diff --git a/pipeline_service/agent_loop_v2.py b/pipeline_service/agent_loop_v2.py
index 552e13c..22fc725 100644
--- a/pipeline_service/agent_loop_v2.py
+++ b/pipeline_service/agent_loop_v2.py
@@ -966,7 +966,7 @@ class AgentExecutor:
         """简单 token 估算（中文 ~1.5 字符/token，英文 ~4 字符/token）"""
         total = 0
         for m in self._msgs:
-            content = m.get("content", "")
+            content = m.get("content") or ""
             # 简单估算：平均每 2 字符 1 token
             total += len(content) // 2 + 1
         return total
@@ -974,10 +974,10 @@ class AgentExecutor:
     async def _summarize(self, messages: list) -> str:
         """压缩消息为摘要"""
         if len(messages) <= 2:
-            return "\n".join(m.get("content", "")[:200] for m in messages)
+            return "\n".join((m.get("content") or "")[:200] for m in messages)
 
         text = "\n".join(
-            f"[{m['role']}]: {m.get('content', '')[:500]}"
+            f"[{m['role']}]: {(m.get('content') or '')[:500]}"
             for m in messages
         )