Merge claudedo/973ea49ec0a642ea9b1ddcff9b71b6fe

src/ClaudeDo.Worker/State/TaskStateService.cs

@@ -16,6 +16,7 @@ public sealed class TaskStateService : ITaskStateService
     private readonly IQueueWaker _waker;
     private readonly PlanningChainCoordinator _chain;
     private readonly RunCancellationRegistry _runCancels;
+    private readonly Func<IActiveMergeState> _mergeState;
     private readonly ILogger<TaskStateService> _logger;
 
     public TaskStateService(
@@ -24,6 +25,7 @@ public sealed class TaskStateService : ITaskStateService
         IQueueWaker waker,
         PlanningChainCoordinator chain,
         RunCancellationRegistry runCancels,
+        Func<IActiveMergeState> mergeState,
         ILogger<TaskStateService> logger)
     {
         _dbFactory = dbFactory;
@@ -31,6 +33,7 @@ public sealed class TaskStateService : ITaskStateService
         _waker = waker;
         _chain = chain;
         _runCancels = runCancels;
+        _mergeState = mergeState;
         _logger = logger;
     }
 
@@ -255,6 +258,14 @@ public sealed class TaskStateService : ITaskStateService
     public async Task<TransitionResult> CancelAsync(
         string taskId, DateTime finishedAt, CancellationToken ct, bool allowFromIdle = false)
     {
+        // A unit merge drains its children's worktrees onto the target branch while the parent
+        // sits in WaitingForReview for the whole (potentially minutes-long) drain. Cancelling out
+        // from under it would flip the parent to Cancelled while the orchestrator keeps merging —
+        // FinalizeParentDoneAsync then finds the parent no longer WaitingForReview and gives up,
+        // leaving the merged children's diffs stranded with no way to roll them back.
+        if (_mergeState().HasActiveMerge(taskId))
+            return new TransitionResult(false, "A merge is in progress for this task; wait for it to finish before cancelling.");
+
         List<string> cancelledChildIds;
         await using (var ctx = await _dbFactory.CreateDbContextAsync(ct))
         {