feat(merge): in-app 3-way merge editor (chunk 2b)

Replace the whole-file conflict resolver with a real 3-way merge editor
built on the line-level hunk pipeline.

- ConflictModels: MergeFile/MergeFileSegment/MergeConflictBlock with
  Compose() that reassembles stable text + chosen resolutions
- ConflictResolverViewModel (same seam contract): loads conflict
  documents, flattens conflicts for one-at-a-time navigation, per-block
  Accept Ours/Base/Theirs/Both + editable result, binary files block continue
- ConflictResolverView: 3-column Base|Ours|Theirs + editable result via
  AvaloniaEdit with TextMate syntax highlighting by file extension;
  editors synced in code-behind
- add Avalonia.AvaloniaEdit + AvaloniaEdit.TextMate + TextMateSharp.Grammars;
  AvaloniaEdit theme StyleInclude in App.axaml
- rewrite ConflictResolverViewModel tests (load/gating/compose/nav/binary/abort)

src/ClaudeDo.App/App.axaml

@@ -31,6 +31,7 @@
 
     <Application.Styles>
         <FluentTheme />
+        <StyleInclude Source="avares://AvaloniaEdit/Themes/Fluent/AvaloniaEdit.xaml" />
         <StyleInclude Source="avares://ClaudeDo.Ui/Design/IslandStyles.axaml" />
         <!-- Global defaults: every Window inherits Inter Tight + body size.
              Controls that need mono opt in via their own class/style. -->

src/ClaudeDo.App/ClaudeDo.App.csproj

@@ -18,6 +18,8 @@
     <PackageReference Include="Avalonia.Desktop" Version="12.0.4" />
     <PackageReference Include="Avalonia.Themes.Fluent" Version="12.0.4" />
     <PackageReference Include="Avalonia.Fonts.Inter" Version="12.0.4" />
+    <!-- Direct ref so the App.axaml AvaloniaEdit theme (avares://AvaloniaEdit/...) resolves at runtime. -->
+    <PackageReference Include="Avalonia.AvaloniaEdit" Version="12.0.0" />
     <PackageReference Include="AvaloniaUI.DiagnosticsSupport" Version="2.2.0">
       <IncludeAssets Condition="'$(Configuration)' != 'Debug'">None</IncludeAssets>
       <PrivateAssets Condition="'$(Configuration)' != 'Debug'">All</PrivateAssets>

src/ClaudeDo.Ui/CLAUDE.md

@@ -23,7 +23,7 @@ ViewModels/
                 UnfinishedPlanning, WeeklyReport, WorkerConnection, Worktree,
                 WorktreesOverview, UnifiedDiffParser
   Planning/   — PlanningDiffViewModel, ConflictResolutionViewModel
-  Conflicts/  — ConflictResolverViewModel
+  Conflicts/  — ConflictResolverViewModel + ConflictModels (MergeFile/MergeFileSegment/MergeConflictBlock)
 Views/        — mirrors the VM layout; Islands/Detail/ holds TaskHeaderBar,
                 DescriptionStepsCard, WorkConsole; plus AgentStripView, SessionTerminalView
 Views/Controls/ — MarkdownView, ModalShell, ThemedDatePicker, DiffLinesView, InheritedBadge
@@ -41,7 +41,7 @@ Design/     — Tokens.axaml (design tokens; merged before styles) + IslandStyle
 - **NotesEditorViewModel** — day navigator + bullet CRUD for daily notes via `INotesApi`.
 - **Modal VMs** — `SettingsModalViewModel` (four tabs: General, Worktrees, Files prompt-paths, Prime Claude incl. `DailyPrepMaxTasks` + prime-schedule rows), `ListSettingsModalViewModel` (name, working dir, commit type, per-list Model/SystemPrompt/AgentPath/MaxTurns with inherited-badge + reset, delete list), `RepoImportModalViewModel` (bulk-create lists from git repos found under chosen parents; already-wired repos disabled), `WeeklyReportModalViewModel` (range pickers default "since last standup weekday → today", cached per range, markdown via MarkdownView), `MergeModalViewModel` (single-task merge form, called from the diff modal), `WorktreesOverviewModalViewModel` (global/per-list worktree rows, batch merge + state ops), `UnfinishedPlanningModalViewModel` (Resume/FinalizeNow/Discard for a draft planning session), `WorkerConnectionModalViewModel` (offline help), `AboutModalViewModel`.
 - **Diff stack** — `UnifiedDiffParser` (static; parses `git diff` output into `DiffFileViewModel`s, detecting added/deleted/renamed/binary files and per-line numbers; `Flatten` injects file-header rows for a combined single-pane view). `DiffModalViewModel` has two modes: live worktree (branch diff vs base, with a Merge action) and commit-range `base..head` (`FromCommitRange = true` — shows a merged task's diff after its worktree is gone; no merge action). The view renders a file list with binary/empty placeholders via `DiffLinesView`.
-- **Planning/Conflicts** — `PlanningDiffViewModel` (per-subtask diffs via `GetPlanningAggregateAsync`, toggle to combined integration-branch diff, conflict warnings), `ConflictResolutionViewModel` (unit-merge conflict dialog: conflicted files, open in VS Code, continue/abort planning merge), `ConflictResolverViewModel` (in-app hunk-by-hunk resolver for single-task merges: start conflict merge, resolve hunks, write resolution, continue/abort).
+- **Planning/Conflicts** — `PlanningDiffViewModel` (per-subtask diffs via `GetPlanningAggregateAsync`, toggle to combined integration-branch diff, conflict warnings), `ConflictResolutionViewModel` (unit-merge conflict dialog: conflicted files, open in VS Code, continue/abort planning merge), `ConflictResolverViewModel` (in-app **3-way merge editor** for single-task merges: starts the conflict merge, parses each conflicted file into stable/conflict `MergeFileSegment`s via the worker's `GetMergeConflictDocuments`, flattens conflicts for one-at-a-time navigation, per-block Accept Ours/Base/Theirs/Both + editable result, composes each file and writes via `WriteConflictResolution`, continue/abort). The view (`Views/Conflicts/ConflictResolverView`) renders a 3-column Base|Ours|Theirs + result using **AvaloniaEdit** with TextMate syntax highlighting by file extension (theme `StyleInclude` in `App.axaml`); editors are synced in code-behind since AvaloniaEdit's `Text` isn't cleanly bindable.
 
