feat(i18n): localize installer with language picker and config write-through

- Init Localizer at app startup (before self-update prompt) and assign to TrExtension.Localizer
- Register ILocalizer in DI; inject into WizardViewModel and SettingsViewModel
- WizardViewModel: SelectedLanguage ComboBox binding with OnSelectedLanguageChanged -> SetLanguage + InstallContext.Language
- WizardWindow.xaml: DockPanel wraps step chips + language ComboBox (right-aligned)
- Localize all installer XAML: WizardWindow, WelcomePage, PathsPage, ServicePage, UiSettingsPage, InstallPage, SettingsWindow, SelfUpdatePromptWindow
- Localize page Title properties and WizardViewModel.NextButtonText via TrExtension.Localizer
- Persist chosen Language in WriteConfigStep and SettingsViewModel.Save into ui.config.json
- Append installer section to en.json (nav, welcome, paths, service, uiSettings, install, settings, selfUpdate)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ClaudeDo.Installer/App.xaml.cs

@@ -1,7 +1,12 @@
+using System.Globalization;
+using System.IO;
+using System.Linq;
 using System.Net.Http;
 using System.Reflection;
 using System.Windows;
 using ClaudeDo.Installer.Core;
+using ClaudeDo.Installer.Localization;
+using ClaudeDo.Localization;
 using ClaudeDo.Releases;
 using ClaudeDo.Installer.Pages.InstallPage;
 using ClaudeDo.Installer.Pages.PathsPage;
@@ -22,6 +27,17 @@ public partial class App : Application
     {
         base.OnStartup(e);
 
+        // --- Initialize localizer as early as possible so all windows can use {loc:Tr} ---
+        var localesDir = Path.Combine(AppContext.BaseDirectory, "locales");
+        var localeStore = LocaleStore.Load(localesDir);
+        var existingSettings = InstallerAppSettings.Load();
+        var initialLang = !string.IsNullOrWhiteSpace(existingSettings.Language)
+            ? existingSettings.Language
+            : CultureResolver.Resolve(CultureInfo.CurrentUICulture.Name,
+                  localeStore.Available.Select(l => l.Code).ToArray(), "en");
+        var localizer = new Localizer(localeStore, initialLang);
+        TrExtension.Localizer = localizer;
+
         // --- Self-update pre-flight ---
         // Resolve current exe path. Assembly.Location may point to a .dll for apphost-based
         // .NET apps; swap to the .exe companion when that happens.
@@ -120,7 +136,7 @@ public partial class App : Application
 
         // --- Existing wizard start-up unchanged below this line ---
 
-        _services = BuildServices();
+        _services = BuildServices(localizer);
 
         var context = _services.GetRequiredService<InstallContext>();
         context.InstallerVersion = GetInstallerVersion();
@@ -183,9 +199,10 @@ public partial class App : Application
         return infoAttr?.InformationalVersion ?? "0.0.0";
     }
 
-    private static ServiceProvider BuildServices()
+    private static ServiceProvider BuildServices(ILocalizer localizer)
     {
         var sc = new ServiceCollection();
+        sc.AddSingleton(localizer);
 
         // Core
         sc.AddSingleton<InstallContext>();

src/ClaudeDo.Installer/Core/InstallContext.cs

@@ -36,4 +36,7 @@ public sealed class InstallContext
     // WelcomePage — register the external MCP endpoint with the Claude CLI.
     public bool RegisterMcpWithClaude { get; set; } = true;
     public int ExternalMcpPort { get; set; } = 47_822;
+
+    // Language selection (persisted to ui.config.json)
+    public string Language { get; set; } = "";
 }

src/ClaudeDo.Installer/Pages/InstallPage/InstallPageView.xaml

@@ -2,6 +2,7 @@
              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:local="clr-namespace:ClaudeDo.Installer.Pages.InstallPage"
+             xmlns:loc="clr-namespace:ClaudeDo.Installer.Localization"
              d:DataContext="{d:DesignInstance local:InstallPageViewModel}"
              xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
              xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
@@ -17,8 +18,8 @@
 
         <!-- Header -->
         <StackPanel Grid.Row="0" Margin="0,0,0,16">
-            <TextBlock Text="Installation" FontSize="18" FontWeight="SemiBold" Margin="0,0,0,4"/>
+            <TextBlock Text="{loc:Tr installer.install.title}" FontSize="18" FontWeight="SemiBold" Margin="0,0,0,4"/>
-            <TextBlock Text="Click Install to build and deploy ClaudeDo."
+            <TextBlock Text="{loc:Tr installer.install.subtitle}"
                        Foreground="{StaticResource TextSecondaryBrush}" TextWrapping="Wrap"/>
         </StackPanel>
 
