diff --git a/Dashboard/Controls/PlanViewerControl.xaml b/Dashboard/Controls/PlanViewerControl.xaml
index a3610c9e..f8bdfd8c 100644
--- a/Dashboard/Controls/PlanViewerControl.xaml
+++ b/Dashboard/Controls/PlanViewerControl.xaml
@@ -1,7 +1,10 @@
 <UserControl x:Class="PerformanceMonitorDashboard.Controls.PlanViewerControl"
              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-             Background="{DynamicResource BackgroundBrush}">
+             Background="{DynamicResource BackgroundBrush}"
+             Focusable="True"
+             PreviewMouseDown="PlanViewerControl_PreviewMouseDown"
+             PreviewKeyDown="PlanViewerControl_PreviewKeyDown">
     <Grid>
         <Grid.RowDefinitions>
             <RowDefinition Height="Auto"/>
diff --git a/Dashboard/Controls/PlanViewerControl.xaml.cs b/Dashboard/Controls/PlanViewerControl.xaml.cs
index fc26e470..452eba6f 100644
--- a/Dashboard/Controls/PlanViewerControl.xaml.cs
+++ b/Dashboard/Controls/PlanViewerControl.xaml.cs
@@ -1436,6 +1436,38 @@ private void PlanScrollViewer_PreviewMouseWheel(object sender, MouseWheelEventAr
         }
     }
 
+    private void PlanViewerControl_PreviewMouseDown(object sender, MouseButtonEventArgs e)
+    {
+        Focus();
+    }
+
+    private void PlanViewerControl_PreviewKeyDown(object sender, KeyEventArgs e)
+    {
+        if (e.Key == Key.V && Keyboard.Modifiers == ModifierKeys.Control
+            && e.OriginalSource is not TextBox)
+        {
+            var text = Clipboard.GetText();
+            if (!string.IsNullOrWhiteSpace(text))
+            {
+                e.Handled = true;
+                try
+                {
+                    System.Xml.Linq.XDocument.Parse(text);
+                }
+                catch (System.Xml.XmlException ex)
+                {
+                    MessageBox.Show(
+                        $"The plan XML is not valid:\n\n{ex.Message}",
+                        "Invalid Plan XML",
+                        MessageBoxButton.OK,
+                        MessageBoxImage.Warning);
+                    return;
+                }
+                LoadPlan(text, "Pasted Plan");
+            }
+        }
+    }
+
     #endregion
 
     #region Save & Statement Selection
diff --git a/Dashboard/Controls/QueryPerformanceContent.xaml b/Dashboard/Controls/QueryPerformanceContent.xaml
index b7c71c9d..c2b50c41 100644
--- a/Dashboard/Controls/QueryPerformanceContent.xaml
+++ b/Dashboard/Controls/QueryPerformanceContent.xaml
@@ -32,8 +32,12 @@
                     <MenuItem.Icon><TextBlock Text="📊"/></MenuItem.Icon>
                 </MenuItem>
                 <Separator/>
-                <MenuItem Header="View Plan" Click="ViewEstimatedPlan_Click"/>
-                <MenuItem Header="Get Actual Plan" Click="GetActualPlan_Click"/>
+                <MenuItem Header="View Plan" Click="ViewEstimatedPlan_Click">
+                    <MenuItem.Icon><TextBlock Text="🔍"/></MenuItem.Icon>
+                </MenuItem>
+                <MenuItem Header="Get Actual Plan" Click="GetActualPlan_Click">
+                    <MenuItem.Icon><TextBlock Text="▶"/></MenuItem.Icon>
+                </MenuItem>
             </ContextMenu>
 
             <Style x:Key="DefaultRowStyle" TargetType="DataGridRow">
diff --git a/Dashboard/MainWindow.xaml b/Dashboard/MainWindow.xaml
index 7bc9579d..1edd0c28 100644
--- a/Dashboard/MainWindow.xaml
+++ b/Dashboard/MainWindow.xaml
@@ -183,6 +183,16 @@
                             </Border>
                         </Grid>
                     </Button>
+                    <Button x:Name="OpenPlanViewerButton"
+                            Click="OpenPlanViewer_Click"
+                            Height="32"
+                            Margin="0,0,0,8"
+                            ToolTip="Open or paste an execution plan (independent of any server)">
+                        <StackPanel Orientation="Horizontal">
+                            <TextBlock Text="&#x1F50D;" FontSize="12" VerticalAlignment="Center" Margin="0,0,6,0"/>
+                            <TextBlock Text="Open Plan Viewer" VerticalAlignment="Center"/>
+                        </StackPanel>
+                    </Button>
                     <Separator Margin="0,0,0,8"/>
                     <Button x:Name="RefreshAllButton"
                             Content="&#x21BB; Refresh All Status"
diff --git a/Dashboard/MainWindow.xaml.cs b/Dashboard/MainWindow.xaml.cs
index be8ab37b..2aaf20ad 100644
--- a/Dashboard/MainWindow.xaml.cs
+++ b/Dashboard/MainWindow.xaml.cs
@@ -47,7 +47,9 @@ public partial class MainWindow : Window
         private TabItem? _nocTab;
         private LandingPage? _landingPage;
         private TabItem? _alertsTab;
+        private TabItem? _planViewerTab;
         private AlertsHistoryContent? _alertsHistoryContent;
+
         private McpHostService? _mcpHostService;
         private CancellationTokenSource? _mcpCts;
 
@@ -76,6 +78,7 @@ public partial class MainWindow : Window
         private const double CollapsedWidth = 52;
         private const string NocTabId = "__NOC_OVERVIEW__";
         private const string AlertsTabId = "__ALERTS_HISTORY__";
+        private const string PlanViewerTabId = "__PLAN_VIEWER__";
 
         public MainWindow()
         {
@@ -688,6 +691,15 @@ private void CloseTab_Click(object sender, RoutedEventArgs e)
                         _alertsHistoryContent = null;
                     }
                 }
+                else if (tabId == PlanViewerTabId)
+                {
+                    if (_planViewerTab != null)
+                    {
+                        ServerTabControl.Items.Remove(_planViewerTab);
+                        _planViewerTab = null;
+                        _mainPlanTabControl = null;
+                    }
+                }
                 else if (_openTabs.TryGetValue(tabId, out var tabToClose))
                 {
                     _openTabs.Remove(tabId);
@@ -1651,5 +1663,418 @@ private void UnsilenceServer_Click(object sender, RoutedEventArgs e)
         }
 
         #endregion
+
+        #region Main Window Plan Viewer
+
+        private const string PlanAddTabId = "__PLAN_ADD_TAB__";
+        private TabControl? _mainPlanTabControl;
+        private Grid? _planViewerContainer;
+
+        private void OpenPlanViewer_Click(object sender, RoutedEventArgs e)
+        {
+            if (_planViewerTab != null && ServerTabControl.Items.Contains(_planViewerTab))
+            {
+                AddNewEmptyPlanSubTab();
+                ServerTabControl.SelectedItem = _planViewerTab;
