refactor(ui): single IDialogService replaces scattered Show* dialog seams

Collapses the ~10 per-modal Show*Modal Func callbacks (wired separately on the shell and the lists island) into one IDialogService + WindowDialogService impl. Removes the RepoImport/WorktreesOverview dialog construction duplicated across MainWindow and ListsIslandView, plus the Confirm/Error dialogs duplicated in both code-behinds. Shell/lists Open* commands now route through an injected Dialogs handle (propagated shell->lists); the per-list worktrees overview also wires conflict resolution now, matching the global one. No VM ctor changes (Dialogs is a settable seam), so no test-fake impact.

src/ClaudeDo.Ui/Services/IDialogService.cs

@@ -0,0 +1,30 @@
+using System.Threading.Tasks;
+using ClaudeDo.Ui.ViewModels.Conflicts;
+using ClaudeDo.Ui.ViewModels.Modals;
+
+namespace ClaudeDo.Ui.Services;
+
+/// <summary>
+/// Single seam for opening modal dialogs. Replaces the per-modal <c>Show*Modal</c>
+/// Func callbacks that were previously wired separately on the shell and the lists
+/// island (and the Confirm/Error dialogs duplicated in both code-behinds). The view
+/// layer supplies the implementation (<see cref="ClaudeDo.Ui.Views.WindowDialogService"/>);
+/// callers build + initialize the VM and hand it here to be shown.
+/// </summary>
+public interface IDialogService
+{
+    Task ShowAboutAsync(AboutModalViewModel vm);
+    Task ShowWeeklyReportAsync(WeeklyReportModalViewModel vm);
+    Task ShowSettingsAsync(SettingsModalViewModel vm);
+    Task ShowListSettingsAsync(ListSettingsModalViewModel vm);
+    Task ShowRepoImportAsync(RepoImportModalViewModel vm);
+    Task ShowWorktreesOverviewAsync(WorktreesOverviewModalViewModel vm);
+    Task ShowWorkerConnectionAsync(WorkerConnectionModalViewModel vm);
+    Task ShowConflictResolverAsync(ConflictResolverViewModel vm);
+
+    /// <summary>Modal yes/no confirmation. Returns true only when confirmed.</summary>
+    Task<bool> ConfirmAsync(string message);
+
+    /// <summary>Modal error notice with a single dismiss button.</summary>
+    Task ShowErrorAsync(string message);
+}

src/ClaudeDo.Ui/ViewModels/Islands/ListsIslandViewModel.cs

@@ -27,28 +27,25 @@ public sealed partial class ListsIslandViewModel : ViewModelBase, IDisposable
     public event EventHandler? FocusSearchRequested;
     public void RequestFocusSearch() => FocusSearchRequested?.Invoke(this, EventArgs.Empty);
 
-    public Func<SettingsModalViewModel, Task>? ShowSettingsModal { get; set; }
+    public IDialogService? Dialogs { get; set; }
-    public Func<ListSettingsModalViewModel, System.Threading.Tasks.Task>? ShowListSettingsModal { get; set; }
-    public Func<WorktreesOverviewModalViewModel, Task>? ShowWorktreesOverviewModal { get; set; }
-    public Func<RepoImportModalViewModel, System.Threading.Tasks.Task>? ShowRepoImportModal { get; set; }
 
     [RelayCommand]
     private async Task OpenSettings()
     {
-        if (ShowSettingsModal is null || _services is null) return;
+        if (Dialogs is null || _services is null) return;
         var settingsVm = _services.GetRequiredService<SettingsModalViewModel>();
         await settingsVm.LoadAsync();
-        await ShowSettingsModal(settingsVm);
+        await Dialogs.ShowSettingsAsync(settingsVm);
     }
 
