First headless test + scroll-into-view fix

DecompileAsEnumerableTest exercises the full path: open mscorlib, navigate
to Enumerable.AsEnumerable, render the decompilation, verify text and
verify the row centred in the assembly tree. Writing it surfaced two
pre-existing bugs the manual smoke-test missed:

ILSpy.Tests/AssemblyTree/AssemblyTreeModelTests.cs

@@ -46,7 +46,10 @@ public class AssemblyTreeModelTests
 		model.Initialize();
 
 		model.AssemblyList.Should().NotBeNull("Initialize loads or creates the default AssemblyList.");
-		model.Root.Should().NotBeNull("Initialize wires Root to an AssemblyListTreeNode of the loaded list.");
+		// Cast through object so the generic AwesomeAssertions Should() resolves, not the
+		// TreeNodeAssertionsExtensions.Should(SharpTreeNode) shadow that landed in this commit
+		// (its TreeNodeAssertions surface doesn't expose NotBeNull).
+		((object?)model.Root).Should().NotBeNull("Initialize wires Root to an AssemblyListTreeNode of the loaded list.");
 	}
 
 	[AvaloniaTest]

ILSpy.Tests/DecompileAsEnumerableTest.cs

@@ -0,0 +1,76 @@
+// 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.Linq;
+using System.Threading.Tasks;
+
+using AwesomeAssertions;
+
+using Avalonia.Headless.NUnit;
+
+using global::ILSpy.AppEnv;
+using global::ILSpy.TreeNodes;
+using global::ILSpy.ViewModels;
+using global::ILSpy.Views;
+
+using NUnit.Framework;
+
+namespace ICSharpCode.ILSpy.Tests;
+
+[TestFixture]
+public class DecompileAsEnumerableTest
+{
+	[AvaloniaTest]
+	public async Task Selecting_AsEnumerable_Method_Decompiles_Into_Document_View()
+	{
+		var window = AppComposition.Current.GetExport<MainWindow>();
+		window.Show();
+		var vm = (MainWindowViewModel)window.DataContext!;
+
+		// MainWindow.Opened triggers AssemblyTreeModel.Initialize, which queues the default
+		// assembly list (System.Private.CoreLib, System, System.Linq) for async loading.
+		await vm.AssemblyTreeModel.WaitForAssembliesAsync(minimumCount: 3);
+
+		// Walk via the production FindNodeByPath (used by SessionSettings.ActiveTreeViewPath
+		// save/restore) down to the type. First segment is the assembly short name; the helper
+		// substitutes the file path AssemblyTreeNode.ToString returns.
+		var typeNode = vm.AssemblyTreeModel.FindNode<TypeTreeNode>(
+			"System.Linq", "System.Linq", "System.Linq.Enumerable");
+
+		// Method-level stable identities are built via ILAmbience and impractical to author by
+		// hand, so we expand the type and pick the overload by name. Enumerable has only one
+		// AsEnumerable, so this is unambiguous.
+		typeNode.EnsureLazyChildren();
+		var methodNode = typeNode.Children.OfType<MethodTreeNode>()
+			.Single(m => m.MethodDefinition.Name == "AsEnumerable");
+		methodNode.MethodDefinition.IsExtensionMethod.Should().BeTrue();
+
+		// Selecting the node routes through DockWorkspace -> the active decompiler tab.
+		vm.AssemblyTreeModel.SelectedItem = methodNode;
+
+		var tab = await vm.DockWorkspace.WaitForDecompiledTextAsync();
+		tab.Text.Should().Contain("AsEnumerable");
+		tab.Text.Should().Contain("IEnumerable<TSource>");
+		tab.Text.Should().Contain("return source");
+
+		// Selecting a deeply-nested node must scroll the assembly tree so it's centered.
+		methodNode.Should().Be().CenteredInView();
+
+		window.CaptureAndShow();
+	}
+}