+                Dispatcher.BeginInvoke(DispatcherPriority.Loaded, new Action(() => _planViewerContainer?.Focus()));
+                return;
+            }
+            OpenPlanViewerTab();
+        }
+
+        private void OpenPlanViewerTab()
+        {
+            if (_planViewerTab != null && ServerTabControl.Items.Contains(_planViewerTab))
+            {
+                ServerTabControl.SelectedItem = _planViewerTab;
+                return;
+            }
+
+            _mainPlanTabControl = new TabControl
+
+            {
+                Background = System.Windows.Media.Brushes.Transparent,
+                BorderThickness = new Thickness(0)
+            };
+
+            // "+" tab at the end of the inner strip
+            var addTabHeader = new TextBlock
+            {
+                Text = "+",
+                FontSize = 14,
+                FontWeight = FontWeights.Bold,
+                VerticalAlignment = VerticalAlignment.Center,
+                ToolTip = "Open a new plan sub-tab"
+            };
+            var addTab = new TabItem
+            {
+                Header = addTabHeader,
+                Tag = PlanAddTabId,
+                Content = new Grid() // no content needed
+            };
+            _mainPlanTabControl.Items.Add(addTab);
+
+            _mainPlanTabControl.SelectionChanged += (_, _) =>
+            {
+                if (_mainPlanTabControl.SelectedItem is TabItem { Tag: string t } && t == PlanAddTabId)
+                {
+                    var newSub = AddNewEmptyPlanSubTab();
+                    _mainPlanTabControl.SelectedItem = newSub;
+                }
+            };
+
+            var container = new Grid();
+            container.AllowDrop = true;
+            container.Focusable = true;
+            container.DragOver += MainWindowPlanViewer_DragOver;
+            container.Drop += MainWindowPlanViewer_Drop;
+            container.KeyDown += MainWindowPlanViewer_KeyDown;
+            container.Children.Add(_mainPlanTabControl);
+            _planViewerContainer = container;
+
+            var header = new StackPanel { Orientation = Orientation.Horizontal };
+            header.Children.Add(new TextBlock
+            {
+                Text = "Plan Viewer",
+                VerticalAlignment = VerticalAlignment.Center,
+                FontWeight = FontWeights.SemiBold
+            });
+            var closeBtn = new Button
+            {
+                Style = (Style)FindResource("TabCloseButton"),
+                Tag = PlanViewerTabId
+            };
+            closeBtn.Click += CloseTab_Click;
+            header.Children.Add(closeBtn);
+
+            _planViewerTab = new TabItem
+            {
+                Header = header,
+                Content = container,
+                Tag = PlanViewerTabId
+            };
+
+            ServerTabControl.Items.Add(_planViewerTab);
+            ServerTabControl.SelectedItem = _planViewerTab;
+
+            // Open the first empty sub-tab immediately
+            AddNewEmptyPlanSubTab();
+            Dispatcher.BeginInvoke(DispatcherPriority.Loaded, new Action(() => _planViewerContainer?.Focus()));
+        }
+
+        /// <summary>
+        /// Adds a new empty "New Plan" sub-tab to the inner plan TabControl and selects it.
+        /// Returns the newly created sub-tab.
+        /// </summary>
+        private TabItem AddNewEmptyPlanSubTab()
+        {
+            // --- Empty state layer ---
+            var emptyState = new Grid();
+            var dashedRect = new System.Windows.Shapes.Rectangle
+            {
+                Margin = new Thickness(24),
+                Stroke = (System.Windows.Media.Brush)FindResource("ForegroundMutedBrush"),
+                StrokeThickness = 1.5,
+                StrokeDashArray = new System.Windows.Media.DoubleCollection { 6, 4 },
+                RadiusX = 10, RadiusY = 10,
+                Opacity = 0.25
+            };
+            var emptyStack = new StackPanel { HorizontalAlignment = HorizontalAlignment.Center, VerticalAlignment = VerticalAlignment.Center };
+            emptyStack.Children.Add(new TextBlock
+            {
+                Text = "\uE896",
+                FontFamily = new System.Windows.Media.FontFamily("Segoe MDL2 Assets"),
+                FontSize = 52,
+                HorizontalAlignment = HorizontalAlignment.Center,
+                Foreground = (System.Windows.Media.Brush)FindResource("ForegroundMutedBrush"),
+                Opacity = 0.45,
+                Margin = new Thickness(0, 0, 0, 12)
+            });
+            emptyStack.Children.Add(new TextBlock
+            {
+                Text = "New Plan",
+                FontSize = 20,
+                FontWeight = FontWeights.Light,
+                Foreground = (System.Windows.Media.Brush)FindResource("ForegroundMutedBrush"),
+                HorizontalAlignment = HorizontalAlignment.Center
+            });
+            emptyStack.Children.Add(new TextBlock
+            {
+                Text = "Open or paste execution plan XML to render it",
+                FontSize = 13,
+                Foreground = (System.Windows.Media.Brush)FindResource("ForegroundMutedBrush"),
+                HorizontalAlignment = HorizontalAlignment.Center,
+                Margin = new Thickness(0, 8, 0, 0)
+            });
+            var btnPanel = new StackPanel { Orientation = Orientation.Horizontal, HorizontalAlignment = HorizontalAlignment.Center, Margin = new Thickness(0, 20, 0, 0) };
+            var openBtn = new Button { Content = "Open .sqlplan File", Height = 28, Padding = new Thickness(12, 0, 12, 0), ToolTip = "Open a .sqlplan or .xml file from disk" };
+            var pasteBtn = new Button { Content = "Paste XML", Height = 28, Padding = new Thickness(12, 0, 12, 0), Margin = new Thickness(8, 0, 0, 0), ToolTip = "Paste execution plan XML to render it (or use Ctrl+V)" };
+            btnPanel.Children.Add(openBtn);
+            btnPanel.Children.Add(pasteBtn);
+            emptyStack.Children.Add(btnPanel);
+            emptyStack.Children.Add(new TextBlock
+            {
+                Text = "or drag & drop a .sqlplan file anywhere in this area",
+                FontSize = 11,
+                Foreground = (System.Windows.Media.Brush)FindResource("ForegroundMutedBrush"),
+                HorizontalAlignment = HorizontalAlignment.Center,
+                Margin = new Thickness(0, 12, 0, 0)
+            });
+            emptyState.Children.Add(dashedRect);
+            emptyState.Children.Add(emptyStack);
