diff --git a/src/ClaudeDo.Ui/Services/WorkerClient.cs b/src/ClaudeDo.Ui/Services/WorkerClient.cs
index 9083a92..859b1a7 100644
--- a/src/ClaudeDo.Ui/Services/WorkerClient.cs
+++ b/src/ClaudeDo.Ui/Services/WorkerClient.cs
@@ -55,6 +55,8 @@ public partial class WorkerClient : ObservableObject, IAsyncDisposable, IWorkerC
     public event Action<string>? PlanningMergeAbortedEvent;
     public event Action<string>? PlanningCompletedEvent;
 
+    public string? LastMergeAllTarget { get; private set; }
+
     public WorkerClient(string signalRUrl)
     {
         _hub = new HubConnectionBuilder()
@@ -420,6 +422,7 @@ public partial class WorkerClient : ObservableObject, IAsyncDisposable, IWorkerC
 
     public async Task MergeAllPlanningAsync(string planningTaskId, string targetBranch)
     {
+        LastMergeAllTarget = targetBranch;
         await _hub.InvokeAsync("MergeAllPlanning", planningTaskId, targetBranch);
     }
 
diff --git a/src/ClaudeDo.Ui/ViewModels/IslandsShellViewModel.cs b/src/ClaudeDo.Ui/ViewModels/IslandsShellViewModel.cs
index 50e760b..4a7f600 100644
--- a/src/ClaudeDo.Ui/ViewModels/IslandsShellViewModel.cs
+++ b/src/ClaudeDo.Ui/ViewModels/IslandsShellViewModel.cs
@@ -4,9 +4,12 @@ using System.Threading;
 using System.Threading.Tasks;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
+using ClaudeDo.Data;
 using ClaudeDo.Data.Models;
 using ClaudeDo.Ui.Services;
 using ClaudeDo.Ui.ViewModels.Islands;
+using ClaudeDo.Ui.ViewModels.Planning;
+using Microsoft.EntityFrameworkCore;
 
 namespace ClaudeDo.Ui.ViewModels;
 
@@ -27,6 +30,10 @@ public sealed partial class IslandsShellViewModel : ViewModelBase
 
     private readonly UpdateCheckService _updateCheck;
     private readonly InstallerLocator _installerLocator;
+    private readonly IDbContextFactory<ClaudeDoDbContext>? _dbFactory;
+
+    // Set by MainWindow to open the conflict resolution dialog.
+    public Func<ConflictResolutionViewModel, Task>? ShowConflictDialog { get; set; }
 
     [ObservableProperty] private bool _isUpdateBannerVisible;
     [ObservableProperty] private string? _updateBannerLatestVersion;
@@ -84,6 +91,47 @@ public sealed partial class IslandsShellViewModel : ViewModelBase
         WorkerLogText = null;
     }
 
+    private void OnPlanningMergeConflict(string planningTaskId, string subtaskId, IReadOnlyList<string> conflictedFiles)
+    {
+        // Already on UI thread (WorkerClient dispatches via Dispatcher.UIThread.Post).
+        _ = OpenConflictDialogAsync(planningTaskId, subtaskId, conflictedFiles);
+    }
+
+    private async Task OpenConflictDialogAsync(string planningTaskId, string subtaskId, IReadOnlyList<string> conflictedFiles)
+    {
+        if (ShowConflictDialog == null || _dbFactory == null) return;
+
+        string subtaskTitle = subtaskId;
+        string worktreePath = System.Environment.CurrentDirectory;
+        string targetBranch = Worker?.LastMergeAllTarget ?? "main";
+
+        try
+        {
+            await using var ctx = await _dbFactory.CreateDbContextAsync();
+            var entity = await ctx.Tasks
+                .Include(t => t.Worktree)
+                .AsNoTracking()
+                .FirstOrDefaultAsync(t => t.Id == subtaskId);
+            if (entity != null)
+            {
+                subtaskTitle = entity.Title;
+                if (entity.Worktree?.Path is { } p)
+                    worktreePath = p;
+            }
+        }
+        catch { /* Non-fatal: fall back to subtaskId and cwd */ }
+
+        var vm = new ConflictResolutionViewModel(
+            Worker!,
+            planningTaskId,
+            subtaskTitle,
+            targetBranch,
+            conflictedFiles,
+            worktreePath);
+
+        await ShowConflictDialog(vm);
+    }
+
     // For tests only — does NOT wire up events.
     internal IslandsShellViewModel() { }
 
