fix(ui): suppress auto-open conflict resolver during MCP-driven merges

review_task/continue_merge on a planning parent always leaves conflicts in
the tree, and the UI auto-opened the resolver on every PlanningMergeConflict
broadcast regardless of who started the merge -- so a running Claude session
resolving a unit-merge conflict could race a human editing the same shared
checkout in a resolver window neither of them asked for.

PlanningMergeOrchestrator.StartAsync now takes an externallyDriven flag (set
by ExternalMcpService's MCP-driven review_task path, left false for the UI's
ApproveReview) that rides along on the PlanningMergeConflict broadcast. The
UI only auto-opens the resolver when it's false; otherwise it shows a
persistent banner with a manual "Open resolver" button, cleared on
PlanningMergeAborted/PlanningCompleted. A new GetActiveExternalConflictsAsync
query (checked against GitService.IsMidMergeAsync rather than the in-memory
flag alone) lets the UI resync the banner on reconnect instead of trusting a
one-shot broadcast that isn't replayed after a restart.

The childless single-task conflict path was checked and needed no change --
it only broadcasts the generic TaskUpdated, never PlanningMergeConflict.

src/ClaudeDo.Localization/locales/de.json

@@ -629,6 +629,10 @@
       "available": "Update verfügbar: v",
       "updateNow": "Jetzt aktualisieren",
       "dismiss": "Ausblenden"
+    },
+    "externalMerge": {
+      "banner": "Eine Claude-Session löst gerade einen Merge-Konflikt auf — bitte keine Dateien im Repository bearbeiten.",
+      "open": "Resolver öffnen"
     }
   },
   "vm": {

src/ClaudeDo.Localization/locales/en.json

@@ -629,6 +629,10 @@
       "available": "Update available: v",
       "updateNow": "Update now",
       "dismiss": "Dismiss"
+    },
+    "externalMerge": {
+      "banner": "A Claude session is resolving a merge conflict — don't edit files in the repository.",
+      "open": "Open resolver"
     }
   },
   "vm": {

src/ClaudeDo.Ui/Services/Interfaces/IWorkerClient.cs

@@ -35,7 +35,10 @@ public interface IWorkerClient : INotifyPropertyChanged
 
     event Action<string, string>? PlanningMergeStartedEvent;
     event Action<string, string>? PlanningSubtaskMergedEvent;
-    event Action<string, string, IReadOnlyList<string>>? PlanningMergeConflictEvent;
+    /// <summary>(planningTaskId, subtaskId, conflictedFiles, externallyDriven). externallyDriven
+    /// is true when an MCP session (not the UI) started the unit merge — the resolver must not
+    /// auto-open in that case.</summary>
+    event Action<string, string, IReadOnlyList<string>, bool>? PlanningMergeConflictEvent;
     event Action<string>? PlanningMergeAbortedEvent;
     event Action<string>? PlanningCompletedEvent;
 
@@ -117,6 +120,9 @@ public interface IWorkerClient : INotifyPropertyChanged
     Task<CombinedDiffResultDto?> BuildPlanningIntegrationBranchAsync(string planningTaskId, string targetBranch);
     Task ContinuePlanningMergeAsync(string planningTaskId);
     Task AbortPlanningMergeAsync(string planningTaskId);
+    /// <summary>Unit merges currently paused on a conflict that an MCP session started. Called
+    /// on (re)connect to recover the "don't auto-open" banner state after a UI restart.</summary>
+    Task<IReadOnlyList<PlanningMergeConflictStateDto>> GetActiveExternalPlanningMergeConflictsAsync();
     Task QueuePlanningSubtasksAsync(string parentTaskId, CancellationToken ct = default);
     Task<string?> GetWeekReportAsync(DateOnly start, DateOnly end);
     Task<string> GenerateWeekReportAsync(DateOnly start, DateOnly end);

src/ClaudeDo.Ui/Services/WorkerClient.cs

@@ -66,7 +66,7 @@ public partial class WorkerClient : ObservableObject, IAsyncDisposable, IWorkerC
 
     public event Action<string, string>? PlanningMergeStartedEvent;
     public event Action<string, string>? PlanningSubtaskMergedEvent;
-    public event Action<string, string, IReadOnlyList<string>>? PlanningMergeConflictEvent;
+    public event Action<string, string, IReadOnlyList<string>, bool>? PlanningMergeConflictEvent;
     public event Action<string>? PlanningMergeAbortedEvent;
     public event Action<string>? PlanningCompletedEvent;
 
