false);
 });
 
-test('Stage 4 reuses pure overlay placements and fit probes agree with the live scene', () => {
+test('Stage 4 reuses pure overlay placements, and fit and the live frame share one snapshot', () => {
   const owner = room('owner', 0, 0, 100, 100);
   const space = {
     id: 'floor', title: 'Floor', cellCm: 5, vb: [0, 0, 100, 100], bg: null,
     rooms: [owner], wall_segments: [], room_drafts: [], partitions: [], wall_columns: [],
   };
-  const wallSilhouettes = [{
-    outer: buildIsoFootprintPolygon([0, 50], [4, 60], ISO_WALL_HEIGHT),
-  }];
+  const structure = structureOf(wallRect(-4, -10, 4, 110));
   const input = {
     space,
     devices: [{ id: 'device', space: 'floor', marker: { room_id: 'owner' } }],
@@ -406,7 +410,7 @@ test('Stage 4 reuses pure overlay placements and fit probes agree with the live
     referenceView: { x: 0, y: 0, w: 100, h: 100 },
     display: { showNames: false, cardFontScale: 1 },
     layers: { structural: true, shadows: true },
-    wallSilhouettes,
+    structure,
     iconPct: 3.4,
     deviceBasePct: 3.4,
     showLqi: false,
@@ -442,9 +446,10 @@ test('Stage 4 reuses pure overlay placements and fit probes agree with the live
   const resized = buildIsoOverlayRenderScene({ ...input, stageSize: { width: 40, height: 40 } });
   assert.strictEqual(resized, live, '#714: a stage resize is not a layout event either');
 
-  const fit = buildIsoOverlayRenderScene({ ...input, resolveCollisions: false });
-  assert.deepEqual(fit.devices.get('device')?.visualScene, live.devices.get('device')?.visualScene,
-    '#713: fit and live placements agree — there is no search to differ by');
+  // #724: the fit envelope and the live frame ask with the same inputs and read
+  // one snapshot — there is no search for them to differ by (#713).
+  const fit = buildIsoOverlayRenderScene({ ...input });
+  assert.strictEqual(fit, live, 'fit and live share one render-scene snapshot');
 
   const zoomed = buildIsoOverlayRenderScene({ ...input, view: { x: -10, y: -10, w: 120, h: 120 } });
   assert.strictEqual(zoomed, live,
@@ -462,7 +467,6 @@ test('render scene keeps coincident devices coincident, leaves labels alone and
     id: 'floor', title: 'Floor', cellCm: 5, vb: [0, 0, 400, 400], bg: null,
     rooms: [owner], wall_segments: [], room_drafts: [], partitions: [], wall_columns: [],
   };
-  const walls = [];
   const devices = ['b', 'a', 'c'].map((id) => ({
     id, space: 'floor', marker: { room_id: 'owner', x: 200, y: 200 },
   }));
@@ -471,7 +475,7 @@ test('render scene keeps coincident devices coincident, leaves labels alone and
     view: { x: 0, y: 0, w: 400, h: 400 },
     display: { showNames: true, cardFontScale: 1 },
     layers: { structural: true, shadows: true },
-    wallSilhouettes: walls,
+    structure: structureOf(),
     iconPct: 3.4, deviceBasePct: 3.4, showLqi: false, cellCm: 5,
     kioskIconScale: 1, kioskFontScale: 1,
     stageSize: { width: 200, height: 200 },
@@ -505,9 +509,9 @@ test('render scene keeps coincident devices coincident, leaves labels alone and
   const permuted = buildIsoOverlayRenderScene({ ...input, devices: [...devices].reverse() });
   assert.strictEqual(permuted, scene,
     'HA registry permutations reuse the same immutable group layout snapshot');
-  const fit = buildIsoOverlayRenderScene({ ...input, resolveCollisions: false });
-  assert.deepEqual(fit.devices.get('a').visualScene, scene.devices.get('a').visualScene,
-    'fit probing and the live scene place the cluster identically');
+  const fit = buildIsoOverlayRenderScene({ ...input });
+  assert.strictEqual(fit.devices.get('a'), scene.devices.get('a'),
+    'fit probing and the live scene read the same placement');
 });
 
