erikdarlingdata · erikdarlingdata · Jul 28, 2026 · Jul 28, 2026
diff --git a/src/PlanViewer.App/AboutWindow.axaml.cs b/src/PlanViewer.App/AboutWindow.axaml.cs
@@ -10,7 +10,6 @@
 using System.Runtime.InteropServices;
 using Avalonia.Controls;
 using Avalonia.Input;
-using Avalonia.Input.Platform;
 using Avalonia.Interactivity;
 using PlanViewer.App.Mcp;
 using PlanViewer.App.Services;
@@ -111,12 +110,9 @@ private async void CopyMcpCommand_Click(object? sender, RoutedEventArgs e)
     {
         var port = int.TryParse(McpPortInput.Text, out var p) && p >= 1024 && p <= 65535 ? p : 5152;
         var command = $"claude mcp add --transport streamable-http --scope user performance-studio http://localhost:{port}/";
-        var clipboard = TopLevel.GetTopLevel(this)?.Clipboard;
-        if (clipboard != null)
-        {
-            await clipboard.SetTextAsync(command);
-            McpCopyStatus.Text = "Copied to clipboard!";
-        }
+        McpCopyStatus.Text = await ClipboardHelper.TrySetTextAsync(this, command)
+            ? "Copied to clipboard!"
+            : "Clipboard busy - try again";
     }
 
     private string? _updateUrl;

diff --git a/src/PlanViewer.App/App.axaml.cs b/src/PlanViewer.App/App.axaml.cs
@@ -21,6 +21,10 @@ public override void Initialize()
 
     public override void OnFrameworkInitializationCompleted()
     {
+        // Before any window exists: route every TextBox clipboard operation through
+        // the guarded helper so a locked clipboard can't crash the app (issue #415).
+        TextBoxClipboardGuard.Register();
+
         if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
         {
             desktop.MainWindow = new MainWindow();

diff --git a/src/PlanViewer.App/Controls/PlanViewerControl.Interaction.cs b/src/PlanViewer.App/Controls/PlanViewerControl.Interaction.cs
@@ -7,6 +7,7 @@
 using Avalonia.Interactivity;
 using Avalonia.Media;
 using Avalonia.Platform.Storage;
+using PlanViewer.App.Services;
 using PlanViewer.Core.Models;
 
 namespace PlanViewer.App.Controls;
@@ -138,12 +139,8 @@ private ContextMenu BuildCanvasContextMenu()
         return menu;
     }
 
-    private async System.Threading.Tasks.Task SetClipboardTextAsync(string text)
-    {
-        var topLevel = TopLevel.GetTopLevel(this);
-        if (topLevel?.Clipboard != null)
-            await topLevel.Clipboard.SetTextAsync(text);
-    }
+    private System.Threading.Tasks.Task SetClipboardTextAsync(string text)
+        => ClipboardHelper.TrySetTextAsync(this, text);
 
     private void ZoomIn_Click(object? sender, RoutedEventArgs e) => SetZoom(_zoomLevel + ZoomStep);
 

diff --git a/src/PlanViewer.App/Controls/PlanViewerControl.Schema.cs b/src/PlanViewer.App/Controls/PlanViewerControl.Schema.cs
@@ -10,6 +10,7 @@
 using Avalonia.Media;
 using AvaloniaEdit.TextMate;
 using Microsoft.Data.SqlClient;
+using PlanViewer.App.Services;
 using PlanViewer.Core.Interfaces;
 using PlanViewer.Core.Models;
 using PlanViewer.Core.Services;
@@ -117,19 +118,13 @@ private void ShowSchemaResult(string title, string content)
         var copyItem = new MenuItem { Header = "Copy" };
         copyItem.Click += async (_, _) =>
         {
-            var clipboard = TopLevel.GetTopLevel(this)?.Clipboard;
-            if (clipboard == null) return;
             var sel = editor.TextArea.Selection;
             if (!sel.IsEmpty)
-                await clipboard.SetTextAsync(sel.GetText());
+                await ClipboardHelper.TrySetTextAsync(this, sel.GetText());
         };
         var copyAllItem = new MenuItem { Header = "Copy All" };
         copyAllItem.Click += async (_, _) =>
-        {
-            var clipboard = TopLevel.GetTopLevel(this)?.Clipboard;
-            if (clipboard == null) return;
-            await clipboard.SetTextAsync(editor.Text);
-        };
+            await ClipboardHelper.TrySetTextAsync(this, editor.Text);
         var selectAllItem = new MenuItem { Header = "Select All" };
         selectAllItem.Click += (_, _) => editor.SelectAll();
         editor.TextArea.ContextMenu = new ContextMenu