@@ -89,11 +90,11 @@
 
         <!-- Action buttons -->
         <StackPanel Grid.Row="3" Orientation="Horizontal" HorizontalAlignment="Right" Margin="0,12,0,0">
-            <Button Content="Cancel" Command="{Binding CancelInstallCommand}"
+            <Button Content="{loc:Tr installer.nav.cancel}" Command="{Binding CancelInstallCommand}"
                     Visibility="{Binding IsInstalling, Converter={StaticResource BoolToVisConverter}}"
                     Margin="0,0,8,0"/>
 
-            <Button Content="Launch ClaudeDo" Command="{Binding LaunchAppCommand}"
+            <Button Content="{loc:Tr installer.install.launch}" Command="{Binding LaunchAppCommand}"
                     Style="{StaticResource AccentButton}"
                     Visibility="{Binding IsComplete, Converter={StaticResource BoolToVisConverter}}"/>
         </StackPanel>

src/ClaudeDo.Installer/Pages/InstallPage/InstallPageViewModel.cs

@@ -3,6 +3,7 @@ using System.Diagnostics;
 using System.Windows;
 using System.Windows.Controls;
 using ClaudeDo.Installer.Core;
+using ClaudeDo.Installer.Localization;
 using ClaudeDo.Installer.Steps;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
@@ -29,7 +30,7 @@ public partial class InstallPageViewModel : ObservableObject, IInstallerPage
     private InstallPageView? _view;
     private CancellationTokenSource? _cts;
 
-    public string Title => "Install";
+    public string Title => TrExtension.Localizer?["installer.install.title"] ?? "Install";
     public string Icon => "\uE896";
     public int Order => 99;
     public bool ShowInWizard => true;

src/ClaudeDo.Installer/Pages/PathsPage/PathsPageView.xaml

@@ -2,6 +2,7 @@
              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:local="clr-namespace:ClaudeDo.Installer.Pages.PathsPage"
+             xmlns:loc="clr-namespace:ClaudeDo.Installer.Localization"
              d:DataContext="{d:DesignInstance local:PathsPageViewModel}"
              xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
              xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
@@ -9,28 +10,28 @@
 
     <ScrollViewer VerticalScrollBarVisibility="Auto">
         <StackPanel MaxWidth="520">
-            <TextBlock Text="Data Paths" FontSize="18" FontWeight="SemiBold" Margin="0,0,0,4"/>
+            <TextBlock Text="{loc:Tr installer.paths.title}" FontSize="18" FontWeight="SemiBold" Margin="0,0,0,4"/>
-            <TextBlock Text="Configure where ClaudeDo stores its data."
+            <TextBlock Text="{loc:Tr installer.paths.subtitle}"
                        Foreground="{StaticResource TextSecondaryBrush}" Margin="0,0,0,20"
                        TextWrapping="Wrap"/>
 
-            <Label Content="Database Path"/>
+            <Label Content="{loc:Tr installer.paths.databasePath}"/>
             <TextBox Text="{Binding DbPath, UpdateSourceTrigger=PropertyChanged}" Margin="0,0,0,12"/>
 
-            <Label Content="Log Directory"/>
+            <Label Content="{loc:Tr installer.paths.logDirectory}"/>
             <TextBox Text="{Binding LogRoot, UpdateSourceTrigger=PropertyChanged}" Margin="0,0,0,12"/>
 
-            <Label Content="Sandbox Root"/>
+            <Label Content="{loc:Tr installer.paths.sandboxRoot}"/>
             <TextBox Text="{Binding SandboxRoot, UpdateSourceTrigger=PropertyChanged}" Margin="0,0,0,12"/>
 
-            <Label Content="Worktree Strategy"/>
+            <Label Content="{loc:Tr installer.paths.worktreeStrategy}"/>
             <ComboBox SelectedItem="{Binding WorktreeRootStrategy}" Margin="0,0,0,12">
                 <sys:String xmlns:sys="clr-namespace:System;assembly=mscorlib">sibling</sys:String>
                 <sys:String xmlns:sys="clr-namespace:System;assembly=mscorlib">central</sys:String>
             </ComboBox>
 