 test('#711 состояние устройства не двигает значки: раскладка не пересчитывается, границы видят бейдж', () => {
@@ -516,7 +520,7 @@ test('#711 состояние устройства не двигает знач
     id: 'floor-710', title: 'Floor', cellCm: 5, vb: [0, 0, 400, 400], bg: null,
     rooms: [owner], wall_segments: [], room_drafts: [], partitions: [], wall_columns: [],
   };
-  const wallSilhouettes = [{ outer: buildIsoFootprintPolygon([150, 200], [154, 260], ISO_WALL_HEIGHT) }];
+  const structure = structureOf(wallRect(146, 140, 154, 260));
   const devices = ['lamp', 'plug', 'sensor'].map((id, index) => ({
     id, space: 'floor-710', marker: { room_id: 'owner', x: 160 + index * 4, y: 200 },
   }));
@@ -533,7 +537,7 @@ test('#711 состояние устройства не двигает знач
     view: { x: 0, y: 0, w: 400, h: 400 },
     display: { showNames: false, cardFontScale: 1 },
     layers: { structural: true, shadows: true },
-    wallSilhouettes,
+    structure,
     iconPct: 3.4, deviceBasePct: 3.4, showLqi: false, cellCm: 5,
     kioskIconScale: 1, kioskFontScale: 1,
     stageSize: { width: 200, height: 200 },
@@ -562,26 +566,6 @@ test('#711 состояние устройства не двигает знач
   }
 });
 
-test('structural wall silhouettes reuse every visible side quad', () => {
-  const walls = [[[[45, 20], [55, 20], [55, 80], [45, 80]]]];
-  const scene = resolveIsoScene({
-    source: {
-      key: 'visible-side-silhouettes',
-      build: () => ({ walls, floor: walls, openings: [], openingSurfaces: [] }),
-    },
-    cache: new Map(),
-    cellCm: 5,
-    liveFrame: { x: 0, y: 0, w: 100, h: 100 },
-  });
-  assert.ok(scene.geometry.sides.length > 0, 'fixture exposes visible vertical wall faces');
-  assert.equal(scene.wallSilhouettes.length, 1 + scene.geometry.sides.length,
-    'the silhouette set contains the top footprint and every visible side');
-  scene.geometry.sides.forEach((face, index) => {
-    assert.strictEqual(scene.wallSilhouettes[index + 1].outer, face.points,
-      `visible side ${index} reuses its exact render quad`);
-  });
-});
-
 test('orphan hosted openings never become phantom Stage 4 volumes', () => {
   const base = {
     type: 'door', rx: 20, ry: 30, rlen: 40, angle: 0,
@@ -719,7 +703,7 @@ test('removed contact shadows are never read while ambient shadow capability rem
       display: { showBorders: true, hideOpenings: false },
       scene: {
         key: 'solid-retry', geometry,
-        floor: { footprintPath: '', sides: [] }, wallSilhouettes: [],
+        floor: { footprintPath: '', sides: [] },
         openings: [], openingSurfaces: [], frame: { x: 0, y: 0, w: 100, h: 100 },
       },
       openings: [], amountOf: () => 0, overlays: () => null, cellCm: 5,
@@ -846,7 +830,7 @@ const perfFixture = () => {
     id: 'floor', title: 'Floor', cellCm: 5, vb: [0, 0, 100, 100], bg: null,
     rooms: [owner], wall_segments: [], room_drafts: [], partitions: [], wall_columns: [],
   };
-  const wallSilhouettes = [{ outer: buildIsoFootprintPolygon([0, 50], [4, 60], ISO_WALL_HEIGHT) }];
+  const structure = structureOf(wallRect(-4, -10, 4, 110));
   const input = {
     space,
     devices: [{ id: 'device', space: 'floor', marker: { room_id: 'owner' } }],
@@ -855,7 +839,7 @@ const perfFixture = () => {
     referenceView: { x: 0, y: 0, w: 100, h: 100 },
     display: { showNames: false, cardFontScale: 1 },
     layers: { structural: true, shadows: true },
-    wallSilhouettes,
+    structure,
     iconPct: 3.4, deviceBasePct: 3.4, showLqi: false, cellCm: 5,
     kioskIconScale: 1, kioskFontScale: 1,
     stageSize: { width: 100, height: 100 },
@@ -870,7 +854,7 @@ const perfFixture = () => {
     openingEntityAvailable: () => false,
     openingWallIndex: () => ({ adjacencyEps: 0.1, edges: [] }),
   };
-  return { input, wallSilhouettes };
+  return { input, structure };
 };
 
