diff --git a/app/main.py b/app/main.py
index 09c60e6..31aea58 100755
--- a/app/main.py
+++ b/app/main.py
@@ -1181,8 +1181,9 @@ async def api_add_shopping_item(payload: ShoppingItemCreate):
         category=payload.category,
         note=payload.note or ""
     )
-    await shopping_ws_manager.broadcast({"action": "items_updated", "items": get_shopping_list()})
-    return {"status": "ok", "item": item}
+    current_items = get_shopping_list()
+    await shopping_ws_manager.broadcast({"action": "items_updated", "items": current_items})
+    return {"status": "ok", "item": item, "items": current_items}
 
 
 @app.put("/api/shopping-list/{item_id}")
diff --git a/app/templates/shopping_list.html b/app/templates/shopping_list.html
index c7b7090..1b7c009 100644
--- a/app/templates/shopping_list.html
+++ b/app/templates/shopping_list.html
@@ -955,10 +955,25 @@
       localStorage.setItem('wtc_shop_cats_cache', JSON.stringify(allCategories));
     }
 
+    function deduplicateItems(items) {
+      if (!Array.isArray(items)) return [];
+      const seenIds = new Set();
+      const unique = [];
+      for (const item of items) {
+        if (!item) continue;
+        const key = item.id ? `id_${item.id}` : `name_${(item.item_name || '').toLowerCase().trim()}_${item.checked ? '1' : '0'}`;
+        if (!seenIds.has(key)) {
+          seenIds.add(key);
+          unique.push(item);
+        }
+      }
+      return unique;
+    }
+
     function saveLocalCache(items) {
-      allItems = items;
+      allItems = deduplicateItems(items);
       try {
-        localStorage.setItem('wtc_shop_items_cache', JSON.stringify(items));
+        localStorage.setItem('wtc_shop_items_cache', JSON.stringify(allItems));
       } catch (e) {
         console.warn('LocalStorage voll oder nicht verfügbar:', e);
       }
@@ -1227,8 +1242,8 @@
       const emptyState = document.getElementById('empty-state');
       if (!container) return;
 
-      // Filter anwenden
-      let filtered = allItems;
+      // Filter anwenden (dedupliziert gegen parallele WebSocket- & Fetch-Ereignisse)
+      let filtered = deduplicateItems(allItems);
       if (currentFilterCategory !== null) {
         filtered = filtered.filter(it => (it.category || 'Sonstiges') === currentFilterCategory);
       }
@@ -1459,12 +1474,19 @@
         });
         if (res.ok) {
           const data = await res.json();
-          if (data.item) {
-            allItems.push(data.item);
-            saveLocalCache(allItems);
-            renderShoppingList();
-            renderCategoryFilterChips();
+          if (data.items && Array.isArray(data.items)) {
+            allItems = data.items;
+          } else if (data.item) {
+            const existingIdx = allItems.findIndex(it => it.id === data.item.id);
+            if (existingIdx >= 0) {
+              allItems[existingIdx] = data.item;
+            } else {
+              allItems.push(data.item);
+            }
           }
+          saveLocalCache(allItems);
+          renderShoppingList();
+          renderCategoryFilterChips();
         } else {
           throw new Error('Server-Fehler');
         }
@@ -1480,7 +1502,12 @@
           checked: false,
           source: ''
         };
-        allItems.push(tempItem);
+        const existingIdx = allItems.findIndex(it => (it.item_name || '').toLowerCase().trim() === name.toLowerCase().trim() && !it.checked);
+        if (existingIdx >= 0) {
+          allItems[existingIdx] = tempItem;
+        } else {
+          allItems.push(tempItem);
+        }
         pushOfflineQueue({ method: 'POST', url: '/api/shopping-list', body: payload });
         saveLocalCache(allItems);
         renderShoppingList();