diff --git a/inventoryManager.lua b/inventoryManager.lua
index 52bef6c..1097592 100644
--- a/inventoryManager.lua
+++ b/inventoryManager.lua
@@ -597,6 +597,7 @@ local activeAlerts = {}
 local cache = {
     catalogue  = {},    -- itemName -> { {chest=name, total=N}, ... }
     itemList   = {},    -- sorted list of { name, total }
+    itemListDirty = false, -- lazy rebuild flag for itemList
     grandTotal = 0,
     chestCount = 0,
     totalSlots = 0,
@@ -668,36 +669,66 @@ local function adjustCache(itemName, chestName, delta)
         end
     end
 
-    -- 2) Rebuild itemList from catalogue (lightweight — just totals)
+    -- 2) Mark itemList as needing rebuild (deferred until actually read)
+    cache.itemListDirty = true
+
+    -- 3) Update grandTotal incrementally
+    cache.grandTotal = cache.grandTotal + delta
+end
+
+--- Rebuild itemList from catalogue if dirty (lazy rebuild)
+local function ensureItemList()
+    if not cache.itemListDirty then return end
     local itemList = {}
     local grandTotal = 0
-    for name, sources in pairs(cat) do
+    for name, sources in pairs(cache.catalogue) do
         local total = 0
         for _, s in ipairs(sources) do total = total + s.total end
         grandTotal = grandTotal + total
         table.insert(itemList, { name = name, total = total })
     end
     table.sort(itemList, function(a, b) return a.total > b.total end)
-
     cache.itemList   = itemList
     cache.grandTotal = grandTotal
+    cache.itemListDirty = false
 end
 
 -------------------------------------------------
--- Inventory helpers
+-- Inventory helpers (cached peripheral lists)
 -------------------------------------------------
 
+local PERIPHERAL_CACHE_TTL = 5  -- seconds
+local cachedChests = nil
+local cachedChestsTime = 0
+local cachedFurnaces = nil
+local cachedFurnacesTime = 0
+
+local function invalidatePeripheralCaches()
+    cachedChests = nil
+    cachedFurnaces = nil
+end
+
 local function getChests()
+    local now = os.clock()
+    if cachedChests and (now - cachedChestsTime) < PERIPHERAL_CACHE_TTL then
+        return cachedChests
+    end
     local chests = {}
     for _, name in ipairs(peripheral.getNames()) do
         if peripheral.getType(name) == "minecraft:chest" then
             table.insert(chests, name)
         end
     end
+    cachedChests = chests
+    cachedChestsTime = now
     return chests
 end
 
 local function getFurnaces()
+    local now = os.clock()
+    if cachedFurnaces and (now - cachedFurnacesTime) < PERIPHERAL_CACHE_TTL then
+        return cachedFurnaces
+    end
     local furnaces = {}
     for _, ftype in ipairs(FURNACE_TYPES) do
         for _, name in ipairs(peripheral.getNames()) do
@@ -706,6 +737,8 @@ local function getFurnaces()
             end
         end
     end
+    cachedFurnaces = furnaces
+    cachedFurnacesTime = now
     return furnaces
 end
 
@@ -996,6 +1029,7 @@ end
 
 -- Get items filtered by search query
 local function getFilteredItems()
+    ensureItemList()
     local filtered = {}
     for _, item in ipairs(cache.itemList) do
         if searchQuery == "" then
@@ -1358,6 +1392,7 @@ local function drawDashboard()
         end
 
         -- ===== Footer (h-1) =====
+        ensureItemList()
         monFill(h - 1, colors.gray)
         local footerLeft = string.format(" Total: %d items | %d types ",
             cache.grandTotal, #cache.itemList)
@@ -2821,6 +2856,7 @@ end
 
 local function broadcastState()
     if not networkModem then return end
+    ensureItemList()
     local state = {
         type            = "state",
         cache           = {