diff --git a/src/daemon/spawner.py b/src/daemon/spawner.py
index 9eeb8dd..3336d48 100644
--- a/src/daemon/spawner.py
+++ b/src/daemon/spawner.py
@@ -153,6 +153,11 @@ MAIL_RETRY_PROMPT = """你收到一个续杯提醒。你的任务在执行过程
 """
 
 
+class AgentBusyError(Exception):
+    """Agent 被 counter 占用，无法 spawn"""
+    pass
+
+
 class AgentSpawner:
     """Agent spawn 管理"""
 
@@ -167,6 +172,7 @@ class AgentSpawner:
         gateway_timeout: float = 600.0,
         max_retries: int = 3,
         max_monitor_timeouts: int = 3,
+        counter: Optional[Any] = None,
     ):
         """
         Args:
@@ -185,6 +191,8 @@ class AgentSpawner:
         self.gateway_timeout = gateway_timeout
         self.max_retries = max_retries
         self.max_monitor_timeouts = max_monitor_timeouts
+        # v2.7.2: counter 引用（spawn_full_agent 内部 acquire/release）
+        self.counter = counter
 
         # session 注册表 {session_id: {...}}
         self._sessions: Dict[str, Dict[str, Any]] = {}