@@ -93,11 +141,13 @@ public sealed partial class IslandsShellViewModel : ViewModelBase
         DetailsIslandViewModel details,
         WorkerClient worker,
         UpdateCheckService updateCheck,
-        InstallerLocator installerLocator)
+        InstallerLocator installerLocator,
+        IDbContextFactory<ClaudeDoDbContext> dbFactory)
     {
         Lists = lists; Tasks = tasks; Details = details; Worker = worker;
         _updateCheck = updateCheck;
         _installerLocator = installerLocator;
+        _dbFactory = dbFactory;
         Lists.SelectionChanged += (_, _) => Tasks.LoadForList(Lists.SelectedList);
         Tasks.SelectionChanged += (_, _) => Details.Bind(Tasks.SelectedTask);
         Tasks.TasksChanged     += (_, _) => _ = Lists.RefreshCountsAsync();
@@ -122,6 +172,7 @@ public sealed partial class IslandsShellViewModel : ViewModelBase
             }
         };
         Worker.WorkerLogReceivedEvent += OnWorkerLogReceived;
+        Worker.PlanningMergeConflictEvent += OnPlanningMergeConflict;
         _clearTimer.Elapsed += (_, _) =>
         {
             if (Dispatcher.UIThread.CheckAccess())
diff --git a/src/ClaudeDo.Ui/ViewModels/Planning/ConflictResolutionViewModel.cs b/src/ClaudeDo.Ui/ViewModels/Planning/ConflictResolutionViewModel.cs
new file mode 100644
index 0000000..18d1e54
--- /dev/null
+++ b/src/ClaudeDo.Ui/ViewModels/Planning/ConflictResolutionViewModel.cs
@@ -0,0 +1,83 @@
+using System.Diagnostics;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using ClaudeDo.Ui.Services;
+
+namespace ClaudeDo.Ui.ViewModels.Planning;
+
+public sealed partial class ConflictResolutionViewModel : ObservableObject
+{
+    private readonly IWorkerClient _worker;
+    private readonly string _planningTaskId;
+    private readonly string _worktreePath;
+
+    public string SubtaskTitle { get; }
+    public string TargetBranch { get; }
+    public IReadOnlyList<string> ConflictedFiles { get; }
+
+    [ObservableProperty] private string? _vsCodeError;
+    [ObservableProperty] private string? _actionError;
+
+    public Action? CloseRequested { get; set; }
+
+    public ConflictResolutionViewModel(
+        IWorkerClient worker,
+        string planningTaskId,
+        string subtaskTitle,
+        string targetBranch,
+        IReadOnlyList<string> conflictedFiles,
+        string worktreePath)
+    {
+        _worker = worker;
+        _planningTaskId = planningTaskId;
+        _worktreePath = worktreePath;
+        SubtaskTitle = subtaskTitle;
+        TargetBranch = targetBranch;
+        ConflictedFiles = conflictedFiles;
+    }
+
+    [RelayCommand]
+    private void OpenInVsCode()
+    {
+        try
+        {
+            var args = string.Join(" ", ConflictedFiles.Select(f => $"\"{f}\""));
+            Process.Start(new ProcessStartInfo
+            {
+                FileName = "code",
+                Arguments = args,
+                WorkingDirectory = _worktreePath,
+                UseShellExecute = true,
+            });
+            VsCodeError = null;
+        }
+        catch (Exception ex)
+        {
+            VsCodeError = $"Could not launch VS Code: {ex.Message}. Paths are listed above — copy them manually.";
+        }
+    }
+
+    [RelayCommand]
+    private async Task ContinueAsync()
+    {
+        ActionError = null;
+        try
+        {
+            await _worker.ContinuePlanningMergeAsync(_planningTaskId);
+            CloseRequested?.Invoke();
+        }
+        catch (Exception ex) { ActionError = ex.Message; }
+    }
+
+    [RelayCommand]
+    private async Task AbortAsync()
+    {
+        ActionError = null;
+        try
+        {
+            await _worker.AbortPlanningMergeAsync(_planningTaskId);
+            CloseRequested?.Invoke();
+        }
+        catch (Exception ex) { ActionError = ex.Message; }
+    }
+}
diff --git a/src/ClaudeDo.Ui/Views/MainWindow.axaml.cs b/src/ClaudeDo.Ui/Views/MainWindow.axaml.cs
index 01a17aa..463700f 100644
--- a/src/ClaudeDo.Ui/Views/MainWindow.axaml.cs
+++ b/src/ClaudeDo.Ui/Views/MainWindow.axaml.cs
@@ -1,6 +1,7 @@
 using Avalonia.Controls;
 using Avalonia.Input;
 using ClaudeDo.Ui.ViewModels;
+using ClaudeDo.Ui.Views.Planning;
 
 namespace ClaudeDo.Ui.Views;
 