             <StackPanel Visibility="{Binding IsCentralVisible, Converter={StaticResource BoolToVisConverter}}">
-                <Label Content="Central Worktree Root"/>
+                <Label Content="{loc:Tr installer.paths.centralWorktreeRoot}"/>
                 <TextBox Text="{Binding CentralWorktreeRoot, UpdateSourceTrigger=PropertyChanged}" Margin="0,0,0,12"/>
             </StackPanel>
 

src/ClaudeDo.Installer/Pages/PathsPage/PathsPageViewModel.cs

@@ -1,5 +1,6 @@
 using System.Windows.Controls;
 using ClaudeDo.Installer.Core;
+using ClaudeDo.Installer.Localization;
 using CommunityToolkit.Mvvm.ComponentModel;
 
 namespace ClaudeDo.Installer.Pages.PathsPage;
@@ -9,7 +10,7 @@ public partial class PathsPageViewModel : ObservableObject, IInstallerPage
     private readonly InstallContext _context;
     private PathsPageView? _view;
 
-    public string Title => "Paths";
+    public string Title => TrExtension.Localizer?["installer.paths.title"] ?? "Paths";
     public string Icon => "\uE8B7";
     public int Order => 1;
     public bool ShowInWizard => true;

src/ClaudeDo.Installer/Pages/ServicePage/ServicePageView.xaml

@@ -2,6 +2,7 @@
              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:local="clr-namespace:ClaudeDo.Installer.Pages.ServicePage"
+             xmlns:loc="clr-namespace:ClaudeDo.Installer.Localization"
              d:DataContext="{d:DesignInstance local:ServicePageViewModel}"
              xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
              xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
@@ -9,37 +10,37 @@
 
     <ScrollViewer VerticalScrollBarVisibility="Auto">
         <StackPanel MaxWidth="520">
-            <TextBlock Text="Worker" FontSize="18" FontWeight="SemiBold" Margin="0,0,0,4"/>
+            <TextBlock Text="{loc:Tr installer.service.title}" FontSize="18" FontWeight="SemiBold" Margin="0,0,0,4"/>
-            <TextBlock Text="Configure the ClaudeDo background worker."
+            <TextBlock Text="{loc:Tr installer.service.subtitle}"
                        Foreground="{StaticResource TextSecondaryBrush}" Margin="0,0,0,20"
                        TextWrapping="Wrap"/>
 
-            <Label Content="SignalR Port"/>
+            <Label Content="{loc:Tr installer.service.signalRPort}"/>
             <TextBox Text="{Binding SignalRPort, UpdateSourceTrigger=PropertyChanged}" Margin="0,0,0,12"/>
 
-            <Label Content="Queue Backstop Interval (ms)"/>
+            <Label Content="{loc:Tr installer.service.queueBackstopInterval}"/>
             <TextBox Text="{Binding QueueBackstopIntervalMs, UpdateSourceTrigger=PropertyChanged}" Margin="0,0,0,12"/>
 
-            <Label Content="Claude CLI Path"/>
+            <Label Content="{loc:Tr installer.service.claudeCliPath}"/>
             <Grid Margin="0,0,0,12">
                 <Grid.ColumnDefinitions>
                     <ColumnDefinition Width="*"/>
                     <ColumnDefinition Width="Auto"/>
                 </Grid.ColumnDefinitions>
                 <TextBox Grid.Column="0" Text="{Binding ClaudeBin, UpdateSourceTrigger=PropertyChanged}"/>
-                <Button Grid.Column="1" Content="Browse..." Command="{Binding BrowseClaudeCommand}"
+                <Button Grid.Column="1" Content="{loc:Tr installer.nav.browse}" Command="{Binding BrowseClaudeCommand}"
                         Margin="8,0,0,0"/>
             </Grid>
 
             <Separator Margin="0,4,0,12"/>
 
-            <TextBlock Text="The worker runs as you (the logged-in user) via a per-user logon task, so it can use your Claude CLI authentication."
+            <TextBlock Text="{loc:Tr installer.service.autostartHint}"
                        Foreground="{StaticResource TextDimBrush}" FontSize="11" Margin="0,0,0,12"
                        TextWrapping="Wrap"/>
 
-            <CheckBox Content="Start worker automatically at logon" IsChecked="{Binding AutoStart}" Margin="0,0,0,12"/>
+            <CheckBox Content="{loc:Tr installer.service.autostart}" IsChecked="{Binding AutoStart}" Margin="0,0,0,12"/>
 
