Integrate Dock.Avalonia for the layout

Replaces the temporary 3-column Grid placeholder in MainWindow with a
Dock.Avalonia DockControl driven by an ILSpyDockFactory and orchestrated
by a [Shared] DockWorkspace exported via MEF.

Assisted-by: Claude:claude-opus-4-7:Claude Code

Directory.Packages.props

@@ -25,8 +25,10 @@
     <PackageVersion Include="Avalonia.Xaml.Behaviors" Version="11.3.0.6" />
     <PackageVersion Include="AvaloniaUI.DiagnosticsSupport" Version="2.2.1" />
     <PackageVersion Include="Dock.Avalonia" Version="$(DockVersion)" />
+    <PackageVersion Include="Dock.Avalonia.Themes.Fluent" Version="$(DockVersion)" />
     <PackageVersion Include="Dock.Model" Version="$(DockVersion)" />
     <PackageVersion Include="Dock.Model.Mvvm" Version="$(DockVersion)" />
+    <PackageVersion Include="Dock.Serializer.SystemTextJson" Version="$(DockVersion)" />
     <PackageVersion Include="ProDataGrid" Version="12.0.0" />
     <PackageVersion Include="CommunityToolkit.Mvvm" Version="8.4.2" />
     <PackageVersion Include="AwesomeAssertions" Version="9.4.0" />

ILSpy.Tests/Docking/DockWorkspaceTests.cs

@@ -0,0 +1,48 @@
+// Copyright (c) 2026 AlphaSierraPapa for the SharpDevelop Team
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using Avalonia.Headless.NUnit;
+
+using AwesomeAssertions;
+
+using ILSpy.AppEnv;
+using ILSpy.Docking;
+
+using NUnit.Framework;
+
+namespace ICSharpCode.ILSpy.Tests.Docking;
+
+// DockWorkspace is the MEF-shared wrapper that holds the Dock.Avalonia factory + the root
+// layout. If MEF can't construct it (e.g., missing AssemblyTreeModel / SearchPaneModel /
+// AnalyzerTreeViewModel imports), the entire dock surface never materializes. Asserting
+// at the export layer catches that before we wire it into the DockControl.
+[TestFixture]
+public class DockWorkspaceTests
+{
+	[AvaloniaTest]
+	public void DockWorkspace_resolves_and_exposes_root_layout_with_three_tool_panes()
+	{
+		var workspace = AppComposition.Current.GetExport<DockWorkspace>();
+		workspace.Should().NotBeNull("DockWorkspace is [Export][Shared] in ILSpy.Docking.");
+
+		workspace.Layout.Should().NotBeNull("ILSpyDockFactory.CreateLayout() wires the root dock in the ctor.");
+		workspace.Factory.Should().NotBeNull();
+		workspace.ToolPaneMenuItems.Should().HaveCount(3,
+			"AssemblyTree, Search, and Analyzers are the three tool panes wired at this point.");
+	}
+}

ILSpy/Analyzers/AnalyzerTreeView.axaml

@@ -0,0 +1,12 @@
+<UserControl xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             xmlns:analyzers="using:ILSpy.Analyzers"
+             mc:Ignorable="d" d:DesignWidth="400" d:DesignHeight="200"
+             x:Class="ILSpy.Analyzers.AnalyzerTreeView"
+             x:DataType="analyzers:AnalyzerTreeViewModel">
+	<TextBlock HorizontalAlignment="Center" VerticalAlignment="Center"
+	           Foreground="Gray" FontStyle="Italic"
+	           Text="Analyzer results will appear here." />
+</UserControl>

ILSpy/Analyzers/AnalyzerTreeView.axaml.cs

@@ -0,0 +1,30 @@
+// Copyright (c) 2026 AlphaSierraPapa for the SharpDevelop Team
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using Avalonia.Controls;
+
+namespace ILSpy.Analyzers
+{
+	public partial class AnalyzerTreeView : UserControl
+	{
+		public AnalyzerTreeView()
+		{
+			InitializeComponent();
+		}
+	}
+}

ILSpy/Analyzers/AnalyzerTreeViewModel.cs

@@ -0,0 +1,37 @@
+// Copyright (c) 2026 AlphaSierraPapa for the SharpDevelop Team
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using System.Composition;
+
+using ILSpy.ViewModels;
+
+namespace ILSpy.Analyzers
+{
+	[Export]
+	[Shared]
+	public class AnalyzerTreeViewModel : ToolPaneModel
+	{
+		public const string PaneContentId = "Analyzer";
+
+		public AnalyzerTreeViewModel()
+		{
+			Id = PaneContentId;
+			Title = "Analyzer";
+		}
+	}
+}

