Use single tap handler for functions flyout: add named Flyout with Opened/Closed handlers, remove per-row Tapped, and attach handler to flyout root at runtime. Handler finds tapped ListBoxItem and executes InsertFunctionCommand.

src/AdvancedCalculator/Views/MainView.axaml

@@ -134,7 +134,11 @@
 					<Button Grid.Column="1" Command="{Binding ToggleFunctionsCommand}" Margin="0,0,6,0" MinHeight="40" MinWidth="40"
 							AutomationProperties.Name="Toggle functions panel">
             <Button.Flyout>
-                <Flyout IsOpen="{Binding IsFunctionsPanelOpen, Mode=TwoWay}" Placement="BottomEdgeAlignedLeft">
+                <Flyout x:Name="FunctionsFlyout"
+                        IsOpen="{Binding IsFunctionsPanelOpen, Mode=TwoWay}"
+                        Placement="BottomEdgeAlignedLeft"
+                        Opened="OnFunctionsFlyoutOpened"
+                        Closed="OnFunctionsFlyoutClosed">
                     <Border x:Name="FunctionsPanelRoot" Padding="8" MinWidth="360" MaxHeight="420">
                         <ScrollViewer>
                             <StackPanel>
@@ -156,7 +160,6 @@
                                                     <ListBox.ItemTemplate>
                                                         <DataTemplate x:DataType="m:FunctionDefinitionItem">
                                                             <Border Background="Transparent" Padding="8" MinHeight="36"
-                                                                    Tapped="OnFunctionsItemTapped"
                                                                     AutomationProperties.Name="Insert function">
                                                                 <Grid ColumnDefinitions="*,Auto">
                                                                     <StackPanel>

src/AdvancedCalculator/Views/MainView.axaml.cs

@@ -21,6 +21,7 @@ public partial class MainView : UserControl
 
     private MainViewModel? _vm;
     private ListBox? _historyList;
+    private Border? _functionsPanelRoot;
 
     private void OnAttachedToVisualTree(object? sender, VisualTreeAttachmentEventArgs e)
     {
@@ -38,7 +39,7 @@ public partial class MainView : UserControl
                 RoutingStrategies.Tunnel | RoutingStrategies.Bubble);
         }
 
-        // Functions list item taps are handled per-row via XAML (OnFunctionsItemTapped)
+        // Functions flyout wiring is done via Opened/Closed events
     }
 
     private void OnDetachedFromVisualTree(object? sender, VisualTreeAttachmentEventArgs e)
@@ -52,6 +53,12 @@ public partial class MainView : UserControl
             _historyList.RemoveHandler(InputElement.TappedEvent, OnHistoryTapped);
             _historyList = null;
         }
+        // Detach functions panel tap handler if still attached
+        if (_functionsPanelRoot is not null)
+        {
+            _functionsPanelRoot.RemoveHandler(InputElement.TappedEvent, OnFunctionsItemTapped);
+            _functionsPanelRoot = null;
+        }
         _vm = null;
     }
 
@@ -91,7 +98,20 @@ public partial class MainView : UserControl
         if (sender is not IControl control)
             return;
         if (control.DataContext is not FunctionDefinitionItem item)
-            return;
+        {
+            // If attached to panel root, walk up from the source to a ListBoxItem and use its DataContext
+            if (sender is IVisual root && e.Source is IVisual src)
+            {
+                var lbi = src.FindAncestorOfType<ListBoxItem>();
+                if (lbi?.DataContext is not FunctionDefinitionItem rowItem)
+                    return;
+                item = rowItem;
+            }
+            else
+            {
+                return;
+            }
+        }
 
         var vm = DataContext as MainViewModel;
         if (vm?.InsertFunctionCommand.CanExecute(item) == true)
@@ -100,4 +120,27 @@ public partial class MainView : UserControl
             e.Handled = true;
         }
     }
+
+    private void OnFunctionsFlyoutOpened(object? sender, EventArgs e)
+    {
+        // Flyout content is rendered in a popup; find by name at TopLevel
+        var top = TopLevel.GetTopLevel(this);
+        if (top is null) return;
+        var panel = top.FindDescendantOfType<Border>(b => b.Name == "FunctionsPanelRoot");
+        if (panel is null) return;
+
+        // Attach a single tap handler to the flyout content root
+        panel.AddHandler(InputElement.TappedEvent, OnFunctionsItemTapped,
+            RoutingStrategies.Tunnel | RoutingStrategies.Bubble);
+        _functionsPanelRoot = panel;
+    }
+
+    private void OnFunctionsFlyoutClosed(object? sender, EventArgs e)
+    {
+        if (_functionsPanelRoot is not null)
+        {
+            _functionsPanelRoot.RemoveHandler(InputElement.TappedEvent, OnFunctionsItemTapped);
+            _functionsPanelRoot = null;
+        }
+    }
 }