-            <Label Content="Restart Delay (ms)"/>
+            <Label Content="{loc:Tr installer.service.restartDelay}"/>
             <TextBox Text="{Binding RestartDelayMs, UpdateSourceTrigger=PropertyChanged}" Margin="0,0,0,12"/>
 
             <TextBlock Text="{Binding ValidationError}" Foreground="{StaticResource ErrorBrush}" FontSize="11"

src/ClaudeDo.Installer/Pages/ServicePage/ServicePageViewModel.cs

@@ -1,5 +1,6 @@
 using System.Windows.Controls;
 using ClaudeDo.Installer.Core;
+using ClaudeDo.Installer.Localization;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
 using Microsoft.Win32;
@@ -11,7 +12,7 @@ public partial class ServicePageViewModel : ObservableObject, IInstallerPage
     private readonly InstallContext _context;
     private ServicePageView? _view;
 
-    public string Title => "Service";
+    public string Title => TrExtension.Localizer?["installer.service.title"] ?? "Service";
     public string Icon => "\uE912";
     public int Order => 2;
     public bool ShowInWizard => true;

src/ClaudeDo.Installer/Pages/UiSettingsPage/UiSettingsPageView.xaml

@@ -2,6 +2,7 @@
              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:local="clr-namespace:ClaudeDo.Installer.Pages.UiSettingsPage"
+             xmlns:loc="clr-namespace:ClaudeDo.Installer.Localization"
              d:DataContext="{d:DesignInstance local:UiSettingsPageViewModel}"
              xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
              xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
@@ -9,22 +10,22 @@
 
     <ScrollViewer VerticalScrollBarVisibility="Auto">
         <StackPanel MaxWidth="520">
-            <TextBlock Text="UI Settings" FontSize="18" FontWeight="SemiBold" Margin="0,0,0,4"/>
+            <TextBlock Text="{loc:Tr installer.uiSettings.title}" FontSize="18" FontWeight="SemiBold" Margin="0,0,0,4"/>
-            <TextBlock Text="Configure the ClaudeDo desktop UI connection settings."
+            <TextBlock Text="{loc:Tr installer.uiSettings.subtitle}"
                        Foreground="{StaticResource TextSecondaryBrush}" Margin="0,0,0,20"
                        TextWrapping="Wrap"/>
 
-            <CheckBox Content="Sync with service settings" IsChecked="{Binding IsSynced}" Margin="0,0,0,16"/>
+            <CheckBox Content="{loc:Tr installer.uiSettings.syncWithService}" IsChecked="{Binding IsSynced}" Margin="0,0,0,16"/>
 
-            <Label Content="SignalR URL"/>
+            <Label Content="{loc:Tr installer.uiSettings.signalRUrl}"/>
             <TextBox Text="{Binding SignalRUrl, UpdateSourceTrigger=PropertyChanged}"
                      IsReadOnly="{Binding IsSynced}" Margin="0,0,0,12"/>
 
-            <Label Content="Database Path"/>
+            <Label Content="{loc:Tr installer.paths.databasePath}"/>
             <TextBox Text="{Binding UiDbPath, UpdateSourceTrigger=PropertyChanged}"
                      IsReadOnly="{Binding IsSynced}" Margin="0,0,0,12"/>
 
-            <TextBlock Text="When synced, these values are derived from the Service and Paths pages."
+            <TextBlock Text="{loc:Tr installer.uiSettings.syncHint}"
                        Foreground="{StaticResource TextDimBrush}" FontSize="11" TextWrapping="Wrap"
                        Visibility="{Binding IsSynced, Converter={StaticResource BoolToVisConverter}}"
                        Margin="0,0,0,12"/>

src/ClaudeDo.Installer/Pages/UiSettingsPage/UiSettingsPageViewModel.cs

@@ -1,5 +1,6 @@
 using System.Windows.Controls;
 using ClaudeDo.Installer.Core;
+using ClaudeDo.Installer.Localization;
 using CommunityToolkit.Mvvm.ComponentModel;
 
 namespace ClaudeDo.Installer.Pages.UiSettingsPage;
@@ -9,7 +10,7 @@ public partial class UiSettingsPageViewModel : ObservableObject, IInstallerPage
     private readonly InstallContext _context;
     private UiSettingsPageView? _view;
 