 ## Services
 

src/ClaudeDo.Ui/ClaudeDo.Ui.csproj

@@ -8,6 +8,9 @@
 
   <ItemGroup>
     <PackageReference Include="Avalonia" Version="12.0.4" />
+    <PackageReference Include="Avalonia.AvaloniaEdit" Version="12.0.0" />
+    <PackageReference Include="AvaloniaEdit.TextMate" Version="12.0.0" />
+    <PackageReference Include="TextMateSharp.Grammars" Version="2.0.3" />
     <PackageReference Include="CommunityToolkit.Mvvm" Version="8.4.1" />
     <PackageReference Include="Microsoft.AspNetCore.SignalR.Client" Version="8.0.11" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="8.0.1" />

src/ClaudeDo.Ui/ViewModels/Conflicts/ConflictModels.cs

@@ -5,45 +5,74 @@ using CommunityToolkit.Mvvm.Input;
 
 namespace ClaudeDo.Ui.ViewModels.Conflicts;
 
-public sealed partial class ConflictHunk : ObservableObject
+/// <summary>
+/// One conflict region in a file: the two competing versions (and the merge base when the
+/// merge used diff3 style), plus the chosen <see cref="Resolution"/> (null until resolved).
+/// </summary>
+public sealed partial class MergeConflictBlock : ObservableObject
 {
     public string Ours { get; }
-    public string Theirs { get; }
     public string? Base { get; }
+    public string Theirs { get; }
 
     [ObservableProperty] private string? _resolution;
 
     public bool IsResolved => Resolution is not null;
+    public bool HasBase => Base is not null;
 
-    public ConflictHunk(string ours, string theirs, string? @base)
+    public MergeConflictBlock(string ours, string? @base, string theirs)
     {
         Ours = ours;
-        Theirs = theirs;
         Base = @base;
+        Theirs = theirs;
     }
 
     partial void OnResolutionChanged(string? value) => OnPropertyChanged(nameof(IsResolved));
 
-    [RelayCommand] private void AcceptCurrent()  => Resolution = Ours;
-    [RelayCommand] private void AcceptIncoming() => Resolution = Theirs;
-    [RelayCommand] private void AcceptBoth()     => Resolution = Ours + Theirs;
-    [RelayCommand] private void EditManually()   => Resolution ??= Ours;
+    [RelayCommand] private void AcceptOurs()   => Resolution = Ours;
+    [RelayCommand] private void AcceptTheirs() => Resolution = Theirs;
+    [RelayCommand] private void AcceptBoth()   => Resolution = Ours + Theirs;
+    [RelayCommand] private void AcceptBase()   => Resolution = Base ?? "";
 }
 
-public sealed class ConflictFile
+/// <summary>An ordered piece of a conflicted file: either stable common text or a conflict block.</summary>
+public sealed class MergeFileSegment
 {
-    public string Path { get; }
-    public IReadOnlyList<ConflictHunk> Hunks { get; }
+    public bool IsConflict { get; }
+    public string StableText { get; }
+    public MergeConflictBlock? Conflict { get; }
 
-    public ConflictFile(string path, IReadOnlyList<ConflictHunk> hunks)
+    private MergeFileSegment(bool isConflict, string stableText, MergeConflictBlock? conflict)
     {
-        Path = path;
-        Hunks = hunks;
+        IsConflict = isConflict;
+        StableText = stableText;
+        Conflict = conflict;
     }
 