 test('#570 supersedes #473 W1: selection reuses the cue-free low placement', () => {
@@ -885,15 +869,110 @@ test('#570 supersedes #473 W1: selection reuses the cue-free low placement', ()
   assert.strictEqual(again, selected, 'clearing selection keeps the same immutable placement');
 });
 
-test('#473 W2 after #713: walls no longer move a tile, the cache still follows the silhouette array', () => {
+test('#473 W2 after #724: walls never move a tile, the cache follows the structural wall geometry', () => {
   const { input } = perfFixture();
   const withWall = buildIsoOverlayRenderScene(input).devices.get('device');
-  const noWalls = buildIsoOverlayRenderScene({ ...input, wallSilhouettes: [] }).devices.get('device');
-  assert.notStrictEqual(noWalls, withWall, 'a new geometry array is a new cache slot');
+  const noWalls = buildIsoOverlayRenderScene({ ...input, structure: structureOf() }).devices.get('device');
+  assert.notStrictEqual(noWalls, withWall, 'a new wall geometry is a new cache slot');
   assert.deepEqual(noWalls.visualScene, withWall.visualScene,
     'the tile position does not depend on nearby walls');
 });
 
+// #724 AC2: the overlay caches follow the wall geometry of the structural scene
+// on the production path — createIsoStructuralSource → resolveIsoScene (the
+// LRU) → buildIsoOverlayRenderScene({ structure: scene.geometry }).
+const unhostedWalls = (poly, cm) => poly.map((a, index) => ({
+  key: wallKey(a, poly[(index + 1) % poly.length], 1), cm,
+}));
+const overlayInput = (space, structure, overrides = {}) => ({
+  space, structure, openings: [],
+  devices: [{ id: 'device', space: space.id }],
+  view: { x: 0, y: 0, w: 100, h: 100 },
+  display: { showNames: false, cardFontScale: 1 },
+  iconPct: 3.4, deviceBasePct: 3.4, showLqi: false, cellCm: 5,
+  kioskIconScale: 1, kioskFontScale: 1,
+  stageSize: { width: 100, height: 100 },
+  positionOf: () => ({ x: 50, y: 50 }),
+  presentationOf: () => ({
+    scale: 1, valueText: null, valueFullText: '', valueBadge: null,
+    tempText: null, humText: null, lqiText: null,
+    pulse: { animated: false, diameterScale: 1 },
+  }),
+  labelPositionOf: () => ({ x: 0, y: 0 }),
+  labelScaleOf: () => 1,
+  openingEntityAvailable: () => false,
+  openingWallIndex: () => ({ adjacencyEps: 0.1, edges: [] }),
+  ...overrides,
+});
+
+test('#724 AC2: the overlay scene survives zoom, resize and HA state, and is rebuilt when a wall changes', () => {
+  const square = cacheRoom({ wall_ids: [] });
+  const cache = new Map();
+  const structural = (cm) => {
+    const input = structuralInput({ room: square, walls: unhostedWalls(square.poly, cm), coordinateScale: 1 });
+    return { space: input.space, scene: resolveIsoScene({
+      source: createIsoStructuralSource(input), cache, cellCm: 5, liveFrame: { x: 0, y: 0, w: 100, h: 100 },
+    }) };
+  };
+  const thin = structural(20);
+  assert.ok(thin.scene.geometry.sides.length > 0, 'fixture has real wall bodies');
+  const live = buildIsoOverlayRenderScene(overlayInput(thin.space, thin.scene.geometry));
+
+  // Same walls: the structural LRU hands out the same geometry, and neither
+  // zoom, a stage resize nor an HA state change is a layout event.
+  const again = structural(20);
+  assert.strictEqual(again.scene.geometry, thin.scene.geometry);