-    public string Title => "UI Settings";
+    public string Title => TrExtension.Localizer?["installer.uiSettings.title"] ?? "UI Settings";
     public string Icon => "\uE771";
     public int Order => 3;
     public bool ShowInWizard => true;

src/ClaudeDo.Installer/Pages/WelcomePage/WelcomePageView.xaml

@@ -2,6 +2,7 @@
              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:local="clr-namespace:ClaudeDo.Installer.Pages.WelcomePage"
+             xmlns:loc="clr-namespace:ClaudeDo.Installer.Localization"
              d:DataContext="{d:DesignInstance local:WelcomePageViewModel}"
              xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
              xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
@@ -14,7 +15,7 @@
             <TextBlock Text="{Binding Subheading}" TextWrapping="Wrap"
                        Foreground="{StaticResource TextSecondaryBrush}" Margin="0,0,0,24"/>
 
-            <Label Content="Install Directory"/>
+            <Label Content="{loc:Tr installer.welcome.installDirectory}"/>
             <Grid Margin="0,0,0,4">
                 <Grid.ColumnDefinitions>
                     <ColumnDefinition Width="*"/>
@@ -24,7 +25,7 @@
                          Text="{Binding InstallDirectory, UpdateSourceTrigger=PropertyChanged}"
                          IsEnabled="{Binding InstallDirEditable}"/>
                 <Button Grid.Column="1"
-                        Content="Browse..."
+                        Content="{loc:Tr installer.nav.browse}"
                         Margin="8,0,0,0"
                         Command="{Binding BrowseInstallCommand}"
                         IsEnabled="{Binding InstallDirEditable}"/>
@@ -32,10 +33,10 @@
             <TextBlock Text="{Binding InstallError}" Foreground="{StaticResource ErrorBrush}" FontSize="11"
                        Visibility="{Binding InstallError, Converter={StaticResource NullToCollapsedConverter}}"/>
 
-            <CheckBox Content="Register MCP server with Claude"
+            <CheckBox Content="{loc:Tr installer.welcome.registerMcp}"
                       IsChecked="{Binding RegisterMcp}"
                       Margin="0,24,0,0"/>
-            <TextBlock Text="Runs 'claude mcp add' so Claude can view and manage your ClaudeDo tasks. You can change this later."
+            <TextBlock Text="{loc:Tr installer.welcome.registerMcpHint}"
                        TextWrapping="Wrap" FontSize="11"
                        Foreground="{StaticResource TextSecondaryBrush}"
                        Margin="0,4,0,0"/>

src/ClaudeDo.Installer/Pages/WelcomePage/WelcomePageViewModel.cs

@@ -1,6 +1,7 @@
 using System.IO;
 using System.Windows.Controls;
 using ClaudeDo.Installer.Core;
+using ClaudeDo.Installer.Localization;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
 using Microsoft.Win32;
@@ -12,7 +13,7 @@ public partial class WelcomePageViewModel : ObservableObject, IInstallerPage
     private readonly InstallContext _context;
     private WelcomePageView? _view;
 
-    public string Title => "Welcome";
+    public string Title => TrExtension.Localizer?["installer.welcome.title"] ?? "Welcome";
     public string Icon => "\uE80F";
     public int Order => 0;
     public bool ShowInWizard => true;
@@ -37,17 +38,18 @@ public partial class WelcomePageViewModel : ObservableObject, IInstallerPage
             ? @"C:\Program Files\ClaudeDo"
             : _context.InstallDirectory;
 
+        var loc = TrExtension.Localizer;
         switch (_context.Mode)
         {
             case InstallerMode.FreshInstall:
-                Heading = "Install ClaudeDo";
+                Heading = loc?["installer.welcome.heading"] ?? "Install ClaudeDo";
-                Subheading = "Choose where to install ClaudeDo, then click Next.";
+                Subheading = loc?["installer.welcome.subheading"] ?? "Choose where to install ClaudeDo, then click Next.";
                 InstallDirEditable = true;
                 break;
 
             case InstallerMode.Update:
                 Heading = $"Update ClaudeDo  {_context.InstalledVersion ?? "?"}  ->  {_context.LatestVersion ?? "?"}";
-                Subheading = "Your tasks, config, and database will be preserved. Click Next to continue.";
+                Subheading = loc?["installer.welcome.updateSubheading"] ?? "Your tasks, config, and database will be preserved. Click Next to continue.";
                 InstallDirEditable = false; // stay where we were installed
                 break;
 

