SimonCropp · Oct 28, 2026 · Oct 28, 2026
diff --git a/claude.md b/claude.md
@@ -39,7 +39,7 @@ dotnet run -c Release --project src/DiffEngineViewer.Windows.Benchmarks -- --fil
 
 **Target Frameworks:**
 - DiffEngine library: net462, net472, net48, net6.0, net7.0, net8.0, net9.0, net10.0 (Windows also includes .NET Framework targets)
-- DiffEngineTray: net10.0 Windows Forms application
+- DiffEngineTray: net10.0 Windows Forms application, on DiffEngineTray.Core (net10.0, every platform)
 - Tests: net10.0 (net48 on Windows)
 
 ## Architecture Overview
@@ -677,7 +677,17 @@ the comment there about not caching "nothing staged" asks for.
   `libX11` is left of them.
 
 **DiffEngineTray (`src/DiffEngineTray/`):**
-- Windows Forms tray application that handles pending file diffs
+- Windows Forms tray application that handles pending file diffs, in two projects. `src/DiffEngineTray.Core`
+  is everything that is not WinForms - `Tracker`, both inline hosts, `PiperServer`, the settings,
+  `DebugReport`, `IssueLauncher` and the Windows API helpers `ProcessEx` and `FileLockKiller`, which
+  compile anywhere and run only on Windows until they have Unix paths - and builds on every
+  platform, so a macOS or Linux head can be put on it. `src/DiffEngineTray` is the Windows head:
+  `Program`, the menu, the forms, the hot keys (`KeyRegister`, `KeyName`, which parses into WinForms'
+  `Keys`), the icons and the Run key. Two seams cross between them. `LockedFilesPolicy.AlwaysKill` is
+  the core's, and the question a locked file asks is the head's form (`LockedFilesHandler`).
+  `IssueLauncher.Declined` declines in the core, which has no toolkit to ask with, and the head
+  hands it `IssueQuestion`'s MessageBox first thing in Main. The core is signed and named in
+  DiffEngine's `InternalsVisibleTo`, and names the head and the tests in its own
 - `PiperServer` - TCP server (localhost, 3492) receiving move/delete payloads from DiffEngine.
   Deliberately a second listener beside the viewer protocol, not debt: its format is frozen
   (every stable DiffEngine embeds PiperClient, pinned in test projects while the tray updates

diff --git a/src/DiffEngine.slnx b/src/DiffEngine.slnx
@@ -84,6 +84,10 @@
     <BuildType Solution="Release-NotWindows|*" Project="Release" />
     <Build Solution="Release-NotWindows|*" Project="false" />
   </Project>
+  <!-- Builds everywhere: the tray's non-WinForms half, which a macOS or Linux head shares. -->
+  <Project Path="DiffEngineTray.Core/DiffEngineTray.Core.csproj">
+    <BuildType Solution="Release-NotWindows|*" Project="Release" />
+  </Project>
   <Project Path="FakeDiffTool/FakeDiffTool.csproj">
     <BuildType Solution="Release-NotWindows|*" Project="Release" />
     <!--

