diff --git a/agents/s11_autonomous_agents.py b/agents/s11_autonomous_agents.py
index 5eabdb9..59fe3f7 100644
--- a/agents/s11_autonomous_agents.py
+++ b/agents/s11_autonomous_agents.py
@@ -142,6 +142,8 @@ def claim_task(task_id: int, owner: str) -> str:
         if not path.exists():
             return f"Error: Task {task_id} not found"
         task = json.loads(path.read_text())
+        if task.get("owner") or task.get("status") != "pending":
+            return f"Error: Task {task_id} has already been claimed by someone else"
         task["owner"] = owner
         task["status"] = "in_progress"
         path.write_text(json.dumps(task, indent=2))
@@ -274,7 +276,9 @@ class TeammateManager:
                 unclaimed = scan_unclaimed_tasks()
                 if unclaimed:
                     task = unclaimed[0]
-                    claim_task(task["id"], name)
+                    result = claim_task(task["id"], name)
+                    if result.startswith("Error"):
+                        continue
                     task_prompt = (
                         f"<auto-claimed>Task #{task['id']}: {task['subject']}\n"
                         f"{task.get('description', '')}</auto-claimed>"