@@ -10,6 +11,19 @@ public partial class MainWindow : Window
     {
         InitializeComponent();
         KeyDown += OnWindowKeyDown;
+        DataContextChanged += OnDataContextChanged;
+    }
+
+    private void OnDataContextChanged(object? sender, EventArgs e)
+    {
+        if (DataContext is IslandsShellViewModel vm)
+        {
+            vm.ShowConflictDialog = async (conflictVm) =>
+            {
+                var modal = new ConflictResolutionView { DataContext = conflictVm };
+                await modal.ShowDialog(this);
+            };
+        }
     }
 
     private void OnWindowKeyDown(object? sender, KeyEventArgs e)
diff --git a/src/ClaudeDo.Ui/Views/Planning/ConflictResolutionView.axaml b/src/ClaudeDo.Ui/Views/Planning/ConflictResolutionView.axaml
new file mode 100644
index 0000000..b2b2e2f
--- /dev/null
+++ b/src/ClaudeDo.Ui/Views/Planning/ConflictResolutionView.axaml
@@ -0,0 +1,65 @@
+<Window xmlns="https://github.com/avaloniaui"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:vm="using:ClaudeDo.Ui.ViewModels.Planning"
+        x:DataType="vm:ConflictResolutionViewModel"
+        x:Class="ClaudeDo.Ui.Views.Planning.ConflictResolutionView"
+        Title="Merge conflict"
+        Width="560" SizeToContent="Height"
+        SystemDecorations="None"
+        ExtendClientAreaToDecorationsHint="True"
+        WindowStartupLocation="CenterOwner"
+        Background="{StaticResource SurfaceBrush}">
+
+  <Window.KeyBindings>
+    <KeyBinding Gesture="Escape" Command="{Binding AbortCommand}"/>
+  </Window.KeyBindings>
+
+  <Border Background="{StaticResource SurfaceBrush}"
+          BorderBrush="{StaticResource LineBrush}"
+          BorderThickness="1">
+    <Grid RowDefinitions="36,*">
+
+      <!-- Title bar / drag handle -->
+      <Border Grid.Row="0"
+              x:Name="TitleBar"
+              Background="{StaticResource Surface2Brush}"
+              BorderBrush="{StaticResource LineBrush}"
+              BorderThickness="0,0,0,1"
+              PointerPressed="TitleBar_PointerPressed">
+        <Grid ColumnDefinitions="*,Auto" Margin="14,0">
+          <TextBlock Text="Merge conflict"
+                     VerticalAlignment="Center"
+                     FontFamily="{StaticResource MonoFamily}"
+                     FontSize="12"
+                     Foreground="{StaticResource TextDimBrush}"/>
+        </Grid>
+      </Border>
+
+      <!-- Content -->
+      <StackPanel Grid.Row="1" Spacing="12" Margin="16" MinWidth="520">
+        <TextBlock FontWeight="SemiBold" FontSize="16"
+                   Text="{Binding SubtaskTitle, StringFormat='Conflicts in subtask: {0}'}"/>
+        <TextBlock Text="{Binding TargetBranch, StringFormat='Merging into: {0}'}" Opacity="0.7"/>
+        <ItemsControl ItemsSource="{Binding ConflictedFiles}">
+          <ItemsControl.ItemTemplate>
+            <DataTemplate>
+              <TextBlock Text="{Binding}" FontFamily="Consolas,Menlo,monospace"/>
+            </DataTemplate>
+          </ItemsControl.ItemTemplate>
+        </ItemsControl>
+        <TextBlock Text="{Binding VsCodeError}" Foreground="OrangeRed"
+                   IsVisible="{Binding VsCodeError, Converter={x:Static ObjectConverters.IsNotNull}}"
+                   TextWrapping="Wrap"/>
+        <TextBlock Text="{Binding ActionError}" Foreground="OrangeRed"
+                   IsVisible="{Binding ActionError, Converter={x:Static ObjectConverters.IsNotNull}}"
+                   TextWrapping="Wrap"/>
+        <StackPanel Orientation="Horizontal" Spacing="8" HorizontalAlignment="Right" Margin="0,4,0,4">
+          <Button Content="Open all in VS Code" Command="{Binding OpenInVsCodeCommand}"/>
+          <Button Content="I've resolved — continue" Command="{Binding ContinueCommand}"/>
+          <Button Content="Abort this merge" Command="{Binding AbortCommand}"/>
+        </StackPanel>