     [RelayCommand]
     private async System.Threading.Tasks.Task OpenListSettingsAsync(ListNavItemViewModel? row)
     {
-        if (row is null || ShowListSettingsModal is null || _services is null) return;
+        if (row is null || Dialogs is null || _services is null) return;
         var rawId = row.Id.StartsWith("user:", StringComparison.Ordinal) ? row.Id["user:".Length..] : row.Id;
         var vm = _services.GetRequiredService<ListSettingsModalViewModel>();
         await vm.LoadAsync(rawId, row.Name, row.WorkingDir, row.DefaultCommitType);
-        await ShowListSettingsModal(vm);
+        await Dialogs.ShowListSettingsAsync(vm);
         if (vm.Deleted) await LoadAsync();
         else await RefreshRowAsync(row.Id);
     }
@@ -56,10 +53,10 @@ public sealed partial class ListsIslandViewModel : ViewModelBase, IDisposable
     [RelayCommand]
     private async System.Threading.Tasks.Task OpenRepoImportAsync()
     {
-        if (ShowRepoImportModal is null || _services is null) return;
+        if (Dialogs is null || _services is null) return;
         var vm = _services.GetRequiredService<RepoImportModalViewModel>();
         await vm.LoadAsync();
-        await ShowRepoImportModal(vm);
+        await Dialogs.ShowRepoImportAsync(vm);
         await LoadAsync();
     }
 
@@ -68,7 +65,7 @@ public sealed partial class ListsIslandViewModel : ViewModelBase, IDisposable
     [RelayCommand]
     private async Task OpenWorktreesOverviewAsync(ListNavItemViewModel? row)
     {
-        if (row is null || ShowWorktreesOverviewModal is null || _services is null) return;
+        if (row is null || Dialogs is null || _services is null) return;
         if (row.Kind != ListKind.User) return;
         if (_worktreesOverviewOpen) return;
         _worktreesOverviewOpen = true;
@@ -78,7 +75,7 @@ public sealed partial class ListsIslandViewModel : ViewModelBase, IDisposable
             var vm = _services.GetRequiredService<WorktreesOverviewModalViewModel>();
             vm.Configure(rawId, row.Name);
             await vm.LoadAsync();
-            await ShowWorktreesOverviewModal(vm);
+            await Dialogs.ShowWorktreesOverviewAsync(vm);
         }
         finally { _worktreesOverviewOpen = false; }
     }
@@ -297,11 +294,11 @@ public sealed partial class ListsIslandViewModel : ViewModelBase, IDisposable
         UserLists.Add(item);
         SelectedList = item;
 
-        if (ShowListSettingsModal is not null && _services is not null)
+        if (Dialogs is not null && _services is not null)
         {
             var vm = _services.GetRequiredService<ListSettingsModalViewModel>();
             await vm.LoadAsync(entity.Id, entity.Name, entity.WorkingDir, entity.DefaultCommitType);
-            await ShowListSettingsModal(vm);
+            await Dialogs.ShowListSettingsAsync(vm);
             if (vm.Deleted) await LoadAsync();
             else await RefreshRowAsync(item.Id);
         }

src/ClaudeDo.Ui/ViewModels/IslandsShellViewModel.cs

@@ -41,35 +41,30 @@ public sealed partial class IslandsShellViewModel : ViewModelBase, IDisposable
 
     public Func<MergeModalViewModel> ResolveMergeVm => _mergeVmFactory;
 
-    // Layer C seam: composition root sets the factory; MainWindow sets the dialog opener.
+    // Layer C seam: composition root sets the factory; the dialog service shows the resolver.
-    // The integrator connects Layer A/B's RequestConflictResolution(taskId, target) to this method.
     public Func<string, ClaudeDo.Ui.ViewModels.Conflicts.ConflictResolverViewModel>? ConflictResolverFactory { get; set; }
-    public Func<ClaudeDo.Ui.ViewModels.Conflicts.ConflictResolverViewModel, Task>? ShowConflictResolver { get; set; }
+
+    // Single dialog seam (set by MainWindow); propagated to the lists island.
+    private IDialogService? _dialogs;
+    public IDialogService? Dialogs
+    {
+        get => _dialogs;
+        set
+        {
+            _dialogs = value;
+            if (Lists is not null) Lists.Dialogs = value;
+        }
+    }
 