-    public bool AllHunksResolved => Hunks.Count > 0 && Hunks.All(h => h.IsResolved);
-
-    /// <summary>Merged file content: concatenation of each hunk's resolution
-    /// (single whole-file hunk today; concatenation stays correct for multi-hunk later).</summary>
-    public string ComposeResolvedContent() => string.Concat(Hunks.Select(h => h.Resolution));
+    public static MergeFileSegment Stable(string text) => new(false, text, null);
+    public static MergeFileSegment FromConflict(MergeConflictBlock block) => new(true, "", block);
+}
+
+/// <summary>A conflicted file: its ordered segments (for reassembly) and just its conflict blocks.</summary>
+public sealed class MergeFile
+{
+    public string Path { get; }
+    public bool IsBinary { get; }
+    public IReadOnlyList<MergeFileSegment> Segments { get; }
+    public IReadOnlyList<MergeConflictBlock> Conflicts { get; }
+
+    public MergeFile(string path, bool isBinary, IReadOnlyList<MergeFileSegment> segments)
+    {
+        Path = path;
+        IsBinary = isBinary;
+        Segments = segments;
+        Conflicts = segments.Where(s => s.IsConflict).Select(s => s.Conflict!).ToList();
+    }
+
+    /// <summary>A binary file can't be resolved in-app; a text file is done once every block is resolved.</summary>
+    public bool AllResolved => !IsBinary && Conflicts.All(c => c.IsResolved);
+
+    /// <summary>Reassemble the file: stable text verbatim, each conflict replaced by its resolution.</summary>
+    public string Compose() => string.Concat(
+        Segments.Select(s => s.IsConflict ? (s.Conflict!.Resolution ?? s.Conflict.Ours) : s.StableText));
 }

src/ClaudeDo.Ui/ViewModels/Conflicts/ConflictResolverViewModel.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.ComponentModel;
 using System.Linq;
@@ -14,23 +15,61 @@ public sealed partial class ConflictResolverViewModel : ObservableObject
     private readonly IWorkerClient _worker;
     private readonly string _taskId;
 
-    public ObservableCollection<ConflictFile> Files { get; } = new();
+    public ObservableCollection<MergeFile> Files { get; } = new();
+
+    // All text conflicts across all files, flattened for one-at-a-time navigation.
+    private readonly List<(MergeFile File, MergeConflictBlock Block)> _flat = new();
 
     [ObservableProperty] private bool _isBusy;
     [ObservableProperty] private string? _error;
-    [ObservableProperty] private bool _canContinue;
+
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(ContinueHint))]
+    private bool _canContinue;
+
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(HasCurrent))]
+    private MergeConflictBlock? _current;
+
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(PositionText))]
+    [NotifyPropertyChangedFor(nameof(CurrentPath))]
+    [NotifyCanExecuteChangedFor(nameof(NextCommand))]
+    [NotifyCanExecuteChangedFor(nameof(PreviousCommand))]
+    private int _currentIndex = -1;
+
+    public bool HasCurrent => Current is not null;
+    public int TotalConflicts => _flat.Count;
+    public int ResolvedCount => _flat.Count(x => x.Block.IsResolved);
+    public string? CurrentPath => InRange ? _flat[CurrentIndex].File.Path : null;
+
+    public string PositionText => _flat.Count == 0
+        ? "No text conflicts"
+        : $"Conflict {CurrentIndex + 1} of {_flat.Count}  ·  {ResolvedCount} resolved";
+
+    public IReadOnlyList<string> BinaryFilePaths => Files.Where(f => f.IsBinary).Select(f => f.Path).ToList();
+    public bool HasBinaryFiles => Files.Any(f => f.IsBinary);
+
+    public string ContinueHint => HasBinaryFiles
+        ? "Binary conflicts must be resolved externally — abort and resolve in your editor."
+        : "";
+
+    private bool InRange => CurrentIndex >= 0 && CurrentIndex < _flat.Count;
 
     public string TaskId => _taskId;
     public Action? CloseRequested { get; set; }
 
+    /// <summary>Raised when the current conflict changes so the view can reload its editors.</summary>
+    public event Action? CurrentChanged;
+
     public ConflictResolverViewModel(IWorkerClient worker, string taskId)
     {
         _worker = worker;
         _taskId = taskId;
     }
 
-    /// <summary>Starts the conflict merge and loads ours/theirs/base per file.
-    /// Returns true when there are conflicts to resolve (caller should show the dialog).</summary>
+    /// <summary>Starts the conflict merge and loads the conflicted files as line-level segments.
+    /// Returns true when there is something to resolve (caller should show the dialog).</summary>
     public async Task<bool> OpenAsync(string targetBranch)
     {
         IsBusy = true;
@@ -45,19 +84,24 @@ public sealed partial class ConflictResolverViewModel : ObservableObject
                 return false;
             }
 
-            var conflicts = await _worker.GetMergeConflictsAsync(_taskId);
+            var docs = await _worker.GetMergeConflictDocumentsAsync(_taskId);
             Files.Clear();
-            foreach (var f in conflicts.Files)
+            _flat.Clear();
+            foreach (var f in docs.Files)
             {
-                var hunks = f.Hunks.Select(h =>
-                {
-                    var hk = new ConflictHunk(h.Ours, h.Theirs, h.Base);
-                    hk.PropertyChanged += OnHunkChanged;
-                    return hk;
-                }).ToList();
-                Files.Add(new ConflictFile(f.Path, hunks));
+                var segments = f.Segments.Select(s => s.IsConflict
+                    ? MergeFileSegment.FromConflict(Hook(new MergeConflictBlock(s.Ours, s.Base, s.Theirs)))
+                    : MergeFileSegment.Stable(s.Text)).ToList();
+                var file = new MergeFile(f.Path, f.IsBinary, segments);
+                Files.Add(file);
+                foreach (var c in file.Conflicts) _flat.Add((file, c));
             }
+
+            OnPropertyChanged(nameof(TotalConflicts));
+            OnPropertyChanged(nameof(BinaryFilePaths));
+            OnPropertyChanged(nameof(HasBinaryFiles));
             RecomputeCanContinue();
+            if (_flat.Count > 0) MoveTo(0);
             return Files.Count > 0;
         }
         catch (Exception ex)
@@ -68,14 +112,41 @@ public sealed partial class ConflictResolverViewModel : ObservableObject
         finally { IsBusy = false; }
     }
 
