diff --git a/src/stores/useModelStore.ts b/src/stores/useModelStore.ts
index 8eeae17..11182e9 100644
--- a/src/stores/useModelStore.ts
+++ b/src/stores/useModelStore.ts
@@ -505,9 +505,48 @@ export const useModelStore = create<ModelStore>((set, get) => ({
   resetChecklist: () => set({ checklist: defaultChecklist.map(i => ({ ...i })) }),
 
   measureMode: false,
-  setMeasureMode: (measureMode) => set((s) => ({ measureMode, measurePoints: [], positionMode: measureMode ? false : s.positionMode })),
+  setMeasureMode: (measureMode) => set((s) => ({ measureMode, measurePoints: [], positionMode: measureMode ? false : s.positionMode, selectionMode: measureMode ? false : s.selectionMode })),
   positionMode: false,
-  setPositionMode: (positionMode) => set((s) => ({ positionMode, measureMode: positionMode ? false : s.measureMode })),
+  setPositionMode: (positionMode) => set((s) => ({ positionMode, measureMode: positionMode ? false : s.measureMode, selectionMode: positionMode ? false : s.selectionMode })),
+
+  // ── Selection state ─────────────────────────────────────
+  selectionMode: false,
+  setSelectionMode: (on) => set((s) => ({
+    selectionMode: on,
+    measureMode: on ? false : s.measureMode,
+    positionMode: on ? false : s.positionMode,
+    selectedElementKeys: on ? s.selectedElementKeys : new Set(),
+  })),
+  selectedElementKeys: new Set<string>(),
+  hiddenElementKeys: new Set<string>(),
+  isolatedElementKeys: null,
+  visibilityNonce: 0,
+  toggleElementSelection: (key) => set((s) => {
+    const next = new Set(s.selectedElementKeys);
+    if (next.has(key)) next.delete(key); else next.add(key);
+    return { selectedElementKeys: next, visibilityNonce: s.visibilityNonce + 1 };
+  }),
+  clearElementSelection: () => set((s) => ({ selectedElementKeys: new Set(), visibilityNonce: s.visibilityNonce + 1 })),
+  hideSelectedElements: () => set((s) => {
+    if (s.selectedElementKeys.size === 0) return {} as Partial<ModelStore>;
+    const hidden = new Set(s.hiddenElementKeys);
+    s.selectedElementKeys.forEach(k => hidden.add(k));
+    const active = s.models.find(m => m.id === s.activeModelId);
+    if (active) saveVisibility(active.fileName, hidden, s.isolatedElementKeys);
+    return { hiddenElementKeys: hidden, selectedElementKeys: new Set(), visibilityNonce: s.visibilityNonce + 1 };
+  }),
+  isolateSelectedElements: () => set((s) => {
+    if (s.selectedElementKeys.size === 0) return {} as Partial<ModelStore>;
+    const iso = new Set(s.selectedElementKeys);
+    const active = s.models.find(m => m.id === s.activeModelId);
+    if (active) saveVisibility(active.fileName, s.hiddenElementKeys, iso);
+    return { isolatedElementKeys: iso, selectedElementKeys: new Set(), visibilityNonce: s.visibilityNonce + 1 };
+  }),
+  showAllElements: () => set((s) => {
+    const active = s.models.find(m => m.id === s.activeModelId);
+    if (active) saveVisibility(active.fileName, new Set(), null);
+    return { hiddenElementKeys: new Set(), isolatedElementKeys: null, selectedElementKeys: new Set(), visibilityNonce: s.visibilityNonce + 1 };
+  }),
   measurePoints: [],
   addMeasurePoint: (p) => set((state) => {
     const points = [...state.measurePoints, p];