+
+            // --- Viewer layer (hidden until a plan is loaded) ---
+            var viewer = new Controls.PlanViewerControl
+            {
+                Visibility = Visibility.Collapsed
+            };
+
+            // Sub-tab content grid: index 0 = emptyState, index 1 = viewer
+            var subTabContent = new Grid();
+            subTabContent.Children.Add(emptyState);
+            subTabContent.Children.Add(viewer);
+
+            // --- Sub-tab header: label + close button ---
+            var initialLabel = GetUniqueSubTabLabel("New Plan");
+            var labelBlock = new TextBlock
+            {
+                Text = initialLabel,
+                VerticalAlignment = VerticalAlignment.Center,
+                ToolTip = initialLabel
+            };
+            var subCloseBtn = new Button { Style = (Style)FindResource("TabCloseButton") };
+            var subTabHeader = new StackPanel { Orientation = Orientation.Horizontal };
+            subTabHeader.Children.Add(labelBlock);
+            subTabHeader.Children.Add(subCloseBtn);
+
+            var subTab = new TabItem { Header = subTabHeader, Content = subTabContent };
+
+            subCloseBtn.Tag = subTab;
+            subCloseBtn.Click += (_, _) =>
+            {
+                _mainPlanTabControl!.Items.Remove(subTab);
+                // If only the "+" tab remains, re-open a fresh empty sub-tab
+                if (_mainPlanTabControl.Items.Count == 1 &&
+                    _mainPlanTabControl.Items[0] is TabItem { Tag: string t2 } && t2 == PlanAddTabId)
+                {
+                    AddNewEmptyPlanSubTab();
+                }
+            };
+
+            // Wire per-sub-tab buttons with closures over this sub-tab
+            openBtn.Click += (_, _) =>
+            {
+                var dialog = new Microsoft.Win32.OpenFileDialog
+                {
+                    Filter = "SQL Plan Files (*.sqlplan)|*.sqlplan|XML Files (*.xml)|*.xml|All Files (*.*)|*.*",
+                    DefaultExt = ".sqlplan"
+                };
+                if (dialog.ShowDialog() != true) return;
+                try
+                {
+                    var xml = System.IO.File.ReadAllText(dialog.FileName);
+                    LoadPlanIntoSubTab(subTab, xml, System.IO.Path.GetFileName(dialog.FileName));
+                }
+                catch (Exception ex)
+                {
+                    MessageBox.Show($"Failed to open file:\n\n{ex.Message}", "Error",
+                        MessageBoxButton.OK, MessageBoxImage.Error);
+                }
+            };
+
+            pasteBtn.Click += (_, _) =>
+            {
+                var xml = Clipboard.GetText();
+                if (!string.IsNullOrWhiteSpace(xml))
+                {
+                    LoadPlanIntoSubTab(subTab, xml, "Pasted Plan");
+                    return;
+                }
+                MessageBox.Show("The clipboard does not contain any text.", "Paste Plan XML",
+                    MessageBoxButton.OK, MessageBoxImage.Information);
+            };
+
+            // Insert before the "+" tab
+            var addTabIndex = -1;
+            for (var i = 0; i < _mainPlanTabControl!.Items.Count; i++)
+            {
+                if (_mainPlanTabControl.Items[i] is TabItem { Tag: string t3 } && t3 == PlanAddTabId)
+                {
+                    addTabIndex = i;
+                    break;
+                }
+            }
+            if (addTabIndex >= 0)
+                _mainPlanTabControl.Items.Insert(addTabIndex, subTab);
+            else
+                _mainPlanTabControl.Items.Add(subTab);
+
+            _mainPlanTabControl.SelectedItem = subTab;
+            return subTab;
+        }
+
+        /// <summary>
+        /// Loads plan XML into an existing sub-tab (replacing whatever was there before).
+        /// Updates the sub-tab header label and shows the viewer layer.
+        /// </summary>
+        private void LoadPlanIntoSubTab(TabItem subTab, string planXml, string label, string? queryText = null)
+        {
+            try { System.Xml.Linq.XDocument.Parse(planXml); }
+            catch (System.Xml.XmlException ex)
+            {
+                MessageBox.Show(
+                    $"The plan XML is not valid:\n\n{ex.Message}",
+                    "Invalid Plan XML",
+                    MessageBoxButton.OK,
+                    MessageBoxImage.Warning);
+                return;
+            }
+
+            if (subTab.Content is not Grid subTabContent) return;
+            if (subTabContent.Children.Count < 2) return;
+
+            var emptyState = subTabContent.Children[0] as FrameworkElement;
+            var viewer = subTabContent.Children[1] as Controls.PlanViewerControl;
+            if (viewer == null) return;
+
+            viewer.LoadPlan(planXml, label, queryText);
+            emptyState!.Visibility = Visibility.Collapsed;
+            viewer.Visibility = Visibility.Visible;
+
+            // Update header label (unique)
+            var uniqueLabel = GetUniqueSubTabLabel(label);
+            if (subTab.Header is StackPanel headerPanel &&
+                headerPanel.Children[0] is TextBlock headerLabel)
+            {
+                headerLabel.Text = uniqueLabel.Length > 30 ? uniqueLabel[..30] + "\u2026" : uniqueLabel;
+                headerLabel.ToolTip = uniqueLabel;
+            }
+        }
+
+        /// <summary>
+        /// Returns a label that is unique among current inner plan sub-tab headers.
+        /// If <paramref name="baseLabel"/> is already taken, appends " (1)", " (2)", …
+        /// </summary>
+        private string GetUniqueSubTabLabel(string baseLabel)
+        {
+            var existing = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+            foreach (var item in _mainPlanTabControl!.Items)
+            {
+                if (item is TabItem { Tag: string t } && t == PlanAddTabId) continue;
+                if (item is TabItem subTab &&
+                    subTab.Header is StackPanel sp &&
+                    sp.Children[0] is TextBlock tb)
+                    existing.Add(tb.ToolTip as string ?? tb.Text);
+            }
+            if (!existing.Contains(baseLabel)) return baseLabel;
+            var counter = 1;
+            string candidate;
+            do { candidate = $"{baseLabel} ({counter++})"; }
+            while (existing.Contains(candidate));
+            return candidate;
+        }
+
+        /// <summary>
+        /// Returns the currently active real plan sub-tab (skips the "+" tab).