-    private void OnHunkChanged(object? sender, PropertyChangedEventArgs e)
+    private MergeConflictBlock Hook(MergeConflictBlock block)
     {
-        if (e.PropertyName is nameof(ConflictHunk.IsResolved) or nameof(ConflictHunk.Resolution))
-            RecomputeCanContinue();
+        block.PropertyChanged += OnBlockChanged;
+        return block;
     }
 
-    private void RecomputeCanContinue()
-        => CanContinue = Files.Count > 0 && Files.All(f => f.AllHunksResolved);
+    private void OnBlockChanged(object? sender, PropertyChangedEventArgs e)
+    {
+        if (e.PropertyName is nameof(MergeConflictBlock.IsResolved) or nameof(MergeConflictBlock.Resolution))
+        {
+            RecomputeCanContinue();
+            OnPropertyChanged(nameof(ResolvedCount));
+            OnPropertyChanged(nameof(PositionText));
+        }
+    }
+
+    private void RecomputeCanContinue() =>
+        CanContinue = Files.Count > 0 && Files.All(f => f.AllResolved);
+
+    private void MoveTo(int index)
+    {
+        CurrentIndex = index;
+        Current = _flat[index].Block;
+        OnPropertyChanged(nameof(CurrentPath));
+        CurrentChanged?.Invoke();
+    }
+
+    private bool CanGoNext() => CurrentIndex >= 0 && CurrentIndex < _flat.Count - 1;
+    private bool CanGoPrevious() => CurrentIndex > 0;
+
+    [RelayCommand(CanExecute = nameof(CanGoNext))]
+    private void Next() => MoveTo(CurrentIndex + 1);
+
+    [RelayCommand(CanExecute = nameof(CanGoPrevious))]
+    private void Previous() => MoveTo(CurrentIndex - 1);
 
     [RelayCommand]
     private async Task ContinueAsync()
@@ -85,8 +156,8 @@ public sealed partial class ConflictResolverViewModel : ObservableObject
         Error = null;
         try
         {
-            foreach (var file in Files)
-                await _worker.WriteConflictResolutionAsync(_taskId, file.Path, file.ComposeResolvedContent());
+            foreach (var file in Files.Where(f => !f.IsBinary))
+                await _worker.WriteConflictResolutionAsync(_taskId, file.Path, file.Compose());
 
             var result = await _worker.ContinueConflictMergeAsync(_taskId);
             if (string.Equals(result.Status, "merged", StringComparison.Ordinal))

src/ClaudeDo.Ui/Views/Conflicts/ConflictResolverView.axaml

@@ -2,11 +2,12 @@
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:vm="using:ClaudeDo.Ui.ViewModels.Conflicts"
         xmlns:ctl="using:ClaudeDo.Ui.Views.Controls"
+        xmlns:ae="clr-namespace:AvaloniaEdit;assembly=AvaloniaEdit"
         xmlns:loc="using:ClaudeDo.Ui.Localization"
         x:DataType="vm:ConflictResolverViewModel"
         x:Class="ClaudeDo.Ui.Views.Conflicts.ConflictResolverView"
         Title="{loc:Tr conflictResolver.windowTitle}"
-        Width="760" Height="640" MinWidth="560" MinHeight="420"
+        Width="1120" Height="760" MinWidth="840" MinHeight="540"
         CanResize="True"
         WindowDecorations="BorderOnly"
         ExtendClientAreaToDecorationsHint="True"
@@ -18,65 +19,126 @@
     <KeyBinding Gesture="Escape" Command="{Binding AbortCommand}"/>
   </Window.KeyBindings>
 
