diff --git a/ILSpy/Commands/DecompileAllCommand.cs b/ILSpy/Commands/DecompileAllCommand.cs
new file mode 100644
index 000000000..3f5dcddea
--- /dev/null
+++ b/ILSpy/Commands/DecompileAllCommand.cs
@@ -0,0 +1,165 @@
+// 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.
+
+#if DEBUG
+using System;
+using System.Collections.Concurrent;
+using System.Composition;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+using System.Threading.Tasks;
+
+using ICSharpCode.Decompiler;
+using ICSharpCode.ILSpy.Properties;
+using ICSharpCode.ILSpyX;
+
+using ILSpy.AssemblyTree;
+using ILSpy.Docking;
+using ILSpy.Languages;
+using ILSpy.TextView;
+using ILSpy.TreeNodes;
+
+namespace ILSpy.Commands
+{
+	/// <summary>
+	/// DEBUG-only File-menu stress test: decompile every loaded assembly to
+	/// <c>c:\temp\decompiled\&lt;ShortName&gt;.cs</c> in parallel and report per-assembly
+	/// timing in a results tab. Hard-coded output path matches WPF — the command's
+	/// CanExecute gates on that directory existing so it's effectively opt-in.
+	/// </summary>
+	[ExportMainMenuCommand(ParentMenuID = nameof(Resources._File), Header = nameof(Resources.DEBUGDecompile), MenuCategory = nameof(Resources.Open), MenuOrder = 2.5)]
+	[Shared]
+	sealed class DecompileAllCommand : SimpleCommand
+	{
+		const string OutputDir = @"c:\temp\decompiled";
+
+		readonly AssemblyTreeModel assemblyTreeModel;
+		readonly DockWorkspace dockWorkspace;
+
+		[ImportingConstructor]
+		public DecompileAllCommand(AssemblyTreeModel assemblyTreeModel, DockWorkspace dockWorkspace)
+		{
+			this.assemblyTreeModel = assemblyTreeModel;
+			this.dockWorkspace = dockWorkspace;
+		}
+
+		public override bool CanExecute(object? parameter) => Directory.Exists(OutputDir);
+
+		public override void Execute(object? parameter) => _ = ExecuteAsync();
+
+		async Task ExecuteAsync()
+		{
+			try
+			{
+				var report = await dockWorkspace.RunWithCancellation(token => Task.Run(() => {
+					var output = new AvaloniaEditTextOutput { Title = "Decompile All" };
+					var bag = new ConcurrentBag<string>();
+					Parallel.ForEach(
+						Partitioner.Create(assemblyTreeModel.AssemblyList!.GetAssemblies(), loadBalance: true),
+						new ParallelOptions { MaxDegreeOfParallelism = Environment.ProcessorCount, CancellationToken = token },
+						asm => {
+							if (asm.HasLoadError)
+								return;
+							var watch = Stopwatch.StartNew();
+							Exception? ex = null;
+							var path = Path.Combine(OutputDir, asm.ShortName + ".cs");
+							try
+							{
+								using var writer = new StreamWriter(path);
+								var options = new DecompilationOptions {
+									CancellationToken = token,
+									FullDecompilation = true,
+								};
+								new CSharpLanguage().DecompileAssembly(asm, new PlainTextOutput(writer), options);
+							}
+							catch (Exception caught)
+							{
+								ex = caught;
+							}
+							watch.Stop();
+							bag.Add(asm.ShortName + " - " + watch.Elapsed + (ex != null ? " - " + ex.GetType().Name : ""));
+						});
+					foreach (var line in bag.OrderBy(s => s, StringComparer.OrdinalIgnoreCase))
+					{
+						output.Write(line);
+						output.WriteLine();
+					}
+					return output;
+				}, token), "Decompiling all assemblies…");
+				dockWorkspace.ShowText(report);
+			}
+			catch (OperationCanceledException) { }
+		}
+	}
+
+	/// <summary>
+	/// DEBUG-only stress test: re-decompile the current selection 100 times in series
+	/// and report average wall-clock time. Used for tracking decompilation perf
+	/// regressions across changes.