diff --git a/src/DiffEngine/InternalsVisibleTo.cs b/src/DiffEngine/InternalsVisibleTo.cs
@@ -1,6 +1,7 @@
-[assembly: InternalsVisibleTo("DiffEngine.Tests, PublicKey=00240000048000009400000006020000002400005253413100040000010001000f0a8e4bf1639dce01be6592384e7dfc621915b7759fb5cee42ec5d351bcc43460432da1659ee618ca6cab6b8b8e56a5deb5d4ee1a49783d5c2690752502d31ccbfee9b2c697e20359b55ad100cc9370c8e983fd9496f01d761a060d0435bac7243b1832ba95757aa5adbb67df38c213d717b6751e1217cea9fa5c61e9b799dd")]
+[assembly: InternalsVisibleTo("DiffEngine.Tests, PublicKey=00240000048000009400000006020000002400005253413100040000010001000f0a8e4bf1639dce01be6592384e7dfc621915b7759fb5cee42ec5d351bcc43460432da1659ee618ca6cab6b8b8e56a5deb5d4ee1a49783d5c2690752502d31ccbfee9b2c697e20359b55ad100cc9370c8e983fd9496f01d761a060d0435bac7243b1832ba95757aa5adbb67df38c213d717b6751e1217cea9fa5c61e9b799dd")]
 [assembly: InternalsVisibleTo("VersionTests, PublicKey=00240000048000009400000006020000002400005253413100040000010001000f0a8e4bf1639dce01be6592384e7dfc621915b7759fb5cee42ec5d351bcc43460432da1659ee618ca6cab6b8b8e56a5deb5d4ee1a49783d5c2690752502d31ccbfee9b2c697e20359b55ad100cc9370c8e983fd9496f01d761a060d0435bac7243b1832ba95757aa5adbb67df38c213d717b6751e1217cea9fa5c61e9b799dd")]
 [assembly: InternalsVisibleTo("DiffEngineTray, PublicKey=00240000048000009400000006020000002400005253413100040000010001000f0a8e4bf1639dce01be6592384e7dfc621915b7759fb5cee42ec5d351bcc43460432da1659ee618ca6cab6b8b8e56a5deb5d4ee1a49783d5c2690752502d31ccbfee9b2c697e20359b55ad100cc9370c8e983fd9496f01d761a060d0435bac7243b1832ba95757aa5adbb67df38c213d717b6751e1217cea9fa5c61e9b799dd")]
+[assembly: InternalsVisibleTo("DiffEngineTray.Core, PublicKey=00240000048000009400000006020000002400005253413100040000010001000f0a8e4bf1639dce01be6592384e7dfc621915b7759fb5cee42ec5d351bcc43460432da1659ee618ca6cab6b8b8e56a5deb5d4ee1a49783d5c2690752502d31ccbfee9b2c697e20359b55ad100cc9370c8e983fd9496f01d761a060d0435bac7243b1832ba95757aa5adbb67df38c213d717b6751e1217cea9fa5c61e9b799dd")]
 [assembly: InternalsVisibleTo("DiffEngineTray.Tests, PublicKey=00240000048000009400000006020000002400005253413100040000010001000f0a8e4bf1639dce01be6592384e7dfc621915b7759fb5cee42ec5d351bcc43460432da1659ee618ca6cab6b8b8e56a5deb5d4ee1a49783d5c2690752502d31ccbfee9b2c697e20359b55ad100cc9370c8e983fd9496f01d761a060d0435bac7243b1832ba95757aa5adbb67df38c213d717b6751e1217cea9fa5c61e9b799dd")]
 [assembly: InternalsVisibleTo("DiffEngineViewer.Tests, PublicKey=00240000048000009400000006020000002400005253413100040000010001000f0a8e4bf1639dce01be6592384e7dfc621915b7759fb5cee42ec5d351bcc43460432da1659ee618ca6cab6b8b8e56a5deb5d4ee1a49783d5c2690752502d31ccbfee9b2c697e20359b55ad100cc9370c8e983fd9496f01d761a060d0435bac7243b1832ba95757aa5adbb67df38c213d717b6751e1217cea9fa5c61e9b799dd")]
 [assembly: InternalsVisibleTo("DiffEngine.Benchmarks, PublicKey=00240000048000009400000006020000002400005253413100040000010001000f0a8e4bf1639dce01be6592384e7dfc621915b7759fb5cee42ec5d351bcc43460432da1659ee618ca6cab6b8b8e56a5deb5d4ee1a49783d5c2690752502d31ccbfee9b2c697e20359b55ad100cc9370c8e983fd9496f01d761a060d0435bac7243b1832ba95757aa5adbb67df38c213d717b6751e1217cea9fa5c61e9b799dd")]
diff --git a/src/DiffEngineTray/AssemblyLocation.cs → src/DiffEngineTray.Core/AssemblyLocation.cs b/src/DiffEngineTray/AssemblyLocation.cs → src/DiffEngineTray.Core/AssemblyLocation.cs
diff --git a/src/DiffEngineTray/AsyncTimer.cs → src/DiffEngineTray.Core/AsyncTimer.cs b/src/DiffEngineTray/AsyncTimer.cs → src/DiffEngineTray.Core/AsyncTimer.cs
diff --git a/src/DiffEngineTray/DebugReport.cs → src/DiffEngineTray.Core/DebugReport.cs b/src/DiffEngineTray/DebugReport.cs → src/DiffEngineTray.Core/DebugReport.cs
diff --git a/src/DiffEngineTray.Core/DiffEngineTray.Core.csproj b/src/DiffEngineTray.Core/DiffEngineTray.Core.csproj
@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <!--
+  Everything the tray does that is not WinForms: the tracked moves and deletes, the inline queue it
