diff --git a/src/ClaudeDo.Worker/Runner/TaskRunner.cs b/src/ClaudeDo.Worker/Runner/TaskRunner.cs
index 0be91e4..240aa32 100644
--- a/src/ClaudeDo.Worker/Runner/TaskRunner.cs
+++ b/src/ClaudeDo.Worker/Runner/TaskRunner.cs
@@ -331,6 +331,8 @@ public sealed class TaskRunner
         {
             var taskRepo = new TaskRepository(context);
             await taskRepo.MarkDoneAsync(task.Id, finishedAt, result.ResultMarkdown, CancellationToken.None);
+            if (task.ParentTaskId is not null)
+                await taskRepo.TryCompleteParentAsync(task.ParentTaskId, CancellationToken.None);
         }
         await _broadcaster.WorkerLog($"Finished \"{task.Title}\" (done)", WorkerLogLevel.Success, DateTime.UtcNow);
         await _broadcaster.TaskFinished(slot, task.Id, "done", finishedAt);
@@ -346,6 +348,9 @@ public sealed class TaskRunner
         using var context = _dbFactory.CreateDbContext();
         var taskRepo = new TaskRepository(context);
         await taskRepo.MarkFailedAsync(taskId, finishedAt, result.ErrorMarkdown, CancellationToken.None);
+        var justFailed = await taskRepo.GetByIdAsync(taskId, CancellationToken.None);
+        if (justFailed?.ParentTaskId is not null)
+            await taskRepo.TryCompleteParentAsync(justFailed.ParentTaskId, CancellationToken.None);
         await _broadcaster.WorkerLog($"Finished \"{taskTitle}\" (failed)", WorkerLogLevel.Error, DateTime.UtcNow);
         await _broadcaster.TaskFinished(slot, taskId, "failed", finishedAt);
         _logger.LogWarning("Task {TaskId} failed (turns={Turns}): {Error}", taskId, result.TurnCount, result.ErrorMarkdown);
@@ -360,6 +365,9 @@ public sealed class TaskRunner
             using var context = _dbFactory.CreateDbContext();
             var taskRepo = new TaskRepository(context);
             await taskRepo.MarkFailedAsync(taskId, now, error, CancellationToken.None);
+            var justFailed = await taskRepo.GetByIdAsync(taskId, CancellationToken.None);
+            if (justFailed?.ParentTaskId is not null)
+                await taskRepo.TryCompleteParentAsync(justFailed.ParentTaskId, CancellationToken.None);
             await _broadcaster.WorkerLog($"Finished \"{taskTitle}\" (failed)", WorkerLogLevel.Error, DateTime.UtcNow);
             await _broadcaster.TaskFinished(slot, taskId, "failed", now);
             await _broadcaster.TaskUpdated(taskId);
diff --git a/tests/ClaudeDo.Worker.Tests/Runner/TaskRunnerParentCompletionTests.cs b/tests/ClaudeDo.Worker.Tests/Runner/TaskRunnerParentCompletionTests.cs
new file mode 100644
index 0000000..3a2d29d
--- /dev/null
+++ b/tests/ClaudeDo.Worker.Tests/Runner/TaskRunnerParentCompletionTests.cs
@@ -0,0 +1,74 @@
+using ClaudeDo.Data;
+using ClaudeDo.Data.Models;
+using ClaudeDo.Data.Repositories;
+using ClaudeDo.Worker.Tests.Infrastructure;
+using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
+
+namespace ClaudeDo.Worker.Tests.Runner;
+
+public sealed class TaskRunnerParentCompletionTests : IDisposable
+{
+    private readonly DbFixture _db = new();
+    private readonly ClaudeDoDbContext _ctx;
+    private readonly TaskRepository _tasks;
+    private readonly ListRepository _lists;
+
+    public TaskRunnerParentCompletionTests()
+    {
+        _ctx = _db.CreateContext();
+        _tasks = new TaskRepository(_ctx);
+        _lists = new ListRepository(_ctx);
+    }
+
+    public void Dispose() { _ctx.Dispose(); _db.Dispose(); }
+
+    [Fact]
+    public async Task ChildMarkedDone_LastOne_ParentFinalized()
+    {
+        var listId = Guid.NewGuid().ToString();
+        await _lists.AddAsync(new ListEntity { Id = listId, Name = "L", CreatedAt = DateTime.UtcNow });
+
+        var parent = new TaskEntity
+        {
+            Id = Guid.NewGuid().ToString(),
+            ListId = listId,
+            Title = "p",
+            Status = TaskStatus.Planned,
+            CreatedAt = DateTime.UtcNow,
+            CommitType = "chore",
+        };
+        await _tasks.AddAsync(parent);
+
+        var c1 = new TaskEntity
+        {
+            Id = Guid.NewGuid().ToString(),
+            ListId = listId,
+            Title = "c1",
+            Status = TaskStatus.Done,
+            CreatedAt = DateTime.UtcNow,
+            CommitType = "chore",
+            ParentTaskId = parent.Id,
+        };
+        var c2 = new TaskEntity
+        {
+            Id = Guid.NewGuid().ToString(),
+            ListId = listId,
+            Title = "c2",
+            Status = TaskStatus.Running,
+            CreatedAt = DateTime.UtcNow,
+            CommitType = "chore",
+            ParentTaskId = parent.Id,
+        };
+        await _tasks.AddAsync(c1);
+        await _tasks.AddAsync(c2);
+
+        // Simulate the runner finishing the second child:
+        await _tasks.MarkDoneAsync(c2.Id, DateTime.UtcNow, "done");
+        if (c2.ParentTaskId is not null)
+            await _tasks.TryCompleteParentAsync(c2.ParentTaskId);
+
+        var parentLoaded = await _tasks.GetByIdAsync(parent.Id);
+        Assert.Equal(TaskStatus.Done, parentLoaded!.Status);
+        Assert.NotNull(parentLoaded.FinishedAt);
+    }
+}