     public async Task RequestConflictResolutionAsync(string taskId, string targetBranch)
     {
-        if (ConflictResolverFactory is null || ShowConflictResolver is null) return;
+        if (ConflictResolverFactory is null || Dialogs is null) return;
         var vm = ConflictResolverFactory(taskId);
         var hasConflicts = await vm.OpenAsync(targetBranch);
         if (hasConflicts)
-            await ShowConflictResolver(vm);
+            await Dialogs.ShowConflictResolverAsync(vm);
     }
 
-    // Set by MainWindow to open the About dialog.
-    public Func<AboutModalViewModel, Task>? ShowAboutModal { get; set; }
-
-    // Set by MainWindow to open the repo-import dialog.
-    public Func<RepoImportModalViewModel, Task>? ShowRepoImportModal { get; set; }
-
-    // Set by MainWindow to open the global worktrees overview dialog.
-    public Func<WorktreesOverviewModalViewModel, Task>? ShowWorktreesOverviewModal { get; set; }
-
-    // Set by MainWindow to open the weekly report dialog.
-    public Func<WeeklyReportModalViewModel, Task>? ShowWeeklyReportModal { get; set; }
-
-    // Set by MainWindow to open the worker-connection help dialog.
-    public Func<WorkerConnectionModalViewModel, Task>? ShowWorkerConnectionModal { get; set; }
-
     [ObservableProperty] private bool _isUpdateBannerVisible;
     [ObservableProperty] private string? _updateBannerLatestVersion;
     [ObservableProperty] private string? _inlineUpdateStatus;
@@ -149,11 +144,11 @@ public sealed partial class IslandsShellViewModel : ViewModelBase, IDisposable
 
     private async Task OpenPlanningConflictAsync(string planningTaskId, string subtaskId)
     {
-        if (ConflictResolverFactory is null || ShowConflictResolver is null) return;
+        if (ConflictResolverFactory is null || Dialogs is null) return;
         var vm = ConflictResolverFactory(subtaskId);
         var hasConflicts = await vm.OpenForPlanningAsync(planningTaskId, subtaskId);
         if (hasConflicts)
-            await ShowConflictResolver(vm);
+            await Dialogs.ShowConflictResolverAsync(vm);
     }
 
     // For tests only — does NOT wire up events.
@@ -281,7 +276,7 @@ public sealed partial class IslandsShellViewModel : ViewModelBase, IDisposable
     private async Task OpenAbout()
     {
         var vm = new AboutModalViewModel();
-        if (ShowAboutModal is not null) await ShowAboutModal(vm);
+        if (Dialogs is not null) await Dialogs.ShowAboutAsync(vm);
     }
 
     private bool _connectionPromptShown;
@@ -297,7 +292,7 @@ public sealed partial class IslandsShellViewModel : ViewModelBase, IDisposable
     private async Task OpenWorkerConnectionHelpAsync()
     {
         var vm = new WorkerConnectionModalViewModel(_workerLocator, _installerLocator);
-        if (ShowWorkerConnectionModal is not null) await ShowWorkerConnectionModal(vm);
+        if (Dialogs is not null) await Dialogs.ShowWorkerConnectionAsync(vm);
     }
 
     [RelayCommand]
@@ -306,10 +301,10 @@ public sealed partial class IslandsShellViewModel : ViewModelBase, IDisposable
     [RelayCommand]
     private async Task OpenRepoImport()
     {
-        if (ShowRepoImportModal is null || _repoImportVmFactory is null) return;
+        if (Dialogs is null || _repoImportVmFactory is null) return;
         var vm = _repoImportVmFactory();
         await vm.LoadAsync();
-        await ShowRepoImportModal(vm);
+        await Dialogs.ShowRepoImportAsync(vm);
         if (Lists is not null) await Lists.LoadAsync();
     }
 