diff --git a/src/PlanViewer.App/Controls/PlanViewerControl.Statements.cs b/src/PlanViewer.App/Controls/PlanViewerControl.Statements.cs
@@ -8,6 +8,7 @@
 using Avalonia.Interactivity;
 using Avalonia.Layout;
 using Avalonia.Media;
+using PlanViewer.App.Services;
 using PlanViewer.Core.Models;
 using PlanViewer.Core.Services;
 
@@ -168,9 +169,7 @@ private async void CopyStatementText_Click(object? sender, RoutedEventArgs e)
         var text = row.Statement.StatementText;
         if (string.IsNullOrEmpty(text)) return;
 
-        var topLevel = TopLevel.GetTopLevel(this);
-        if (topLevel?.Clipboard != null)
-            await topLevel.Clipboard.SetTextAsync(text);
+        await ClipboardHelper.TrySetTextAsync(this, text);
     }
 
     private void OpenInEditor_Click(object? sender, RoutedEventArgs e)

diff --git a/src/PlanViewer.App/Controls/PlanViewerControl.axaml.cs b/src/PlanViewer.App/Controls/PlanViewerControl.axaml.cs
@@ -164,6 +164,8 @@ public PlanViewerControl()
         _zoomTransform = (ScaleTransform)layoutTransform.LayoutTransform!;
 
         Helpers.DataGridBehaviors.Attach(StatementsGrid);
+        Helpers.DataGridBehaviors.AttachCopyGuard(StatementsGrid,
+            item => item is StatementRow row ? row.Statement.StatementText : null);
 
         // Wire minimap resize grip (defined in AXAML, not in canvas)
         MinimapResizeGrip.PointerPressed += MinimapResizeGrip_PointerPressed;

diff --git a/src/PlanViewer.App/Controls/QuerySessionControl.Editor.cs b/src/PlanViewer.App/Controls/QuerySessionControl.Editor.cs
@@ -10,7 +10,6 @@
 using System.Xml.Linq;
 using Avalonia.Controls;
 using Avalonia.Input;
-using Avalonia.Input.Platform;
 using Avalonia.Interactivity;
 using Avalonia.Layout;
 using Avalonia.Media;
@@ -42,31 +41,27 @@ private void SetupEditorContextMenu()
         var cutItem = new MenuItem { Header = "Cut" };
         cutItem.Click += async (_, _) =>
         {
-            var clipboard = TopLevel.GetTopLevel(this)?.Clipboard;
-            if (clipboard == null) return;
             var selection = QueryEditor.TextArea.Selection;
             if (selection.IsEmpty) return;
             var text = selection.GetText();
-            await clipboard.SetTextAsync(text);
-            selection.ReplaceSelectionWithText("");
+            // Only remove the selection once the text has actually reached the
+            // clipboard; a failed copy must not destroy the user's text.
+            if (await ClipboardHelper.TrySetTextAsync(this, text))
+                selection.ReplaceSelectionWithText("");
         };
 
         var copyItem = new MenuItem { Header = "Copy" };
         copyItem.Click += async (_, _) =>
         {
-            var clipboard = TopLevel.GetTopLevel(this)?.Clipboard;
-            if (clipboard == null) return;
             var selection = QueryEditor.TextArea.Selection;
             if (selection.IsEmpty) return;
-            await clipboard.SetTextAsync(selection.GetText());
+            await ClipboardHelper.TrySetTextAsync(this, selection.GetText());
         };
 
         var pasteItem = new MenuItem { Header = "Paste" };
         pasteItem.Click += async (_, _) =>
         {
-            var clipboard = TopLevel.GetTopLevel(this)?.Clipboard;
-            if (clipboard == null) return;
-            var text = await clipboard.TryGetTextAsync();
+            var text = await ClipboardHelper.TryGetTextAsync(this);
             if (string.IsNullOrEmpty(text)) return;
             QueryEditor.TextArea.PerformTextInput(text);
         };

diff --git a/src/PlanViewer.App/Controls/QuerySessionControl.Format.cs b/src/PlanViewer.App/Controls/QuerySessionControl.Format.cs
@@ -60,19 +60,10 @@ otherwise fall back to the currently selected database */
             source: "Performance Studio",
             isAzureSqlDb: IsAzureConnection);
 