ILSpy/App.axaml

@@ -2,14 +2,29 @@
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              x:Class="ILSpy.App"
              xmlns:local="using:ILSpy"
+             xmlns:tree="using:ILSpy.AssemblyTree"
+             xmlns:search="using:ILSpy.Search"
+             xmlns:analyzers="using:ILSpy.Analyzers"
+             xmlns:dockTheme="using:Dock.Avalonia.Themes.Fluent"
              RequestedThemeVariant="Default">
              <!-- "Default" ThemeVariant follows system theme variant. "Dark" or "Light" are other available options. -->
 
     <Application.DataTemplates>
+        <DataTemplate DataType="tree:AssemblyTreeModel">
+            <tree:AssemblyListPane />
+        </DataTemplate>
+        <DataTemplate DataType="search:SearchPaneModel">
+            <search:SearchPane />
+        </DataTemplate>
+        <DataTemplate DataType="analyzers:AnalyzerTreeViewModel">
+            <analyzers:AnalyzerTreeView />
+        </DataTemplate>
         <local:ViewLocator/>
     </Application.DataTemplates>
 
     <Application.Styles>
         <FluentTheme />
+        <StyleInclude Source="avares://Avalonia.Controls.DataGrid/Themes/Fluent.v2.xaml" />
+        <dockTheme:DockFluentTheme />
     </Application.Styles>
 </Application>

ILSpy/AssemblyTree/AssemblyTreeModel.cs

@@ -18,6 +18,7 @@
 
 using System;
 using System.Composition;
+using System.Runtime.Serialization;
 
 using CommunityToolkit.Mvvm.ComponentModel;
 
@@ -26,21 +27,34 @@ using ICSharpCode.ILSpyX.Settings;
 using ICSharpCode.ILSpyX.TreeView;
 
 using ILSpy.TreeNodes;
+using ILSpy.ViewModels;
 
 namespace ILSpy.AssemblyTree
 {
 	[Export]
 	[Shared]
-	public partial class AssemblyTreeModel : ObservableObject
+	public partial class AssemblyTreeModel : ToolPaneModel
 	{
+		public const string PaneContentId = "AssemblyTree";
+
 		[ObservableProperty]
+		[property: IgnoreDataMember]
 		private SharpTreeNode? root;
 
 		[ObservableProperty]
+		[property: IgnoreDataMember]
 		private SharpTreeNode? selectedItem;
 
+		[IgnoreDataMember]
 		public AssemblyList? AssemblyList { get; private set; }
 
+		public AssemblyTreeModel()
+		{
+			Id = PaneContentId;
+			Title = "Assemblies";
+			CanClose = false;
+		}
+
 		public void Initialize()
 		{
 			var settings = ILSpySettings.Load();

