diff --git a/src/ClaudeDo.Worker/Lifecycle/TaskMergeService.cs b/src/ClaudeDo.Worker/Lifecycle/TaskMergeService.cs
index e8e578a..095bcf4 100644
--- a/src/ClaudeDo.Worker/Lifecycle/TaskMergeService.cs
+++ b/src/ClaudeDo.Worker/Lifecycle/TaskMergeService.cs
@@ -267,6 +267,9 @@ public sealed class TaskMergeService
                 : Blocked(done.Reason ?? "approve failed");
         }
 
+        if (string.IsNullOrWhiteSpace(list.WorkingDir))
+            return Blocked("list has no working directory");
+
         var target = string.IsNullOrWhiteSpace(targetBranch)
             ? await _git.GetCurrentBranchAsync(list.WorkingDir, ct)
             : targetBranch;