-        try
-        {
-            var topLevel = TopLevel.GetTopLevel(this);
-            if (topLevel?.Clipboard != null)
-            {
-                await topLevel.Clipboard.SetTextAsync(reproScript);
-                SetStatus("Repro script copied to clipboard");
-            }
-        }
-        catch (Exception ex)
-        {
-            SetStatus($"Clipboard error: {ex.Message}");
-        }
+        if (await ClipboardHelper.TrySetTextAsync(this, reproScript))
+            SetStatus("Repro script copied to clipboard");
+        else
+            SetStatus("Clipboard busy - could not copy repro script");
     }
 
     private async void Format_Click(object? sender, RoutedEventArgs e)

diff --git a/src/PlanViewer.App/Controls/QuerySessionControl.Schema.cs b/src/PlanViewer.App/Controls/QuerySessionControl.Schema.cs
@@ -104,19 +104,13 @@ private void AddSchemaTab(string label, string content, bool isSql)
         var schemaCopy = new MenuItem { Header = "Copy" };
         schemaCopy.Click += async (_, _) =>
         {
-            var clipboard = TopLevel.GetTopLevel(this)?.Clipboard;
-            if (clipboard == null) return;
             var sel = editor.TextArea.Selection;
             if (!sel.IsEmpty)
-                await clipboard.SetTextAsync(sel.GetText());
+                await ClipboardHelper.TrySetTextAsync(this, sel.GetText());
         };
         var schemaCopyAll = new MenuItem { Header = "Copy All" };
         schemaCopyAll.Click += async (_, _) =>
-        {
-            var clipboard = TopLevel.GetTopLevel(this)?.Clipboard;
-            if (clipboard == null) return;
-            await clipboard.SetTextAsync(editor.Text);
-        };
+            await ClipboardHelper.TrySetTextAsync(this, editor.Text);
         var schemaSelectAll = new MenuItem { Header = "Select All" };
         schemaSelectAll.Click += (_, _) => editor.SelectAll();
         editor.TextArea.ContextMenu = new ContextMenu

diff --git a/src/PlanViewer.App/Controls/QueryStoreGridControl.Selection.cs b/src/PlanViewer.App/Controls/QueryStoreGridControl.Selection.cs
@@ -159,7 +159,7 @@ private void ContextMenu_Opening(object? sender, System.ComponentModel.CancelEve
         CopyPlanHashItem.Tag = row.QueryPlanHash;
         CopyModuleItem.Tag = row.ModuleName;
         CopyQueryTextItem.Tag = row.FullQueryText;
-        CopyRowItem.Tag = $"{row.QueryId}\t{row.PlanId}\t{row.QueryHash}\t{row.QueryPlanHash}\t{row.ModuleName}\t{row.LastExecutedLocal}\t{row.ExecsDisplay}\t{row.TotalCpuDisplay}\t{row.AvgCpuDisplay}\t{row.TotalDurDisplay}\t{row.AvgDurDisplay}\t{row.TotalReadsDisplay}\t{row.AvgReadsDisplay}\t{row.TotalWritesDisplay}\t{row.AvgWritesDisplay}\t{row.TotalPhysReadsDisplay}\t{row.AvgPhysReadsDisplay}\t{row.TotalMemDisplay}\t{row.AvgMemDisplay}\t{row.FullQueryText}";
+        CopyRowItem.Tag = FormatRowForClipboard(row);
 
         CopyQueryIdItem.Click += CopyMenuItem_Click;
         CopyPlanIdItem.Click += CopyMenuItem_Click;
@@ -176,10 +176,10 @@ private async void CopyMenuItem_Click(object? sender, RoutedEventArgs e)
             await SetClipboardTextAsync(text);
     }
 