ILSpy/Docking/DockWorkspace.cs

@@ -0,0 +1,115 @@
+// Copyright (c) 2026 AlphaSierraPapa for the SharpDevelop Team
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using System;
+using System.Collections.Generic;
+using System.Composition;
+
+using Dock.Model.Controls;
+using Dock.Model.Core;
+using Dock.Model.Core.Events;
+
+using ILSpy.Analyzers;
+using ILSpy.AssemblyTree;
+using ILSpy.Search;
+using ILSpy.ViewModels;
+
+namespace ILSpy.Docking
+{
+	[Export]
+	[Shared]
+	public class DockWorkspace
+	{
+		readonly ILSpyDockFactory factory;
+
+		public IFactory Factory => factory;
+
+		public IRootDock Layout { get; }
+
+		public IReadOnlyList<ToolPaneMenuItem> ToolPaneMenuItems { get; }
+
+		[ImportingConstructor]
+		public DockWorkspace(
+			AssemblyTreeModel assemblyTreeModel,
+			SearchPaneModel searchPaneModel,
+			AnalyzerTreeViewModel analyzerTreeViewModel)
+		{
+			factory = new ILSpyDockFactory(assemblyTreeModel, searchPaneModel, analyzerTreeViewModel);
+			Layout = factory.CreateLayout();
+			// Layout/factory initialization (locators, parent/factory wiring) is done by
+			// the DockControl in MainWindow.axaml via InitializeFactory/InitializeLayout.
+
+			ToolPaneMenuItems = new List<ToolPaneMenuItem> {
+				new(assemblyTreeModel, factory),
+				new(searchPaneModel, factory),
+				new(analyzerTreeViewModel, factory),
+			};
+
+			factory.DockableAdded += OnDocumentMembershipChanged;
+			factory.DockableRemoved += OnDocumentMembershipChanged;
+			factory.DockableClosed += OnDocumentMembershipChanged;
+			factory.DockableClosing += OnDockableClosing;
+
+			// TODO: layout persistence (load on startup, save on exit). DockSerializer.SystemTextJson
+			// trips System.Text.Json's MaxDepth=64 limit on our layout because Dock's JsonConverterList<T>
+			// calls JsonSerializer.Serialize per list element, which doesn't preserve the writer's
+			// reference-tracking state between calls — so Owner/Factory back-refs aren't deduplicated as
+			// $ref. Options when revisiting: try Dock.Serializer.Newtonsoft (better cycle handling),
+			// or build a custom JsonSerializerOptions with MaxDepth raised + replicate Dock's internal
+			// polymorphic resolver.
+		}
+
+		void OnDocumentMembershipChanged(object? sender, EventArgs e) => UpdateLastDocumentCanClose();
+
+		// Convert a tool pane's "close" (X button) into "hide" so the Window menu can restore it.
+		// Documents are still closed for real — they get garbage-collected.
+		void OnDockableClosing(object? sender, DockableClosingEventArgs e)
+		{
+			if (e.Dockable is ToolPaneModel toolPane)
+			{
+				e.Cancel = true;
+				factory.HideDockable(toolPane);
+			}
+		}
+
+		// When only one document is open, make it un-closeable so the user can't end up with an
+		// empty document area.
+		void UpdateLastDocumentCanClose()
+		{
+			var docs = factory.Documents?.VisibleDockables;
+			if (docs == null)
+				return;
+			bool canClose = docs.Count > 1;
+			foreach (var d in docs)
+			{
+				d.CanClose = canClose;
+			}
+		}
+
+		public TabPageModel OpenNewTab(TabPageModel tab)
+		{
+			if (factory.Documents != null)
+			{
+				factory.AddDockable(factory.Documents, tab);
+				factory.SetActiveDockable(tab);
+				factory.SetFocusedDockable(factory.Documents, tab);
+			}
+			return tab;
+		}
+	}
+}

ILSpy/Docking/ILSpyDockFactory.cs

@@ -0,0 +1,113 @@
+// Copyright (c) 2026 AlphaSierraPapa for the SharpDevelop Team
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using Dock.Model.Controls;
+using Dock.Model.Core;
+using Dock.Model.Mvvm;
+using Dock.Model.Mvvm.Controls;
+
+using ILSpy.Analyzers;
+using ILSpy.AssemblyTree;
+using ILSpy.Search;
+
+namespace ILSpy.Docking
+{
+	public class ILSpyDockFactory : Factory
+	{
+		readonly AssemblyTreeModel assemblyTreeModel;
+		readonly SearchPaneModel searchPaneModel;
+		readonly AnalyzerTreeViewModel analyzerTreeViewModel;
+
+		public IDocumentDock? Documents { get; private set; }
+
+		public ILSpyDockFactory(
+			AssemblyTreeModel assemblyTreeModel,
+			SearchPaneModel searchPaneModel,
+			AnalyzerTreeViewModel analyzerTreeViewModel)
+		{
+			this.assemblyTreeModel = assemblyTreeModel;
+			this.searchPaneModel = searchPaneModel;
+			this.analyzerTreeViewModel = analyzerTreeViewModel;
+		}
+
+		public override IRootDock CreateLayout()
+		{
+			var leftToolDock = new ToolDock {
+				Id = "LeftTools",
+				Proportion = 0.25,
+				VisibleDockables = CreateList<IDockable>(assemblyTreeModel),
+				ActiveDockable = assemblyTreeModel,
+				Alignment = Alignment.Left,
+			};
+
+			var topToolDock = new ToolDock {
+				Id = "TopTools",
+				Proportion = 0.2,
+				VisibleDockables = CreateList<IDockable>(searchPaneModel),
+				ActiveDockable = searchPaneModel,
+				Alignment = Alignment.Top,
+			};
+
+			var documents = new DocumentDock {
+				Id = "Documents",
+				Title = "Documents",
+				IsCollapsable = false,
+				Proportion = 0.6,
+			};
+			Documents = documents;
+
+			var bottomToolDock = new ToolDock {
+				Id = "BottomTools",
+				Proportion = 0.2,
+				VisibleDockables = CreateList<IDockable>(analyzerTreeViewModel),
+				ActiveDockable = analyzerTreeViewModel,
+				Alignment = Alignment.Bottom,
+			};
+
+			var rightVertical = new ProportionalDock {
+				Id = "RightArea",
+				Orientation = Orientation.Vertical,
+				Proportion = 0.75,
+				VisibleDockables = CreateList<IDockable>(
+					topToolDock,
+					new ProportionalDockSplitter { Id = "TopSplitter" },
+					documents,
+					new ProportionalDockSplitter { Id = "BottomSplitter" },
+					bottomToolDock),
+			};
+
+			var horizontal = new ProportionalDock {
+				Id = "MainLayout",
+				Orientation = Orientation.Horizontal,
+				VisibleDockables = CreateList<IDockable>(
+					leftToolDock,
+					new ProportionalDockSplitter { Id = "LeftSplitter" },
+					rightVertical),
+			};
+
+			var root = CreateRootDock();
+			root.Id = "Root";
+			root.IsCollapsable = false;
+			root.VisibleDockables = CreateList<IDockable>(horizontal);
+			root.DefaultDockable = horizontal;
+			root.ActiveDockable = horizontal;
+
+			return root;
+		}
+	}
+}

