fix: 把完整消息拆成单个字符模拟流式输出

backend/app/agent/agent_service.py

@@ -189,6 +189,20 @@ class AIAgentService:
                     }
         # 处理普通 token
         elif token_content:
+            # 如果内容较长，拆成单个字符模拟流式效果
+            if len(token_content) > 1:
+                import asyncio
+                for char in token_content:
+                    yield {
+                        "type": "llm_token",
+                        "node": node_name,
+                        "token": char,
+                        "reasoning_token": reasoning_token
+                    }
+                    # 短暂暂停，模拟打字效果
+                    await asyncio.sleep(0.01)
+            else:
+                # 内容较短，直接发送
                 yield {
                     "type": "llm_token",
                     "node": node_name,