diff --git a/backend/src/server.ts b/backend/src/server.ts
index 95dc9c9..57f7298 100644
--- a/backend/src/server.ts
+++ b/backend/src/server.ts
@@ -38,11 +38,12 @@ app.get('/api/data', async (req, res) => {
     for (const item of stock) {
       if (item.maxStock !== null && item.maxStock !== undefined) {
         const ordered = orderedQtyById[item.id] || 0;
-        const shouldBeAvailable = ordered < item.maxStock;
-        if (item.available !== shouldBeAvailable) {
+        const isOutOfStock = ordered >= item.maxStock;
+        // Only auto-disable if it's currently marked as available but is actually out of stock
+        if (isOutOfStock && item.available) {
           await prisma.stockItem.update({
             where: { id: item.id },
-            data: { available: shouldBeAvailable }
+            data: { available: false }
           });
         }
       }
@@ -60,38 +61,101 @@ app.get('/api/data', async (req, res) => {
         : null
     }));
 
-    res.json({ stock: stockWithRemaining, orders: parsedOrders, config });
+    // Security: Don't send the admin code to the client
+    const configResponse = config ? { ...config, adminCode: undefined } : null;
+
+    res.json({ stock: stockWithRemaining, orders: parsedOrders, config: configResponse });
   } catch (error) {
     console.error(error);
     res.status(500).json({ error: 'Failed to fetch data' });
   }
 });
 
+// Admin Login
+app.post('/api/login', async (req, res) => {
+  try {
+    const { code } = req.body;
+    const config = await prisma.config.findFirst();
+    if (config && config.adminCode === code) {
+      res.json({ success: true });
+    } else {
+      res.status(401).json({ error: 'Invalid admin code' });
+    }
+  } catch (error) {
+    res.status(500).json({ error: 'Login failed' });
+  }
+});
+
 // Submit a new order
 app.post('/api/orders', async (req, res) => {
   try {
     const { name, phone, items, totalWeight, estimatedTotal } = req.body;
     
-    // Generate simple order number
-    const lastOrder = await prisma.order.findFirst({ orderBy: { id: 'desc' } });
-    const nextId = (lastOrder?.id || 0) + 1;
-    const orderNumber = `#${nextId + 1000}`;
+    // 1. Validate Stock Availability
+    const stockItems = await prisma.stockItem.findMany();
+    const allOrders = await prisma.order.findMany();
+    
+    const orderedQtyById: Record<number, number> = {};
+    for (const order of allOrders) {
+      const parsedItems = JSON.parse(order.items);
+      for (const item of parsedItems) {
+        orderedQtyById[item.id] = (orderedQtyById[item.id] || 0) + (item.qty || 0);
+      }
+    }
 
+    let computedTotalWeight = 0;
+    let computedEstimatedTotal = 0;
+
+    for (const item of items) {
+      const dbItem = stockItems.find(s => s.id === item.id);
+      if (!dbItem) throw new Error(`Item ${item.name} not found`);
+      if (!dbItem.available) throw new Error(`Sorry, ${dbItem.name} has just sold out!`);
+      
+      if (dbItem.maxStock !== null && dbItem.maxStock !== undefined) {
+        const alreadyOrdered = orderedQtyById[dbItem.id] || 0;
+        if (alreadyOrdered + item.qty > dbItem.maxStock) {
+          throw new Error(`Not enough stock for ${dbItem.name}. Only ${Math.max(0, dbItem.maxStock - alreadyOrdered)}${dbItem.unit} remaining.`);
+        }
+      }
+
+      // Recalculate prices server-side
+      const getPrice = (stockItem: any, qty: number) => {
+        if (stockItem.bulk2Threshold > 0 && qty >= stockItem.bulk2Threshold && stockItem.bulk2Price > 0) return stockItem.bulk2Price;
+        if (stockItem.bulk1Threshold > 0 && qty >= stockItem.bulk1Threshold && stockItem.bulk1Price > 0) return stockItem.bulk1Price;
+        return stockItem.price;
+      };
+
+      const finalPrice = getPrice(dbItem, item.qty);
+      item.finalPricePerUnit = finalPrice;
+      item.lineTotal = finalPrice * item.qty;
+      
+      computedTotalWeight += item.qty;
+      computedEstimatedTotal += item.lineTotal;
+    }
+
+    // 2. Create the order
     const order = await prisma.order.create({
       data: {
-        orderNumber,
         name,
         phone,
-        totalWeight,
-        estimatedTotal,
+        totalWeight: computedTotalWeight,
+        estimatedTotal: computedEstimatedTotal,
         items: JSON.stringify(items),
         status: 'Pending'
       }
     });
-    res.json(order);
-  } catch (error) {
+
+    // 3. Generate and update order number based on ID (to avoid race conditions)
+    const orderNumber = `#${order.id + 1000}`;
+    const updatedOrder = await prisma.order.update({
+      where: { id: order.id },
+      data: { orderNumber }
+    });
+
+    res.json(updatedOrder);
+  } catch (error: any) {
     console.error(error);
-    res.status(500).json({ error: 'Failed to submit order' });
+    res.status(400).json({ error: error.message || 'Failed to submit order' });
   }
 });
 
