diff --git a/assets/formulas/it-networking.d4rt b/assets/formulas/it-networking.d4rt
index 14fa848..19dc6a7 100644
--- a/assets/formulas/it-networking.d4rt
+++ b/assets/formulas/it-networking.d4rt
@@ -16,14 +16,27 @@ The network address is calculated by applying the subnet mask to zero out the ho
     ],
     "output": {"name": "network", "unit": "string"},
     "d4rtCode": r"""
+       hostIP = hostIP.toString();
        var parts = hostIP.split('/');
+       if( parts.length != 2 ) {
+         signal('Invalid input format. Expected format: IP/MASK');
+       }
        var ip = parts[0];
-       var mask = int.parse(parts[1]);
-       var octets = ip.split('.').map((e) => int.parse(e)).toList();
+       var mask = int.tryParse(parts[1]);
+       if( mask == null || mask < 0 || mask > 32 ) {
+         signal('Invalid subnet mask. Must be an integer between 0 and 32.');
+       }
+       var octets = ip.split('.').map((e) => int.tryParse(e)).toList();
+       if( octets.length != 4 ) {
+         signal('Invalid IP address format. Expected 4 octets separated by dots.');
+       }
        var hostBits = 32 - mask;
        var shiftAmount = hostBits;
        var networkValue = 0;
        for (var i = 0; i < 4; i++) {
+         if (octets[i] == null || octets[i] < 0 || octets[i] > 255) {
+           signal('Invalid IP address. Each octet must be between 0 and 255.');
+         }
          networkValue = (networkValue << 8) | octets[i];
        }
        networkValue = (networkValue >> shiftAmount) << shiftAmount;
diff --git a/lib/ai/formula_screen.dart b/lib/ai/formula_screen.dart
index 1e6fd8f..21aed33 100644
--- a/lib/ai/formula_screen.dart
+++ b/lib/ai/formula_screen.dart
@@ -135,7 +135,6 @@ class _FormulaScreenState extends State<FormulaScreen> {
       errorHandler.notify(e, stack);
       setState(() {
         _errorMessage = e.toString();
-        _isErrorExpanded = true; // Auto-expand on error
         _result = null;
       });
     }
@@ -254,7 +253,7 @@ class _FormulaScreenState extends State<FormulaScreen> {
       color: Theme.of(context).colorScheme.errorContainer,
       child: ExpansionTile(
         title: Text(
-          '⚠️ There were an error. Show details...',
+          '⚠️ There was an error. Show details...',
           style: Theme.of(context).textTheme.titleMedium?.copyWith(
             fontWeight: FontWeight.bold,
             color: Theme.of(context).colorScheme.onErrorContainer,