diff --git a/tests/ClaudeDo.Ui.Tests/StubWorkerClient.cs b/tests/ClaudeDo.Ui.Tests/StubWorkerClient.cs
new file mode 100644
index 0000000..22498dd
--- /dev/null
+++ b/tests/ClaudeDo.Ui.Tests/StubWorkerClient.cs
@@ -0,0 +1,61 @@
+using System.ComponentModel;
+using ClaudeDo.Data.Models;
+using ClaudeDo.Data.Repositories;
+using ClaudeDo.Ui.Services;
+using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
+
+namespace ClaudeDo.Ui.Tests;
+
+/// <summary>
+/// No-op <see cref="IWorkerClient"/> base for tests. Override only the members a
+/// test actually exercises; everything else returns a benign default. Keeping the
+/// full interface surface here means new interface members only break this file.
+/// </summary>
+public abstract class StubWorkerClient : IWorkerClient
+{
+#pragma warning disable CS0067 // interface-mandated events; tests don't raise them
+    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? ConnectionRestoredEvent;
+    public event Action<string>? WorktreeUpdatedEvent;
+    public event Action<string>? ListUpdatedEvent;
+    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;
+#pragma warning restore CS0067
+
+    public virtual bool IsConnected => false;
+
+    public virtual Task WakeQueueAsync() => Task.CompletedTask;
+    public virtual Task RunNowAsync(string taskId) => Task.CompletedTask;
+    public virtual Task ContinueTaskAsync(string taskId, string followUpPrompt) => Task.CompletedTask;
+    public virtual Task ResetTaskAsync(string taskId) => Task.CompletedTask;
+    public virtual Task CancelTaskAsync(string taskId) => Task.CompletedTask;
+    public virtual Task<List<AgentInfo>> GetAgentsAsync() => Task.FromResult(new List<AgentInfo>());
+    public virtual Task<ListConfigDto?> GetListConfigAsync(string listId) => Task.FromResult<ListConfigDto?>(null);
+    public virtual Task UpdateTaskAgentSettingsAsync(UpdateTaskAgentSettingsDto dto) => Task.CompletedTask;
+    public virtual Task SetTaskStatusAsync(string taskId, TaskStatus status) => Task.CompletedTask;
+    public virtual Task StartPlanningSessionAsync(string taskId, CancellationToken ct = default) => Task.CompletedTask;
+    public virtual Task OpenInteractiveTerminalAsync(string taskId, CancellationToken ct = default) => Task.CompletedTask;
+    public virtual Task ResumePlanningSessionAsync(string taskId, CancellationToken ct = default) => Task.CompletedTask;
+    public virtual Task<DiscardPlanningOutcome> DiscardPlanningSessionAsync(string taskId, bool dequeueQueuedChildren = false, CancellationToken ct = default)
+        => Task.FromResult(new DiscardPlanningOutcome(DiscardPlanningResult.Discarded, 0, 0));
+    public virtual Task FinalizePlanningSessionAsync(string taskId, bool queueAgentTasks = true, CancellationToken ct = default) => Task.CompletedTask;
+    public virtual Task<int> GetPendingDraftCountAsync(string taskId, CancellationToken ct = default) => Task.FromResult(0);
+    public virtual Task<MergeTargetsDto?> GetMergeTargetsAsync(string taskId) => Task.FromResult<MergeTargetsDto?>(null);
+    public virtual Task<IReadOnlyList<SubtaskDiffDto>> GetPlanningAggregateAsync(string planningTaskId)
+        => Task.FromResult<IReadOnlyList<SubtaskDiffDto>>(Array.Empty<SubtaskDiffDto>());
+    public virtual Task<CombinedDiffResultDto?> BuildPlanningIntegrationBranchAsync(string planningTaskId, string targetBranch)
+        => Task.FromResult<CombinedDiffResultDto?>(null);
+    public virtual Task MergeAllPlanningAsync(string planningTaskId, string targetBranch) => Task.CompletedTask;
+    public virtual Task ContinuePlanningMergeAsync(string planningTaskId) => Task.CompletedTask;
+    public virtual Task AbortPlanningMergeAsync(string planningTaskId) => Task.CompletedTask;
+    public virtual Task QueuePlanningSubtasksAsync(string parentTaskId, CancellationToken ct = default) => Task.CompletedTask;
+
+    protected void RaisePropertyChanged(string name) => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
+}
diff --git a/tests/ClaudeDo.Ui.Tests/ViewModels/ConflictResolutionViewModelTests.cs b/tests/ClaudeDo.Ui.Tests/ViewModels/ConflictResolutionViewModelTests.cs
index 4e4a357..01fb7fd 100644
--- a/tests/ClaudeDo.Ui.Tests/ViewModels/ConflictResolutionViewModelTests.cs
+++ b/tests/ClaudeDo.Ui.Tests/ViewModels/ConflictResolutionViewModelTests.cs
@@ -1,4 +1,3 @@
-using System.ComponentModel;
 using ClaudeDo.Data.Models;
 using ClaudeDo.Ui.Services;
 using ClaudeDo.Ui.ViewModels.Planning;
@@ -8,63 +7,21 @@ namespace ClaudeDo.Ui.Tests.ViewModels;
 public class ConflictResolutionViewModelTests
 {
     // ------------------------------------------------------------------ fake
-    private sealed class FakeWorker : IWorkerClient
+    private sealed class FakeWorker : StubWorkerClient
     {
-        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? ConnectionRestoredEvent;
-        public event Action<string>? WorktreeUpdatedEvent;
-        public event Action<string>? ListUpdatedEvent;
-        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 SetTaskStatusAsync(string taskId, ClaudeDo.Data.Models.TaskStatus status) => Task.CompletedTask;
-        public Task SetTaskTagsAsync(string taskId, IEnumerable<string> tagNames) => Task.CompletedTask;
-        public Task<List<string>> GetAllTagsAsync() => Task.FromResult(new List<string>());
-        public Task StartPlanningSessionAsync(string taskId, CancellationToken ct = default) => Task.CompletedTask;
-        public Task ResumePlanningSessionAsync(string taskId, CancellationToken ct = default) => Task.CompletedTask;
-        public Task<ClaudeDo.Data.Repositories.DiscardPlanningOutcome> DiscardPlanningSessionAsync(string taskId, bool dequeueQueuedChildren = false, CancellationToken ct = default)
-            => Task.FromResult(new ClaudeDo.Data.Repositories.DiscardPlanningOutcome(ClaudeDo.Data.Repositories.DiscardPlanningResult.Discarded, 0, 0));
-        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 OpenInteractiveTerminalAsync(string taskId, CancellationToken ct = default) => Task.CompletedTask;
-        public Task QueuePlanningSubtasksAsync(string parentTaskId, CancellationToken ct = default) => Task.CompletedTask;
-
-        public Task ContinuePlanningMergeAsync(string planningTaskId)
+        public override Task ContinuePlanningMergeAsync(string planningTaskId)
         {
             ContinueCalledWith = planningTaskId;
             if (ContinueThrows is not null) throw ContinueThrows;
             return Task.CompletedTask;
         }
 