+  <Window.Styles>
+    <Style Selector="ae|TextEditor">
+      <Setter Property="FontFamily" Value="{StaticResource MonoFont}" />
+      <Setter Property="FontSize"   Value="{StaticResource FontSizeMono}" />
+      <Setter Property="Background" Value="{DynamicResource Surface2Brush}" />
+      <Setter Property="Padding"    Value="6,4" />
+      <Setter Property="WordWrap"   Value="True" />
+    </Style>
+    <Style Selector="Border.col-head">
+      <Setter Property="Padding" Value="8,4" />
+      <Setter Property="BorderThickness" Value="0,0,0,1" />
+      <Setter Property="BorderBrush" Value="{DynamicResource LineBrush}" />
+    </Style>
+  </Window.Styles>
+
   <ctl:ModalShell Title="{loc:Tr conflictResolver.modalTitle}" CloseCommand="{Binding AbortCommand}">
     <ctl:ModalShell.Footer>
-      <StackPanel Orientation="Horizontal" Spacing="8"
-                  HorizontalAlignment="Right" VerticalAlignment="Center">
-        <Button Classes="btn" Content="{loc:Tr conflictResolver.continue}"
-                Command="{Binding ContinueCommand}" IsEnabled="{Binding CanContinue}"/>
-        <Button Classes="btn" Content="{loc:Tr conflictResolver.abort}" Command="{Binding AbortCommand}"/>
-      </StackPanel>
+      <Grid ColumnDefinitions="*,Auto">
+        <TextBlock Grid.Column="0" Classes="meta" VerticalAlignment="Center"
+                   Foreground="{DynamicResource BloodBrush}"
+                   Text="{Binding ContinueHint}"
+                   IsVisible="{Binding HasBinaryFiles}"/>
+        <StackPanel Grid.Column="1" Orientation="Horizontal" Spacing="8">
+          <Button Classes="btn accent" Content="{loc:Tr conflictResolver.continue}"
+                  Command="{Binding ContinueCommand}" IsEnabled="{Binding CanContinue}"/>
+          <Button Classes="btn" Content="{loc:Tr conflictResolver.abort}" Command="{Binding AbortCommand}"/>
+        </StackPanel>
+      </Grid>
     </ctl:ModalShell.Footer>
 
-    <Grid RowDefinitions="Auto,*" Margin="16,12">
-      <TextBlock Grid.Row="0" Classes="meta" Margin="0,0,0,8"
-                 Text="{loc:Tr conflictResolver.loading}"
-                 IsVisible="{Binding IsBusy}"/>
+    <Grid Margin="14,10" RowDefinitions="Auto,Auto,Auto,*,Auto,Auto,*">
+
+      <!-- Busy / error -->
+      <TextBlock Grid.Row="0" Classes="meta" Margin="0,0,0,6"
+                 Text="{loc:Tr conflictResolver.loading}" IsVisible="{Binding IsBusy}"/>
       <TextBlock Grid.Row="0" Classes="meta" Foreground="{DynamicResource BloodBrush}"
                  Text="{Binding Error}" TextWrapping="Wrap"
                  IsVisible="{Binding Error, Converter={x:Static ObjectConverters.IsNotNull}}"/>
 