src/ClaudeDo.Installer/Steps/WriteConfigStep.cs

@@ -31,6 +31,7 @@ public sealed class WriteConfigStep : IInstallStep
             {
                 DbPath = Paths.Expand(ctx.UiDbPath),
                 SignalRUrl = ctx.SignalRUrl,
+                Language = ctx.Language,
             };
             uiCfg.Save();
             progress.Report("Written ui.config.json");

src/ClaudeDo.Installer/Views/SelfUpdatePromptWindow.xaml

@@ -1,6 +1,7 @@
 <Window x:Class="ClaudeDo.Installer.Views.SelfUpdatePromptWindow"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:loc="clr-namespace:ClaudeDo.Installer.Localization"
         Title="ClaudeDo Installer Update"
         Width="460" Height="200"
         WindowStartupLocation="CenterScreen"
@@ -13,13 +14,13 @@
             <RowDefinition Height="*"/>
             <RowDefinition Height="Auto"/>
         </Grid.RowDefinitions>
-        <TextBlock Grid.Row="0" FontSize="16" FontWeight="SemiBold" Text="A newer installer is available"/>
+        <TextBlock Grid.Row="0" FontSize="16" FontWeight="SemiBold" Text="{loc:Tr installer.selfUpdate.heading}"/>
         <TextBlock Grid.Row="1" Margin="0,8,0,0" TextWrapping="Wrap" x:Name="DetailText"/>
         <TextBlock Grid.Row="2" Margin="0,12,0,0" TextWrapping="Wrap" Foreground="#a0a0a0" x:Name="ProgressText" Visibility="Collapsed"/>
         <StackPanel Grid.Row="3" Orientation="Horizontal" HorizontalAlignment="Right">
-            <Button x:Name="UpdateBtn" Content="Update" MinWidth="90" Margin="4,0" Padding="10,4" Click="UpdateBtn_Click" IsDefault="True"/>
+            <Button x:Name="UpdateBtn" Content="{loc:Tr installer.selfUpdate.update}" MinWidth="90" Margin="4,0" Padding="10,4" Click="UpdateBtn_Click" IsDefault="True"/>
-            <Button x:Name="ContinueBtn" Content="Continue anyway" MinWidth="140" Margin="4,0" Padding="10,4" Click="ContinueBtn_Click"/>
+            <Button x:Name="ContinueBtn" Content="{loc:Tr installer.selfUpdate.continueAnyway}" MinWidth="140" Margin="4,0" Padding="10,4" Click="ContinueBtn_Click"/>
-            <Button x:Name="CancelBtn" Content="Cancel" MinWidth="90" Margin="4,0" Padding="10,4" Click="CancelBtn_Click" IsCancel="True"/>
+            <Button x:Name="CancelBtn" Content="{loc:Tr installer.nav.cancel}" MinWidth="90" Margin="4,0" Padding="10,4" Click="CancelBtn_Click" IsCancel="True"/>
         </StackPanel>
     </Grid>
 </Window>

src/ClaudeDo.Installer/Views/SettingsViewModel.cs

@@ -1,5 +1,6 @@
 using System.Windows;
 using ClaudeDo.Installer.Core;
+using ClaudeDo.Localization;
 using ClaudeDo.Releases;
 using ClaudeDo.Installer.Steps;
 using CommunityToolkit.Mvvm.ComponentModel;
@@ -10,6 +11,7 @@ namespace ClaudeDo.Installer.Views;
 public partial class SettingsViewModel : ObservableObject
 {
     private readonly InstallContext _context;
+    private readonly ILocalizer _localizer;
     private readonly IReleaseClient _releases;
     private readonly StopWorkerStep _stopService;
     private readonly StartWorkerStep _startService;
@@ -37,6 +39,7 @@ public partial class SettingsViewModel : ObservableObject
     public SettingsViewModel(
         PageResolver resolver,
         InstallContext context,
+        ILocalizer localizer,
         IReleaseClient releases,
         StopWorkerStep stopService,
         StartWorkerStep startService,
@@ -46,6 +49,7 @@ public partial class SettingsViewModel : ObservableObject
     {
         Pages = resolver.SettingsPages;
         _context = context;
+        _localizer = localizer;
         _releases = releases;
         _stopService = stopService;
         _startService = startService;
@@ -104,6 +108,7 @@ public partial class SettingsViewModel : ObservableObject
         {
             DbPath = _context.UiDbPath,
             SignalRUrl = _context.SignalRUrl,
+            Language = _localizer.CurrentCode,
         };
         uiCfg.Save();
 

src/ClaudeDo.Installer/Views/SettingsWindow.xaml

@@ -2,6 +2,7 @@
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:views="clr-namespace:ClaudeDo.Installer.Views"
+        xmlns:loc="clr-namespace:ClaudeDo.Installer.Localization"
         Title="ClaudeDo Settings"
         Icon="/ClaudeTaskSetup.ico"
         Width="720" Height="520"
@@ -90,16 +91,16 @@
                 </StackPanel>
 