ILSpy/ILSpy.csproj

@@ -34,7 +34,9 @@
     <PackageReference Include="AvaloniaEdit.TextMate" />
     <PackageReference Include="Avalonia.Xaml.Behaviors" />
     <PackageReference Include="Dock.Avalonia" />
+    <PackageReference Include="Dock.Avalonia.Themes.Fluent" />
     <PackageReference Include="Dock.Model.Mvvm" />
+    <PackageReference Include="Dock.Serializer.SystemTextJson" />
     <PackageReference Include="ProDataGrid" />
 
     <!-- MVVM, DI, MEF -->

ILSpy/Search/SearchPane.axaml

@@ -0,0 +1,12 @@
+<UserControl xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             xmlns:search="using:ILSpy.Search"
+             mc:Ignorable="d" d:DesignWidth="400" d:DesignHeight="200"
+             x:Class="ILSpy.Search.SearchPane"
+             x:DataType="search:SearchPaneModel">
+	<TextBlock HorizontalAlignment="Center" VerticalAlignment="Center"
+	           Foreground="Gray" FontStyle="Italic"
+	           Text="Search results will appear here." />
+</UserControl>

ILSpy/Search/SearchPane.axaml.cs

@@ -0,0 +1,30 @@
+// Copyright (c) 2026 AlphaSierraPapa for the SharpDevelop Team
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using Avalonia.Controls;
+
+namespace ILSpy.Search
+{
+	public partial class SearchPane : UserControl
+	{
+		public SearchPane()
+		{
+			InitializeComponent();
+		}
+	}
+}

ILSpy/Search/SearchPaneModel.cs

@@ -0,0 +1,37 @@
+// Copyright (c) 2026 AlphaSierraPapa for the SharpDevelop Team
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using System.Composition;
+
+using ILSpy.ViewModels;
+
+namespace ILSpy.Search
+{
+	[Export]
+	[Shared]
+	public class SearchPaneModel : ToolPaneModel
+	{
+		public const string PaneContentId = "Search";
+
+		public SearchPaneModel()
+		{
+			Id = PaneContentId;
+			Title = "Search";
+		}
+	}
+}

ILSpy/ViewModels/MainWindowViewModel.cs

@@ -18,7 +18,11 @@
 
 using System.Composition;
 
+using Dock.Model.Controls;
+using Dock.Model.Core;
+
 using ILSpy.AssemblyTree;
+using ILSpy.Docking;
 
 namespace ILSpy.ViewModels
 {
@@ -28,12 +32,21 @@ namespace ILSpy.ViewModels
 	{
 		public AssemblyTreeModel AssemblyTreeModel { get; }
 
+		public DockWorkspace DockWorkspace { get; }
+
+		public IFactory DockFactory => DockWorkspace.Factory;
+
+		public IRootDock DockLayout => DockWorkspace.Layout;
+
+		public System.Collections.Generic.IReadOnlyList<ToolPaneMenuItem> ToolPaneMenuItems => DockWorkspace.ToolPaneMenuItems;
+
 		public string Title => "ILSpy";
 
 		[ImportingConstructor]
-		public MainWindowViewModel(AssemblyTreeModel assemblyTreeModel)
+		public MainWindowViewModel(AssemblyTreeModel assemblyTreeModel, DockWorkspace dockWorkspace)
 		{
 			AssemblyTreeModel = assemblyTreeModel;
+			DockWorkspace = dockWorkspace;
 		}
 	}
 }