-      <ScrollViewer Grid.Row="1">
-        <ItemsControl ItemsSource="{Binding Files}">
-          <ItemsControl.ItemTemplate>
-            <DataTemplate x:DataType="vm:ConflictFile">
-              <StackPanel Spacing="8" Margin="0,0,0,16">
-                <TextBlock Classes="path-mono heading" Text="{Binding Path}"/>
-                <ItemsControl ItemsSource="{Binding Hunks}">
-                  <ItemsControl.ItemTemplate>
-                    <DataTemplate x:DataType="vm:ConflictHunk">
-                      <Border BorderBrush="{DynamicResource LineBrush}" BorderThickness="1"
-                              CornerRadius="6" Padding="10" Margin="0,0,0,8">
-                        <StackPanel Spacing="6">
-                          <TextBlock Classes="meta" Text="{loc:Tr conflictResolver.current}"/>
-                          <TextBox Text="{Binding Ours, Mode=OneWay}" IsReadOnly="True"
-                                   AcceptsReturn="True" MaxHeight="120"/>
-                          <TextBlock Classes="meta" Text="{loc:Tr conflictResolver.incoming}"/>
-                          <TextBox Text="{Binding Theirs, Mode=OneWay}" IsReadOnly="True"
-                                   AcceptsReturn="True" MaxHeight="120"/>
-                          <StackPanel Orientation="Horizontal" Spacing="6">
-                            <Button Classes="btn" Content="{loc:Tr conflictResolver.acceptCurrent}"
-                                    Command="{Binding AcceptCurrentCommand}"/>
-                            <Button Classes="btn" Content="{loc:Tr conflictResolver.acceptIncoming}"
-                                    Command="{Binding AcceptIncomingCommand}"/>
-                            <Button Classes="btn" Content="{loc:Tr conflictResolver.acceptBoth}"
-                                    Command="{Binding AcceptBothCommand}"/>
-                            <Button Classes="btn" Content="{loc:Tr conflictResolver.editManually}"
-                                    Command="{Binding EditManuallyCommand}"/>
-                          </StackPanel>
-                          <TextBlock Classes="meta" Text="{loc:Tr conflictResolver.mergedResult}"/>
-                          <TextBox Text="{Binding Resolution, Mode=TwoWay}"
-                                   AcceptsReturn="True" MinHeight="80" MaxHeight="200"/>
-                        </StackPanel>
-                      </Border>
-                    </DataTemplate>
-                  </ItemsControl.ItemTemplate>
-                </ItemsControl>
-              </StackPanel>
-            </DataTemplate>
-          </ItemsControl.ItemTemplate>
-        </ItemsControl>
-      </ScrollViewer>
+      <!-- Binary-conflict banner -->
+      <Border Grid.Row="1" Margin="0,0,0,8" Padding="10,7" CornerRadius="6"
+              Background="{DynamicResource ErrorTintBrush}"
+              BorderBrush="{DynamicResource BloodBrush}" BorderThickness="1"
+              IsVisible="{Binding HasBinaryFiles}">
+        <StackPanel Spacing="3">
+          <TextBlock Classes="meta" Foreground="{DynamicResource BloodBrush}"
+                     Text="Binary files can't be merged here — abort and resolve them in your editor:"/>
+          <ItemsControl ItemsSource="{Binding BinaryFilePaths}">
+            <ItemsControl.ItemTemplate>
+              <DataTemplate x:DataType="x:String">
+                <TextBlock Classes="path-mono" Text="{Binding}"/>
+              </DataTemplate>
+            </ItemsControl.ItemTemplate>
+          </ItemsControl>
+        </StackPanel>
+      </Border>
+
+      <!-- Navigation header -->
+      <Grid Grid.Row="2" ColumnDefinitions="Auto,Auto,*,Auto" Margin="0,0,0,8"
+            IsVisible="{Binding HasCurrent}">
+        <Button Grid.Column="0" Classes="btn" Content="◀ Prev" Margin="0,0,6,0"
+                Command="{Binding PreviousCommand}"/>
+        <Button Grid.Column="1" Classes="btn" Content="Next ▶"
+                Command="{Binding NextCommand}"/>
+        <TextBlock Grid.Column="2" Classes="path-mono" VerticalAlignment="Center"
+                   Margin="14,0" TextTrimming="CharacterEllipsis"
+                   Text="{Binding CurrentPath}"/>
+        <TextBlock Grid.Column="3" Classes="meta" VerticalAlignment="Center"
+                   Foreground="{DynamicResource TextDimBrush}"
+                   Text="{Binding PositionText}"/>
+      </Grid>
+
+      <!-- Three-way columns: Base | Ours | Theirs -->
+      <Grid Grid.Row="3" ColumnDefinitions="*,*,*" IsVisible="{Binding HasCurrent}">
+        <Border Grid.Column="0" BorderBrush="{DynamicResource LineBrush}" BorderThickness="1" CornerRadius="6" Margin="0,0,4,0">
+          <DockPanel>
+            <Border Classes="col-head" DockPanel.Dock="Top">
+              <TextBlock Classes="eyebrow" Text="BASE"/>
+            </Border>
+            <ae:TextEditor Name="BaseEditor" IsReadOnly="True"/>
+          </DockPanel>
+        </Border>
+        <Border Grid.Column="1" BorderBrush="{DynamicResource LineBrush}" BorderThickness="1" CornerRadius="6" Margin="4,0">
+          <DockPanel>
+            <Border Classes="col-head" DockPanel.Dock="Top">
+              <TextBlock Classes="eyebrow" Text="OURS · current (merge target)" Foreground="{DynamicResource MossBrush}"/>
+            </Border>
+            <ae:TextEditor Name="OursEditor" IsReadOnly="True"/>
+          </DockPanel>
+        </Border>
+        <Border Grid.Column="2" BorderBrush="{DynamicResource LineBrush}" BorderThickness="1" CornerRadius="6" Margin="4,0,0,0">
+          <DockPanel>
+            <Border Classes="col-head" DockPanel.Dock="Top">
+              <TextBlock Classes="eyebrow" Text="THEIRS · incoming (task)" Foreground="{DynamicResource AccentBrush}"/>
+            </Border>
+            <ae:TextEditor Name="TheirsEditor" IsReadOnly="True"/>
+          </DockPanel>
+        </Border>
+      </Grid>
+
+      <!-- Accept actions -->
+      <WrapPanel Grid.Row="4" Orientation="Horizontal" Margin="0,8" IsVisible="{Binding HasCurrent}">
+        <Button Classes="btn" Content="Accept Ours" Margin="0,0,8,0"
+                Command="{Binding Current.AcceptOursCommand}"/>
+        <Button Classes="btn" Content="Accept Base" Margin="0,0,8,0"
+                IsEnabled="{Binding Current.HasBase}"
+                Command="{Binding Current.AcceptBaseCommand}"/>
+        <Button Classes="btn" Content="Accept Theirs" Margin="0,0,8,0"
+                Command="{Binding Current.AcceptTheirsCommand}"/>
+        <Button Classes="btn" Content="Accept Both" Margin="0,0,8,0"
+                Command="{Binding Current.AcceptBothCommand}"/>
+      </WrapPanel>
+
+      <!-- Merged result -->
+      <TextBlock Grid.Row="5" Classes="eyebrow" Text="MERGED RESULT" Margin="0,4,0,4"
+                 IsVisible="{Binding HasCurrent}"/>
+      <Border Grid.Row="6" BorderBrush="{DynamicResource LineBrush}" BorderThickness="1" CornerRadius="6"
+              IsVisible="{Binding HasCurrent}">
+        <ae:TextEditor Name="ResultEditor" ShowLineNumbers="True"/>
+      </Border>
     </Grid>
   </ctl:ModalShell>
 </Window>

src/ClaudeDo.Ui/Views/Conflicts/ConflictResolverView.axaml.cs

@@ -1,19 +1,102 @@
+using System;
+using System.ComponentModel;
+using System.IO;
 using Avalonia.Controls;
+using AvaloniaEdit;
+using AvaloniaEdit.TextMate;
 using ClaudeDo.Ui.ViewModels.Conflicts;
+using TextMateSharp.Grammars;
 
 namespace ClaudeDo.Ui.Views.Conflicts;
 
 public partial class ConflictResolverView : Window
 {
+    private ConflictResolverViewModel? _vm;
+    private RegistryOptions? _registry;
+    private TextMate.Installation? _baseTm, _oursTm, _theirsTm, _resultTm;
+    private MergeConflictBlock? _hooked;
+    private bool _reloading;
+
     public ConflictResolverView()
     {
         InitializeComponent();
     }
 
