diff --git a/docs/open.md b/docs/open.md
index 0392c5c..e33840d 100644
--- a/docs/open.md
+++ b/docs/open.md
@@ -154,10 +154,9 @@ Voraussetzung: Gitea-Release unter `git.kuns.dev/releases/ClaudeDo` mit `ClaudeD
 - `tests/.../Runner/ClaudeProcessSmokeTest.cs` existiert nicht. Real-CLI-Test als `[Fact(Skip=...)]`, nur lokal bei `CLAUDE_AUTHENTICATED=1`.
 - **Aufwand:** klein.
 
-### 5.4 ExternalMcpService-Tests 🟡
-- Service exponiert jetzt **18 Tools** (war 11): `ListTaskLists`, `ListTasks`, `GetTask`, `AddTask`, `UpdateTask`, `UpdateTaskStatus`, `ReviewTask`, `RunTaskNow`, `CancelTask`, `DeleteTask`, `GetTaskStatusValues`, `GetTaskWorktree`, `GetTaskDiff`, `MergeTask`, `ListWorktrees`, `CleanupTaskWorktree`, `GetDailyPrepCandidates`, `SetMyDay`.
-- `ExternalMcpServiceTests.cs` hat 14 Tests, plus 4 Sibling-Dateien (`ConfigMcpToolsTests`, `LifecycleMcpToolsTests`, `ListMcpToolsTests`, `RunHistoryMcpToolsTests`).
-- **Ungetestet im External-Ordner:** `GetTaskWorktree`, `GetTaskDiff`, `MergeTask`, `ListWorktrees`, `CleanupTaskWorktree` — je Happy-Path + Error-Pfad ergänzen.
+### 5.4 ExternalMcpService-Tests ✅
+- Service exponiert **18 Tools** (war 11): `ListTaskLists`, `ListTasks`, `GetTask`, `AddTask`, `UpdateTask`, `UpdateTaskStatus`, `ReviewTask`, `RunTaskNow`, `CancelTask`, `DeleteTask`, `GetTaskStatusValues`, `GetTaskWorktree`, `GetTaskDiff`, `MergeTask`, `ListWorktrees`, `CleanupTaskWorktree`, `GetDailyPrepCandidates`, `SetMyDay`.
+- `ExternalMcpServiceTests.cs` hat jetzt 26 Tests (war 14): die zuvor ungetesteten Worktree/Git-Tools (`GetTaskWorktree`, `GetTaskDiff`, `MergeTask`, `ListWorktrees`, `CleanupTaskWorktree`) haben je Error-Pfad + git-gestützten Happy-Path (skippen wenn git fehlt). Plus 4 Sibling-Dateien (`ConfigMcpToolsTests`, `LifecycleMcpToolsTests`, `ListMcpToolsTests`, `RunHistoryMcpToolsTests`).
 
 ---
 
diff --git a/tests/ClaudeDo.Worker.Tests/External/ExternalMcpServiceTests.cs b/tests/ClaudeDo.Worker.Tests/External/ExternalMcpServiceTests.cs
index dfc7e51..2306b0e 100644
--- a/tests/ClaudeDo.Worker.Tests/External/ExternalMcpServiceTests.cs
+++ b/tests/ClaudeDo.Worker.Tests/External/ExternalMcpServiceTests.cs
@@ -56,6 +56,10 @@ public sealed class ExternalMcpServiceTests : IDisposable
     private readonly ListRepository _lists;
     private readonly ExternalFakeHubContext _hub = new();
     private readonly HubBroadcaster _broadcaster;
+    private readonly List<GitRepoFixture> _repos = new();
+    private readonly List<(string repoDir, string wtPath)> _worktreeCleanups = new();
+
+    private static bool GitAvailable => GitRepoFixture.IsGitAvailable();
 
     public ExternalMcpServiceTests()
     {
@@ -65,7 +69,34 @@ public sealed class ExternalMcpServiceTests : IDisposable
         _broadcaster = new HubBroadcaster(_hub);
     }
 