+  owns or drives, the piper port, the settings and the debug report. Built and tested on every
+  platform, so a head for macOS and Linux can be put on it. ProcessEx and FileLockKiller call
+  Windows APIs, which compile anywhere and run only on Windows until they have Unix paths of their
+  own.
+  -->
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <IsPackable>false</IsPackable>
+    <GenerateDocumentationFile>false</GenerateDocumentationFile>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Using Include="DiffEngine" />
+    <Using Include="PlatformHeads" />
+    <PackageReference Include="PlatformHeads.Core" />
+    <PackageReference Include="Serilog" />
+    <PackageReference Include="Serilog.Sinks.File" />
+    <PackageReference Include="ProjectDefaults" PrivateAssets="all" />
+    <ProjectReference Include="..\DiffEngine\DiffEngine.csproj" />
+  </ItemGroup>
+</Project>
diff --git a/src/DiffEngineTray/DirectoryLauncher.cs → src/DiffEngineTray.Core/DirectoryLauncher.cs b/src/DiffEngineTray/DirectoryLauncher.cs → src/DiffEngineTray.Core/DirectoryLauncher.cs
diff --git a/src/DiffEngineTray/ExceptionHandler.cs → src/DiffEngineTray.Core/ExceptionHandler.cs b/src/DiffEngineTray/ExceptionHandler.cs → src/DiffEngineTray.Core/ExceptionHandler.cs
diff --git a/src/DiffEngineTray/FileComparer.cs → src/DiffEngineTray.Core/FileComparer.cs b/src/DiffEngineTray/FileComparer.cs → src/DiffEngineTray.Core/FileComparer.cs
diff --git a/src/DiffEngineTray/FileEx.cs → src/DiffEngineTray.Core/FileEx.cs b/src/DiffEngineTray/FileEx.cs → src/DiffEngineTray.Core/FileEx.cs
diff --git a/src/DiffEngineTray/FileLockKiller.cs → src/DiffEngineTray.Core/FileLockKiller.cs b/src/DiffEngineTray/FileLockKiller.cs → src/DiffEngineTray.Core/FileLockKiller.cs
diff --git a/src/DiffEngineTray.Core/GlobalUsings.cs b/src/DiffEngineTray.Core/GlobalUsings.cs
@@ -0,0 +1,9 @@
+global using System.ComponentModel;
+global using Microsoft.Win32.SafeHandles;
+global using Serilog;
+global using System.Text.Json;
+global using System.Text.Json.Serialization;
+global using System.Diagnostics.CodeAnalysis;
+global using System.Net;
+global using System.Net.Sockets;
+global using System.Reflection;
diff --git a/src/DiffEngineTray/HotKey/HotKey.cs → src/DiffEngineTray.Core/HotKey/HotKey.cs b/src/DiffEngineTray/HotKey/HotKey.cs → src/DiffEngineTray.Core/HotKey/HotKey.cs
diff --git a/src/DiffEngineTray/IInlineHost.cs → src/DiffEngineTray.Core/IInlineHost.cs b/src/DiffEngineTray/IInlineHost.cs → src/DiffEngineTray.Core/IInlineHost.cs
diff --git a/src/DiffEngineTray/ITrackedFiles.cs → src/DiffEngineTray.Core/ITrackedFiles.cs b/src/DiffEngineTray/ITrackedFiles.cs → src/DiffEngineTray.Core/ITrackedFiles.cs
diff --git a/src/DiffEngineTray/IViewerLauncher.cs → src/DiffEngineTray.Core/IViewerLauncher.cs b/src/DiffEngineTray/IViewerLauncher.cs → src/DiffEngineTray.Core/IViewerLauncher.cs
diff --git a/src/DiffEngineTray.Core/InternalsVisibleTo.cs b/src/DiffEngineTray.Core/InternalsVisibleTo.cs
@@ -0,0 +1,2 @@
+[assembly: InternalsVisibleTo("DiffEngineTray, PublicKey=00240000048000009400000006020000002400005253413100040000010001000f0a8e4bf1639dce01be6592384e7dfc621915b7759fb5cee42ec5d351bcc43460432da1659ee618ca6cab6b8b8e56a5deb5d4ee1a49783d5c2690752502d31ccbfee9b2c697e20359b55ad100cc9370c8e983fd9496f01d761a060d0435bac7243b1832ba95757aa5adbb67df38c213d717b6751e1217cea9fa5c61e9b799dd")]
+[assembly: InternalsVisibleTo("DiffEngineTray.Tests, PublicKey=00240000048000009400000006020000002400005253413100040000010001000f0a8e4bf1639dce01be6592384e7dfc621915b7759fb5cee42ec5d351bcc43460432da1659ee618ca6cab6b8b8e56a5deb5d4ee1a49783d5c2690752502d31ccbfee9b2c697e20359b55ad100cc9370c8e983fd9496f01d761a060d0435bac7243b1832ba95757aa5adbb67df38c213d717b6751e1217cea9fa5c61e9b799dd")]
diff --git a/src/DiffEngineTray/IssueLauncher.cs → src/DiffEngineTray.Core/IssueLauncher.cs b/src/DiffEngineTray/IssueLauncher.cs → src/DiffEngineTray.Core/IssueLauncher.cs
@@ -87,19 +87,11 @@ Open an issue on GitHub?
     }
 