-    private async System.Threading.Tasks.Task SetClipboardTextAsync(string text)
-    {
-        var topLevel = Avalonia.Controls.TopLevel.GetTopLevel(this);
-        if (topLevel?.Clipboard != null)
-            await topLevel.Clipboard.SetTextAsync(text);
-    }
+    /// <summary>One results row as a tab-separated line, shared by Copy Row and Ctrl+C.</summary>
+    private static string FormatRowForClipboard(QueryStoreRow row) =>
+        $"{row.QueryId}\t{row.PlanId}\t{row.QueryHash}\t{row.QueryPlanHash}\t{row.ModuleName}\t{row.LastExecutedLocal}\t{row.ExecsDisplay}\t{row.TotalCpuDisplay}\t{row.AvgCpuDisplay}\t{row.TotalDurDisplay}\t{row.AvgDurDisplay}\t{row.TotalReadsDisplay}\t{row.AvgReadsDisplay}\t{row.TotalWritesDisplay}\t{row.AvgWritesDisplay}\t{row.TotalPhysReadsDisplay}\t{row.AvgPhysReadsDisplay}\t{row.TotalMemDisplay}\t{row.AvgMemDisplay}\t{row.FullQueryText}";
+
+    private System.Threading.Tasks.Task SetClipboardTextAsync(string text)
+        => ClipboardHelper.TrySetTextAsync(this, text);
 }
diff --git a/src/PlanViewer.App/Controls/QueryStoreGridControl.axaml.cs b/src/PlanViewer.App/Controls/QueryStoreGridControl.axaml.cs
@@ -86,6 +86,8 @@ public QueryStoreGridControl(ServerConnection serverConnection, ICredentialServi
 
         ResultsGrid.ItemsSource = _filteredRows;
         Helpers.DataGridBehaviors.Attach(ResultsGrid);
+        Helpers.DataGridBehaviors.AttachCopyGuard(ResultsGrid,
+            item => item is QueryStoreRow row ? FormatRowForClipboard(row) : null);
         EnsureFilterPopup();
         SetupColumnHeaders();
         PopulateDatabaseBox(databases, initialDatabase);

diff --git a/src/PlanViewer.App/Controls/QueryStoreHistoryControl.axaml.cs b/src/PlanViewer.App/Controls/QueryStoreHistoryControl.axaml.cs
@@ -9,6 +9,7 @@
 using Avalonia.Interactivity;
 using Avalonia.Media;
 using Avalonia.VisualTree;
+using PlanViewer.App.Services;
 using PlanViewer.Core.Models;
 using PlanViewer.Core.Services;
 using ScottPlot;
@@ -135,6 +136,8 @@ public QueryStoreHistoryControl(string connectionString, string queryHash,
 		InitializeComponent();
 
 		Helpers.DataGridBehaviors.Attach(HistoryDataGrid);
+		Helpers.DataGridBehaviors.AttachCopyGuard(HistoryDataGrid,
+			item => item is QueryStoreHistoryRow row ? FormatRowForClipboard(row) : null);
 
 		QueryIdentifierText.Text = $"Query Store History: {queryHash} in [{database}]";
 		QueryTextBox.Text = queryText;
@@ -307,11 +310,33 @@ private void MetricSelector_SelectionChanged(object? sender, SelectionChangedEve
 	private async void CopyQuery_Click(object? sender, RoutedEventArgs e)
 	{
 		if (string.IsNullOrEmpty(_queryText)) return;
-		var clipboard = TopLevel.GetTopLevel(this)?.Clipboard;
-		if (clipboard != null)
-			await clipboard.SetTextAsync(_queryText);
+		await ClipboardHelper.TrySetTextAsync(this, _queryText);
 	}
 
+	/// <summary>One history row as a tab-separated line matching the grid's column order.</summary>
+	private static string FormatRowForClipboard(QueryStoreHistoryRow row) =>
+		string.Join("\t",
+			row.QueryPlanHash,
+			row.IntervalStartLocal,
+			row.CountExecutions,
+			row.AvgDurationMsDisplay,
+			row.AvgCpuMsDisplay,
+			row.AvgLogicalReadsDisplay,
+			row.AvgLogicalWritesDisplay,
+			row.AvgPhysicalReadsDisplay,
+			row.AvgMemoryMbDisplay,
+			row.AvgRowcountDisplay,
+			row.TotalDurationMsDisplay,
+			row.TotalCpuMsDisplay,
+			row.TotalLogicalReadsDisplay,
+			row.TotalLogicalWritesDisplay,
+			row.TotalPhysicalReadsDisplay,
+			row.TotalMemoryMbDisplay,
+			row.MinDop,
+			row.MaxDop,
+			row.LastExecutionLocal,
+			row.ExecutionTypeDesc);
+
 	private void Close_Click(object? sender, RoutedEventArgs e)
 	{
 		// When in a detached window, close it (this destroys the history view)