-        public Task AbortPlanningMergeAsync(string planningTaskId)
+        public override Task AbortPlanningMergeAsync(string planningTaskId)
         {
             AbortCalledWith = planningTaskId;
             if (AbortThrows is not null) throw AbortThrows;
diff --git a/tests/ClaudeDo.Ui.Tests/ViewModels/DetailsIslandPlanningTests.cs b/tests/ClaudeDo.Ui.Tests/ViewModels/DetailsIslandPlanningTests.cs
index 1b16d49..ac689a3 100644
--- a/tests/ClaudeDo.Ui.Tests/ViewModels/DetailsIslandPlanningTests.cs
+++ b/tests/ClaudeDo.Ui.Tests/ViewModels/DetailsIslandPlanningTests.cs
@@ -1,5 +1,4 @@
 using System.Collections.ObjectModel;
-using System.ComponentModel;
 using ClaudeDo.Data;
 using ClaudeDo.Data.Models;
 using ClaudeDo.Ui.Services;
@@ -42,52 +41,11 @@ public class DetailsIslandPlanningTests : IDisposable
         public ClaudeDoDbContext CreateDbContext() => _create();
     }
 
-    private sealed class FakeWorkerClient : IWorkerClient
+    private sealed class FakeWorkerClient : StubWorkerClient
     {
-        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? ConnectionRestoredEvent;
-        public event Action<string>? WorktreeUpdatedEvent;
-        public event Action<string>? ListUpdatedEvent;
-        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 bool IsConnected => false;
         public MergeTargetsDto? MergeTargetsResult { get; set; }
 