@@ -318,14 +313,14 @@ public sealed partial class IslandsShellViewModel : ViewModelBase, IDisposable
     [RelayCommand]
     private async Task OpenWorktreesOverviewGlobalAsync()
     {
-        if (ShowWorktreesOverviewModal is null || _worktreesOverviewOpen) return;
+        if (Dialogs is null || _worktreesOverviewOpen) return;
         _worktreesOverviewOpen = true;
         try
         {
             var vm = _worktreesOverviewVmFactory();
             vm.Configure(null, null);
             await vm.LoadAsync();
-            await ShowWorktreesOverviewModal(vm);
+            await Dialogs.ShowWorktreesOverviewAsync(vm);
         }
         finally { _worktreesOverviewOpen = false; }
     }
@@ -335,13 +330,13 @@ public sealed partial class IslandsShellViewModel : ViewModelBase, IDisposable
     [RelayCommand]
     private async Task OpenWeeklyReport()
     {
-        if (ShowWeeklyReportModal is null || _weeklyReportOpen) return;
+        if (Dialogs is null || _weeklyReportOpen) return;
         _weeklyReportOpen = true;
         try
         {
             var vm = _weeklyReportVmFactory();
             await vm.InitializeAsync();
-            await ShowWeeklyReportModal(vm);
+            await Dialogs.ShowWeeklyReportAsync(vm);
         }
         finally { _weeklyReportOpen = false; }
     }

src/ClaudeDo.Ui/Views/Islands/ListsIslandView.axaml.cs

@@ -25,61 +25,7 @@ public partial class ListsIslandView : UserControl
         DataContextChanged += (_, _) =>
         {
             if (DataContext is ListsIslandViewModel vm)
-            {
                 vm.FocusSearchRequested += (_, _) => SearchBox.Focus();
-                vm.ShowSettingsModal = ShowSettingsAsync;
-                vm.ShowListSettingsModal = async modal =>
-                {
-                    var window = new ListSettingsModalView { DataContext = modal };
-                    modal.CloseAction = () => window.Close();
-                    modal.ConfirmAsync = ShowConfirmAsync;
-                    modal.ShowErrorAsync = ShowErrorDialogAsync;
-                    var top = TopLevel.GetTopLevel(this) as Window;
-                    if (top is null) window.Show();
-                    else await window.ShowDialog(top);
-                };
-                vm.ShowRepoImportModal = async modal =>
-                {
-                    var window = new RepoImportModalView { DataContext = modal };
-                    modal.CloseAction = () => window.Close();
-                    var top = TopLevel.GetTopLevel(this) as Window;
-                    if (top is null) window.Show();
-                    else await window.ShowDialog(top);
-                };
-                vm.ShowWorktreesOverviewModal = async modal =>
-                {
-                    var top = TopLevel.GetTopLevel(this) as Window;
-                    var shell = top?.DataContext as IslandsShellViewModel;
-                    var window = new WorktreesOverviewModalView { DataContext = modal };
-                    modal.CloseAction = () => window.Close();
-                    modal.JumpToTaskAction = (listId, taskId) =>
-                    {
-                        if (shell is not null)
-                            _ = JumpToTaskAsync(shell, listId, taskId);
-                    };
-                    modal.ShowDiffAction = diffVm =>
-                    {
-                        if (top is null) return;
-                        var dlg = new WorktreeModalView { DataContext = diffVm };
-                        diffVm.CloseAction = () => dlg.Close();
-                        _ = diffVm.LoadAsync();
-                        _ = dlg.ShowDialog(top);
-                    };
-                    modal.ConfirmAction = ShowConfirmAsync;
-                    if (shell is not null)
-                    {
-                        modal.ResolveMergeVm = shell.ResolveMergeVm;
-                        modal.ShowMergeAction = async mergeVm =>
-                        {
-                            if (top is null) return;
-                            var mergeDlg = new MergeModalView { DataContext = mergeVm };
-                            await mergeDlg.ShowDialog(top);
-                        };
-                    }
-                    if (top is null) window.Show();
-                    else await window.ShowDialog(top);
-                };
-            }
         };
     }
 
