diff --git a/agents/s08_background_tasks.py b/agents/s08_background_tasks.py
index 390a77780..68b29b6d9 100644
--- a/agents/s08_background_tasks.py
+++ b/agents/s08_background_tasks.py
@@ -51,12 +51,14 @@ class BackgroundManager:
     def __init__(self):
         self.tasks = {}  # task_id -> {status, result, command}
         self._notification_queue = []  # completed task results
-        self._lock = threading.Lock()
+        self._tasks_lock = threading.Lock()  # protect self.tasks
+        self._queue_lock = threading.Lock()  # protect _notification_queue
 
     def run(self, command: str) -> str:
         """Start a background thread, return task_id immediately."""
         task_id = str(uuid.uuid4())[:8]
-        self.tasks[task_id] = {"status": "running", "result": None, "command": command}
+        with self._tasks_lock:
+            self.tasks[task_id] = {"status": "running", "result": None, "command": command}
         thread = threading.Thread(
             target=self._execute, args=(task_id, command), daemon=True
         )
@@ -78,9 +80,10 @@ def _execute(self, task_id: str, command: str):
         except Exception as e:
             output = f"Error: {e}"
             status = "error"
-        self.tasks[task_id]["status"] = status
-        self.tasks[task_id]["result"] = output or "(no output)"
-        with self._lock:
+        with self._tasks_lock:
+            self.tasks[task_id]["status"] = status
+            self.tasks[task_id]["result"] = output or "(no output)"
+        with self._queue_lock:
             self._notification_queue.append({
                 "task_id": task_id,
                 "status": status,
@@ -90,19 +93,20 @@ def _execute(self, task_id: str, command: str):
 
     def check(self, task_id: str = None) -> str:
         """Check status of one task or list all."""
-        if task_id:
-            t = self.tasks.get(task_id)
-            if not t:
-                return f"Error: Unknown task {task_id}"
-            return f"[{t['status']}] {t['command'][:60]}\n{t.get('result') or '(running)'}"
-        lines = []
-        for tid, t in self.tasks.items():
-            lines.append(f"{tid}: [{t['status']}] {t['command'][:60]}")
+        with self._tasks_lock:
+            if task_id:
+                t = self.tasks.get(task_id)
+                if not t:
+                    return f"Error: Unknown task {task_id}"
+                return f"[{t['status']}] {t['command'][:60]}\n{t.get('result') or '(running)'}"
+            lines = []
+            for tid, t in self.tasks.items():
+                lines.append(f"{tid}: [{t['status']}] {t['command'][:60]}")
         return "\n".join(lines) if lines else "No background tasks."
 
     def drain_notifications(self) -> list:
         """Return and clear all pending completion notifications."""
-        with self._lock:
+        with self._queue_lock:
             notifs = list(self._notification_queue)
             self._notification_queue.clear()
         return notifs