ILSpy/ViewModels/TabPageModel.cs

@@ -0,0 +1,26 @@
+// Copyright (c) 2026 AlphaSierraPapa for the SharpDevelop Team
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using Dock.Model.Mvvm.Controls;
+
+namespace ILSpy.ViewModels
+{
+	public abstract class TabPageModel : Document
+	{
+	}
+}

ILSpy/ViewModels/ToolPaneMenuItem.cs

@@ -0,0 +1,59 @@
+// Copyright (c) 2026 AlphaSierraPapa for the SharpDevelop Team
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using CommunityToolkit.Mvvm.ComponentModel;
+
+using Dock.Model.Controls;
+using Dock.Model.Core;
+
+namespace ILSpy.ViewModels
+{
+	public class ToolPaneMenuItem : ObservableObject
+	{
+		readonly ToolPaneModel pane;
+		readonly IFactory factory;
+
+		public ToolPaneMenuItem(ToolPaneModel pane, IFactory factory)
+		{
+			this.pane = pane;
+			this.factory = factory;
+			factory.DockableHidden += OnFactoryVisibilityChanged;
+			factory.DockableRestored += OnFactoryVisibilityChanged;
+		}
+
+		public string? Title => pane.Title;
+
+		public bool IsPaneVisible {
+			get => pane.Owner is not IRootDock;
+			set {
+				if (value == IsPaneVisible)
+					return;
+				if (value)
+					factory.RestoreDockable(pane);
+				else
+					factory.HideDockable(pane);
+				OnPropertyChanged();
+			}
+		}
+
+		void OnFactoryVisibilityChanged(object? sender, System.EventArgs e)
+		{
+			OnPropertyChanged(nameof(IsPaneVisible));
+		}
+	}
+}

ILSpy/ViewModels/ToolPaneModel.cs

@@ -0,0 +1,26 @@
+// Copyright (c) 2026 AlphaSierraPapa for the SharpDevelop Team
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using Dock.Model.Mvvm.Controls;
+
+namespace ILSpy.ViewModels
+{
+	public abstract class ToolPaneModel : Tool
+	{
+	}
+}

ILSpy/Views/MainMenu.axaml

@@ -2,8 +2,10 @@
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
              xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             xmlns:vm="using:ILSpy.ViewModels"
              mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="23"
-             x:Class="ILSpy.MainMenu">
+             x:Class="ILSpy.MainMenu"
+             x:DataType="vm:MainWindowViewModel">
 	<Menu DockPanel.Dock="Top" Name="Menu" Height="23">
 		<MenuItem Header="_File" Tag="_File">
 			<!-- MEF-populated content (task #10) -->
@@ -11,8 +13,15 @@
 		<MenuItem Header="_View" Tag="_View">
 			<!-- API visibility toggles, theme selection, etc. wired in task #10 / #3 -->
 		</MenuItem>
-		<MenuItem Header="_Window" Name="WindowMenuItem" Tag="_Window">
-			<!-- Tool-pane / tab-page entries wired in task #10 -->
+		<MenuItem Header="_Window" Name="WindowMenuItem" Tag="_Window"
+		          ItemsSource="{Binding ToolPaneMenuItems}">
+			<MenuItem.DataTemplates>
+				<DataTemplate DataType="vm:ToolPaneMenuItem">
+					<MenuItem Header="{Binding Title}"
+					          ToggleType="CheckBox"
+					          IsChecked="{Binding IsPaneVisible, Mode=TwoWay}" />
+				</DataTemplate>
+			</MenuItem.DataTemplates>
 		</MenuItem>
 	</Menu>
 </UserControl>

ILSpy/Views/MainWindow.axaml

@@ -2,6 +2,8 @@
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:vm="using:ILSpy.ViewModels"
         xmlns:local="using:ILSpy"
+        xmlns:tree="using:ILSpy.AssemblyTree"
+        xmlns:dock="using:Dock.Avalonia.Controls"
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
         mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="500"
@@ -29,11 +31,9 @@
 			           Margin="8,0" Name="statusLabel" Text="Stand by..." />
 		</Border>
 
-		<!-- Placeholder for DockingManager (task #4: replace with Dock.Avalonia) -->
-		<ContentControl Name="DockHost">
-			<TextBlock HorizontalAlignment="Center" VerticalAlignment="Center"
-			           Foreground="Gray" FontStyle="Italic"
-			           Text="Docking workspace will appear here." />
-		</ContentControl>
+		<dock:DockControl Layout="{Binding DockLayout}"
+		                  Factory="{Binding DockFactory}"
+		                  InitializeFactory="True"
+		                  InitializeLayout="True" />
 	</DockPanel>
 </Window>