ILSpy.Tests/MainWindow/MainWindowTests.cs

@@ -0,0 +1,46 @@
+// 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 global::ILSpy.AppEnv;
+using global::ILSpy.ViewModels;
+using global::ILSpy.Views;
+
+using NUnit.Framework;
+
+namespace ICSharpCode.ILSpy.Tests;
+
+[TestFixture]
+public class MainWindowTests
+{
+	[AvaloniaTest]
+	public void MainWindow_Resolves_From_Composition_And_Shows()
+	{
+		var window = AppComposition.Current.GetExport<MainWindow>();
+		window.Show();
+
+		window.IsVisible.Should().BeTrue();
+		window.Title.Should().Be("ILSpy");
+		window.DataContext.Should().BeOfType<MainWindowViewModel>();
+
+		window.CaptureAndShow();
+	}
+}

ILSpy.Tests/TreeNavigation.cs

@@ -0,0 +1,99 @@
+// 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.Linq;
+
+using ICSharpCode.ILSpyX.TreeView;
+
+using global::ILSpy.AssemblyTree;
+
+namespace ICSharpCode.ILSpy.Tests;
+
+/// <summary>
+/// Path-based tree navigation built on the production
+/// <see cref="AssemblyTreeModel.FindNodeByPath(string[], bool)"/> walk. First segment is an
+/// assembly short name (looked up in the assembly list, substituted with its file path);
+/// the rest are the stable <c>ToString()</c> identities each tree node emits — namespace
+/// name, type reflection name. Member-level identities go through ILAmbience and aren't
+/// hand-authorable, so tests should drill to the type with <see cref="FindNode{T}"/> and
+/// pick the member from <c>typeNode.Children</c> by <c>Name</c>.
+/// </summary>
+public static class TreeNavigation
+{
+	public static SharpTreeNode FindNode(this AssemblyTreeModel atm, params string[] segments)
+	{
+		ArgumentNullException.ThrowIfNull(atm);
+		ArgumentNullException.ThrowIfNull(segments);
+		if (segments.Length == 0)
+			throw new ArgumentException("At least one segment (the assembly short name) is required.", nameof(segments));
+
+		var path = ResolveAssembly(atm, segments);
+		return atm.FindNodeByPath(path, returnBestMatch: false)
+			?? Diagnose(atm, path, segments);
+	}
+
+	public static T FindNode<T>(this AssemblyTreeModel atm, params string[] segments)
+		where T : SharpTreeNode
+	{
+		var node = FindNode(atm, segments);
+		return node as T
+			?? throw new InvalidOperationException(
+				$"Path [{string.Join(" / ", segments)}] resolved to {node.GetType().Name}, expected {typeof(T).Name}.");
+	}
+
+	public static SharpTreeNode SelectNode(this AssemblyTreeModel atm, params string[] segments)
+	{
+		var node = FindNode(atm, segments);
+		atm.SelectedItem = node;
+		return node;
+	}
+
+	public static T SelectNode<T>(this AssemblyTreeModel atm, params string[] segments)
+		where T : SharpTreeNode
+	{
+		var node = FindNode<T>(atm, segments);
+		atm.SelectedItem = node;
+		return node;
+	}
+
+	static string[] ResolveAssembly(AssemblyTreeModel atm, string[] segments)
+	{
+		var shortName = segments[0];
+		var asm = atm.AssemblyList?.GetAssemblies()
+			.FirstOrDefault(a => string.Equals(a.ShortName, shortName, StringComparison.Ordinal))
+			?? throw new InvalidOperationException(
+				$"Assembly with ShortName '{shortName}' is not in the active list. Loaded: " +
+				$"[{string.Join(", ", atm.AssemblyList?.GetAssemblies().Select(a => a.ShortName) ?? Array.Empty<string>())}]");
+
+		var translated = (string[])segments.Clone();
+		translated[0] = asm.FileName;
+		return translated;
+	}
+
+	static SharpTreeNode Diagnose(AssemblyTreeModel atm, string[] stablePath, string[] originalSegments)
+	{
+		var partial = atm.FindNodeByPath(stablePath, returnBestMatch: true);
+		var children = partial == null
+			? "(root null)"
+			: string.Join(", ", partial.Children.Select(c => c.ToString()));
+		throw new InvalidOperationException(
+			$"FindNodeByPath could not resolve [{string.Join(" / ", originalSegments)}]. " +
+			$"Reached '{partial?.ToString() ?? "(null)"}'; available children: [{children}].");
+	}
+}