@@ -182,9 +182,9 @@ public partial class WorkerClient : ObservableObject, IAsyncDisposable, IWorkerC
             Dispatcher.UIThread.Post(() => PlanningSubtaskMergedEvent?.Invoke(planningTaskId, subtaskId));
         });
 
-        _hub.On<string, string, IReadOnlyList<string>>("PlanningMergeConflict", (planningTaskId, subtaskId, conflictedFiles) =>
+        _hub.On<string, string, IReadOnlyList<string>, bool>("PlanningMergeConflict", (planningTaskId, subtaskId, conflictedFiles, externallyDriven) =>
         {
-            Dispatcher.UIThread.Post(() => PlanningMergeConflictEvent?.Invoke(planningTaskId, subtaskId, conflictedFiles));
+            Dispatcher.UIThread.Post(() => PlanningMergeConflictEvent?.Invoke(planningTaskId, subtaskId, conflictedFiles, externallyDriven));
         });
 
         _hub.On<string>("PlanningMergeAborted", planningTaskId =>
@@ -578,6 +578,10 @@ public partial class WorkerClient : ObservableObject, IAsyncDisposable, IWorkerC
         await _hub.InvokeAsync("AbortPlanningMerge", planningTaskId);
     }
 
+    public async Task<IReadOnlyList<PlanningMergeConflictStateDto>> GetActiveExternalPlanningMergeConflictsAsync()
+        => await TryInvokeAsync<List<PlanningMergeConflictStateDto>>("GetActiveExternalPlanningMergeConflicts")
+           ?? [];
+
     public async Task QueuePlanningSubtasksAsync(string parentTaskId, CancellationToken ct = default)
     {
         await _hub.InvokeAsync("QueuePlanningSubtasksAsync", parentTaskId, ct);
@@ -692,6 +696,7 @@ public sealed record LaunchSpec(
     IReadOnlyDictionary<string, string> Env);
 
 public sealed record ForceRemoveResultDto(bool Removed, string? Reason);
+public sealed record PlanningMergeConflictStateDto(string PlanningTaskId, string SubtaskId);
 public sealed record PendingQuestionDto(string TaskId, string QuestionId, string Question);
 
 public sealed record OnlineInboxStateDto(

src/ClaudeDo.Ui/ViewModels/IslandsShellViewModel.cs

@@ -102,6 +102,12 @@ public sealed partial class IslandsShellViewModel : ViewModelBase, IDisposable
     [ObservableProperty] private string? _updateBannerLatestVersion;
     private bool _bannerDismissedThisSession;
 
+    // planningTaskId -> subtaskId, for unit-merge conflicts an MCP session (not the UI) started.
+    // Kept as a dictionary so a later conflict on the same planning task updates in place instead
+    // of piling up duplicate entries.
+    private readonly Dictionary<string, string> _externalMergeConflicts = new();
+    [ObservableProperty] private bool _isExternalMergeBannerVisible;
+
     [ObservableProperty]
     private double _windowWidth = 1280;
 
@@ -178,13 +184,59 @@ public sealed partial class IslandsShellViewModel : ViewModelBase, IDisposable
         _primeStatusTimer.Start();
     }
 
-    private void OnPlanningMergeConflict(string planningTaskId, string subtaskId, IReadOnlyList<string> conflictedFiles)
+    public void OnPlanningMergeConflict(
+        string planningTaskId, string subtaskId, IReadOnlyList<string> conflictedFiles, bool externallyDriven)
     {
         // Already on UI thread (WorkerClient dispatches via Dispatcher.UIThread.Post).
+        if (externallyDriven)
+        {
+            // An MCP session (review_task/continue_merge) is driving this merge — it owns
+            // resolution. Auto-opening the resolver here raced with the session's own writes
+            // (two parties editing the same shared checkout at once); show a banner instead and
+            // leave the resolver reachable only via a deliberate click.
+            _externalMergeConflicts[planningTaskId] = subtaskId;
+            IsExternalMergeBannerVisible = true;
+            return;
+        }
+
         // A unit-merge conflict resolves in the same in-app 3-way editor as a single-task merge.
         _ = OpenPlanningConflictAsync(planningTaskId, subtaskId);
     }
 
