ClaudeDo/src/ClaudeDo.Ui/Views/Modals/DiffViewerView.axaml

<Window xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vm="using:ClaudeDo.Ui.ViewModels.Modals"
        xmlns:ctl="using:ClaudeDo.Ui.Views.Controls"
        xmlns:loc="using:ClaudeDo.Ui.Localization"
        x:Class="ClaudeDo.Ui.Views.Modals.DiffViewerView"
        x:DataType="vm:DiffViewerViewModel"
        Title="{loc:Tr modals.diff.windowTitle}"
        Width="1200" Height="800" MinWidth="700" MinHeight="450"
        CanResize="True"
        WindowDecorations="BorderOnly"
        ExtendClientAreaToDecorationsHint="True"
        ExtendClientAreaTitleBarHeightHint="-1"
        WindowStartupLocation="CenterOwner"
        Background="{DynamicResource SurfaceBrush}">

  <Window.KeyBindings>
    <KeyBinding Gesture="Escape" Command="{Binding CloseCommand}"/>
  </Window.KeyBindings>

  <ctl:ModalShell Title="{loc:Tr modals.diff.title}" CloseCommand="{Binding CloseCommand}">
    <ctl:ModalShell.Footer>
      <StackPanel Orientation="Horizontal" Spacing="8"
                  HorizontalAlignment="Right" VerticalAlignment="Center">
        <Button Classes="btn" Content="{loc:Tr modals.diff.merge}"
                Command="{Binding MergeCommand}"
                IsVisible="{Binding ShowMerge}"/>
      </StackPanel>
    </ctl:ModalShell.Footer>

    <DockPanel>

      <!-- View toolbar: layout + wrap, both persisted -->
      <StackPanel DockPanel.Dock="Top" Orientation="Horizontal" Spacing="8" Margin="16,8,16,0">
        <ToggleButton Content="{loc:Tr modals.diff.splitView}" IsChecked="{Binding IsSplitView}"/>
        <ToggleButton Content="{loc:Tr modals.diff.wrapLines}" IsChecked="{Binding WrapLines}"/>
      </StackPanel>

      <!-- Planning toolbar: combined-mode toggle + warning/loading -->
      <StackPanel DockPanel.Dock="Top" Orientation="Horizontal" Spacing="8" Margin="16,8,16,0"
                  IsVisible="{Binding IsPlanning}">
        <ToggleButton Content="{loc:Tr planning.diff.previewCombined}" IsChecked="{Binding IsCombinedMode}"/>
        <TextBlock Text="{Binding CombinedWarning}"
                   Foreground="{DynamicResource BloodBrush}"
                   VerticalAlignment="Center"
                   IsVisible="{Binding CombinedWarning, Converter={x:Static ObjectConverters.IsNotNull}}"/>
        <TextBlock Text="{loc:Tr planning.diff.loading}"
                   VerticalAlignment="Center"
                   IsVisible="{Binding IsLoadingCombined}"/>
      </StackPanel>

      <!-- Body: nav | splitter | diff -->
      <Grid ColumnDefinitions="280,4,*" Margin="16">

        <!-- Left nav: file tree (Files) OR subtask list (Planning) -->
        <Border Grid.Column="0" Classes="island">
          <DockPanel>
            <Border DockPanel.Dock="Top" Classes="island-header" IsVisible="{Binding !IsPlanning}">
              <TextBlock Classes="eyebrow" Text="{loc:Tr modals.diff.filesHeader}"/>
            </Border>
            <Panel>
              <!-- Files: folder tree -->
              <TreeView x:Name="FileTree"
                        ItemsSource="{Binding FileTree}"
                        SelectedItem="{Binding SelectedNode, Mode=TwoWay}"
                        Background="Transparent"
                        BorderThickness="0"
                        IsVisible="{Binding !IsPlanning}">
                <TreeView.Styles>
                  <Style Selector="TreeViewItem" x:DataType="vm:DiffTreeNodeViewModel">
                    <Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}"/>
                  </Style>
                </TreeView.Styles>
                <TreeView.ItemTemplate>
                  <TreeDataTemplate DataType="vm:DiffTreeNodeViewModel" ItemsSource="{Binding Children}">
                    <Border Background="Transparent" Tapped="OnNodeTapped" Cursor="Hand" Padding="0,2">
                      <Grid ColumnDefinitions="Auto,*,Auto">
                        <Border Grid.Column="0" Tag="{Binding StatusCode}" CornerRadius="3" Padding="4,0" Margin="0,0,6,0"
                                VerticalAlignment="Center"
                                IsVisible="{Binding StatusCode, Converter={x:Static StringConverters.IsNotNullOrEmpty}}">
                          <TextBlock Text="{Binding StatusCode}"
                                     FontFamily="{DynamicResource MonoFont}" FontSize="{StaticResource FontSizeEyebrow}"
                                     Foreground="{DynamicResource TextBrush}"/>
                        </Border>
                        <TextBlock Grid.Column="1" Classes="meta" Text="{Binding Name}"
                                   VerticalAlignment="Center" TextTrimming="CharacterEllipsis"/>
                        <StackPanel Grid.Column="2" Orientation="Horizontal" Spacing="4" VerticalAlignment="Center"
                                    Margin="0,0,8,0"
                                    IsVisible="{Binding ShowStats}">
                          <TextBlock Foreground="{DynamicResource MossBrightBrush}" FontSize="{StaticResource FontSizeEyebrow}"
                                     Text="{Binding Additions, StringFormat='+{0}'}"/>
                          <TextBlock Foreground="{DynamicResource BloodBrush}" FontSize="{StaticResource FontSizeEyebrow}"
                                     Text="{Binding Deletions, StringFormat='−{0}'}"/>
                        </StackPanel>
                      </Grid>
                    </Border>
                  </TreeDataTemplate>
                </TreeView.ItemTemplate>
              </TreeView>