+      </StackPanel>
+
+    </Grid>
+  </Border>
+</Window>
diff --git a/src/ClaudeDo.Ui/Views/Planning/ConflictResolutionView.axaml.cs b/src/ClaudeDo.Ui/Views/Planning/ConflictResolutionView.axaml.cs
new file mode 100644
index 0000000..161f8a9
--- /dev/null
+++ b/src/ClaudeDo.Ui/Views/Planning/ConflictResolutionView.axaml.cs
@@ -0,0 +1,26 @@
+using Avalonia.Controls;
+using Avalonia.Input;
+using ClaudeDo.Ui.ViewModels.Planning;
+
+namespace ClaudeDo.Ui.Views.Planning;
+
+public partial class ConflictResolutionView : Window
+{
+    public ConflictResolutionView()
+    {
+        InitializeComponent();
+    }
+
+    protected override void OnDataContextChanged(EventArgs e)
+    {
+        base.OnDataContextChanged(e);
+        if (DataContext is ConflictResolutionViewModel vm)
+            vm.CloseRequested = Close;
+    }
+
+    private void TitleBar_PointerPressed(object? sender, PointerPressedEventArgs e)
+    {
+        if (e.GetCurrentPoint(this).Properties.IsLeftButtonPressed)
+            BeginMoveDrag(e);
+    }
+}
diff --git a/tests/ClaudeDo.Ui.Tests/ViewModels/ConflictResolutionViewModelTests.cs b/tests/ClaudeDo.Ui.Tests/ViewModels/ConflictResolutionViewModelTests.cs
new file mode 100644
index 0000000..5e8e355
--- /dev/null
+++ b/tests/ClaudeDo.Ui.Tests/ViewModels/ConflictResolutionViewModelTests.cs
@@ -0,0 +1,139 @@
+using System.ComponentModel;
+using ClaudeDo.Data.Models;
+using ClaudeDo.Ui.Services;
+using ClaudeDo.Ui.ViewModels.Planning;
+
+namespace ClaudeDo.Ui.Tests.ViewModels;
+
+public class ConflictResolutionViewModelTests
+{
+    // ------------------------------------------------------------------ fake
+    private sealed class FakeWorker : IWorkerClient
+    {
+        public bool IsConnected => false;
+
+        public string? ContinueCalledWith { get; private set; }
+        public string? AbortCalledWith { get; private set; }
+        public Exception? ContinueThrows { get; set; }
+        public Exception? AbortThrows { get; set; }
+
+        public event PropertyChangedEventHandler? PropertyChanged;
+        public event Action<string, string, DateTime>? TaskStartedEvent;
+        public event Action<string, string, string, DateTime>? TaskFinishedEvent;
+        public event Action<string>? TaskUpdatedEvent;
+        public event Action<string>? WorktreeUpdatedEvent;
+        public event Action<string, string>? TaskMessageEvent;
+        public event Action<string, string>? PlanningMergeStartedEvent;
+        public event Action<string, string>? PlanningSubtaskMergedEvent;
+        public event Action<string, string, IReadOnlyList<string>>? PlanningMergeConflictEvent;
+        public event Action<string>? PlanningMergeAbortedEvent;
+        public event Action<string>? PlanningCompletedEvent;
+
+        public Task WakeQueueAsync() => Task.CompletedTask;
+        public Task RunNowAsync(string taskId) => Task.CompletedTask;
+        public Task ContinueTaskAsync(string taskId, string followUpPrompt) => Task.CompletedTask;
+        public Task ResetTaskAsync(string taskId) => Task.CompletedTask;
+        public Task CancelTaskAsync(string taskId) => Task.CompletedTask;
+        public Task<List<AgentInfo>> GetAgentsAsync() => Task.FromResult(new List<AgentInfo>());
+        public Task<ListConfigDto?> GetListConfigAsync(string listId) => Task.FromResult<ListConfigDto?>(null);
+        public Task UpdateTaskAgentSettingsAsync(UpdateTaskAgentSettingsDto dto) => Task.CompletedTask;
+        public Task StartPlanningSessionAsync(string taskId, CancellationToken ct = default) => Task.CompletedTask;
+        public Task ResumePlanningSessionAsync(string taskId, CancellationToken ct = default) => Task.CompletedTask;
+        public Task DiscardPlanningSessionAsync(string taskId, CancellationToken ct = default) => Task.CompletedTask;
+        public Task FinalizePlanningSessionAsync(string taskId, bool queueAgentTasks = true, CancellationToken ct = default) => Task.CompletedTask;