+  const zoomed = buildIsoOverlayRenderScene(overlayInput(again.space, again.scene.geometry, {
+    view: { x: 20, y: 20, w: 40, h: 40 }, stageSize: { width: 320, height: 180 },
+  }));
+  assert.strictEqual(zoomed, live, 'zoom and resize reuse the render scene');
+  const lit = buildIsoOverlayRenderScene(overlayInput(again.space, again.scene.geometry, {
+    presentationOf: () => ({
+      scale: 1, valueText: null, valueFullText: '', tempText: null, humText: null, lqiText: null,
+      valueBadge: { configured: true, enabled: true, text: '100 %', fullText: '100 %', position: 'right', tone: 'default' },
+      pulse: { animated: false, diameterScale: 1 },
+    }),
+  }));
+  assert.strictEqual(lit.devices.get('device'), live.devices.get('device'), 'HA state keeps the placement');
+
+  // A thicker wall with the same room: a new structure, so a new scene. A cache
+  // keyed without the walls would serve the placement of the old plan.
+  const thick = structural(30);
+  assert.notEqual(thick.scene.key, thin.scene.key);
+  assert.notStrictEqual(thick.scene.geometry, thin.scene.geometry);
+  const rebuilt = buildIsoOverlayRenderScene(overlayInput(thick.space, thick.scene.geometry));
+  assert.notStrictEqual(rebuilt, live, 'a wall edit rebuilds the overlay scene');
+  assert.notStrictEqual(rebuilt.devices.get('device'), live.devices.get('device'),
+    'and its placements');
+  assert.deepEqual(rebuilt.devices.get('device').visualScene, live.devices.get('device').visualScene,
+    'the tile itself stays where it was: walls never move it');
+});
+
+test('#724 AC2: a room edit that changes the owner is a new structure — no owner of a plan that is gone', () => {
+  const cache = new Map();
+  const structural = (split) => {
+    const base = structuralInput();
+    const rooms = [
+      cacheRoom({ id: 'west', poly: [[0, 0], [split, 0], [split, 100], [0, 100]], wall_ids: [] }),
+      cacheRoom({ id: 'east', poly: [[split, 0], [200, 0], [200, 100], [split, 100]], wall_ids: [] }),
+    ];
+    const space = { ...base.space, vb: [0, 0, 200, 100], rooms };
+    return { space, scene: resolveIsoScene({
+      source: createIsoStructuralSource({ ...base, space }), cache, cellCm: 5,
+      liveFrame: { x: 0, y: 0, w: 200, h: 100 },
+    }) };
+  };
+  const at = { positionOf: () => ({ x: 90, y: 50 }) };
+  const before = structural(100);
+  const west = buildIsoOverlayRenderScene(overlayInput(before.space, before.scene.geometry, at));
+  assert.equal(west.devices.get('device').owner?.id, 'west');
+  const after = structural(80);
+  assert.notEqual(after.scene.key, before.scene.key, 'room geometry is structural');
+  const east = buildIsoOverlayRenderScene(overlayInput(after.space, after.scene.geometry, at));
+  assert.equal(east.devices.get('device').owner?.id, 'east',
+    'the tile at the same point now belongs to the room that grew over it');
+});
+
 test('#713 AC3: live zoom never recomputes placement and every tile gets one straight-up shift', () => {
   const { input } = perfFixture();
   const lift = projectPlanPoint([0, 0], 0)[1] - projectPlanPoint([0, 0], ISO_WALL_HEIGHT)[1];
diff --git a/test/iso-stage6.test.mjs b/test/iso-stage6.test.mjs
index 0e2dfedc..b4810eec 100644
--- a/test/iso-stage6.test.mjs
+++ b/test/iso-stage6.test.mjs
