diff --git a/tests/ClaudeDo.Worker.Tests/External/ExternalMcpServiceTests.cs b/tests/ClaudeDo.Worker.Tests/External/ExternalMcpServiceTests.cs
new file mode 100644
index 0000000..a05c3a9
--- /dev/null
+++ b/tests/ClaudeDo.Worker.Tests/External/ExternalMcpServiceTests.cs
@@ -0,0 +1,101 @@
+using ClaudeDo.Data;
+using ClaudeDo.Data.Models;
+using ClaudeDo.Data.Repositories;
+using ClaudeDo.Worker.External;
+using ClaudeDo.Worker.Hub;
+using ClaudeDo.Worker.Services;
+using ClaudeDo.Worker.Tests.Infrastructure;
+using Microsoft.AspNetCore.SignalR;
+using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
+
+namespace ClaudeDo.Worker.Tests.External;
+
+internal sealed class ExternalRecordingHubClients : IHubClients
+{
+    public ExternalRecordingClientProxy Proxy { get; } = new();
+    public IClientProxy All => Proxy;
+    public IClientProxy AllExcept(IReadOnlyList<string> excludedConnectionIds) => Proxy;
+    public IClientProxy Client(string connectionId) => Proxy;
+    public IClientProxy Clients(IReadOnlyList<string> connectionIds) => Proxy;
+    public IClientProxy Group(string groupName) => Proxy;
+    public IClientProxy GroupExcept(string groupName, IReadOnlyList<string> excludedConnectionIds) => Proxy;
+    public IClientProxy Groups(IReadOnlyList<string> groupNames) => Proxy;
+    public IClientProxy User(string userId) => Proxy;
+    public IClientProxy Users(IReadOnlyList<string> userIds) => Proxy;
+}
+
+internal sealed class ExternalRecordingClientProxy : IClientProxy
+{
+    public List<(string Method, object?[] Args)> Calls { get; } = new();
+    public Task SendCoreAsync(string method, object?[] args, CancellationToken cancellationToken = default)
+    {
+        Calls.Add((method, args));
+        return Task.CompletedTask;
+    }
+}
+
+internal sealed class ExternalFakeHubContext : IHubContext<WorkerHub>
+{
+    public ExternalRecordingHubClients RecordingClients { get; } = new();
+    public IHubClients Clients => RecordingClients;
+    public IGroupManager Groups => throw new NotImplementedException();
+}
+
+public sealed class ExternalMcpServiceTests : IDisposable
+{
+    private readonly DbFixture _db = new();
+    private readonly ClaudeDoDbContext _ctx;
+    private readonly TaskRepository _tasks;
+    private readonly ListRepository _lists;
+    private readonly TagRepository _tags;
+    private readonly ExternalFakeHubContext _hub = new();
+    private readonly HubBroadcaster _broadcaster;
+
+    public ExternalMcpServiceTests()
+    {
+        _ctx = _db.CreateContext();
+        _tasks = new TaskRepository(_ctx);
+        _lists = new ListRepository(_ctx);
+        _tags = new TagRepository(_ctx);
+        _broadcaster = new HubBroadcaster(_hub);
+    }
+
+    public void Dispose() { _ctx.Dispose(); _db.Dispose(); }
+
+    private async Task<string> SeedListAsync(string name = "L")
+    {
+        var id = Guid.NewGuid().ToString();
+        await _lists.AddAsync(new ListEntity { Id = id, Name = name, CreatedAt = DateTime.UtcNow });
+        return id;
+    }
+
+    private async Task<TaskEntity> SeedTaskAsync(string listId, string title = "t", TaskStatus status = TaskStatus.Manual)
+    {
+        var task = new TaskEntity
+        {
+            Id = Guid.NewGuid().ToString(),
+            ListId = listId,
+            Title = title,
+            Status = status,
+            CreatedAt = DateTime.UtcNow,
+            CommitType = "chore",
+        };
+        await _tasks.AddAsync(task);
+        return task;
+    }
+
+    // QueueService is needed by ExternalMcpService's constructor. For tests that
+    // only exercise UpdateTask / DeleteTask / SetTaskTags / ListTags / ListTags,
+    // we never call its WakeQueue/RunNow/CancelTask paths, so a real QueueService
+    // built with the same approach used in QueueServiceTests is sufficient.
+    private ExternalMcpService BuildSut(QueueService queue) =>
+        new(_tasks, _lists, queue, _broadcaster, _tags);
+
+    [Fact]
+    public async Task SeededListAndTask_AreRetrievable()
+    {
+        var listId = await SeedListAsync();
+        var task = await SeedTaskAsync(listId);
+        Assert.NotNull(await _tasks.GetByIdAsync(task.Id));
+    }
+}