                 <CheckBox Grid.Column="1" IsChecked="{Binding RemoveAppData}"
-                          Content="Remove user data (tasks, logs, configs in ~/.todo-app)"
+                          Content="{loc:Tr installer.settings.removeUserData}"
                           Margin="0,0,12,0" VerticalAlignment="Center"/>
-                <Button Grid.Column="2" Content="Uninstall" Margin="0,0,8,0"
+                <Button Grid.Column="2" Content="{loc:Tr installer.settings.uninstall}" Margin="0,0,8,0"
                         Command="{Binding UninstallCommand}"/>
-                <Button Grid.Column="3" Content="Repair" Margin="0,0,8,0"
+                <Button Grid.Column="3" Content="{loc:Tr installer.settings.repair}" Margin="0,0,8,0"
                         Command="{Binding RepairCommand}"/>
-                <Button Grid.Column="4" Content="Save" Margin="0,0,8,0"
+                <Button Grid.Column="4" Content="{loc:Tr installer.settings.save}" Margin="0,0,8,0"
                         Command="{Binding SaveCommand}"
                         Style="{StaticResource AccentButton}"/>
-                <Button Grid.Column="5" Content="Close"
+                <Button Grid.Column="5" Content="{loc:Tr installer.settings.close}"
                         Command="{Binding CloseCommand}"/>
             </Grid>
         </Border>

src/ClaudeDo.Installer/Views/WizardViewModel.cs

@@ -3,6 +3,7 @@ using System.Windows;
 using ClaudeDo.Installer.Core;
 using ClaudeDo.Installer.Pages.InstallPage;
 using ClaudeDo.Installer.Pages.WelcomePage;
+using ClaudeDo.Localization;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
 
@@ -11,8 +12,20 @@ namespace ClaudeDo.Installer.Views;
 public partial class WizardViewModel : ObservableObject
 {
     private readonly InstallContext _context;
+    private readonly ILocalizer _localizer;
 
     public IReadOnlyList<IInstallerPage> Pages { get; }
+    public IReadOnlyList<LanguageOption> Languages { get; }
+
+    [ObservableProperty]
+    private LanguageOption? _selectedLanguage;
+
+    partial void OnSelectedLanguageChanged(LanguageOption? value)
+    {
+        if (value is null) return;
+        _localizer.SetLanguage(value.Value.Code);
+        _context.Language = value.Value.Code;
+    }
 
     [ObservableProperty]
     [NotifyPropertyChangedFor(nameof(CanGoBack))]
@@ -24,14 +37,20 @@ public partial class WizardViewModel : ObservableObject
     public IInstallerPage CurrentPage => Pages[CurrentPageIndex];
     public bool CanGoBack => CurrentPageIndex > 0;
     public bool IsLastPage => CurrentPageIndex == Pages.Count - 1;
-    public string NextButtonText => IsLastPage ? "Install" : "Next \u2192";
+    public string NextButtonText => IsLastPage
+        ? (_localizer["installer.nav.install"])
+        : (_localizer["installer.nav.next"]);
 
     [ObservableProperty]
     private string? _validationError;
 
-    public WizardViewModel(PageResolver resolver, InstallContext context)
+    public WizardViewModel(PageResolver resolver, InstallContext context, ILocalizer localizer)
     {
         _context = context;
+        _localizer = localizer;
+        Languages = localizer.AvailableLanguages;
+        _selectedLanguage = Languages.FirstOrDefault(l => l.Code == localizer.CurrentCode);
+        _context.Language = localizer.CurrentCode;
 
         var all = resolver.WizardPages;
         Pages = context.Mode == InstallerMode.Update