     /// <summary>
-    /// Puts the question, and answers whether it was declined. A field so that a test process can
-    /// decline without anybody being asked: the box is modal, on the desktop of whoever is at the
-    /// machine, and a test run that reached it waited there for a click.
+    /// Puts the question, and answers whether it was declined. Declined until a head says how to
+    /// ask, since asking is a box of a toolkit's own: the Windows head hands over a MessageBox
+    /// (<c>IssueQuestion</c>) as it starts. A field so that a test process can decline without
+    /// anybody being asked: the box is modal, on the desktop of whoever is at the machine, and a
+    /// test run that reached it waited there for a click.
     /// </summary>
-    internal static Func<string, bool> Declined = AskIfOpenIssue;
-
-    static bool AskIfOpenIssue(string text)
-    {
-        var result = MessageBox.Show(
-            text,
-            "DiffEngineTray Error",
-            MessageBoxButtons.YesNo,
-            MessageBoxIcon.Error);
-        return result == DialogResult.No;
-    }
+    internal static Func<string, bool> Declined = _ => true;
 }
diff --git a/src/DiffEngineTray/LinkLauncher.cs → src/DiffEngineTray.Core/LinkLauncher.cs b/src/DiffEngineTray/LinkLauncher.cs → src/DiffEngineTray.Core/LinkLauncher.cs
diff --git a/src/DiffEngineTray/LockedFiles.cs → src/DiffEngineTray.Core/LockedFiles.cs b/src/DiffEngineTray/LockedFiles.cs → src/DiffEngineTray.Core/LockedFiles.cs
diff --git a/src/DiffEngineTray.Core/LockedFilesPolicy.cs b/src/DiffEngineTray.Core/LockedFilesPolicy.cs
@@ -0,0 +1,10 @@
+/// <summary>
+/// Whether a move whose target is locked kills what holds it without asking: the
+/// AlwaysKillLockingProcesses setting, set at startup and from the Options form, and by the
+/// question's own "always" box. Apart from the question, which is a WinForms form in the head, so
+/// the tracker can ask this of a head that has none.
+/// </summary>
+static class LockedFilesPolicy
+{
+    public static bool AlwaysKill { get; set; }
+}
diff --git a/src/DiffEngineTray/LockedFilesResolver.cs → ...iffEngineTray.Core/LockedFilesResolver.cs b/src/DiffEngineTray/LockedFilesResolver.cs → ...iffEngineTray.Core/LockedFilesResolver.cs
diff --git a/src/DiffEngineTray/LockedFilesResponse.cs → ...iffEngineTray.Core/LockedFilesResponse.cs b/src/DiffEngineTray/LockedFilesResponse.cs → ...iffEngineTray.Core/LockedFilesResponse.cs
diff --git a/src/DiffEngineTray/LockingProcess.cs → src/DiffEngineTray.Core/LockingProcess.cs b/src/DiffEngineTray/LockingProcess.cs → src/DiffEngineTray.Core/LockingProcess.cs
diff --git a/src/DiffEngineTray/Logging.cs → src/DiffEngineTray.Core/Logging.cs b/src/DiffEngineTray/Logging.cs → src/DiffEngineTray.Core/Logging.cs