ILSpy.Tests/TreeNodeAssertions.cs

@@ -0,0 +1,202 @@
+// 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.Linq;
+
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Threading;
+using Avalonia.VisualTree;
+
+using AwesomeAssertions;
+
+using ICSharpCode.ILSpyX.TreeView;
+
+using global::ILSpy.AppEnv;
+using global::ILSpy.AssemblyTree;
+using global::ILSpy.Views;
+
+namespace ICSharpCode.ILSpy.Tests;
+
+public static class TreeNodeAssertionsExtensions
+{
+	public static TreeNodeAssertions Should(this SharpTreeNode subject) => new(subject);
+}
+
+public class TreeNodeAssertions
+{
+	public SharpTreeNode Subject { get; }
+
+	public TreeNodeAssertions(SharpTreeNode subject)
+	{
+		Subject = subject ?? throw new ArgumentNullException(nameof(subject));
+	}
+
+	public TreeNodeBeAssertions Be() => new(Subject);
+}
+
+public class TreeNodeBeAssertions
+{
+	static readonly TimeSpan ScrollPollTimeout = TimeSpan.FromSeconds(3);
+
+	public SharpTreeNode Subject { get; }
+
+	public TreeNodeBeAssertions(SharpTreeNode subject)
+	{
+		Subject = subject;
+	}
+
+	public AndConstraint<TreeNodeBeAssertions> ScrolledIntoView(string because = "", params object[] becauseArgs)
+		=> AssertScrollState(centered: false, because, becauseArgs);
+
+	public AndConstraint<TreeNodeBeAssertions> CenteredInView(string because = "", params object[] becauseArgs)
+		=> AssertScrollState(centered: true, because, becauseArgs);
+
+	AndConstraint<TreeNodeBeAssertions> AssertScrollState(bool centered, string because, object[] becauseArgs)
+	{
+		var grid = TryFindGrid(out var failure);
+		if (grid is null)
+		{
+			false.Should().BeTrue(
+				$"cannot verify scroll state for {Describe()}: {failure}{(string.IsNullOrEmpty(because) ? "" : " " + string.Format(because, becauseArgs))}");
+			return new AndConstraint<TreeNodeBeAssertions>(this);
+		}
+
+		var scrollViewer = grid.GetVisualDescendants().OfType<ScrollViewer>().FirstOrDefault()
+			?? throw new InvalidOperationException("DataGrid has no ScrollViewer in its visual tree.");
+
+		// ScrollIntoView is posted at Background priority — give it time to realise the row.
+		var deadline = DateTime.UtcNow + ScrollPollTimeout;
+		DataGridRow? row = null;
+		bool ok = false;
+		while (DateTime.UtcNow < deadline)
+		{
+			Dispatcher.UIThread.RunJobs();
+			row = FindRow(grid, Subject);
+			if (row != null && IsInViewport(row, scrollViewer)
+				&& (!centered || IsRoughlyCentered(row, scrollViewer)))
+			{
+				ok = true;
+				break;
+			}
+		}
+
+		ok.Should().BeTrue(
+			$"{Describe()} should be {(centered ? "centred" : "scrolled into view")}{(string.IsNullOrEmpty(because) ? "" : ", " + string.Format(because, becauseArgs))}, " +
+			BuildState(scrollViewer, row));
+
+		return new AndConstraint<TreeNodeBeAssertions>(this);
+	}
+
+	static DataGrid? TryFindGrid(out string? failure)
+	{
+		var window = FindActiveWindow();
+		if (window is null)
+		{
+			failure = "no active Avalonia Window";
+			return null;
+		}
+