diff --git a/src/PlanViewer.App/Dialogs/SettingsWindow.axaml.cs b/src/PlanViewer.App/Dialogs/SettingsWindow.axaml.cs
@@ -332,6 +332,9 @@ private Control BuildScriptOptionsSection()
 			FontSize = 13,
 		};
 
+		Helpers.DataGridBehaviors.AttachCopyGuard(_formatGrid,
+			item => item is FormatOptionRow row ? $"{row.Name}\t{row.CurrentValue}" : null);
+
 		_formatGrid.Columns.Add(new DataGridTextColumn
 		{
 			Header = "Setting",

diff --git a/src/PlanViewer.App/Helpers/DataGridBehaviors.cs b/src/PlanViewer.App/Helpers/DataGridBehaviors.cs
@@ -1,15 +1,17 @@
 using System;
+using System.Collections.Generic;
 using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Controls.Primitives;
 using Avalonia.Input;
 using Avalonia.Interactivity;
 using Avalonia.VisualTree;
+using PlanViewer.App.Services;
 
 namespace PlanViewer.App.Helpers;
 
 /// <summary>
-/// Attaches middle-mouse-button pan behavior to a DataGrid.
+/// Attached input behaviors for DataGrids: middle-mouse pan and guarded clipboard copy.
 /// </summary>
 public static class DataGridBehaviors
 {
@@ -19,6 +21,52 @@ public static void Attach(DataGrid grid)
         AttachMiddleClickPan(grid);
     }
 
+    /// <summary>
+    /// Replaces the DataGrid's built-in Ctrl+C / Ctrl+Insert copy, which awaits the
+    /// clipboard unguarded inside Avalonia and can crash the app when the clipboard
+    /// is locked by another process (issue #415). The tunnel handler runs before the
+    /// grid's own key handling and routes the copy through ClipboardHelper instead.
+    /// <paramref name="formatRow"/> turns one selected row item into its clipboard
+    /// line; return null to skip the item.
+    /// </summary>
+    public static void AttachCopyGuard(DataGrid grid, Func<object, string?> formatRow)
+    {
+        grid.AddHandler(InputElement.KeyDownEvent, (_, e) =>
+        {
+            // Mirror the built-in copy's exact gate: platform command modifier
+            // (Ctrl; Cmd on macOS), no Shift, no Alt.
+            var commandModifiers = TopLevel.GetTopLevel(grid)?.PlatformSettings?.HotkeyConfiguration.CommandModifiers
+                ?? KeyModifiers.Control;
+            if (e.Key is not (Key.C or Key.Insert)
+                || !e.KeyModifiers.HasFlag(commandModifiers)
+                || e.KeyModifiers.HasFlag(KeyModifiers.Shift)
+                || e.KeyModifiers.HasFlag(KeyModifiers.Alt))
+                return;
+
+            // In-cell editors own their Ctrl+C (e.g. the settings grid's TextBoxes).
+            if (e.Source is Visual source && source.FindAncestorOfType<TextBox>(includeSelf: true) != null)
+                return;
+
+            var selected = grid.SelectedItems;
+            if (selected == null || selected.Count == 0)
+                return;
+
+            // Take over whenever rows are selected so the DataGrid's unguarded
+            // built-in copy never runs, even if no line ends up on the clipboard.
+            e.Handled = true;
+
+            var lines = new List<string>();
+            foreach (var item in selected)
+            {
+                if (item != null && formatRow(item) is { } line)
+                    lines.Add(line);
+            }
+
+            if (lines.Count > 0)
+                _ = ClipboardHelper.TrySetTextAsync(grid, string.Join(Environment.NewLine, lines));
+        }, RoutingStrategies.Tunnel);
+    }
+
     // ─────────────────────────────────────────────────────────────────────────
     // Middle-mouse-button drag → pan (scroll) the grid
     // ─────────────────────────────────────────────────────────────────────────