@@ -211,95 +157,4 @@ public partial class ListsIslandView : UserControl
         return idx + 1 < vm.UserLists.Count ? vm.UserLists[idx + 1] : null;
     }
 
-    private async System.Threading.Tasks.Task ShowSettingsAsync(SettingsModalViewModel settingsVm)
-    {
-        var owner = TopLevel.GetTopLevel(this) as Window;
-        if (owner == null) return;
-        var modal = new SettingsModalView { DataContext = settingsVm };
-        await modal.ShowDialog(owner);
-    }
-
-    private static System.Threading.Tasks.Task JumpToTaskAsync(IslandsShellViewModel s, string listId, string taskId)
-        => JumpToTaskHelper.SelectAsync(s, listId, taskId);
-
-    private async System.Threading.Tasks.Task ShowErrorDialogAsync(string message)
-    {
-        var owner = TopLevel.GetTopLevel(this) as Window;
-        if (owner is null) return;
-
-        var ok = new Button { Content = "OK", MinWidth = 90 };
-        var dialog = new Window
-        {
-            Title = "Error",
-            Width = 360,
-            SizeToContent = SizeToContent.Height,
-            CanResize = false,
-            WindowStartupLocation = WindowStartupLocation.CenterOwner,
-            ShowInTaskbar = false,
-            Background = this.FindResource("SurfaceBrush") as IBrush,
-            Content = new StackPanel
-            {
-                Spacing = 16,
-                Margin = new Thickness(20),
-                Children =
-                {
-                    new TextBlock { Text = message, TextWrapping = TextWrapping.Wrap },
-                    new StackPanel
-                    {
-                        Orientation = Orientation.Horizontal,
-                        Spacing = 8,
-                        HorizontalAlignment = HorizontalAlignment.Right,
-                        Children = { ok },
-                    },
-                },
-            },
-        };
-
-        ok.Click += (_, _) => dialog.Close();
-        await dialog.ShowDialog(owner);
-    }
-
-    private async System.Threading.Tasks.Task<bool> ShowConfirmAsync(string message)
-    {
-        var owner = TopLevel.GetTopLevel(this) as Window;
-        if (owner is null) return false;
-
-        var tcs = new TaskCompletionSource<bool>();
-        var cancel = new Button { Content = "Cancel", MinWidth = 90 };
-        var confirm = new Button { Content = "Confirm", MinWidth = 90, Classes = { "danger" } };
-
-        var dialog = new Window
-        {
-            Title = "Confirm",
-            Width = 380,
-            SizeToContent = SizeToContent.Height,
-            CanResize = false,
-            WindowStartupLocation = WindowStartupLocation.CenterOwner,
-            ShowInTaskbar = false,
-            Background = this.FindResource("SurfaceBrush") as IBrush,
-            Content = new StackPanel
-            {
-                Margin = new Thickness(20),
-                Spacing = 16,
-                Children =
-                {
-                    new TextBlock { Text = message, TextWrapping = TextWrapping.Wrap },
-                    new StackPanel
-                    {
-                        Orientation = Orientation.Horizontal,
-                        HorizontalAlignment = HorizontalAlignment.Right,
-                        Spacing = 8,
-                        Children = { cancel, confirm },
-                    },
-                },
-            },
-        };
-
-        cancel.Click += (_, _) => { tcs.TrySetResult(false); dialog.Close(); };
-        confirm.Click += (_, _) => { tcs.TrySetResult(true); dialog.Close(); };
-        dialog.Closed += (_, _) => tcs.TrySetResult(false);
-
-        _ = dialog.ShowDialog(owner);
-        return await tcs.Task;
-    }
 }