src/ClaudeDo.Installer/Views/WizardWindow.xaml

@@ -2,6 +2,7 @@
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:views="clr-namespace:ClaudeDo.Installer.Views"
+        xmlns:loc="clr-namespace:ClaudeDo.Installer.Localization"
         Title="ClaudeDo Installer"
         Icon="/ClaudeTaskSetup.ico"
         Width="720" Height="520"
@@ -27,6 +28,12 @@
         <Border Grid.Row="0" Background="{StaticResource IslandBgBrush}"
                 BorderBrush="{StaticResource BorderSubtleBrush}" BorderThickness="0,0,0,1"
                 Padding="20,14">
+            <DockPanel>
+                <ComboBox DockPanel.Dock="Right"
+                          ItemsSource="{Binding Languages}"
+                          SelectedItem="{Binding SelectedLanguage, Mode=TwoWay}"
+                          DisplayMemberPath="Name"
+                          Width="150" HorizontalAlignment="Right" VerticalAlignment="Center"/>
                 <ItemsControl ItemsSource="{Binding Pages}">
                     <ItemsControl.ItemsPanel>
                         <ItemsPanelTemplate>
@@ -61,6 +68,7 @@
                         </DataTemplate>
                     </ItemsControl.ItemTemplate>
                 </ItemsControl>
+            </DockPanel>
         </Border>
 
         <!-- Page Content -->
@@ -85,7 +93,7 @@
                            VerticalAlignment="Center" FontSize="12"
                            Visibility="{Binding ValidationError, Converter={StaticResource NullToCollapsedConverter}}"/>
 
-                <Button Grid.Column="1" Content="Back"
+                <Button Grid.Column="1" Content="{loc:Tr installer.nav.back}"
                         Command="{Binding GoBackCommand}"
                         IsEnabled="{Binding CanGoBack}"
                         Margin="0,0,8,0" MinWidth="80"/>

src/ClaudeDo.Localization/locales/en.json

@@ -262,6 +262,67 @@
       "emptyStateHint": "No report for this range yet. Click “Generate”."
     }
   },
+  "installer": {
+    "nav": {
+      "back": "Back",
+      "next": "Next →",
+      "install": "Install",
+      "browse": "Browse...",
+      "cancel": "Cancel"
+    },
+    "welcome": {
+      "title": "Welcome",
+      "heading": "Install ClaudeDo",
+      "subheading": "Choose where to install ClaudeDo, then click Next.",
+      "updateSubheading": "Your tasks, config, and database will be preserved. Click Next to continue.",
+      "installDirectory": "Install Directory",
+      "registerMcp": "Register MCP server with Claude",
+      "registerMcpHint": "Runs 'claude mcp add' so Claude can view and manage your ClaudeDo tasks. You can change this later."
+    },
+    "paths": {
+      "title": "Data Paths",
+      "subtitle": "Configure where ClaudeDo stores its data.",
+      "databasePath": "Database Path",
+      "logDirectory": "Log Directory",
+      "sandboxRoot": "Sandbox Root",
+      "worktreeStrategy": "Worktree Strategy",
+      "centralWorktreeRoot": "Central Worktree Root"
+    },
+    "service": {
+      "title": "Worker",
+      "subtitle": "Configure the ClaudeDo background worker.",
+      "signalRPort": "SignalR Port",
+      "queueBackstopInterval": "Queue Backstop Interval (ms)",
+      "claudeCliPath": "Claude CLI Path",
+      "autostart": "Start worker automatically at logon",
+      "autostartHint": "The worker runs as you (the logged-in user) via a per-user logon task, so it can use your Claude CLI authentication.",
+      "restartDelay": "Restart Delay (ms)"
+    },
+    "uiSettings": {
+      "title": "UI Settings",
+      "subtitle": "Configure the ClaudeDo desktop UI connection settings.",
+      "syncWithService": "Sync with service settings",
+      "signalRUrl": "SignalR URL",
+      "syncHint": "When synced, these values are derived from the Service and Paths pages."
+    },
+    "install": {
+      "title": "Installation",
+      "subtitle": "Click Install to build and deploy ClaudeDo.",
+      "launch": "Launch ClaudeDo"
+    },
+    "settings": {
+      "removeUserData": "Remove user data (tasks, logs, configs in ~/.todo-app)",
+      "uninstall": "Uninstall",
+      "repair": "Repair",
+      "save": "Save",
+      "close": "Close"
+    },
+    "selfUpdate": {
+      "heading": "A newer installer is available",
+      "update": "Update",
+      "continueAnyway": "Continue anyway"
+    }
+  },
   "planning": {
     "conflict": {
       "windowTitle": "Merge conflict",