fix(ui): guard Bind/LoadForList against interleaved DbContext awaits

Added CancellationTokenSource per-load in both DetailsIslandViewModel
and TasksIslandViewModel. Public entry points cancel any in-flight load
before starting a new one. DB calls and collection mutations after awaits
are guarded with ThrowIfCancellationRequested. DetailsIslandViewModel
now sets _subscribedTaskId only after the DB confirms the entity exists,
preventing the SignalR handler from routing messages to a stale load.

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

src/ClaudeDo.Ui/ViewModels/Islands/DetailsIslandViewModel.cs

@@ -41,6 +41,8 @@ public sealed partial class DetailsIslandViewModel : ViewModelBase
     // The task ID we are currently subscribed to for live log messages
     private string? _subscribedTaskId;
 
+    private CancellationTokenSource? _loadCts;
+
     // Set by the view so OpenDiffCommand can show the modal as a dialog
     public Func<DiffModalViewModel, System.Threading.Tasks.Task>? ShowDiffModal { get; set; }
 
@@ -72,8 +74,13 @@ public sealed partial class DetailsIslandViewModel : ViewModelBase
         Log.Add(new LogLineViewModel { Kind = kind, Text = line });
     }
 
-    public async void Bind(TaskRowViewModel? row)
+    public void Bind(TaskRowViewModel? row)
     {
+        _loadCts?.Cancel();
+        _loadCts?.Dispose();
+        _loadCts = new CancellationTokenSource();
+        var ct = _loadCts.Token;
+
         Task = row;
         Log.Clear();
         Subtasks.Clear();
@@ -90,14 +97,19 @@ public sealed partial class DetailsIslandViewModel : ViewModelBase
             return;
         }
 
-        // Wire live-log subscription to new task
+        _ = BindAsync(row, ct);
-        _subscribedTaskId = row.Id;
+    }
 
+    private async System.Threading.Tasks.Task BindAsync(TaskRowViewModel row, CancellationToken ct)
+    {
+        try
+        {
             await using var ctx = _dbFactory.CreateDbContext();
             var taskRepo = new TaskRepository(ctx);
             var subtaskRepo = new SubtaskRepository(ctx);
 
             var entity = await taskRepo.GetByIdAsync(row.Id);
+            ct.ThrowIfCancellationRequested();
             if (entity == null) return;
 
             EditableTitle = entity.Title;
@@ -107,10 +119,16 @@ public sealed partial class DetailsIslandViewModel : ViewModelBase
             BranchLine = entity.Worktree is { } w ? $"{w.BranchName} \u2190 main" : null;
             AgentStatusLabel = entity.Status.ToString();
 
+            // Subscribe only after DB load confirms the task exists
+            _subscribedTaskId = row.Id;
+
             var subs = await subtaskRepo.GetByTaskIdAsync(row.Id);
+            ct.ThrowIfCancellationRequested();
             foreach (var s in subs)
                 Subtasks.Add(new SubtaskRowViewModel { Id = s.Id, Title = s.Title, Done = s.Completed });
         }
+        catch (OperationCanceledException) { }
+    }
 
     [RelayCommand(CanExecute = nameof(CanOpenDiff))]
     private async System.Threading.Tasks.Task OpenDiffAsync()

src/ClaudeDo.Ui/ViewModels/Islands/TasksIslandViewModel.cs

@@ -12,6 +12,7 @@ public sealed partial class TasksIslandViewModel : ViewModelBase
 {
     private readonly IDbContextFactory<ClaudeDoDbContext> _dbFactory;
     private ListNavItemViewModel? _currentList;
+    private CancellationTokenSource? _loadCts;
 
     public event EventHandler? SelectionChanged;
     public event EventHandler? FocusAddTaskRequested;
@@ -30,8 +31,13 @@ public sealed partial class TasksIslandViewModel : ViewModelBase
         _dbFactory = dbFactory;
     }
 
-    public async void LoadForList(ListNavItemViewModel? list)
+    public void LoadForList(ListNavItemViewModel? list)
     {
+        _loadCts?.Cancel();
+        _loadCts?.Dispose();
+        _loadCts = new CancellationTokenSource();
+        var ct = _loadCts.Token;
+
         _currentList = list;
         Items.Clear();
         if (list is null) return;
@@ -39,11 +45,20 @@ public sealed partial class TasksIslandViewModel : ViewModelBase
         HeaderTitle = list.Name;
         HeaderEyebrow = DateTime.Now.ToString("dddd · MMM dd").ToUpperInvariant();
 
-        await using var db = await _dbFactory.CreateDbContextAsync();
+        _ = LoadForListAsync(list, ct);
+    }
+
+    private async Task LoadForListAsync(ListNavItemViewModel list, CancellationToken ct)
+    {
+        try
+        {
+            await using var db = await _dbFactory.CreateDbContextAsync(ct);
             var all = await db.Tasks
                 .Include(t => t.List)
                 .Include(t => t.Worktree)
-            .ToListAsync();
+                .ToListAsync(ct);
+
+            ct.ThrowIfCancellationRequested();
 
             IEnumerable<TaskEntity> filtered = list.Kind switch
             {
@@ -61,6 +76,8 @@ public sealed partial class TasksIslandViewModel : ViewModelBase
 
             UpdateSubtitle();
         }
+        catch (OperationCanceledException) { }
+    }
 
     private void UpdateSubtitle()
     {