diff --git a/frontend/src/App.tsx b/frontend/src/App.tsx
index 4cb8122..56141f1 100644
--- a/frontend/src/App.tsx
+++ b/frontend/src/App.tsx
@@ -16,24 +16,16 @@ function App() {
   const [showAdminLogin, setShowAdminLogin] = useState(false);
   const [adminCodeInput, setAdminCodeInput] = useState('');
   const [notification, setNotification] = useState<string | null>(null);
-  const [adminCode, setAdminCode] = useState('1234');
   const [config, setConfig] = useState<any>(null);
   const [confirmModal, setConfirmModal] = useState<{ show: boolean, message: string, onConfirm: (() => void) | null }>({ show: false, message: '', onConfirm: null });
   const [pickerItem, setPickerItem] = useState<any>(null);
 
-  useEffect(() => {
-    refreshData();
-    const intervalId = setInterval(refreshData, 5000);
-    return () => clearInterval(intervalId);
-  }, []);
-
   const refreshData = async () => {
     try {
       const data = await API.fetchData();
       setStock(data.stock);
       setOrders(data.orders.sort((a: any, b: any) => new Date(b.timestamp).getTime() - new Date(a.timestamp).getTime()));
       if (data.config) {
-        setAdminCode(data.config.adminCode || '1234');
         setConfig(data.config);
       }
       setIsLoading(false);
@@ -42,6 +34,11 @@ function App() {
     }
   };
 
+  useEffect(() => {
+    refreshData();
+    const intervalId = setInterval(refreshData, 5000);
+    return () => clearInterval(intervalId);
+  }, []);
   const showNotification = (msg: string) => {
     setNotification(msg);
     setTimeout(() => setNotification(null), 3000);
@@ -110,19 +107,20 @@ function App() {
       refreshData();
       showNotification("Order Request Sent!");
       return order;
-    } catch (error) {
-      showNotification("Error submitting order.");
+    } catch (error: any) {
+      showNotification(error.message || "Error submitting order.");
       throw error;
     }
   };
 
-  const handleAdminLogin = () => {
-    if (adminCodeInput === adminCode) {
+  const handleAdminLogin = async () => {
+    try {
+      await API.login(adminCodeInput);
       setView('admin');
       setShowAdminLogin(false);
       setAdminCodeInput('');
       showNotification("Logged in as Admin");
-    } else {
+    } catch (err) {
       showNotification("Incorrect Admin Code");
     }
   };
diff --git a/frontend/src/services/api.ts b/frontend/src/services/api.ts
index 1efda57..c9abeb5 100644
--- a/frontend/src/services/api.ts
+++ b/frontend/src/services/api.ts
@@ -36,5 +36,14 @@ export const API = {
         headers: { 'Content-Type': 'application/json' },
         body: JSON.stringify(cfg)
     }),
-    resetDB: () => fetch(`${API_BASE}/api/reset`, { method: 'POST' })
+    resetDB: () => fetch(`${API_BASE}/api/reset`, { method: 'POST' }),
+    login: async (code: string) => {
+        const res = await fetch(`${API_BASE}/api/login`, {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/json' },
+            body: JSON.stringify({ code })
+        });
+        if (!res.ok) throw new Error('Invalid code');
+        return res.json();
+    }
 };