+		var pane = window.GetVisualDescendants().OfType<AssemblyListPane>().FirstOrDefault();
+		if (pane is null)
+		{
+			failure = "AssemblyListPane is not in the visual tree (the assembly tree pane isn't shown)";
+			return null;
+		}
+
+		var grid = pane.GetVisualDescendants().OfType<DataGrid>().FirstOrDefault(g => g.Name == "TreeGrid");
+		if (grid is null)
+		{
+			failure = "TreeGrid DataGrid not found inside AssemblyListPane";
+			return null;
+		}
+
+		failure = null;
+		return grid;
+	}
+
+	static Window? FindActiveWindow()
+	{
+		// ApplicationLifetime is null in headless; the [Shared] MainWindow export gives us
+		// the same instance the test resolved.
+		try
+		{
+			return AppComposition.Current.GetExport<MainWindow>();
+		}
+		catch
+		{
+			return null;
+		}
+	}
+
+	static DataGridRow? FindRow(DataGrid grid, SharpTreeNode target)
+	{
+		foreach (var row in grid.GetVisualDescendants().OfType<DataGridRow>())
+		{
+			var ctx = row.DataContext;
+			if (ReferenceEquals(ctx, target))
+				return row;
+			// HierarchicalNode wraps the underlying item via .Item.
+			var itemProp = ctx?.GetType().GetProperty("Item");
+			if (itemProp is not null && ReferenceEquals(itemProp.GetValue(ctx), target))
+				return row;
+		}
+		return null;
+	}
+
+	static bool IsInViewport(DataGridRow row, ScrollViewer scrollViewer)
+	{
+		var topLeft = row.TranslatePoint(new Point(0, 0), scrollViewer);
+		if (topLeft is null)
+			return false;
+		var top = topLeft.Value.Y;
+		var bottom = top + row.Bounds.Height;
+		return top >= 0 && bottom <= scrollViewer.Viewport.Height + 0.5;
+	}
+
+	static bool IsRoughlyCentered(DataGridRow row, ScrollViewer scrollViewer)
+	{
+		var topLeft = row.TranslatePoint(new Point(0, 0), scrollViewer);
+		if (topLeft is null)
+			return false;
+		var rowMid = topLeft.Value.Y + row.Bounds.Height / 2;
+		var viewportMid = scrollViewer.Viewport.Height / 2;
+		// Accept rows clamped at the start/end of the list as "as centred as possible".
+		var nearTopClamp = scrollViewer.Offset.Y <= 0.5;
+		var nearBottomClamp = scrollViewer.Offset.Y >= scrollViewer.Extent.Height - scrollViewer.Viewport.Height - 0.5;
+		return Math.Abs(rowMid - viewportMid) <= row.Bounds.Height || nearTopClamp || nearBottomClamp;
+	}
+
+	string BuildState(ScrollViewer scrollViewer, DataGridRow? row)
+	{
+		if (row is null)
+			return $"but no DataGridRow has been realised for it (offset={scrollViewer.Offset}, viewport={scrollViewer.Viewport}, extent={scrollViewer.Extent})";
+		var topLeft = row.TranslatePoint(new Point(0, 0), scrollViewer);
+		var top = topLeft?.Y;
+		var bottom = top + row.Bounds.Height;
+		return $"but its row sits at {top:0.#}..{bottom:0.#} relative to the viewport " +
+			$"(viewport height {scrollViewer.Viewport.Height:0.#}, offset {scrollViewer.Offset.Y:0.#}, extent {scrollViewer.Extent.Height:0.#})";
+	}
+
+	string Describe()
+	{
+		var text = Subject.Text?.ToString();
+		return string.IsNullOrEmpty(text) ? Subject.GetType().Name : $"\"{text}\"";
+	}
+}