diff --git a/src/DiffEngineTray/OwnedInlineHost.cs → src/DiffEngineTray.Core/OwnedInlineHost.cs b/src/DiffEngineTray/OwnedInlineHost.cs → src/DiffEngineTray.Core/OwnedInlineHost.cs
diff --git a/src/DiffEngineTray/Payloads/DeletePayload.cs → ...EngineTray.Core/Payloads/DeletePayload.cs b/src/DiffEngineTray/Payloads/DeletePayload.cs → ...EngineTray.Core/Payloads/DeletePayload.cs
diff --git a/src/DiffEngineTray/Payloads/MovePayload.cs → ...ffEngineTray.Core/Payloads/MovePayload.cs b/src/DiffEngineTray/Payloads/MovePayload.cs → ...ffEngineTray.Core/Payloads/MovePayload.cs
diff --git a/src/DiffEngineTray/PendingSnapshot.cs → src/DiffEngineTray.Core/PendingSnapshot.cs b/src/DiffEngineTray/PendingSnapshot.cs → src/DiffEngineTray.Core/PendingSnapshot.cs
diff --git a/src/DiffEngineTray/PiperServer.cs → src/DiffEngineTray.Core/PiperServer.cs b/src/DiffEngineTray/PiperServer.cs → src/DiffEngineTray.Core/PiperServer.cs
diff --git a/src/DiffEngineTray/ProcessEx.cs → src/DiffEngineTray.Core/ProcessEx.cs b/src/DiffEngineTray/ProcessEx.cs → src/DiffEngineTray.Core/ProcessEx.cs
diff --git a/src/DiffEngineTray/RemoteInlineHost.cs → src/DiffEngineTray.Core/RemoteInlineHost.cs b/src/DiffEngineTray/RemoteInlineHost.cs → src/DiffEngineTray.Core/RemoteInlineHost.cs
diff --git a/src/DiffEngineTray/Serializer.cs → src/DiffEngineTray.Core/Serializer.cs b/src/DiffEngineTray/Serializer.cs → src/DiffEngineTray.Core/Serializer.cs
diff --git a/src/DiffEngineTray/Settings/Settings.cs → src/DiffEngineTray.Core/Settings/Settings.cs b/src/DiffEngineTray/Settings/Settings.cs → src/DiffEngineTray.Core/Settings/Settings.cs
diff --git a/...iffEngineTray/Settings/SettingsContext.cs → ...gineTray.Core/Settings/SettingsContext.cs b/...iffEngineTray/Settings/SettingsContext.cs → ...gineTray.Core/Settings/SettingsContext.cs
diff --git a/...DiffEngineTray/Settings/SettingsHelper.cs → ...ngineTray.Core/Settings/SettingsHelper.cs b/...DiffEngineTray/Settings/SettingsHelper.cs → ...ngineTray.Core/Settings/SettingsHelper.cs
diff --git a/src/DiffEngineTray/TrackedDelete.cs → src/DiffEngineTray.Core/TrackedDelete.cs b/src/DiffEngineTray/TrackedDelete.cs → src/DiffEngineTray.Core/TrackedDelete.cs
diff --git a/src/DiffEngineTray/TrackedMove.cs → src/DiffEngineTray.Core/TrackedMove.cs b/src/DiffEngineTray/TrackedMove.cs → src/DiffEngineTray.Core/TrackedMove.cs
diff --git a/src/DiffEngineTray/Tracker.cs → src/DiffEngineTray.Core/Tracker.cs b/src/DiffEngineTray/Tracker.cs → src/DiffEngineTray.Core/Tracker.cs
@@ -1115,7 +1115,7 @@ bool ShouldKill(TrackedMove move, LockedFiles locked, AcceptBatch batch)
         // as locked with "accept from the tray menu" - where the same accept killed without asking.
         if (move.KillLockingProcess ||
             batch.KillWithoutPrompt ||
-            LockedFilesHandler.AlwaysKill)
+            LockedFilesPolicy.AlwaysKill)
         {
             return true;
         }