+    public void OnPlanningMergeAborted(string planningTaskId) => ClearExternalMergeConflict(planningTaskId);
+    public void OnPlanningMergeCompleted(string planningTaskId) => ClearExternalMergeConflict(planningTaskId);
+
+    private void ClearExternalMergeConflict(string planningTaskId)
+    {
+        _externalMergeConflicts.Remove(planningTaskId);
+        IsExternalMergeBannerVisible = _externalMergeConflicts.Count > 0;
+    }
+
+    /// <summary>Re-syncs the external-merge banner from the worker on (re)connect — the
+    /// one-shot PlanningMergeConflict broadcast isn't replayed after a UI restart, so this is
+    /// the recovery path. The worker checks MERGE_HEAD before reporting a conflict as active,
+    /// so a session that died mid-merge without cleaning up doesn't leave a stale banner up.</summary>
+    private async Task RefreshExternalMergeConflictsAsync()
+    {
+        if (Worker is null) return;
+        IReadOnlyList<PlanningMergeConflictStateDto> active;
+        try { active = await Worker.GetActiveExternalPlanningMergeConflictsAsync(); }
+        catch { return; }
+
+        _externalMergeConflicts.Clear();
+        foreach (var c in active)
+            _externalMergeConflicts[c.PlanningTaskId] = c.SubtaskId;
+        IsExternalMergeBannerVisible = _externalMergeConflicts.Count > 0;
+    }
+
+    [RelayCommand]
+    private Task OpenExternalMergeConflictAsync()
+    {
+        if (_externalMergeConflicts.Count == 0) return Task.CompletedTask;
+        var (planningTaskId, subtaskId) = _externalMergeConflicts.First();
+        return OpenPlanningConflictAsync(planningTaskId, subtaskId);
+    }
+
     private async Task OpenPlanningConflictAsync(string planningTaskId, string subtaskId)
     {
         if (ConflictResolverFactory is null || Dialogs is null) return;
@@ -287,6 +339,9 @@ public sealed partial class IslandsShellViewModel : ViewModelBase, IDisposable
         };
         Worker.WorkerLogReceivedEvent += OnWorkerLogReceived;
         Worker.PlanningMergeConflictEvent += OnPlanningMergeConflict;
+        Worker.PlanningMergeAbortedEvent += OnPlanningMergeAborted;
+        Worker.PlanningCompletedEvent += OnPlanningMergeCompleted;
+        Worker.ConnectionRestoredEvent += () => _ = RefreshExternalMergeConflictsAsync();
         Worker.PrimeFired += OnPrimeFired;
         _clearTimer.Elapsed += (_, _) =>
         {

src/ClaudeDo.Ui/Views/MainWindow.axaml

@@ -258,5 +258,27 @@
       </StackPanel>
     </Border>
 
+    <!-- External merge popup card — bottom-left corner, while an MCP session owns an
+         unresolved unit-merge conflict. Does not auto-dismiss; stays until the merge ends. -->
+    <Border Grid.Row="0" Grid.RowSpan="3"
+            VerticalAlignment="Bottom" HorizontalAlignment="Left"
+            Margin="16,0,0,30"
+            ZIndex="100"
+            IsVisible="{Binding IsExternalMergeBannerVisible}"
+            Background="{DynamicResource DeepBrush}"
+            BorderBrush="{DynamicResource PeatBrush}"
+            BorderThickness="1"
+            CornerRadius="6"
+            Padding="14,10">
+      <StackPanel Spacing="8" Width="300">
+        <TextBlock Classes="body" Text="{loc:Tr shell.externalMerge.banner}" TextWrapping="Wrap"/>
+        <StackPanel Orientation="Horizontal" Spacing="8" HorizontalAlignment="Right">
+          <Button Classes="btn"
+                  Content="{loc:Tr shell.externalMerge.open}"
+                  Command="{Binding OpenExternalMergeConflictCommand}"/>
+        </StackPanel>
+      </StackPanel>
+    </Border>
+
   </Grid>
 </Window>