+        /// </summary>
+        private TabItem? GetActivePlanSubTab()
+        {
+            if (_mainPlanTabControl == null) return null;
+            if (_mainPlanTabControl.SelectedItem is TabItem { Tag: string t } && t == PlanAddTabId)
+                return null;
+            return _mainPlanTabControl.SelectedItem as TabItem;
+        }
+
+        public void OpenMainWindowPlanTab(string planXml, string label, string? queryText = null)
+        {
+            if (_planViewerTab == null || !ServerTabControl.Items.Contains(_planViewerTab))
+                OpenPlanViewerTab();
+
+            var activeSubTab = GetActivePlanSubTab();
+            if (activeSubTab?.Content is Grid g &&
+                g.Children.Count >= 2 &&
+                g.Children[1] is Controls.PlanViewerControl { Visibility: Visibility.Collapsed })
+            {
+                // Active sub-tab is empty — load into it
+                LoadPlanIntoSubTab(activeSubTab, planXml, label, queryText);
+            }
+            else
+            {
+                // Active sub-tab already has a plan — open a new one
+                var newSubTab = AddNewEmptyPlanSubTab();
+                LoadPlanIntoSubTab(newSubTab, planXml, label, queryText);
+            }
+
+            ServerTabControl.SelectedItem = _planViewerTab;
+        }
+
+        private void MainWindowPlanViewer_DragOver(object sender, DragEventArgs e)
+        {
+            if (e.Data.GetDataPresent(DataFormats.FileDrop))
+            {
+                var files = e.Data.GetData(DataFormats.FileDrop) as string[];
+                if (files?.Length > 0 && IsPlanFile(files[0]))
+                {
+                    e.Effects = DragDropEffects.Copy;
+                    e.Handled = true;
+                    return;
+                }
+            }
+            e.Effects = DragDropEffects.None;
+            e.Handled = true;
+        }
+
+        private void MainWindowPlanViewer_Drop(object sender, DragEventArgs e)
+        {
+            if (!e.Data.GetDataPresent(DataFormats.FileDrop)) return;
+            var files = e.Data.GetData(DataFormats.FileDrop) as string[];
+            if (files?.Length > 0 && IsPlanFile(files[0]))
+                LoadMainWindowPlanFromFileIntoActiveTab(files[0]);
+        }
+
+        private void MainWindowPlanViewer_KeyDown(object sender, System.Windows.Input.KeyEventArgs e)
+        {
+            if (e.Key == System.Windows.Input.Key.V &&
+                System.Windows.Input.Keyboard.Modifiers == System.Windows.Input.ModifierKeys.Control &&
+                e.OriginalSource is not System.Windows.Controls.TextBox)
+            {
+                var xml = Clipboard.GetText();
+                if (!string.IsNullOrWhiteSpace(xml))
+                {
+                    e.Handled = true;
+                    LoadPlanIntoActivePlanSubTab(xml, "Pasted Plan");
+                }
+            }
+        }
+
+        private void LoadMainWindowPlanFromFileIntoActiveTab(string path)
+        {
+            try
+            {
+                var xml = System.IO.File.ReadAllText(path);
+                LoadPlanIntoActivePlanSubTab(xml, System.IO.Path.GetFileName(path));
+            }
+            catch (Exception ex)
+            {
+                MessageBox.Show($"Failed to open file:\n\n{ex.Message}", "Error",
+                    MessageBoxButton.OK, MessageBoxImage.Error);
+            }
+        }
+
+        private void LoadPlanIntoActivePlanSubTab(string planXml, string label)
+        {
+            var activeSubTab = GetActivePlanSubTab();
+            if (activeSubTab != null)
+                LoadPlanIntoSubTab(activeSubTab, planXml, label);
+        }
+
+        private static bool IsPlanFile(string path)
+        {
+            var ext = System.IO.Path.GetExtension(path);
+            return string.Equals(ext, ".sqlplan", StringComparison.OrdinalIgnoreCase)
+                || string.Equals(ext, ".xml", StringComparison.OrdinalIgnoreCase);
+        }
+
+        #endregion
     }
 }
diff --git a/Dashboard/ServerTab.xaml b/Dashboard/ServerTab.xaml
index c9bffc01..571d5ed4 100644
--- a/Dashboard/ServerTab.xaml
+++ b/Dashboard/ServerTab.xaml
@@ -412,15 +412,28 @@
 
             <!-- Plan Viewer Tab -->
             <TabItem Header="Plan Viewer" x:Name="PlanViewerTabItem">
-                <Grid>
-                    <StackPanel x:Name="PlanEmptyState" HorizontalAlignment="Center"
-                                VerticalAlignment="Center">
-                        <TextBlock Text="No Plan Loaded" FontSize="20" FontWeight="Light"
-                                   Foreground="{DynamicResource ForegroundMutedBrush}" HorizontalAlignment="Center"/>
-                        <TextBlock Text="Right-click a query row and choose 'View Plan' or 'Get Actual Plan'"
-                                   FontSize="13" Foreground="{DynamicResource ForegroundMutedBrush}"
-                                   HorizontalAlignment="Center" Margin="0,8,0,0"/>
-                    </StackPanel>
+                <Grid Background="Transparent">
+                    <Grid x:Name="PlanEmptyState">
+                        <!-- Dashed drop-zone border fills the whole tab -->
+                        <Rectangle Margin="24"
+                                   Stroke="{DynamicResource ForegroundMutedBrush}"
+                                   StrokeThickness="1.5"
+                                   StrokeDashArray="6,4"
+                                   RadiusX="10" RadiusY="10"
+                                   Opacity="0.25"/>
+                        <!-- Centered content -->
+                        <StackPanel HorizontalAlignment="Center" VerticalAlignment="Center">
+                            <TextBlock Text="&#xE896;" FontFamily="Segoe MDL2 Assets" FontSize="52"
+                                       HorizontalAlignment="Center"
+                                       Foreground="{DynamicResource ForegroundMutedBrush}" Opacity="0.45"
+                                       Margin="0,0,0,12"/>
+                            <TextBlock Text="No Plan Loaded" FontSize="20" FontWeight="Light"
+                                       Foreground="{DynamicResource ForegroundMutedBrush}" HorizontalAlignment="Center"/>
+                            <TextBlock Text="Right-click a query row and choose 'View Plan' or 'Get Actual Plan'"
+                                       FontSize="13" Foreground="{DynamicResource ForegroundMutedBrush}"
+                                       HorizontalAlignment="Center" Margin="0,8,0,0"/>
+                        </StackPanel>
+                    </Grid>
                     <StackPanel x:Name="PlanLoadingState" HorizontalAlignment="Center"
                                 VerticalAlignment="Center" Visibility="Collapsed">
                         <ProgressBar IsIndeterminate="True" Width="200" Height="4" Margin="0,0,0,12"/>
diff --git a/Dashboard/ServerTab.xaml.cs b/Dashboard/ServerTab.xaml.cs
index 027631bc..390ccc79 100644
--- a/Dashboard/ServerTab.xaml.cs
+++ b/Dashboard/ServerTab.xaml.cs