              <!-- Planning: subtask list -->
              <ListBox ItemsSource="{Binding Subtasks}"
                       SelectedItem="{Binding SelectedSubtask}"
                       IsEnabled="{Binding !IsCombinedMode}"
                       IsVisible="{Binding IsPlanning}"
                       Background="Transparent"
                       BorderThickness="0"
                       ScrollViewer.HorizontalScrollBarVisibility="Disabled">
                <ListBox.ItemTemplate>
                  <DataTemplate x:DataType="vm:SubtaskDiffRow">
                    <Border Padding="10,8" Background="Transparent">
                      <StackPanel Spacing="2">
                        <TextBlock Classes="title" Text="{Binding Title}" TextTrimming="CharacterEllipsis"/>
                        <TextBlock Classes="meta" Text="{Binding DiffStat}"/>
                      </StackPanel>
                    </Border>
                  </DataTemplate>
                </ListBox.ItemTemplate>
              </ListBox>
            </Panel>
          </DockPanel>
        </Border>

        <GridSplitter Grid.Column="1" ResizeDirection="Columns" Background="{DynamicResource LineBrush}"/>

        <!-- Right: diff content (Files per-file pane OR Planning flat diff) -->
        <Border Grid.Column="2" Classes="island">
          <Panel>

            <!-- Files mode: per-file pane with header + placeholders -->
            <DockPanel IsVisible="{Binding !IsPlanning}">
              <Border DockPanel.Dock="Top" Classes="island-header"
                      IsVisible="{Binding SelectedFile, Converter={x:Static ObjectConverters.IsNotNull}}">
                <Grid ColumnDefinitions="Auto,*">
                  <Border Grid.Column="0" Tag="{Binding SelectedFile.StatusCode}"
                          CornerRadius="3" Padding="4,0" Margin="0,0,8,0" VerticalAlignment="Center">
                    <TextBlock Text="{Binding SelectedFile.StatusCode}"
                               FontFamily="{DynamicResource MonoFont}" FontSize="{StaticResource FontSizeEyebrow}"
                               Foreground="{DynamicResource TextBrush}"/>
                  </Border>
                  <TextBlock Grid.Column="1" Classes="path-mono" Text="{Binding SelectedFile.HeaderPath}"
                             VerticalAlignment="Center" TextTrimming="PrefixCharacterEllipsis"/>
                </Grid>
              </Border>

              <Grid Background="{DynamicResource VoidBrush}">
                <TextBlock Classes="body" Text="{Binding StatusMessage}"
                           IsVisible="{Binding StatusMessage, Converter={x:Static StringConverters.IsNotNullOrEmpty}}"
                           HorizontalAlignment="Center" VerticalAlignment="Center"/>
                <TextBlock Classes="body" Text="{loc:Tr modals.diff.binary}"
                           Foreground="{DynamicResource TextMuteBrush}"
                           IsVisible="{Binding SelectedFile.IsBinary}"
                           HorizontalAlignment="Center" VerticalAlignment="Center"/>
                <TextBlock Classes="body" Text="{loc:Tr modals.diff.empty}"
                           Foreground="{DynamicResource TextMuteBrush}"
                           IsVisible="{Binding SelectedFile.IsEmptyContent}"
                           HorizontalAlignment="Center" VerticalAlignment="Center"/>
                <ctl:DiffTextView IsVisible="{Binding SelectedFile.HasLines}"
                                  File="{Binding SelectedFile}"
                                  IsSplit="{Binding IsSplitView}"
                                  WrapLines="{Binding WrapLines}"/>
              </Grid>
            </DockPanel>

            <!-- Planning mode: flat aggregate/combined diff -->
            <Grid Background="{DynamicResource VoidBrush}" IsVisible="{Binding IsPlanning}">
              <ScrollViewer HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">
                <ctl:DiffLinesView Lines="{Binding DiffLines}"/>
              </ScrollViewer>
            </Grid>

          </Panel>
        </Border>
      </Grid>

    </DockPanel>
  </ctl:ModalShell>
</Window>