diff --git a/src/DiffEngineTray/TrayViewerDirectory.cs → ...iffEngineTray.Core/TrayViewerDirectory.cs b/src/DiffEngineTray/TrayViewerDirectory.cs → ...iffEngineTray.Core/TrayViewerDirectory.cs
diff --git a/src/DiffEngineTray/VersionReader.cs → src/DiffEngineTray.Core/VersionReader.cs b/src/DiffEngineTray/VersionReader.cs → src/DiffEngineTray.Core/VersionReader.cs
diff --git a/src/DiffEngineTray.Tests/ProgramEntryPointTest.cs b/src/DiffEngineTray.Tests/ProgramEntryPointTest.cs
@@ -18,7 +18,8 @@ public class ProgramEntryPointTest
     [Test]
     public async Task TheEntryPointStartsOnAnStaThread()
     {
-        var entryPoint = typeof(Tracker).Assembly.EntryPoint!;
+        // The Windows head's own assembly. Tracker is the core's, a library with no entry point
+        var entryPoint = typeof(MenuBuilder).Assembly.EntryPoint!;
 
         await Assert.That(entryPoint.GetCustomAttribute<STAThreadAttribute>()).IsNotNull();
     }

diff --git a/src/DiffEngineTray.Tests/TrackerTrackedFilesTest.cs b/src/DiffEngineTray.Tests/TrackerTrackedFilesTest.cs
@@ -380,9 +380,9 @@ public TrackerTrackedFilesTest()
     [Test]
     public async Task AlwaysKillAppliesToAnAcceptArrivingOverTheSocket()
     {
-        var previous = LockedFilesHandler.AlwaysKill;
+        var previous = LockedFilesPolicy.AlwaysKill;
         // The stored preference, which Program loads into this at startup
-        LockedFilesHandler.AlwaysKill = true;
+        LockedFilesPolicy.AlwaysKill = true;
         try
         {
             await File.WriteAllTextAsync(temp, "new");
@@ -409,7 +409,7 @@ public async Task AlwaysKillAppliesToAnAcceptArrivingOverTheSocket()
         }
         finally
         {
-            LockedFilesHandler.AlwaysKill = previous;
+            LockedFilesPolicy.AlwaysKill = previous;
         }
     }
 }
diff --git a/src/DiffEngineTray/DiffEngineTray.csproj b/src/DiffEngineTray/DiffEngineTray.csproj
@@ -36,6 +36,8 @@
     <PackageReference Include="Serilog.Sinks.File" />
     <PackageReference Include="ProjectDefaults" PrivateAssets="all" />
     <ProjectReference Include="..\DiffEngine\DiffEngine.csproj" />
+    <!-- Everything that is not WinForms, which a head for another platform shares. -->
+    <ProjectReference Include="..\DiffEngineTray.Core\DiffEngineTray.Core.csproj" />
   </ItemGroup>
 