-    protected override void OnDataContextChanged(System.EventArgs e)
+    protected override void OnDataContextChanged(EventArgs e)
     {
         base.OnDataContextChanged(e);
-        if (DataContext is ConflictResolverViewModel vm)
-            vm.CloseRequested = Close;
+
+        if (_vm is not null) _vm.CurrentChanged -= ReloadEditors;
+        _vm = DataContext as ConflictResolverViewModel;
+        if (_vm is null) return;
+
+        _vm.CloseRequested = Close;
+        EnsureTextMate();
+        _vm.CurrentChanged += ReloadEditors;
+        ResultEditor.TextChanged += OnResultEditorChanged;
+        ReloadEditors();
+    }
+
+    private void EnsureTextMate()
+    {
+        if (_registry is not null) return;
+        _registry = new RegistryOptions(ThemeName.DarkPlus);
+        _baseTm   = BaseEditor.InstallTextMate(_registry);
+        _oursTm   = OursEditor.InstallTextMate(_registry);
+        _theirsTm = TheirsEditor.InstallTextMate(_registry);
+        _resultTm = ResultEditor.InstallTextMate(_registry);
+    }
+
+    private void ReloadEditors()
+    {
+        if (_vm is null) return;
+        _reloading = true;
+        try
+        {
+            if (_hooked is not null) _hooked.PropertyChanged -= OnCurrentResolutionChanged;
+            _hooked = _vm.Current;
+            if (_hooked is not null) _hooked.PropertyChanged += OnCurrentResolutionChanged;
+
+            BaseEditor.Text   = _vm.Current?.Base ?? "";
+            OursEditor.Text   = _vm.Current?.Ours ?? "";
+            TheirsEditor.Text = _vm.Current?.Theirs ?? "";
+            ResultEditor.Text = _vm.Current?.Resolution ?? "";
+            ApplyGrammar(_vm.CurrentPath);
+        }
+        finally { _reloading = false; }
+    }
+
+    // User edits in the result editor flow back to the current conflict's resolution.
+    private void OnResultEditorChanged(object? sender, EventArgs e)
+    {
+        if (_reloading || _vm?.Current is null) return;
+        _vm.Current.Resolution = ResultEditor.Text;
+    }
+
+    // Accept-buttons set Resolution on the VM; mirror that into the result editor.
+    private void OnCurrentResolutionChanged(object? sender, PropertyChangedEventArgs e)
+    {
+        if (_reloading || e.PropertyName != nameof(MergeConflictBlock.Resolution)) return;
+        var resolved = _vm?.Current?.Resolution ?? "";
+        if (ResultEditor.Text == resolved) return;
+        _reloading = true;
+        try { ResultEditor.Text = resolved; }
+        finally { _reloading = false; }
+    }
+
+    private void ApplyGrammar(string? path)
+    {
+        if (_registry is null || string.IsNullOrEmpty(path)) return;
+        var ext = Path.GetExtension(path);
+        if (string.IsNullOrEmpty(ext)) return;
+
+        var language = _registry.GetLanguageByExtension(ext);
+        if (language is null) return;
+
+        var scope = _registry.GetScopeByLanguageId(language.Id);
+        _baseTm?.SetGrammar(scope);
+        _oursTm?.SetGrammar(scope);
+        _theirsTm?.SetGrammar(scope);
+        _resultTm?.SetGrammar(scope);
     }
 }

tests/ClaudeDo.Ui.Tests/ViewModels/ConflictResolverViewModelTests.cs

@@ -8,6 +8,15 @@ namespace ClaudeDo.Ui.Tests.ViewModels;
 
 public class ConflictResolverViewModelTests
 {
+    // A file split as: stable "a\n", one conflict, stable "z\n".
+    private static ConflictDocumentDto OneConflictFile(string path = "README.md") =>
+        new(path, false, new[]
+        {
+            new MergeSegmentDto(false, "a\n", "", null, ""),
+            new MergeSegmentDto(true, "", "ours\n", "base\n", "theirs\n"),
+            new MergeSegmentDto(false, "z\n", "", null, ""),
+        });
+
     private sealed class FakeWorker : StubWorkerClient
     {
         public string? WrittenPath;
@@ -15,15 +24,13 @@ public class ConflictResolverViewModelTests
         public bool Continued;
         public bool Aborted;
         public string ContinueStatus = "merged";
+        public IReadOnlyList<ConflictDocumentDto> Docs = new[] { OneConflictFile() };
 
         public override Task<MergeResultDto> StartConflictMergeAsync(string taskId, string targetBranch)
             => Task.FromResult(new MergeResultDto("conflict", new[] { "README.md" }, null));
 