src/ClaudeDo.Worker/External/ExternalMcpService.cs

@@ -423,7 +423,10 @@ public sealed class ExternalMcpService
 
             if (hasChildren)
             {
-                await _planningMerge.StartAsync(taskId, targetBranch ?? "", cancellationToken);
+                // externallyDriven: true — this call came from an MCP session, not the UI's
+                // Approve button. A unit-merge conflict must not auto-open the in-app resolver;
+                // the driving session resolves it via continue_merge/abort_merge instead.
+                await _planningMerge.StartAsync(taskId, targetBranch ?? "", cancellationToken, externallyDriven: true);
                 var parentDone = (await _tasks.GetByIdAsync(taskId, cancellationToken))!.Status == TaskStatus.Done;
                 mergeStatus = parentDone ? TaskMergeService.StatusMerged : TaskMergeService.StatusConflict;
                 if (!parentDone)

src/ClaudeDo.Worker/Hub/HubBroadcaster.cs

@@ -55,8 +55,9 @@ public sealed class HubBroadcaster : IPrimeBroadcaster, IRefineBroadcaster
     public Task PlanningSubtaskMerged(string planningTaskId, string subtaskId) =>
         _hub.Clients.All.SendAsync("PlanningSubtaskMerged", planningTaskId, subtaskId);
 
-    public Task PlanningMergeConflict(string planningTaskId, string subtaskId, IReadOnlyList<string> files) =>
-        _hub.Clients.All.SendAsync("PlanningMergeConflict", planningTaskId, subtaskId, files);
+    public Task PlanningMergeConflict(
+        string planningTaskId, string subtaskId, IReadOnlyList<string> files, bool externallyDriven) =>
+        _hub.Clients.All.SendAsync("PlanningMergeConflict", planningTaskId, subtaskId, files, externallyDriven);
 
     public Task PlanningMergeAborted(string planningTaskId) =>
         _hub.Clients.All.SendAsync("PlanningMergeAborted", planningTaskId);

src/ClaudeDo.Worker/Hub/WorkerHub.cs

@@ -76,6 +76,7 @@ public record WorktreeOverviewDto(
     bool PathExistsOnDisk);
 
 public record ForceRemoveResultDto(bool Removed, string? Reason);
+public record PlanningMergeConflictStateDto(string PlanningTaskId, string SubtaskId);
 public record PendingQuestionDto(string TaskId, string QuestionId, string Question);
 public record MergeResultDto(string Status, IReadOnlyList<string> ConflictFiles, string? ErrorMessage);
 public record MergePreviewDto(string Status, IReadOnlyList<string> ConflictFiles, int ChangedFileCount);
@@ -916,6 +917,17 @@ public sealed class WorkerHub : Microsoft.AspNetCore.SignalR.Hub
         catch (InvalidOperationException ex) { throw new HubException(ex.Message); }
     }
 
+    /// <summary>Unit merges currently paused on a conflict that an MCP session (not the UI)
+    /// started. The UI calls this on (re)connect to recover the "don't auto-open the resolver"
+    /// banner after a restart, since the one-shot PlanningMergeConflict broadcast isn't replayed.</summary>
+    public async Task<List<PlanningMergeConflictStateDto>> GetActiveExternalPlanningMergeConflicts()
+    {
+        var conflicts = await _planningMergeOrchestrator.GetActiveExternalConflictsAsync(CancellationToken.None);
+        return conflicts
+            .Select(c => new PlanningMergeConflictStateDto(c.PlanningTaskId, c.SubtaskId))
+            .ToList();
+    }
+
     public async Task<List<PrimeScheduleDto>> ListPrimeSchedules()
     {
         using var ctx = _dbFactory.CreateDbContext();

src/ClaudeDo.Worker/Planning/PlanningMergeOrchestrator.cs

@@ -10,6 +10,9 @@ using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
 
 namespace ClaudeDo.Worker.Planning;
 
