diff --git a/custom_components/shopping_list_manager/const.py b/custom_components/shopping_list_manager/const.py
index bdb838e..45a7d4b 100644
--- a/custom_components/shopping_list_manager/const.py
+++ b/custom_components/shopping_list_manager/const.py
@@ -1,12 +1,92 @@
 """Constants for Shopping List Manager."""
 
+# Domain
 DOMAIN = "shopping_list_manager"
 
-# Storage keys
-STORAGE_VERSION = 1
+# Storage Keys
+STORAGE_VERSION = 2
+STORAGE_KEY_LISTS = f"{DOMAIN}.lists"
+STORAGE_KEY_ITEMS = f"{DOMAIN}.items"
 STORAGE_KEY_PRODUCTS = f"{DOMAIN}.products"
-STORAGE_KEY_ACTIVE = f"{DOMAIN}.active_list"
-LISTS_STORE_KEY = "shopping_list_manager.lists"
+STORAGE_KEY_CATEGORIES = f"{DOMAIN}.categories"
+
+# WebSocket Commands - Lists
+WS_TYPE_LISTS_GET_ALL = f"{DOMAIN}/lists/get_all"
+WS_TYPE_LISTS_CREATE = f"{DOMAIN}/lists/create"
+WS_TYPE_LISTS_UPDATE = f"{DOMAIN}/lists/update"
+WS_TYPE_LISTS_DELETE = f"{DOMAIN}/lists/delete"
+WS_TYPE_LISTS_SET_ACTIVE = f"{DOMAIN}/lists/set_active"
+
+# WebSocket Commands - Items
+WS_TYPE_ITEMS_GET = f"{DOMAIN}/items/get"
+WS_TYPE_ITEMS_ADD = f"{DOMAIN}/items/add"
+WS_TYPE_ITEMS_UPDATE = f"{DOMAIN}/items/update"
+WS_TYPE_ITEMS_CHECK = f"{DOMAIN}/items/check"
+WS_TYPE_ITEMS_DELETE = f"{DOMAIN}/items/delete"
+WS_TYPE_ITEMS_REORDER = f"{DOMAIN}/items/reorder"
+WS_TYPE_ITEMS_BULK_CHECK = f"{DOMAIN}/items/bulk_check"
+WS_TYPE_ITEMS_CLEAR_CHECKED = f"{DOMAIN}/items/clear_checked"
+WS_TYPE_ITEMS_GET_TOTAL = f"{DOMAIN}/items/get_total"
+
+# WebSocket Commands - Products
+WS_TYPE_PRODUCTS_SEARCH = f"{DOMAIN}/products/search"
+WS_TYPE_PRODUCTS_SUGGESTIONS = f"{DOMAIN}/products/suggestions"
+WS_TYPE_PRODUCTS_ADD = f"{DOMAIN}/products/add"
+WS_TYPE_PRODUCTS_UPDATE = f"{DOMAIN}/products/update"
+WS_TYPE_PRODUCTS_DELETE = f"{DOMAIN}/products/delete"
+
+# WebSocket Commands - Categories
+WS_TYPE_CATEGORIES_GET_ALL = f"{DOMAIN}/categories/get_all"
+WS_TYPE_CATEGORIES_REORDER = f"{DOMAIN}/categories/reorder"
+
+# WebSocket Commands - Subscriptions
+WS_TYPE_SUBSCRIBE = f"{DOMAIN}/subscribe"
+WS_TYPE_UNSUBSCRIBE = f"{DOMAIN}/unsubscribe"
+
+# WebSocket Commands - Barcode (Phase 5)
+WS_TYPE_BARCODE_SCAN = f"{DOMAIN}/barcode/scan"
+WS_TYPE_BARCODE_ADD = f"{DOMAIN}/barcode/add_to_list"
+
+# WebSocket Commands - OpenFoodFacts (Phase 5)
+WS_TYPE_OFF_FETCH = f"{DOMAIN}/openfoodfacts/fetch"
+WS_TYPE_OFF_IMPORT = f"{DOMAIN}/openfoodfacts/import"
 
 # Events
-EVENT_SHOPPING_LIST_UPDATED = f"{DOMAIN}_updated"
+EVENT_ITEM_ADDED = f"{DOMAIN}_item_added"
+EVENT_ITEM_UPDATED = f"{DOMAIN}_item_updated"
+EVENT_ITEM_CHECKED = f"{DOMAIN}_item_checked"
+EVENT_ITEM_DELETED = f"{DOMAIN}_item_deleted"
+EVENT_LIST_UPDATED = f"{DOMAIN}_list_updated"
+EVENT_LIST_DELETED = f"{DOMAIN}_list_deleted"
+
+# Image Configuration
+IMAGE_FORMAT = "webp"
+IMAGE_SIZE = 200  # 200x200px
+IMAGE_QUALITY = 85
+IMAGE_MAX_SIZE_KB = 15
+
+# Metric Units (always metric, regardless of country)
+METRIC_UNITS = {
+    "weight": ["kg", "g"],
+    "volume": ["L", "mL"],
+    "count": ["units", "pack", "loaf", "dozen"]
+}
+
+# Default quantities for common products (NZ-focused, can be country-specific later)
+DEFAULT_QUANTITIES = {
+    "milk": {"quantity": 2, "unit": "L"},
+    "bread": {"quantity": 1, "unit": "loaf"},
+    "butter": {"quantity": 500, "unit": "g"},
+    "eggs": {"quantity": 12, "unit": "units"},
+    "cheese": {"quantity": 1, "unit": "kg"},
+    "yogurt": {"quantity": 1, "unit": "kg"},
+    "flour": {"quantity": 1, "unit": "kg"},
+    "sugar": {"quantity": 1, "unit": "kg"},
+    "rice": {"quantity": 1, "unit": "kg"},
+    "pasta": {"quantity": 500, "unit": "g"}
+}
+
+# Paths
+CATEGORIES_FILE = "categories.json"
+PRODUCTS_CATALOG_FILE = "products_catalog.json"
+IMAGES_PATH = "images/products"