-    public void Dispose() { _ctx.Dispose(); _db.Dispose(); }
+    public void Dispose()
+    {
+        foreach (var (repoDir, wtPath) in _worktreeCleanups)
+        {
+            try { GitRepoFixture.RunGit(repoDir, "worktree", "remove", "--force", wtPath); } catch { }
+        }
+        foreach (var r in _repos) r.Dispose();
+        _ctx.Dispose();
+        _db.Dispose();
+    }
+
+    private async Task<(TaskEntity task, ListEntity list, WorktreeContext wt)> SeedWorktreeAsync(
+        TaskStatus status = TaskStatus.Done)
+    {
+        var repo = new GitRepoFixture();
+        _repos.Add(repo);
+
+        var listId = Guid.NewGuid().ToString();
+        var list = new ListEntity { Id = listId, Name = "L", WorkingDir = repo.RepoDir, CreatedAt = DateTime.UtcNow };
+        await _lists.AddAsync(list);
+        var task = await SeedTaskAsync(listId, status: status);
+
+        var cfg = new WorkerConfig { WorktreeRootStrategy = "sibling" };
+        var mgr = new WorktreeManager(new GitService(), _db.CreateFactory(), cfg, NullLogger<WorktreeManager>.Instance);
+        var wt = await mgr.CreateAsync(task, list, CancellationToken.None);
+        _worktreeCleanups.Add((repo.RepoDir, wt.WorktreePath));
+        return (task, list, wt);
+    }
 