+/// <summary>A unit-merge conflict currently paused, driven by an MCP session rather than the UI.</summary>
+public sealed record ExternalPlanningMergeConflict(string PlanningTaskId, string SubtaskId);
+
 public sealed class PlanningMergeOrchestrator
 {
     private readonly IDbContextFactory<ClaudeDoDbContext> _dbFactory;
@@ -25,6 +28,11 @@ public sealed class PlanningMergeOrchestrator
         public required string TargetBranch { get; init; }
         public required Queue<string> RemainingSubtaskIds { get; init; }
         public required bool IsPlanning { get; init; }
+        public required string WorkingDir { get; init; }
+        /// <summary>True when this unit merge was started by an MCP tool call (e.g. review_task
+        /// from a running Claude session) rather than a direct UI action. Conflicts on such a
+        /// merge must not auto-pop the in-app resolver — the driving session owns resolution.</summary>
+        public required bool ExternallyDriven { get; init; }
         public string? CurrentSubtaskId { get; set; }
     }
 
@@ -48,7 +56,8 @@ public sealed class PlanningMergeOrchestrator
         _logger = logger;
     }
 
-    public async Task StartAsync(string parentTaskId, string targetBranch, CancellationToken ct)
+    public async Task StartAsync(
+        string parentTaskId, string targetBranch, CancellationToken ct, bool externallyDriven = false)
     {
         string workingDir;
         List<TaskEntity> children;
@@ -100,7 +109,14 @@ public sealed class PlanningMergeOrchestrator
 
         var queue = new Queue<string>(idsToMerge);
 
-        var state = new State { TargetBranch = targetBranch, RemainingSubtaskIds = queue, IsPlanning = isPlanning };
+        var state = new State
+        {
+            TargetBranch = targetBranch,
+            RemainingSubtaskIds = queue,
+            IsPlanning = isPlanning,
+            WorkingDir = workingDir,
+            ExternallyDriven = externallyDriven,
+        };
         if (!_states.TryAdd(parentTaskId, state))
             throw new InvalidOperationException($"Merge already in progress for {parentTaskId}.");
 
@@ -112,6 +128,23 @@ public sealed class PlanningMergeOrchestrator
     public bool HasActiveMerge(string parentTaskId) =>
         _states.TryGetValue(parentTaskId, out var s) && s.CurrentSubtaskId is not null;
 
+    /// <summary>Externally-driven unit merges currently paused on a conflict, so the UI can
+    /// recover this on reconnect instead of relying solely on the one-shot broadcast. Checked
+    /// against <see cref="GitService.IsMidMergeAsync"/> rather than trusting the in-memory flag
+    /// alone, so a stale entry (e.g. the repo was already resolved through another path) never
+    /// reports an external merge that no longer exists.</summary>
+    public async Task<IReadOnlyList<ExternalPlanningMergeConflict>> GetActiveExternalConflictsAsync(CancellationToken ct)
+    {
+        var result = new List<ExternalPlanningMergeConflict>();
+        foreach (var (planningTaskId, state) in _states)
+        {
+            if (!state.ExternallyDriven || state.CurrentSubtaskId is null) continue;
+            if (!await _git.IsMidMergeAsync(state.WorkingDir, ct)) continue;
+            result.Add(new ExternalPlanningMergeConflict(planningTaskId, state.CurrentSubtaskId));
+        }
+        return result;
+    }
+
     public async Task ContinueAsync(string planningTaskId, CancellationToken ct)
     {
         if (!_states.TryGetValue(planningTaskId, out var state) || state.CurrentSubtaskId is null)
@@ -123,7 +156,7 @@ public sealed class PlanningMergeOrchestrator
 
         if (result.Status == TaskMergeService.StatusConflict)
         {
-            await _broadcaster.PlanningMergeConflict(planningTaskId, current, result.ConflictFiles);
+            await _broadcaster.PlanningMergeConflict(planningTaskId, current, result.ConflictFiles, state.ExternallyDriven);
             return;
         }
 
@@ -200,7 +233,8 @@ public sealed class PlanningMergeOrchestrator
 
                 if (result.Status == TaskMergeService.StatusConflict)
                 {
-                    await _broadcaster.PlanningMergeConflict(planningTaskId, subtaskId, result.ConflictFiles);
+                    await _broadcaster.PlanningMergeConflict(
+                        planningTaskId, subtaskId, result.ConflictFiles, state.ExternallyDriven);
                     keepState = true;
                     return;
                 }