   <!--

diff --git a/src/DiffEngineTray/IssueQuestion.cs b/src/DiffEngineTray/IssueQuestion.cs
@@ -0,0 +1,17 @@
+/// <summary>
+/// How the Windows head asks whether to open an issue for a failure: a modal box, which the core's
+/// <see cref="IssueLauncher" /> has no toolkit to show. Handed over in <see cref="Program" />'s
+/// Main, before anything can fail.
+/// </summary>
+static class IssueQuestion
+{
+    public static bool Declined(string text)
+    {
+        var result = MessageBox.Show(
+            text,
+            "DiffEngineTray Error",
+            MessageBoxButtons.YesNo,
+            MessageBoxIcon.Error);
+        return result == DialogResult.No;
+    }
+}
diff --git a/src/DiffEngineTray/LockedFilesHandler.cs b/src/DiffEngineTray/LockedFilesHandler.cs
@@ -1,10 +1,8 @@
 static class LockedFilesHandler
 {
-    public static bool AlwaysKill { get; set; }
-
     public static LockedFilesResponse Resolve(TrackedMove move, LockedFiles locked)
     {
-        if (AlwaysKill)
+        if (LockedFilesPolicy.AlwaysKill)
         {
             return LockedFilesResponse.Kill;
         }
@@ -14,7 +12,7 @@ public static LockedFilesResponse Resolve(TrackedMove move, LockedFiles locked)
 
         if (form.AlwaysKill)
         {
-            AlwaysKill = true;
+            LockedFilesPolicy.AlwaysKill = true;
             Persist();
         }
 

diff --git a/src/DiffEngineTray/Program.cs b/src/DiffEngineTray/Program.cs
@@ -17,6 +17,7 @@ static class Program
     [STAThread]
     static void Main()
     {
+        IssueLauncher.Declined = IssueQuestion.Declined;
         TrayViewerDirectory.Register();
         Logging.Init();
         Application.EnableVisualStyles();
@@ -75,7 +76,7 @@ void Warn(string message) =>
             return;
         }
 
-        LockedFilesHandler.AlwaysKill = settings.AlwaysKillLockingProcesses;
+        LockedFilesPolicy.AlwaysKill = settings.AlwaysKillLockingProcesses;
 
         // Ownership of the inline queue is decided here, once, by whether the bind succeeds, and
         // never transfers. Usually the tray wins, because it starts at login. A viewer that was

diff --git a/src/DiffEngineTray/Settings/OptionsFormLauncher.cs b/src/DiffEngineTray/Settings/OptionsFormLauncher.cs
@@ -43,7 +43,7 @@ static async Task<IReadOnlyCollection<string>> Save(KeyRegister keyRegister, Tra
         }
 
         await SettingsHelper.Write(settings);
-        LockedFilesHandler.AlwaysKill = settings.AlwaysKillLockingProcesses;
+        LockedFilesPolicy.AlwaysKill = settings.AlwaysKillLockingProcesses;
         return [];
     }
 

diff --git a/src/Packaging.Tests/Package.DiffEngineTray.verified.txt b/src/Packaging.Tests/Package.DiffEngineTray.verified.txt
@@ -6,6 +6,7 @@ nuget.md
 package/services/metadata/core-properties/{guid}.psmdcp
 tools/net10.0/any/DiffEngine.dll
 tools/net10.0/any/DiffEngine.xml
+tools/net10.0/any/DiffEngineTray.Core.dll
 tools/net10.0/any/DiffEngineTray.deps.json
 tools/net10.0/any/DiffEngineTray.dll
 tools/net10.0/any/DiffEngineTray.runtimeconfig.json
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		[assembly: InternalsVisibleTo("DiffEngineTray, PublicKey=00240000048000009400000006020000002400005253413100040000010001000f0a8e4bf1639dce01be6592384e7dfc621915b7759fb5cee42ec5d351bcc43460432da1659ee618ca6cab6b8b8e56a5deb5d4ee1a49783d5c2690752502d31ccbfee9b2c697e20359b55ad100cc9370c8e983fd9496f01d761a060d0435bac7243b1832ba95757aa5adbb67df38c213d717b6751e1217cea9fa5c61e9b799dd")]
		[assembly: InternalsVisibleTo("DiffEngineTray.Tests, PublicKey=00240000048000009400000006020000002400005253413100040000010001000f0a8e4bf1639dce01be6592384e7dfc621915b7759fb5cee42ec5d351bcc43460432da1659ee618ca6cab6b8b8e56a5deb5d4ee1a49783d5c2690752502d31ccbfee9b2c697e20359b55ad100cc9370c8e983fd9496f01d761a060d0435bac7243b1832ba95757aa5adbb67df38c213d717b6751e1217cea9fa5c61e9b799dd")]