-        public override Task<MergeConflictsDto> GetMergeConflictsAsync(string taskId)
-            => Task.FromResult(new MergeConflictsDto(taskId, new[]
-            {
-                new ConflictFileDto("README.md", new[] { new ConflictHunkDto("ours\n", "theirs\n", "base\n") })
-            }));
+        public override Task<MergeConflictDocumentsDto> GetMergeConflictDocumentsAsync(string taskId)
+            => Task.FromResult(new MergeConflictDocumentsDto(taskId, Docs));
 
         public override Task WriteConflictResolutionAsync(string taskId, string path, string resolvedContent)
         {
@@ -43,19 +50,23 @@ public class ConflictResolverViewModelTests
     public async Task OpenAsync_LoadsConflicts_AndBlocksContinueUntilResolved()
     {
         var vm = new ConflictResolverViewModel(new FakeWorker(), "task-1");
+
         var hasConflicts = await vm.OpenAsync("main");
 
         Assert.True(hasConflicts);
         var file = Assert.Single(vm.Files);
         Assert.Equal("README.md", file.Path);
+        Assert.Equal(1, vm.TotalConflicts);
+        Assert.NotNull(vm.Current);
         Assert.False(vm.CanContinue);
 
-        file.Hunks[0].AcceptIncomingCommand.Execute(null);
+        vm.Current!.AcceptTheirsCommand.Execute(null);
         Assert.True(vm.CanContinue);
+        Assert.Equal(1, vm.ResolvedCount);
     }
 
     [Fact]
-    public async Task Continue_WritesComposedResolution_AndClosesOnMerged()
+    public async Task Continue_WritesComposedFile_AndClosesOnMerged()
     {
         var worker = new FakeWorker();
         var vm = new ConflictResolverViewModel(worker, "task-1");
@@ -63,11 +74,12 @@ public class ConflictResolverViewModelTests
         vm.CloseRequested = () => closed = true;
 
         await vm.OpenAsync("main");
-        vm.Files[0].Hunks[0].AcceptCurrentCommand.Execute(null);
+        vm.Current!.AcceptOursCommand.Execute(null);   // choose "ours\n" for the single conflict
         await vm.ContinueCommand.ExecuteAsync(null);
 
         Assert.Equal("README.md", worker.WrittenPath);
-        Assert.Equal("ours\n", worker.WrittenContent);
+        // stable "a\n" + chosen "ours\n" + stable "z\n"
+        Assert.Equal("a\nours\nz\n", worker.WrittenContent);
         Assert.True(worker.Continued);
         Assert.True(closed);
     }
@@ -81,13 +93,60 @@ public class ConflictResolverViewModelTests
         vm.CloseRequested = () => closed = true;
 
         await vm.OpenAsync("main");
-        vm.Files[0].Hunks[0].AcceptBothCommand.Execute(null);
+        vm.Current!.AcceptBothCommand.Execute(null);
         await vm.ContinueCommand.ExecuteAsync(null);
 
         Assert.False(closed);
         Assert.NotNull(vm.Error);
     }
 
+    [Fact]
+    public async Task Navigation_MovesBetweenConflicts_AcrossTheFlattenedList()
+    {
+        var worker = new FakeWorker
+        {
+            Docs = new[]
+            {
+                new ConflictDocumentDto("a.cs", false, new[]
+                {
+                    new MergeSegmentDto(true, "", "o1\n", null, "t1\n"),
+                    new MergeSegmentDto(false, "mid\n", "", null, ""),
+                    new MergeSegmentDto(true, "", "o2\n", null, "t2\n"),
+                }),
+            },
+        };
+        var vm = new ConflictResolverViewModel(worker, "task-1");
+
+        await vm.OpenAsync("main");
+
+        Assert.Equal(2, vm.TotalConflicts);
+        Assert.Equal("o1\n", vm.Current!.Ours);
+        Assert.False(vm.PreviousCommand.CanExecute(null));
+        Assert.True(vm.NextCommand.CanExecute(null));
+
+        vm.NextCommand.Execute(null);
+        Assert.Equal("o2\n", vm.Current!.Ours);
+        Assert.False(vm.NextCommand.CanExecute(null));
+        Assert.True(vm.PreviousCommand.CanExecute(null));
+    }
+
+    [Fact]
+    public async Task BinaryConflict_BlocksContinue()
+    {
+        var worker = new FakeWorker
+        {
+            Docs = new[] { new ConflictDocumentDto("logo.png", true, System.Array.Empty<MergeSegmentDto>()) },
+        };
+        var vm = new ConflictResolverViewModel(worker, "task-1");
+
+        var hasConflicts = await vm.OpenAsync("main");
+
+        Assert.True(hasConflicts);          // file is shown
+        Assert.True(vm.HasBinaryFiles);
+        Assert.Equal(0, vm.TotalConflicts); // nothing to resolve in-app
+        Assert.False(vm.CanContinue);       // binary blocks continue
+    }
+
     [Fact]
     public async Task Abort_CallsWorkerAndCloses()
     {