src/ClaudeDo.Ui/Views/MainWindow.axaml.cs

@@ -42,65 +42,7 @@ public partial class MainWindow : Window
     {
         if (DataContext is IslandsShellViewModel vm)
         {
-            vm.ShowAboutModal = async (aboutVm) =>
+            vm.Dialogs = new WindowDialogService(this);
-            {
-                var dlg = new AboutModalView { DataContext = aboutVm };
-                var tcs = new TaskCompletionSource<bool>();
-                aboutVm.CloseAction = () => { dlg.Close(); tcs.TrySetResult(true); };
-                await dlg.ShowDialog(this);
-            };
-            vm.ShowWeeklyReportModal = async (modal) =>
-            {
-                var dlg = new WeeklyReportModalView { DataContext = modal };
-                modal.CloseAction = () => dlg.Close();
-                await dlg.ShowDialog(this);
-            };
-            vm.ShowWorktreesOverviewModal = async (modal) =>
-            {
-                var dlg = new WorktreesOverviewModalView { DataContext = modal };
-                modal.CloseAction = () => dlg.Close();
-                modal.JumpToTaskAction = (listId, taskId) =>
-                {
-                    if (DataContext is IslandsShellViewModel s)
-                        _ = JumpToTaskAsync(s, listId, taskId);
-                };
-                modal.ShowDiffAction = diffVm =>
-                {
-                    var diffDlg = new WorktreeModalView { DataContext = diffVm };
-                    diffVm.CloseAction = () => diffDlg.Close();
-                    _ = diffVm.LoadAsync();
-                    _ = diffDlg.ShowDialog(this);
-                };
-                modal.ConfirmAction = ShowConfirmAsync;
-                modal.ResolveMergeVm = vm.ResolveMergeVm;
-                modal.ShowMergeAction = async mergeVm =>
-                {
-                    var mergeDlg = new MergeModalView { DataContext = mergeVm };
-                    await mergeDlg.ShowDialog(this);
-                };
-                modal.RequestConflictResolution = (taskId, target) =>
-                    DataContext is IslandsShellViewModel s
-                        ? s.RequestConflictResolutionAsync(taskId, target)
-                        : System.Threading.Tasks.Task.CompletedTask;
-                await dlg.ShowDialog(this);
-            };
-            vm.ShowRepoImportModal = async (modal) =>
-            {
-                var dlg = new RepoImportModalView { DataContext = modal };
-                modal.CloseAction = () => dlg.Close();
-                await dlg.ShowDialog(this);
-            };
-            vm.ShowWorkerConnectionModal = async (connVm) =>
-            {
-                var dlg = new WorkerConnectionModalView { DataContext = connVm };
-                connVm.CloseAction = () => dlg.Close();
-                await dlg.ShowDialog(this);
-            };
-            vm.ShowConflictResolver = async (resolverVm) =>
-            {
-                var dlg = new ClaudeDo.Ui.Views.Conflicts.ConflictResolverView { DataContext = resolverVm };
-                await dlg.ShowDialog(this);
-            };
         }
     }
 
@@ -132,47 +74,4 @@ public partial class MainWindow : Window
         if (DataContext is IslandsShellViewModel vm) vm.WindowWidth = Bounds.Width;
     }
 