-        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 SetTaskStatusAsync(string taskId, TaskStatus status) => Task.CompletedTask;
-        public Task SetTaskTagsAsync(string taskId, IEnumerable<string> tagNames) => Task.CompletedTask;
-        public Task<List<string>> GetAllTagsAsync() => Task.FromResult(new List<string>());
-        public Task StartPlanningSessionAsync(string taskId, CancellationToken ct = default) => Task.CompletedTask;
-        public Task ResumePlanningSessionAsync(string taskId, CancellationToken ct = default) => Task.CompletedTask;
-        public Task<ClaudeDo.Data.Repositories.DiscardPlanningOutcome> DiscardPlanningSessionAsync(string taskId, bool dequeueQueuedChildren = false, CancellationToken ct = default)
-            => Task.FromResult(new ClaudeDo.Data.Repositories.DiscardPlanningOutcome(ClaudeDo.Data.Repositories.DiscardPlanningResult.Discarded, 0, 0));
-        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(MergeTargetsResult);
-        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) => Task.CompletedTask;
-        public Task AbortPlanningMergeAsync(string planningTaskId) => Task.CompletedTask;
-        public Task OpenInteractiveTerminalAsync(string taskId, CancellationToken ct = default) => Task.CompletedTask;
-        public Task QueuePlanningSubtasksAsync(string parentTaskId, CancellationToken ct = default) => Task.CompletedTask;
+        public override Task<MergeTargetsDto?> GetMergeTargetsAsync(string taskId) => Task.FromResult(MergeTargetsResult);
     }
 
     private sealed class NullServiceProvider : IServiceProvider
diff --git a/tests/ClaudeDo.Ui.Tests/ViewModels/PlanningDiffViewModelTests.cs b/tests/ClaudeDo.Ui.Tests/ViewModels/PlanningDiffViewModelTests.cs
index f8f6b68..4e1e530 100644
--- a/tests/ClaudeDo.Ui.Tests/ViewModels/PlanningDiffViewModelTests.cs
+++ b/tests/ClaudeDo.Ui.Tests/ViewModels/PlanningDiffViewModelTests.cs
@@ -1,4 +1,3 @@
-using System.ComponentModel;
 using ClaudeDo.Data.Models;
 using ClaudeDo.Ui.Services;
 using ClaudeDo.Ui.ViewModels.Planning;
@@ -7,54 +6,15 @@ namespace ClaudeDo.Ui.Tests.ViewModels;
 
 public class PlanningDiffViewModelTests
 {
-    private sealed class FakePlanningWorker : IWorkerClient
+    private sealed class FakePlanningWorker : StubWorkerClient
     {
-        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? ConnectionRestoredEvent;
-        public event Action<string>? WorktreeUpdatedEvent;
-        public event Action<string>? ListUpdatedEvent;
-        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 bool IsConnected => false;
-
         public IReadOnlyList<SubtaskDiffDto> AggregateResult { get; set; } = Array.Empty<SubtaskDiffDto>();
         public CombinedDiffResultDto? CombinedResult { get; set; }
 
-        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 SetTaskStatusAsync(string taskId, ClaudeDo.Data.Models.TaskStatus status) => Task.CompletedTask;
-        public Task SetTaskTagsAsync(string taskId, IEnumerable<string> tagNames) => Task.CompletedTask;
-        public Task<List<string>> GetAllTagsAsync() => Task.FromResult(new List<string>());
-        public Task StartPlanningSessionAsync(string taskId, CancellationToken ct = default) => Task.CompletedTask;
-        public Task ResumePlanningSessionAsync(string taskId, CancellationToken ct = default) => Task.CompletedTask;
-        public Task<ClaudeDo.Data.Repositories.DiscardPlanningOutcome> DiscardPlanningSessionAsync(string taskId, bool dequeueQueuedChildren = false, CancellationToken ct = default)
-            => Task.FromResult(new ClaudeDo.Data.Repositories.DiscardPlanningOutcome(ClaudeDo.Data.Repositories.DiscardPlanningResult.Discarded, 0, 0));
-        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) =>
+        public override Task<IReadOnlyList<SubtaskDiffDto>> GetPlanningAggregateAsync(string planningTaskId) =>
             Task.FromResult(AggregateResult);
-        public Task<CombinedDiffResultDto?> BuildPlanningIntegrationBranchAsync(string planningTaskId, string targetBranch) =>
+        public override Task<CombinedDiffResultDto?> BuildPlanningIntegrationBranchAsync(string planningTaskId, string targetBranch) =>
             Task.FromResult(CombinedResult);
-        public Task MergeAllPlanningAsync(string planningTaskId, string targetBranch) => Task.CompletedTask;
-        public Task ContinuePlanningMergeAsync(string planningTaskId) => Task.CompletedTask;
-        public Task AbortPlanningMergeAsync(string planningTaskId) => Task.CompletedTask;
-        public Task OpenInteractiveTerminalAsync(string taskId, CancellationToken ct = default) => Task.CompletedTask;
-        public Task QueuePlanningSubtasksAsync(string parentTaskId, CancellationToken ct = default) => Task.CompletedTask;
     }
 
     [Fact]