ILSpy.Tests/Waiters.cs

@@ -0,0 +1,85 @@
+// 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.Linq;
+using System.Runtime.CompilerServices;
+using System.Threading.Tasks;
+
+using Avalonia.Threading;
+
+using global::ILSpy.AssemblyTree;
+using global::ILSpy.Docking;
+using global::ILSpy.TextView;
+
+namespace ICSharpCode.ILSpy.Tests;
+
+public static class Waiters
+{
+	static readonly TimeSpan DefaultTimeout = TimeSpan.FromSeconds(15);
+	static readonly TimeSpan PollInterval = TimeSpan.FromMilliseconds(25);
+
+	public static async Task WaitForAsync(
+		Func<bool> predicate,
+		TimeSpan? timeout = null,
+		[CallerArgumentExpression(nameof(predicate))] string? description = null)
+	{
+		ArgumentNullException.ThrowIfNull(predicate);
+		var deadline = DateTime.UtcNow + (timeout ?? DefaultTimeout);
+		while (DateTime.UtcNow < deadline)
+		{
+			if (predicate())
+				return;
+			Dispatcher.UIThread.RunJobs();
+			await Task.Delay(PollInterval);
+		}
+		throw new TimeoutException(
+			$"Timed out after {(timeout ?? DefaultTimeout).TotalSeconds:0.#}s waiting for: {description}");
+	}
+
+	public static async Task WaitForAssembliesAsync(
+		this AssemblyTreeModel atm,
+		int minimumCount = 1,
+		TimeSpan? timeout = null)
+	{
+		ArgumentNullException.ThrowIfNull(atm);
+		await WaitForAsync(
+			() => (atm.AssemblyList?.GetAssemblies().Length ?? 0) >= minimumCount,
+			timeout,
+			$"AssemblyList to contain >= {minimumCount} assemblies");
+		var assemblies = atm.AssemblyList!.GetAssemblies();
+		await Task.WhenAll(assemblies.Select(a => a.GetLoadResultAsync()));
+	}
+
+	public static async Task<DecompilerTabPageModel> WaitForDecompiledTextAsync(
+		this DockWorkspace dock,
+		TimeSpan? timeout = null)
+	{
+		ArgumentNullException.ThrowIfNull(dock);
+		var documents = ((ILSpyDockFactory)dock.Factory).Documents
+			?? throw new InvalidOperationException("DockWorkspace has no document dock yet.");
+
+		await WaitForAsync(
+			() => documents.ActiveDockable is DecompilerTabPageModel { IsDecompiling: false } tab
+				&& !string.IsNullOrEmpty(tab.Text),
+			timeout,
+			"active decompiler tab to finish decompiling and produce text");
+
+		return (DecompilerTabPageModel)documents.ActiveDockable!;
+	}
+}

ILSpy/AssemblyTree/AssemblyListPane.axaml.cs

@@ -16,8 +16,10 @@
 // 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;
 using System.ComponentModel;
+using System.Linq;
 
 using Avalonia;
 using Avalonia.Controls;
@@ -33,8 +35,8 @@ namespace ILSpy.AssemblyTree
 {
 	public partial class AssemblyListPane : UserControl
 	{
-		// Set while propagating model.SelectedItem → DataGrid.SelectedItem so the resulting
-		// SelectionChanged event doesn't bounce right back into the model.
+		// Suppresses the SelectionChanged → model bounce while we're pushing the model's
+		// selection into the DataGrid.
 		bool syncingSelection;
 
 		public AssemblyListPane()
@@ -72,15 +74,12 @@ namespace ILSpy.AssemblyTree
 			if (TreeGrid.HierarchicalModel is not IHierarchicalModel hm)
 				return;
 
-			// Build the SharpTreeNode path from a root (a child of the hidden AssemblyListTreeNode)
-			// down to the target.
 			var path = new System.Collections.Generic.List<SharpTreeNode>();
 			for (var n = target; n.Parent != null; n = n.Parent)
 				path.Add(n);
 			path.Reverse();
 