-    private static System.Threading.Tasks.Task JumpToTaskAsync(IslandsShellViewModel s, string listId, string taskId)
-        => JumpToTaskHelper.SelectAsync(s, listId, taskId);
-
-    private async System.Threading.Tasks.Task<bool> ShowConfirmAsync(string message)
-    {
-        var tcs = new TaskCompletionSource<bool>();
-        var cancel = new Button { Content = "Cancel", MinWidth = 90 };
-        var confirm = new Button { Content = "Confirm", MinWidth = 90, Classes = { "danger" } };
-
-        var dialog = new Window
-        {
-            Title = "Confirm",
-            Width = 380,
-            SizeToContent = SizeToContent.Height,
-            CanResize = false,
-            WindowStartupLocation = WindowStartupLocation.CenterOwner,
-            ShowInTaskbar = false,
-            Background = this.FindResource("SurfaceBrush") as IBrush,
-            Content = new StackPanel
-            {
-                Margin = new Thickness(20),
-                Spacing = 16,
-                Children =
-                {
-                    new TextBlock { Text = message, TextWrapping = TextWrapping.Wrap },
-                    new StackPanel
-                    {
-                        Orientation = Orientation.Horizontal,
-                        HorizontalAlignment = HorizontalAlignment.Right,
-                        Spacing = 8,
-                        Children = { cancel, confirm },
-                    },
-                },
-            },
-        };
-
-        cancel.Click += (_, _) => { tcs.TrySetResult(false); dialog.Close(); };
-        confirm.Click += (_, _) => { tcs.TrySetResult(true); dialog.Close(); };
-        dialog.Closed += (_, _) => tcs.TrySetResult(false);
-
-        _ = dialog.ShowDialog(this);
-        return await tcs.Task;
-    }
 }