@@ -169,6 +169,20 @@ private void CancelPlanButton_Click(object sender, RoutedEventArgs e)
 
         private void OpenPlanTab(string planXml, string label, string? queryText = null)
         {
+            try
+            {
+                System.Xml.Linq.XDocument.Parse(planXml);
+            }
+            catch (System.Xml.XmlException ex)
+            {
+                MessageBox.Show(
+                    $"The plan XML is not valid:\n\n{ex.Message}",
+                    "Invalid Plan XML",
+                    MessageBoxButton.OK,
+                    MessageBoxImage.Warning);
+                return;
+            }
+
             HidePlanLoading();
             var viewer = new Controls.PlanViewerControl();
             viewer.LoadPlan(planXml, label, queryText);
@@ -446,6 +460,19 @@ private async void ServerTab_KeyDown(object sender, System.Windows.Input.KeyEven
                     e.Handled = true;
                     await LoadDataAsync();
                 }
+                else if (e.Key == System.Windows.Input.Key.V &&
+                         System.Windows.Input.Keyboard.Modifiers == System.Windows.Input.ModifierKeys.Control &&
+                         e.OriginalSource is not System.Windows.Controls.TextBox &&
+                         PlanViewerTabItem.IsSelected)
+                {
+                    var xml = System.Windows.Clipboard.GetText();
+                    if (!string.IsNullOrWhiteSpace(xml))
+                    {
+                        e.Handled = true;
+                        OpenPlanTab(xml, "Pasted Plan");
+                        PlanViewerTabItem.IsSelected = true;
+                    }
+                }
             }
             catch (Exception ex)
             {
diff --git a/Lite/Controls/PlanViewerControl.xaml b/Lite/Controls/PlanViewerControl.xaml
index cb398e19..322b6b22 100644
--- a/Lite/Controls/PlanViewerControl.xaml
+++ b/Lite/Controls/PlanViewerControl.xaml
@@ -1,7 +1,10 @@
 <UserControl x:Class="PerformanceMonitorLite.Controls.PlanViewerControl"
              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-             Background="{DynamicResource BackgroundBrush}">
+             Background="{DynamicResource BackgroundBrush}"
+             Focusable="True"
+             PreviewMouseDown="PlanViewerControl_PreviewMouseDown"
+             PreviewKeyDown="PlanViewerControl_PreviewKeyDown">
     <Grid>
         <Grid.RowDefinitions>
             <RowDefinition Height="Auto"/>
diff --git a/Lite/Controls/PlanViewerControl.xaml.cs b/Lite/Controls/PlanViewerControl.xaml.cs
index 69e639da..0e6f1838 100644
--- a/Lite/Controls/PlanViewerControl.xaml.cs
+++ b/Lite/Controls/PlanViewerControl.xaml.cs
@@ -1441,6 +1441,38 @@ private void PlanScrollViewer_PreviewMouseWheel(object sender, MouseWheelEventAr
         }
     }
 
+    private void PlanViewerControl_PreviewMouseDown(object sender, MouseButtonEventArgs e)
+    {
+        Focus();
+    }
+
+    private void PlanViewerControl_PreviewKeyDown(object sender, KeyEventArgs e)
+    {
+        if (e.Key == Key.V && Keyboard.Modifiers == ModifierKeys.Control
+            && e.OriginalSource is not TextBox)
+        {
+            var text = Clipboard.GetText();
+            if (!string.IsNullOrWhiteSpace(text))
+            {
+                e.Handled = true;
+                try
+                {
+                    System.Xml.Linq.XDocument.Parse(text);
+                }
+                catch (System.Xml.XmlException ex)
+                {
+                    MessageBox.Show(
+                        $"The plan XML is not valid:\n\n{ex.Message}",
+                        "Invalid Plan XML",
+                        MessageBoxButton.OK,
+                        MessageBoxImage.Warning);
+                    return;
+                }
+                LoadPlan(text, "Pasted Plan");
+            }
+        }
+    }
+
     #endregion
 
     #region Save & Statement Selection
diff --git a/Lite/Controls/ServerTab.xaml b/Lite/Controls/ServerTab.xaml
index 8ba12c32..3a41d101 100644
--- a/Lite/Controls/ServerTab.xaml
+++ b/Lite/Controls/ServerTab.xaml
@@ -656,15 +656,28 @@
 
             <!-- Plan Viewer Tab -->
             <TabItem Header="Plan Viewer" x:Name="PlanViewerTabItem">
-                <Grid>
-                    <StackPanel x:Name="PlanEmptyState" HorizontalAlignment="Center"
-                                VerticalAlignment="Center">
-                        <TextBlock Text="No Plan Loaded" FontSize="20" FontWeight="Light"
-                                   Foreground="{DynamicResource ForegroundMutedBrush}" HorizontalAlignment="Center"/>
-                        <TextBlock Text="Right-click a query row and choose 'View Plan' or 'Get Actual Plan'"
-                                   FontSize="13" Foreground="{DynamicResource ForegroundMutedBrush}"
-                                   HorizontalAlignment="Center" Margin="0,8,0,0"/>
-                    </StackPanel>
+                <Grid Background="Transparent">
+                    <Grid x:Name="PlanEmptyState">
+                        <!-- Dashed drop-zone border fills the whole tab -->
+                        <Rectangle Margin="24"
+                                   Stroke="{DynamicResource ForegroundMutedBrush}"
+                                   StrokeThickness="1.5"
+                                   StrokeDashArray="6,4"
+                                   RadiusX="10" RadiusY="10"
+                                   Opacity="0.25"/>
+                        <!-- Centered content -->
+                        <StackPanel HorizontalAlignment="Center" VerticalAlignment="Center">
+                            <TextBlock Text="&#xE896;" FontFamily="Segoe MDL2 Assets" FontSize="52"
+                                       HorizontalAlignment="Center"
+                                       Foreground="{DynamicResource ForegroundMutedBrush}" Opacity="0.45"
+                                       Margin="0,0,0,12"/>
+                            <TextBlock Text="No Plan Loaded" FontSize="20" FontWeight="Light"
+                                       Foreground="{DynamicResource ForegroundMutedBrush}" HorizontalAlignment="Center"/>
+                            <TextBlock Text="Right-click a query row and choose 'View Plan' or 'Get Actual Plan'"
+                                       FontSize="13" Foreground="{DynamicResource ForegroundMutedBrush}"
+                                       HorizontalAlignment="Center" Margin="0,8,0,0"/>
+                        </StackPanel>
+                    </Grid>
                     <StackPanel x:Name="PlanLoadingState" HorizontalAlignment="Center"
                                 VerticalAlignment="Center" Visibility="Collapsed">
                         <ProgressBar IsIndeterminate="True" Width="200" Height="4" Margin="0,0,0,12"/>
diff --git a/Lite/Controls/ServerTab.xaml.cs b/Lite/Controls/ServerTab.xaml.cs
index 800d2a87..87ff451b 100644
--- a/Lite/Controls/ServerTab.xaml.cs
+++ b/Lite/Controls/ServerTab.xaml.cs
@@ -2726,6 +2726,20 @@ private void HidePlanLoading()
 
