diff --git a/docs/open.md b/docs/open.md
index 631d7ae..a63164d 100644
--- a/docs/open.md
+++ b/docs/open.md
@@ -208,8 +208,8 @@ Diese Punkte standen 2026-04-30 noch als offen/partial und sind verifiziert fert
 
 | Stelle | Issue | Status |
 |---|---|---|
-| `TaskRunner.cs:70` `if (list.WorkingDir is not null)` | Inline-Verzweigung Worktree vs. Non-Worktree; Strategy-Pattern erst wenn die Methode wächst | ⬜ |
-| `App.axaml.cs:13` `public static ServiceProvider Services` | Service-Locator-Antipattern, toleriert weil nur in `OnFrameworkInitializationCompleted` genutzt | ⬜ |
+| `TaskRunner` Worktree-vs-Sandbox-Branch | In `PrepareRunDirectoryAsync` ausgelagert (kleiner Helper, kein Strategy-Pattern — bei 2 Pfaden Over-Engineering). `RunAsync` liest jetzt linear. | ✅ |
+| `App.Services` statischer ServiceProvider | Entfernt: `App` bekommt den Provider per Constructor-Injection über `AppBuilder.Configure(() => new App(services))`; parameterloser Ctor + `BuildAvaloniaApp()` bleiben für den Designer. **UI-Start manuell smoke-testen** (kein headless-Lauf möglich). | ✅ |
 
 ---
 
diff --git a/src/ClaudeDo.App/App.axaml.cs b/src/ClaudeDo.App/App.axaml.cs
index aaed0c0..09bc866 100644
--- a/src/ClaudeDo.App/App.axaml.cs
+++ b/src/ClaudeDo.App/App.axaml.cs
@@ -1,3 +1,4 @@
+using System;
 using Avalonia;
 using Avalonia.Controls.ApplicationLifetimes;
 using Avalonia.Markup.Xaml;
@@ -10,7 +11,12 @@ namespace ClaudeDo.App;
 
 public partial class App : Application
 {
-    public static ServiceProvider Services { get; set; } = null!;
+    private readonly IServiceProvider? _services;
+
+    // Parameterless ctor is required by the XAML previewer / designer.
+    public App() { }
+
+    public App(IServiceProvider services) => _services = services;
 
     public override void Initialize()
     {
@@ -21,16 +27,19 @@ public partial class App : Application
     {
         if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
         {
+            var services = _services
+                ?? throw new InvalidOperationException("App was constructed without a service provider.");
+
             FocusClearing.Install();
 
             desktop.MainWindow = new MainWindow
             {
-                DataContext = Services.GetRequiredService<IslandsShellViewModel>(),
+                DataContext = services.GetRequiredService<IslandsShellViewModel>(),
             };
 
             // Kick off the SignalR retry loop — reconnects indefinitely if the worker
             // is not up yet, or goes down and comes back.
-            _ = Services.GetRequiredService<WorkerClient>().StartAsync();
+            _ = services.GetRequiredService<WorkerClient>().StartAsync();
         }
 
         base.OnFrameworkInitializationCompleted();
diff --git a/src/ClaudeDo.App/Program.cs b/src/ClaudeDo.App/Program.cs
index f4b8056..0c68eb0 100644
--- a/src/ClaudeDo.App/Program.cs
+++ b/src/ClaudeDo.App/Program.cs
@@ -35,7 +35,6 @@ sealed class Program
             SetCurrentProcessExplicitAppUserModelID("ClaudeDo.App");
 
         var services = BuildServices();
-        App.Services = services;
 
         using (var scope = services.CreateScope())
         {
@@ -45,7 +44,7 @@ sealed class Program
 
         try
         {
-            BuildAvaloniaApp()
+            ConfigureAppBuilder(AppBuilder.Configure(() => new App(services)))
                 .StartWithClassicDesktopLifetime(args);
         }
         finally
@@ -58,8 +57,12 @@ sealed class Program
         }
     }
 
+    // Parameterless entry point required by the XAML previewer / designer.
     public static AppBuilder BuildAvaloniaApp()
-        => AppBuilder.Configure<App>()
+        => ConfigureAppBuilder(AppBuilder.Configure<App>());
+
+    private static AppBuilder ConfigureAppBuilder(AppBuilder builder)
+        => builder
             .UsePlatformDetect()
 #if DEBUG
             .WithDeveloperTools()
diff --git a/src/ClaudeDo.Worker/Runner/TaskRunner.cs b/src/ClaudeDo.Worker/Runner/TaskRunner.cs
index 5c573a8..6646e31 100644
--- a/src/ClaudeDo.Worker/Runner/TaskRunner.cs
+++ b/src/ClaudeDo.Worker/Runner/TaskRunner.cs
@@ -64,29 +64,14 @@ public sealed class TaskRunner
             }
 
             // Determine working directory: worktree or sandbox.
-            WorktreeContext? wtCtx = null;
-            string runDir;
-
-            if (list.WorkingDir is not null)
+            var prep = await PrepareRunDirectoryAsync(task, list, ct);
+            if (prep.FailureReason is not null)
             {
-                try
-                {
-                    wtCtx = await _wtManager.CreateAsync(task, list, ct);
-                    await _broadcaster.WorkerLog($"Created worktree for \"{task.Title}\"", WorkerLogLevel.Info, DateTime.UtcNow);
-                    runDir = wtCtx.WorktreePath;
-                }
-                catch (Exception ex)
-                {
-                    _logger.LogError(ex, "Failed to create worktree for task {TaskId}", task.Id);
-                    await MarkFailed(task.Id, task.Title, slot, $"Worktree creation failed: {ex.Message}");
-                    return;
-                }
-            }
-            else
-            {
-                runDir = Path.Combine(_cfg.SandboxRoot, task.Id);
-                Directory.CreateDirectory(runDir);
+                await MarkFailed(task.Id, task.Title, slot, prep.FailureReason);
+                return;
             }
+            var wtCtx = prep.WtCtx;
+            var runDir = prep.RunDir!;
 
             var resolvedConfig = await ResolveConfigAsync(task, listConfig, null, ct);
 
@@ -216,6 +201,30 @@ public sealed class TaskRunner
         await _broadcaster.TaskUpdated(taskId);
     }
 
+    private readonly record struct RunDirResult(string? RunDir, WorktreeContext? WtCtx, string? FailureReason);
+
+    private async Task<RunDirResult> PrepareRunDirectoryAsync(TaskEntity task, ListEntity list, CancellationToken ct)
+    {
+        if (list.WorkingDir is not null)
+        {
+            try
+            {
+                var wtCtx = await _wtManager.CreateAsync(task, list, ct);
+                await _broadcaster.WorkerLog($"Created worktree for \"{task.Title}\"", WorkerLogLevel.Info, DateTime.UtcNow);
+                return new RunDirResult(wtCtx.WorktreePath, wtCtx, null);
+            }
+            catch (Exception ex)
+            {
+                _logger.LogError(ex, "Failed to create worktree for task {TaskId}", task.Id);
+                return new RunDirResult(null, null, $"Worktree creation failed: {ex.Message}");
+            }
+        }
+
+        var sandboxDir = Path.Combine(_cfg.SandboxRoot, task.Id);
+        Directory.CreateDirectory(sandboxDir);
+        return new RunDirResult(sandboxDir, null, null);
+    }
+
     private async Task<RunResult> RunOnceAsync(
         string taskId, string taskTitle, string slot, string runDir, ClaudeRunConfig config,
         int runNumber, bool isRetry, string prompt, CancellationToken ct)