-			// Walk top-down: ProDataGrid only materialises children of expanded nodes, so each
-			// ancestor must be expanded before FindNode can locate the next level's wrapper.
+			// Each ancestor must be expanded before FindNode can locate the next level's wrapper.
 			BeginSync();
 			HierarchicalNode? hNode = null;
 			for (int i = 0; i < path.Count; i++)
@@ -101,15 +100,46 @@ namespace ILSpy.AssemblyTree
 				return;
 			}
 			TreeGrid.SelectedItem = target;
-			TreeGrid.ScrollIntoView(target, TreeGrid.Columns[0]);
+			// Pass the HierarchicalNode wrapper (DataGrid.IndexOf is against the wrappers, not
+			// the underlying SharpTreeNodes), and defer past Expand's pending child-realization
+			// notifications — synchronously the wrapper isn't in the visible list yet.
+			var scrollTarget = hNode!;
+			global::Avalonia.Threading.Dispatcher.UIThread.Post(
+				() => CenterRowInView(scrollTarget),
+				global::Avalonia.Threading.DispatcherPriority.Background);
 			EndSync();
 		}
 
+		// DataGrid.ScrollIntoView only brings the row to the nearest viewport edge; we want
+		// it centred (matching the WPF host).
+		void CenterRowInView(HierarchicalNode node)
+		{
+			TreeGrid.ScrollIntoView(node, TreeGrid.Columns[0]);
+
+			var row = TreeGrid.GetVisualDescendants().OfType<DataGridRow>()
+				.FirstOrDefault(r => ReferenceEquals(r.DataContext, node));
+			if (row is null)
+				return;
+
+			var scrollViewer = TreeGrid.GetVisualDescendants().OfType<ScrollViewer>().FirstOrDefault();
+			if (scrollViewer is null)
+				return;
+
+			var rowTopInViewer = row.TranslatePoint(new Point(0, 0), scrollViewer);
+			if (rowTopInViewer is null)
+				return;
+
+			var desiredTop = (scrollViewer.Viewport.Height - row.Bounds.Height) / 2;
+			var newOffsetY = scrollViewer.Offset.Y + (rowTopInViewer.Value.Y - desiredTop);
+			var maxOffset = Math.Max(0, scrollViewer.Extent.Height - scrollViewer.Viewport.Height);
+			newOffsetY = Math.Clamp(newOffsetY, 0, maxOffset);
+			scrollViewer.Offset = new Vector(scrollViewer.Offset.X, newOffsetY);
+		}
+
 		void BeginSync() => syncingSelection = true;
 
-		// Hold the guard across one dispatch tick so any deferred SelectionChanged emits the
-		// DataGrid raises in response to our programmatic Expand / SelectedItem / ScrollIntoView
-		// calls don't bounce back into model.SelectedItem and cancel the navigation.
+		// Released on a Background dispatch tick so any DataGrid SelectionChanged the Expand /
+		// SelectedItem / ScrollIntoView calls trigger doesn't bounce back into the model.
 		void EndSync() => global::Avalonia.Threading.Dispatcher.UIThread.Post(
 			() => syncingSelection = false,
 			global::Avalonia.Threading.DispatcherPriority.Background);

ILSpy/TreeNodes/NamespaceTreeNode.cs

@@ -46,6 +46,11 @@ namespace ILSpy.TreeNodes
 
 		public override object Icon => Images.Images.Namespace;
 
+		// Stable identity for SessionSettings.ActiveTreeViewPath (used by AssemblyTreeModel.
+		// FindNodeByPath / GetPathForNode). Without this override the default Object.ToString
+		// returns the type name, which makes save/restore of namespace selections silently fail.
+		public override string ToString() => name;
+
 		protected override void LoadChildren()
 		{
 			var metadata = module.Metadata;