     private void OpenPlanTab(string planXml, string label, string? queryText = null)
     {
+        try
+        {
+            System.Xml.Linq.XDocument.Parse(planXml);
+        }
+        catch (System.Xml.XmlException ex)
+        {
+            MessageBox.Show(
+                $"The plan XML is not valid:\n\n{ex.Message}",
+                "Invalid Plan XML",
+                MessageBoxButton.OK,
+                MessageBoxImage.Warning);
+            return;
+        }
+
         HidePlanLoading();
         var viewer = new PlanViewerControl();
         viewer.LoadPlan(planXml, label, queryText);
diff --git a/Lite/MainWindow.xaml b/Lite/MainWindow.xaml
index 4db4f1b8..9240b39e 100644
--- a/Lite/MainWindow.xaml
+++ b/Lite/MainWindow.xaml
@@ -156,10 +156,18 @@
                 </ListView>
 
                 <!-- Sidebar Footer -->
-                <Border Grid.Row="2" Padding="12" Background="{DynamicResource BackgroundLightBrush}">
+                <Border Grid.Row="2" Padding="12" Background="{DynamicResource BackgroundLightBrush}"
+                        BorderBrush="{DynamicResource BorderBrush}" BorderThickness="0,1,0,0">
                     <StackPanel>
                         <Button x:Name="AddServerButton" Content="+ Add Server" Click="AddServerButton_Click"/>
                         <Button x:Name="ManageServersButton" Content="Manage Servers" Click="ManageServersButton_Click" Margin="0,8,0,0"/>
+                        <Button Click="OpenPlanViewerButton_Click" Margin="0,8,0,0"
+                                ToolTip="Open or paste an execution plan (independent of any server)">
+                            <StackPanel Orientation="Horizontal">
+                                <TextBlock Text="&#x1F50D;" FontSize="12" VerticalAlignment="Center" Margin="0,0,6,0"/>
+                                <TextBlock Text="Open Plan Viewer" VerticalAlignment="Center"/>
+                            </StackPanel>
+                        </Button>
                         <Button x:Name="SettingsButton" Click="SettingsButton_Click" Margin="0,8,0,0">
                             <StackPanel Orientation="Horizontal">
                                 <TextBlock Text="&#xE713;" FontFamily="Segoe MDL2 Assets" FontSize="12" VerticalAlignment="Center" Margin="0,0,6,0"/>
@@ -271,6 +279,24 @@
                     <TabItem Header="Alert History" x:Name="AlertsTab">
                         <controls:AlertsHistoryTab x:Name="AlertsHistoryContent"/>
                     </TabItem>
+                    <TabItem x:Name="MainWindowPlanViewerTab" Visibility="Collapsed">
+                        <TabItem.Header>
+                            <StackPanel Orientation="Horizontal">
+                                <TextBlock Text="Plan Viewer" VerticalAlignment="Center" FontWeight="SemiBold"/>
+                                <Button Style="{DynamicResource TabCloseButton}"
+                                        Click="MainWindowPlanViewerClose_Click"
+                                        Margin="4,0,0,0"/>
+                            </StackPanel>
+                        </TabItem.Header>
+                        <Grid AllowDrop="True" PreviewDrop="MainWindowPlanViewer_Drop"
+                              PreviewDragOver="MainWindowPlanViewer_DragOver"
+                              Background="Transparent"
+                              Focusable="True" KeyDown="MainWindowPlanViewer_KeyDown">
+                            <TabControl x:Name="MainWindowPlanTabControl"
+                                        Background="Transparent"
+                                        BorderThickness="0"/>
+                        </Grid>
+                    </TabItem>
                 </TabControl>
             </Grid>
 
diff --git a/Lite/MainWindow.xaml.cs b/Lite/MainWindow.xaml.cs
index 0c8427d6..beba2b76 100644
--- a/Lite/MainWindow.xaml.cs
+++ b/Lite/MainWindow.xaml.cs
@@ -1449,4 +1449,390 @@ private static string FormatDuration(long seconds)
             if (seconds < 3600) return $"{seconds / 60}m {seconds % 60}s";
             return $"{seconds / 3600}h {(seconds % 3600) / 60}m";
         }
+
+        private void OpenPlanViewerButton_Click(object sender, RoutedEventArgs e)
+        {
+            EnsurePlanTabControlInitialized();
+            EmptyStatePanel.Visibility = Visibility.Collapsed;
+            ServerTabControl.Visibility = Visibility.Visible;
+            MainWindowPlanViewerTab.Visibility = Visibility.Visible;
+            if (MainWindowPlanViewerTab.IsSelected)
+            {
+                // Already on Plan Viewer — just add a new empty sub-tab
+                AddNewEmptyPlanSubTab();
+            }
+            else
+            {
+                MainWindowPlanViewerTab.IsSelected = true;
+                AddNewEmptyPlanSubTab();
+            }
+            Dispatcher.BeginInvoke(DispatcherPriority.Loaded, new Action(() => MainWindowPlanTabControl.Focus()));
+        }
+
+        private void MainWindowPlanViewerClose_Click(object sender, RoutedEventArgs e)
+        {
+            // Reset inner tab control so next open starts fresh
+            MainWindowPlanTabControl.Items.Clear();
+            _planTabControlInitialized = false;
+            MainWindowPlanViewerTab.Visibility = Visibility.Collapsed;
+            // Select first visible tab
+            foreach (TabItem item in ServerTabControl.Items)
+            {
+                if (item.Visibility == Visibility.Visible && item != MainWindowPlanViewerTab)
+                {
+                    item.IsSelected = true;
+                    break;
+                }
+            }
+        }
+
+        #region Main Window Plan Viewer
+
+        private const string LitePlanAddTabId = "__PLAN_ADD_TAB__";
+        private bool _planTabControlInitialized;
+
+        private void EnsurePlanTabControlInitialized()
+        {
+            if (_planTabControlInitialized) return;
+            _planTabControlInitialized = true;
+
+            // "+" tab at the end
+            var addTabHeader = new TextBlock
+            {
+                Text = "+",
+                FontSize = 14,
+                FontWeight = FontWeights.Bold,
+                VerticalAlignment = VerticalAlignment.Center,
+                ToolTip = "Open a new plan sub-tab"
+            };
+            var addTab = new TabItem
+            {
+                Header = addTabHeader,
+                Tag = LitePlanAddTabId,
+                Content = new Grid()
+            };
+            MainWindowPlanTabControl.Items.Add(addTab);
+
+            MainWindowPlanTabControl.SelectionChanged += (_, _) =>
+            {
+                if (MainWindowPlanTabControl.SelectedItem is TabItem { Tag: string t } && t == LitePlanAddTabId)
+                {
+                    var newSub = AddNewEmptyPlanSubTab();
+                    MainWindowPlanTabControl.SelectedItem = newSub;
+                }
+            };
+        }
+
+        /// <summary>
+        /// Adds a new empty "New Plan" sub-tab to the inner plan TabControl and selects it.