src/ClaudeDo.Ui/Views/WindowDialogService.cs

@@ -0,0 +1,167 @@
+using System.Threading.Tasks;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Layout;
+using Avalonia.Media;
+using ClaudeDo.Ui.Services;
+using ClaudeDo.Ui.ViewModels;
+using ClaudeDo.Ui.ViewModels.Conflicts;
+using ClaudeDo.Ui.ViewModels.Modals;
+using ClaudeDo.Ui.Views.Conflicts;
+using ClaudeDo.Ui.Views.Modals;
+
+namespace ClaudeDo.Ui.Views;
+
+/// <summary>
+/// Window-backed <see cref="IDialogService"/>. Owns every modal-view construction, the
+/// shared Confirm/Error dialogs, and the worktrees-overview sub-callbacks that reach back
+/// into the shell (jump-to-task, merge, conflict resolution). Created by <see cref="MainWindow"/>
+/// with itself as the owner window; the shell resolves lazily from the owner's DataContext so
+/// the service and shell don't form a construction cycle.
+/// </summary>
+public sealed class WindowDialogService : IDialogService
+{
+    private readonly Window _owner;
+
+    public WindowDialogService(Window owner) => _owner = owner;
+
+    private IslandsShellViewModel? Shell => _owner.DataContext as IslandsShellViewModel;
+
+    public async Task ShowAboutAsync(AboutModalViewModel vm)
+    {
+        var dlg = new AboutModalView { DataContext = vm };
+        vm.CloseAction = () => dlg.Close();
+        await dlg.ShowDialog(_owner);
+    }
+
+    public async Task ShowWeeklyReportAsync(WeeklyReportModalViewModel vm)
+    {
+        var dlg = new WeeklyReportModalView { DataContext = vm };
+        vm.CloseAction = () => dlg.Close();
+        await dlg.ShowDialog(_owner);
+    }
+
+    public async Task ShowSettingsAsync(SettingsModalViewModel vm)
+    {
+        var dlg = new SettingsModalView { DataContext = vm };
+        await dlg.ShowDialog(_owner);
+    }
+
+    public async Task ShowListSettingsAsync(ListSettingsModalViewModel vm)
+    {
+        var dlg = new ListSettingsModalView { DataContext = vm };
+        vm.CloseAction = () => dlg.Close();
+        vm.ConfirmAsync = ConfirmAsync;
+        vm.ShowErrorAsync = ShowErrorAsync;
+        await dlg.ShowDialog(_owner);
+    }
+
+    public async Task ShowRepoImportAsync(RepoImportModalViewModel vm)
+    {
+        var dlg = new RepoImportModalView { DataContext = vm };
+        vm.CloseAction = () => dlg.Close();
+        await dlg.ShowDialog(_owner);
+    }
+
+    public async Task ShowWorktreesOverviewAsync(WorktreesOverviewModalViewModel vm)
+    {
+        var dlg = new WorktreesOverviewModalView { DataContext = vm };
+        vm.CloseAction = () => dlg.Close();
+        vm.JumpToTaskAction = (listId, taskId) =>
+        {
+            if (Shell is { } s) _ = JumpToTaskHelper.SelectAsync(s, listId, taskId);
+        };
+        vm.ShowDiffAction = diffVm =>
+        {
+            var diffDlg = new WorktreeModalView { DataContext = diffVm };
+            diffVm.CloseAction = () => diffDlg.Close();
+            _ = diffVm.LoadAsync();
+            _ = diffDlg.ShowDialog(_owner);
+        };
+        vm.ConfirmAction = ConfirmAsync;
+        if (Shell is { } shell)
+        {
+            vm.ResolveMergeVm = shell.ResolveMergeVm;
+            vm.ShowMergeAction = async mergeVm =>
+            {
+                var mergeDlg = new MergeModalView { DataContext = mergeVm };
+                await mergeDlg.ShowDialog(_owner);
+            };
+            vm.RequestConflictResolution = (taskId, target) =>
+                shell.RequestConflictResolutionAsync(taskId, target);
+        }
+        await dlg.ShowDialog(_owner);
+    }
+
+    public async Task ShowWorkerConnectionAsync(WorkerConnectionModalViewModel vm)
+    {
+        var dlg = new WorkerConnectionModalView { DataContext = vm };
+        vm.CloseAction = () => dlg.Close();
+        await dlg.ShowDialog(_owner);
+    }
+
+    public async Task ShowConflictResolverAsync(ConflictResolverViewModel vm)
+    {
+        var dlg = new ConflictResolverView { DataContext = vm };
+        await dlg.ShowDialog(_owner);
+    }
+
+    public Task<bool> ConfirmAsync(string message)
+    {
+        var tcs = new TaskCompletionSource<bool>();
+        var cancel = new Button { Content = "Cancel", MinWidth = 90 };
+        var confirm = new Button { Content = "Confirm", MinWidth = 90, Classes = { "danger" } };
+
+        var dialog = NoticeWindow("Confirm", 380, message,
+            new StackPanel
+            {
+                Orientation = Orientation.Horizontal,
+                HorizontalAlignment = HorizontalAlignment.Right,
+                Spacing = 8,
+                Children = { cancel, confirm },
+            });
+
+        cancel.Click += (_, _) => { tcs.TrySetResult(false); dialog.Close(); };
+        confirm.Click += (_, _) => { tcs.TrySetResult(true); dialog.Close(); };
+        dialog.Closed += (_, _) => tcs.TrySetResult(false);
+
+        _ = dialog.ShowDialog(_owner);
+        return tcs.Task;
+    }
+
+    public Task ShowErrorAsync(string message)
+    {
+        var ok = new Button { Content = "OK", MinWidth = 90 };
+        var dialog = NoticeWindow("Error", 360, message,
+            new StackPanel
+            {
+                Orientation = Orientation.Horizontal,
+                HorizontalAlignment = HorizontalAlignment.Right,
+                Spacing = 8,
+                Children = { ok },
+            });
+        ok.Click += (_, _) => dialog.Close();
+        return dialog.ShowDialog(_owner);
+    }
+
+    private Window NoticeWindow(string title, double width, string message, StackPanel buttons) => new()
+    {
+        Title = title,
+        Width = width,
+        SizeToContent = SizeToContent.Height,
+        CanResize = false,
+        WindowStartupLocation = WindowStartupLocation.CenterOwner,
+        ShowInTaskbar = false,
+        Background = _owner.FindResource("SurfaceBrush") as IBrush,
+        Content = new StackPanel
+        {
+            Margin = new Thickness(20),
+            Spacing = 16,
+            Children =
+            {
+                new TextBlock { Text = message, TextWrapping = TextWrapping.Wrap },
+                buttons,
+            },
+        },
+    };
+}