+        public Task<int> GetPendingDraftCountAsync(string taskId, CancellationToken ct = default) => Task.FromResult(0);
+        public Task<MergeTargetsDto?> GetMergeTargetsAsync(string taskId) => Task.FromResult<MergeTargetsDto?>(null);
+        public Task<IReadOnlyList<SubtaskDiffDto>> GetPlanningAggregateAsync(string planningTaskId) =>
+            Task.FromResult<IReadOnlyList<SubtaskDiffDto>>(Array.Empty<SubtaskDiffDto>());
+        public Task<CombinedDiffResultDto?> BuildPlanningIntegrationBranchAsync(string planningTaskId, string targetBranch) =>
+            Task.FromResult<CombinedDiffResultDto?>(null);
+        public Task MergeAllPlanningAsync(string planningTaskId, string targetBranch) => Task.CompletedTask;
+
+        public Task ContinuePlanningMergeAsync(string planningTaskId)
+        {
+            ContinueCalledWith = planningTaskId;
+            if (ContinueThrows is not null) throw ContinueThrows;
+            return Task.CompletedTask;
+        }
+
+        public Task AbortPlanningMergeAsync(string planningTaskId)
+        {
+            AbortCalledWith = planningTaskId;
+            if (AbortThrows is not null) throw AbortThrows;
+            return Task.CompletedTask;
+        }
+    }
+
+    private static ConflictResolutionViewModel BuildVm(FakeWorker worker, string planningTaskId = "plan-1") =>
+        new ConflictResolutionViewModel(
+            worker,
+            planningTaskId,
+            subtaskTitle: "My subtask",
+            targetBranch: "main",
+            conflictedFiles: new[] { "src/Foo.cs", "src/Bar.cs" },
+            worktreePath: "C:/worktrees/plan-1");
+
+    // ------------------------------------------------------------------ tests
+
+    [Fact]
+    public async Task ContinueAsync_CallsHub_AndClosesOnSuccess()
+    {
+        var worker = new FakeWorker();
+        var vm = BuildVm(worker, "plan-42");
+        bool closeCalled = false;
+        vm.CloseRequested = () => closeCalled = true;
+
+        await vm.ContinueCommand.ExecuteAsync(null);
+
+        Assert.Equal("plan-42", worker.ContinueCalledWith);
+        Assert.True(closeCalled);
+        Assert.Null(vm.ActionError);
+    }
+
+    [Fact]
+    public async Task ContinueAsync_HubThrows_ShowsActionErrorAndStaysOpen()
+    {
+        var worker = new FakeWorker { ContinueThrows = new InvalidOperationException("hub down") };
+        var vm = BuildVm(worker);
+        bool closeCalled = false;
+        vm.CloseRequested = () => closeCalled = true;
+
+        await vm.ContinueCommand.ExecuteAsync(null);
+
+        Assert.False(closeCalled);
+        Assert.Equal("hub down", vm.ActionError);
+    }
+
+    [Fact]
+    public async Task AbortAsync_CallsHub_AndClosesOnSuccess()
+    {
+        var worker = new FakeWorker();
+        var vm = BuildVm(worker, "plan-99");
+        bool closeCalled = false;
+        vm.CloseRequested = () => closeCalled = true;
+
+        await vm.AbortCommand.ExecuteAsync(null);
+
+        Assert.Equal("plan-99", worker.AbortCalledWith);
+        Assert.True(closeCalled);
+        Assert.Null(vm.ActionError);
+    }
+
+    [Fact]
+    public async Task AbortAsync_HubThrows_ShowsActionError()
+    {
+        var worker = new FakeWorker { AbortThrows = new InvalidOperationException("abort failed") };
+        var vm = BuildVm(worker);
+        bool closeCalled = false;
+        vm.CloseRequested = () => closeCalled = true;
+
+        await vm.AbortCommand.ExecuteAsync(null);
+
+        Assert.False(closeCalled);
+        Assert.Equal("abort failed", vm.ActionError);
+    }
+
+    // OpenInVsCode is not unit-tested here because abstracting Process.Start
+    // would require an indirection layer that isn't part of the approved design.
+    // The error path is covered by the VsCodeError property being set on catch.
+}