+        /// Returns the newly created sub-tab.
+        /// </summary>
+        private TabItem AddNewEmptyPlanSubTab()
+        {
+            EnsurePlanTabControlInitialized();
+
+            // --- Empty state layer ---
+            var emptyState = new Grid();
+            var dashedRect = new System.Windows.Shapes.Rectangle
+            {
+                Margin = new Thickness(24),
+                Stroke = (System.Windows.Media.Brush)FindResource("ForegroundMutedBrush"),
+                StrokeThickness = 1.5,
+                StrokeDashArray = new System.Windows.Media.DoubleCollection { 6, 4 },
+                RadiusX = 10, RadiusY = 10,
+                Opacity = 0.25
+            };
+            var emptyStack = new StackPanel { HorizontalAlignment = HorizontalAlignment.Center, VerticalAlignment = VerticalAlignment.Center };
+            emptyStack.Children.Add(new TextBlock
+            {
+                Text = "\uE896",
+                FontFamily = new System.Windows.Media.FontFamily("Segoe MDL2 Assets"),
+                FontSize = 52,
+                HorizontalAlignment = HorizontalAlignment.Center,
+                Foreground = (System.Windows.Media.Brush)FindResource("ForegroundMutedBrush"),
+                Opacity = 0.45,
+                Margin = new Thickness(0, 0, 0, 12)
+            });
+            emptyStack.Children.Add(new TextBlock
+            {
+                Text = "New Plan",
+                FontSize = 20,
+                FontWeight = FontWeights.Light,
+                Foreground = (System.Windows.Media.Brush)FindResource("ForegroundMutedBrush"),
+                HorizontalAlignment = HorizontalAlignment.Center
+            });
+            emptyStack.Children.Add(new TextBlock
+            {
+                Text = "Open or paste execution plan XML to render it",
+                FontSize = 13,
+                Foreground = (System.Windows.Media.Brush)FindResource("ForegroundMutedBrush"),
+                HorizontalAlignment = HorizontalAlignment.Center,
+                Margin = new Thickness(0, 8, 0, 0)
+            });
+            var btnPanel = new StackPanel { Orientation = Orientation.Horizontal, HorizontalAlignment = HorizontalAlignment.Center, Margin = new Thickness(0, 20, 0, 0) };
+            var openBtn = new Button { Content = "Open .sqlplan File", Height = 28, Padding = new Thickness(12, 0, 12, 0), ToolTip = "Open a .sqlplan or .xml file from disk" };
+            var pasteBtn = new Button { Content = "Paste XML", Height = 28, Padding = new Thickness(12, 0, 12, 0), Margin = new Thickness(8, 0, 0, 0), ToolTip = "Paste execution plan XML to render it (or use Ctrl+V)" };
+            btnPanel.Children.Add(openBtn);
+            btnPanel.Children.Add(pasteBtn);
+            emptyStack.Children.Add(btnPanel);
+            emptyStack.Children.Add(new TextBlock
+            {
+                Text = "or drag & drop a .sqlplan file anywhere in this area",
+                FontSize = 11,
+                Foreground = (System.Windows.Media.Brush)FindResource("ForegroundMutedBrush"),
+                HorizontalAlignment = HorizontalAlignment.Center,
+                Margin = new Thickness(0, 12, 0, 0)
+            });
+            emptyState.Children.Add(dashedRect);
+            emptyState.Children.Add(emptyStack);
+
+            // --- Viewer layer (hidden until a plan is loaded) ---
+            var viewer = new Controls.PlanViewerControl
+            {
+                Visibility = Visibility.Collapsed
+            };
+
+            // Sub-tab content grid: index 0 = emptyState, index 1 = viewer
+            var subTabContent = new Grid();
+            subTabContent.Children.Add(emptyState);
+            subTabContent.Children.Add(viewer);
+
+            // --- Sub-tab header: label + close button ---
+            var initialLabel = GetUniqueSubTabLabel("New Plan");
+            var labelBlock = new TextBlock
+            {
+                Text = initialLabel,
+                VerticalAlignment = VerticalAlignment.Center,
+                ToolTip = initialLabel
+            };
+            var subCloseBtn = new Button { Style = (Style)FindResource("TabCloseButton") };
+            var subTabHeader = new StackPanel { Orientation = Orientation.Horizontal };
+            subTabHeader.Children.Add(labelBlock);
+            subTabHeader.Children.Add(subCloseBtn);
+
+            var subTab = new TabItem { Header = subTabHeader, Content = subTabContent };
+
+            subCloseBtn.Tag = subTab;
+            subCloseBtn.Click += (_, _) =>
+            {
+                MainWindowPlanTabControl.Items.Remove(subTab);
+                // If only the "+" tab remains, open a fresh empty sub-tab
+                if (MainWindowPlanTabControl.Items.Count == 1 &&
+                    MainWindowPlanTabControl.Items[0] is TabItem { Tag: string t2 } && t2 == LitePlanAddTabId)
+                {
+                    AddNewEmptyPlanSubTab();
+                }
+            };
+
+            // Wire per-sub-tab buttons
+            openBtn.Click += (_, _) =>
+            {
+                var dialog = new Microsoft.Win32.OpenFileDialog
+                {
+                    Filter = "SQL Plan Files (*.sqlplan)|*.sqlplan|XML Files (*.xml)|*.xml|All Files (*.*)|*.*",
+                    DefaultExt = ".sqlplan"
+                };
+                if (dialog.ShowDialog() != true) return;
+                try
+                {
+                    var xml = System.IO.File.ReadAllText(dialog.FileName);
+                    LoadPlanIntoSubTab(subTab, xml, System.IO.Path.GetFileName(dialog.FileName));
+                }
+                catch (Exception ex)
+                {
+                    MessageBox.Show($"Failed to open file:\n\n{ex.Message}", "Error",
+                        MessageBoxButton.OK, MessageBoxImage.Error);
+                }
+            };
+
+            pasteBtn.Click += (_, _) =>
+            {
+                var xml = Clipboard.GetText();
+                if (!string.IsNullOrWhiteSpace(xml))
+                {
+                    LoadPlanIntoSubTab(subTab, xml, "Pasted Plan");
+                    return;
+                }
+                MessageBox.Show("The clipboard does not contain any text.", "Paste Plan XML",
+                    MessageBoxButton.OK, MessageBoxImage.Information);
+            };
+
+            // Insert before "+" tab
+            var addTabIndex = -1;
+            for (var i = 0; i < MainWindowPlanTabControl.Items.Count; i++)
+            {
+                if (MainWindowPlanTabControl.Items[i] is TabItem { Tag: string t3 } && t3 == LitePlanAddTabId)
+                {
+                    addTabIndex = i;
+                    break;
+                }
+            }
+            if (addTabIndex >= 0)
+                MainWindowPlanTabControl.Items.Insert(addTabIndex, subTab);
+            else
+                MainWindowPlanTabControl.Items.Add(subTab);
+
+            MainWindowPlanTabControl.SelectedItem = subTab;
+            return subTab;
+        }
+
+        /// <summary>
+        /// Loads plan XML into an existing sub-tab (replacing whatever was there before).