+	/// </summary>
+	[ExportMainMenuCommand(ParentMenuID = nameof(Resources._File), Header = nameof(Resources.DEBUGDecompile100x), MenuCategory = nameof(Resources.Open), MenuOrder = 2.6)]
+	[Shared]
+	sealed class Decompile100TimesCommand : SimpleCommand
+	{
+		const int NumRuns = 100;
+
+		readonly AssemblyTreeModel assemblyTreeModel;
+		readonly LanguageService languageService;
+		readonly DockWorkspace dockWorkspace;
+
+		[ImportingConstructor]
+		public Decompile100TimesCommand(AssemblyTreeModel assemblyTreeModel, LanguageService languageService, DockWorkspace dockWorkspace)
+		{
+			this.assemblyTreeModel = assemblyTreeModel;
+			this.languageService = languageService;
+			this.dockWorkspace = dockWorkspace;
+		}
+
+		public override void Execute(object? parameter) => _ = ExecuteAsync();
+
+		async Task ExecuteAsync()
+		{
+			var language = languageService.CurrentLanguage;
+			var nodes = assemblyTreeModel.SelectedItems.OfType<ILSpyTreeNode>().ToArray();
+			if (nodes.Length == 0)
+				return;
+			try
+			{
+				var report = await dockWorkspace.RunWithCancellation(token => Task.Run(() => {
+					var watch = Stopwatch.StartNew();
+					var options = new DecompilationOptions { CancellationToken = token };
+					for (int i = 0; i < NumRuns; i++)
+					{
+						foreach (var node in nodes)
+							node.Decompile(language, new PlainTextOutput(), options);
+					}
+					watch.Stop();
+					var output = new AvaloniaEditTextOutput { Title = "Decompile 100×" };
+					var msPerRun = watch.Elapsed.TotalMilliseconds / NumRuns;
+					output.Write($"Average time: {msPerRun:f1}ms");
+					output.WriteLine();
+					return output;
+				}, token), "Decompiling 100×…");
+				dockWorkspace.ShowText(report);
+			}
+			catch (OperationCanceledException) { }
+		}
+	}
+}
+#endif
diff --git a/ILSpy/Commands/FileCommands.cs b/ILSpy/Commands/FileCommands.cs
index bd8abf25e..445d865ac 100644
--- a/ILSpy/Commands/FileCommands.cs
+++ b/ILSpy/Commands/FileCommands.cs
@@ -107,19 +107,8 @@ namespace ILSpy.Commands
 		public override void Execute(object? parameter) => assemblyTreeModel.Refresh();
 	}
 
-	[ExportMainMenuCommand(ParentMenuID = nameof(Resources._File), Header = nameof(Resources.DEBUGDecompile), MenuCategory = nameof(Resources.Open), MenuOrder = 2.5)]
-	[Shared]
-	sealed class DecompileAllCommand : SimpleCommand
-	{
-		public override void Execute(object? parameter) => NotImplementedDialog.Show(Resources.DEBUGDecompile);
-	}
-
-	[ExportMainMenuCommand(ParentMenuID = nameof(Resources._File), Header = nameof(Resources.DEBUGDecompile100x), MenuCategory = nameof(Resources.Open), MenuOrder = 2.6)]
-	[Shared]
-	sealed class Decompile100TimesCommand : SimpleCommand
-	{
-		public override void Execute(object? parameter) => NotImplementedDialog.Show(Resources.DEBUGDecompile100x);
-	}
+	// DEBUG-only DecompileAllCommand + Decompile100TimesCommand live in DecompileAllCommand.cs;
+	// the stubs that lived here were replaced with the real implementations in `<commit>`.
 
 	[ExportMainMenuCommand(ParentMenuID = nameof(Resources._File), Header = nameof(Resources.DEBUGDisassemble), MenuCategory = nameof(Resources.Open), MenuOrder = 2.5)]
 	[Shared]