     private async Task<string> SeedListAsync(string name = "L")
     {
@@ -412,4 +443,156 @@ public sealed class ExternalMcpServiceTests : IDisposable
         var dto = await svc.SetMyDay(id, false, null, CancellationToken.None);
         Assert.False(dto.IsMyDay);
     }
+
+    // ── GetTaskWorktree ────────────────────────────────────────────────────────
+
+    [Fact]
+    public async Task GetTaskWorktree_NoWorktree_Throws()
+    {
+        var listId = await SeedListAsync();
+        var task = await SeedTaskAsync(listId);
+        var sut = BuildSut(CreateQueue());
+
+        await Assert.ThrowsAsync<InvalidOperationException>(
+            () => sut.GetTaskWorktree(task.Id, CancellationToken.None));
+    }
+
+    [Fact]
+    public async Task GetTaskWorktree_ReturnsBranchAndBaseCommit()
+    {
+        if (!GitAvailable) { Assert.True(true, "git not available -- skipping"); return; }
+
+        var (task, _, wt) = await SeedWorktreeAsync();
+        var sut = BuildSut(CreateQueue());
+
+        var info = await sut.GetTaskWorktree(task.Id, CancellationToken.None);
+
+        Assert.Equal(wt.BranchName, info.Branch);
+        Assert.Equal(wt.BaseCommit, info.BaseCommit);
+        Assert.Equal(0, info.Ahead);
+        Assert.False(info.IsDirty);
+    }
+
+    // ── GetTaskDiff ────────────────────────────────────────────────────────────
+
+    [Fact]
+    public async Task GetTaskDiff_NoWorktree_Throws()
+    {
+        var listId = await SeedListAsync();
+        var task = await SeedTaskAsync(listId);
+        var sut = BuildSut(CreateQueue());
+
+        await Assert.ThrowsAsync<InvalidOperationException>(
+            () => sut.GetTaskDiff(task.Id, false, CancellationToken.None));
+    }
+
+    [Fact]
+    public async Task GetTaskDiff_AfterCommit_ListsChangedFile()
+    {
+        if (!GitAvailable) { Assert.True(true, "git not available -- skipping"); return; }
+
+        var (task, list, wt) = await SeedWorktreeAsync();
+        File.WriteAllText(Path.Combine(wt.WorktreePath, "added.txt"), "content");
+
+        var cfg = new WorkerConfig { WorktreeRootStrategy = "sibling" };
+        var mgr = new WorktreeManager(new GitService(), _db.CreateFactory(), cfg, NullLogger<WorktreeManager>.Instance);
+        await mgr.CommitIfChangedAsync(wt, task, list, CancellationToken.None);
+
+        var sut = BuildSut(CreateQueue());
+        var diff = await sut.GetTaskDiff(task.Id, false, CancellationToken.None);
+
+        Assert.Contains("added.txt", diff.Files);
+        Assert.False(diff.Truncated);
+    }
+
+    // ── MergeTask ──────────────────────────────────────────────────────────────
+
+    [Fact]
+    public async Task MergeTask_NotDone_Throws()
+    {
+        var listId = await SeedListAsync();
+        var task = await SeedTaskAsync(listId, status: TaskStatus.Idle);
+        var sut = BuildSut(CreateQueue());
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
+            () => sut.MergeTask(task.Id, "main", true, false, CancellationToken.None));
+        Assert.Contains("Done", ex.Message);
+    }
+
+    [Fact]
+    public async Task MergeTask_DryRun_DoesNotMerge()
+    {
+        if (!GitAvailable) { Assert.True(true, "git not available -- skipping"); return; }
+
+        var (task, _, _) = await SeedWorktreeAsync(TaskStatus.Done);
+        var sut = BuildSut(CreateQueue());
+
+        var result = await sut.MergeTask(task.Id, "main", true, dryRun: true, CancellationToken.None);
+
+        Assert.False(result.Merged);
+        Assert.Null(result.MergeCommit);
+    }
+
+    // ── ListWorktrees ──────────────────────────────────────────────────────────
+
+    [Fact]
+    public async Task ListWorktrees_Empty_ReturnsEmpty()
+    {
+        var sut = BuildSut(CreateQueue());
+
+        var rows = await sut.ListWorktrees(CancellationToken.None);
+
+        Assert.Empty(rows);
+    }
+
+    [Fact]
+    public async Task ListWorktrees_ReturnsCreatedWorktree()
+    {
+        if (!GitAvailable) { Assert.True(true, "git not available -- skipping"); return; }
+
+        var (task, _, _) = await SeedWorktreeAsync();
+        var sut = BuildSut(CreateQueue());
+
+        var rows = await sut.ListWorktrees(CancellationToken.None);
+
+        Assert.Contains(rows, r => r.TaskId == task.Id);
+    }
+
+    // ── CleanupTaskWorktree ────────────────────────────────────────────────────
+
+    [Fact]
+    public async Task CleanupTaskWorktree_NotFound_Throws()
+    {
+        var sut = BuildSut(CreateQueue());
+
+        await Assert.ThrowsAsync<InvalidOperationException>(
+            () => sut.CleanupTaskWorktree("does-not-exist", false, CancellationToken.None));
+    }
+
+    [Fact]
+    public async Task CleanupTaskWorktree_Running_Throws()
+    {
+        if (!GitAvailable) { Assert.True(true, "git not available -- skipping"); return; }
+
+        var (task, _, _) = await SeedWorktreeAsync(TaskStatus.Running);
+        var sut = BuildSut(CreateQueue());
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
+            () => sut.CleanupTaskWorktree(task.Id, false, CancellationToken.None));
+        Assert.Contains("running", ex.Message, StringComparison.OrdinalIgnoreCase);
+    }
+
+    [Fact]
+    public async Task CleanupTaskWorktree_CleanWorktree_Removes()
+    {
+        if (!GitAvailable) { Assert.True(true, "git not available -- skipping"); return; }
+
+        var (task, _, wt) = await SeedWorktreeAsync(TaskStatus.Done);
+        var sut = BuildSut(CreateQueue());
+
+        var result = await sut.CleanupTaskWorktree(task.Id, false, CancellationToken.None);
+
+        Assert.True(result.Removed);
+        Assert.False(Directory.Exists(wt.WorktreePath));
+    }
 }