+        /// </summary>
+        private void LoadPlanIntoSubTab(TabItem subTab, string planXml, string label, string? queryText = null)
+        {
+            try { System.Xml.Linq.XDocument.Parse(planXml); }
+            catch (System.Xml.XmlException ex)
+            {
+                MessageBox.Show(
+                    $"The plan XML is not valid:\n\n{ex.Message}",
+                    "Invalid Plan XML",
+                    MessageBoxButton.OK,
+                    MessageBoxImage.Warning);
+                return;
+            }
+
+            if (subTab.Content is not Grid subTabContent) return;
+            if (subTabContent.Children.Count < 2) return;
+
+            var emptyState = subTabContent.Children[0] as FrameworkElement;
+            var viewer = subTabContent.Children[1] as Controls.PlanViewerControl;
+            if (viewer == null) return;
+
+            viewer.LoadPlan(planXml, label, queryText);
+            emptyState!.Visibility = Visibility.Collapsed;
+            viewer.Visibility = Visibility.Visible;
+
+            var uniqueLabel = GetUniqueSubTabLabel(label);
+            if (subTab.Header is StackPanel headerPanel &&
+                headerPanel.Children[0] is TextBlock headerLabel)
+            {
+                headerLabel.Text = uniqueLabel.Length > 30 ? uniqueLabel[..30] + "\u2026" : uniqueLabel;
+                headerLabel.ToolTip = uniqueLabel;
+            }
+        }
+
+        /// <summary>
+        /// Returns a label that is unique among current inner plan sub-tab headers.
+        /// If <paramref name="baseLabel"/> is already taken, appends " (1)", " (2)", …
+        /// </summary>
+        private string GetUniqueSubTabLabel(string baseLabel)
+        {
+            var existing = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+            foreach (var item in MainWindowPlanTabControl.Items)
+            {
+                if (item is TabItem { Tag: string t } && t == LitePlanAddTabId) continue;
+                if (item is TabItem subTab &&
+                    subTab.Header is StackPanel sp &&
+                    sp.Children[0] is TextBlock tb)
+                    existing.Add(tb.ToolTip as string ?? tb.Text);
+            }
+            if (!existing.Contains(baseLabel)) return baseLabel;
+            var counter = 1;
+            string candidate;
+            do { candidate = $"{baseLabel} ({counter++})"; }
+            while (existing.Contains(candidate));
+            return candidate;
+        }
+
+        /// <summary>
+        /// Returns the currently active real plan sub-tab (skips the "+" tab).
+        /// </summary>
+        private TabItem? GetActivePlanSubTab()
+        {
+            if (MainWindowPlanTabControl.SelectedItem is TabItem { Tag: string t } && t == LitePlanAddTabId)
+                return null;
+            return MainWindowPlanTabControl.SelectedItem as TabItem;
+        }
+
+        public void OpenMainWindowPlanTab(string planXml, string label, string? queryText = null)
+        {
+            EnsurePlanTabControlInitialized();
+            MainWindowPlanViewerTab.Visibility = Visibility.Visible;
+
+            var activeSubTab = GetActivePlanSubTab();
+            if (activeSubTab?.Content is Grid g &&
+                g.Children.Count >= 2 &&
+                g.Children[1] is Controls.PlanViewerControl { Visibility: Visibility.Collapsed })
+            {
+                LoadPlanIntoSubTab(activeSubTab, planXml, label, queryText);
+            }
+            else
+            {
+                var newSubTab = AddNewEmptyPlanSubTab();
+                LoadPlanIntoSubTab(newSubTab, planXml, label, queryText);
+            }
+
+            MainWindowPlanViewerTab.IsSelected = true;
+            ServerTabControl.Visibility = Visibility.Visible;
+        }
+
+        private void MainWindowPlanViewer_DragOver(object sender, DragEventArgs e)
+        {
+            if (e.Data.GetDataPresent(DataFormats.FileDrop))
+            {
+                var files = e.Data.GetData(DataFormats.FileDrop) as string[];
+                if (files?.Length > 0 && IsPlanFile(files[0]))
+                {
+                    e.Effects = DragDropEffects.Copy;
+                    e.Handled = true;
+                    return;
+                }
+            }
+            e.Effects = DragDropEffects.None;
+            e.Handled = true;
+        }
+
+        private void MainWindowPlanViewer_Drop(object sender, DragEventArgs e)
+        {
+            if (!e.Data.GetDataPresent(DataFormats.FileDrop)) return;
+            var files = e.Data.GetData(DataFormats.FileDrop) as string[];
+            if (files?.Length > 0 && IsPlanFile(files[0]))
+                LoadMainWindowPlanFromFileIntoActiveTab(files[0]);
+        }
+
+        private void MainWindowPlanViewer_KeyDown(object sender, System.Windows.Input.KeyEventArgs e)
+        {
+            if (e.Key == System.Windows.Input.Key.V &&
+                System.Windows.Input.Keyboard.Modifiers == System.Windows.Input.ModifierKeys.Control &&
+                e.OriginalSource is not System.Windows.Controls.TextBox)
+            {
+                var xml = Clipboard.GetText();
+                if (!string.IsNullOrWhiteSpace(xml))
+                {
+                    e.Handled = true;
+                    LoadPlanIntoActivePlanSubTab(xml, "Pasted Plan");
+                }
+            }
+        }
+
+        private void LoadMainWindowPlanFromFileIntoActiveTab(string path)
+        {
+            try
+            {
+                var xml = System.IO.File.ReadAllText(path);
+                LoadPlanIntoActivePlanSubTab(xml, System.IO.Path.GetFileName(path));
+            }
+            catch (Exception ex)
+            {
+                MessageBox.Show($"Failed to load plan file:\n{ex.Message}", "Load Error",
+                    MessageBoxButton.OK, MessageBoxImage.Error);
+            }
+        }
+
+        private void LoadPlanIntoActivePlanSubTab(string planXml, string label)
+        {
+            var activeSubTab = GetActivePlanSubTab();
+            if (activeSubTab != null)
+                LoadPlanIntoSubTab(activeSubTab, planXml, label);
+        }
+
+        private static bool IsPlanFile(string path)
+        {
+            var ext = System.IO.Path.GetExtension(path);
+            return string.Equals(ext, ".sqlplan", StringComparison.OrdinalIgnoreCase)
+                || string.Equals(ext, ".xml", StringComparison.OrdinalIgnoreCase);
+        }
+
+        #endregion
     }