@@ -197,7 +197,8 @@ test('#649 AC3 layout and collisions see the 2.5D tile size (× ISO_ICON_SCALE)'
   };
   const scene = buildIsoOverlayRenderScene({
     space, devices: [{ id: 'd1' }], openings: [], view: { x: 0, y: 0, w: 1000, h: 1000 },
-    display: { showNames: false, cardFontScale: 1 }, layers: { shadows: true }, wallSilhouettes: [],
+    display: { showNames: false, cardFontScale: 1 }, layers: { shadows: true },
+    structure: { topPath: '', topFaces: [], sides: [], contactPath: '', edgeCount: 0 },
     iconPct: 3, deviceBasePct: 3, showLqi: false, cellCm: 5, kioskIconScale: 1, kioskFontScale: 1,
     stageSize: { width: 1000, height: 1000 }, positionOf: () => ({ x: 500, y: 500 }),
     presentationOf: () => presentation, labelPositionOf: () => ({ x: 0, y: 0 }), labelScaleOf: () => 1,
diff --git a/test/isometric-contract.test.mjs b/test/isometric-contract.test.mjs
index 43cddfc8..49817e91 100644
--- a/test/isometric-contract.test.mjs
+++ b/test/isometric-contract.test.mjs
@@ -167,7 +167,7 @@ test('Stage 4 structural cache fingerprints geometry/camera/heights and excludes
   assert.match(sceneRender, /const floorEdgeHeight = gridVisualUnits\(ISO_FLOOR_EDGE_HEIGHT, input\.cellCm\)/);
   assert.match(sceneRender, /const raisedHeight = gridVisualUnits\(ISO_RAISED_OVERLAY_HEIGHT, input\.cellCm\)/);
   assert.match(sceneRender, /camera: ISO_CAMERA,[\s\S]*?wallHeight,[\s\S]*?raisedHeight,[\s\S]*?floorEdgeHeight,[\s\S]*?algorithm: 6/);
-  const source = section(sceneRender, 'export function createIsoStructuralSource', 'const unknownArray');
+  const source = section(sceneRender, 'export function createIsoStructuralSource', 'export interface ResolveIsoSceneInput');
   const roomProjection = section(sceneRender,
     'export function isoStructuralRoomGeometry', 'export type IsoStructuralOpeningHost');
   for (const field of ['id', 'x', 'y', 'w', 'h', 'poly', 'wall_ids'])
@@ -204,8 +204,13 @@ test('Stage 4 structural cache fingerprints geometry/camera/heights and excludes
   assert.match(sceneRender, /projectIsoOpening\(basis, amountOf\(opening\)\)/);
   assert.match(sceneRender, /lruWrite\(input\.cache, input\.source\.key, value, 8\)/);
   assert.match(card, /data-hp-iso-structural-builds=\$\{iso \? this\._isoStructuralBuildCount : nothing\}/);
-  assert.match(sceneRender, /const wallTops = isoWallSilhouettesOf\(structural\.walls, wallHeight\)/);
-  assert.match(sceneRender, /wallSilhouettes:\s*Object\.freeze\(\[[\s\S]*?\.\.\.wallTops,[\s\S]*?\.\.\.geometry\.sides\.map\(\(face\) => \(\{ outer: face\.points \}\)\),[\s\S]*?\]\)/);
+  // #724: the overlay caches are keyed by the structural wall geometry itself —
+  // no silhouette array is built only to be that key.
+  assert.match(sceneRender, /geometry: buildIsoWallGeometry\(structural\.walls, ISO_CAMERA, wallHeight\)/);
+  assert.match(sceneRender, /structure: IsoWallGeometry;/);
+  assert.match(sceneRender, /let placements = isoOverlayPlacementCache\.get\(input\.structure\)/);
+  assert.match(sceneRender, /const previous = isoOverlayRenderSceneCache\.get\(input\.structure\)/);
+  assert.doesNotMatch(sceneRender, /wallSilhouettes|isoWallSilhouettesOf|resolveCollisions/);
 });
 
 test('show_borders:false keeps the Flat floor plane and removes every volume cue', () => {