fix(sse): properly handle MCP tool errors and send error responses to client

- Enhance exception handling in agent_task() to capture and send structured error messages via SSE stream
- Add [DONE] marker to outer exception handler to ensure proper stream termination
- Improve MCP tool loading error handling in init_agent() to prevent cascading failures
- Add detailed error logging with traceback for debugging

Fixes RemoteProtocolError that occurred when MCP tool calls failed,
which previously caused incomplete chunked read errors and connection drops.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

agent/deep_assistant.py

@@ -102,8 +102,11 @@ async def get_tools_from_mcp(mcp):
         logger.info(f"get_tools_from_mcp: loaded {len(mcp_tools)} tools, elapsed: {time.time() - start_time:.3f}s")
         return mcp_tools
     except Exception as e:
+        import traceback
+        error_details = traceback.format_exc()
         # 发生异常时返回空列表，避免上层调用报错
-        logger.info(f"get_tools_from_mcp: error {e}, elapsed: {time.time() - start_time:.3f}s")
+        logger.error(f"get_tools_from_mcp: error {str(e)}, elapsed: {time.time() - start_time:.3f}s")
+        logger.error(f"Full traceback: {error_details}")
         return []
 
 async def init_agent(config: AgentConfig):
@@ -139,7 +142,12 @@ async def init_agent(config: AgentConfig):
     config.mcp_settings = system_prompt
 
     # 获取 mcp_tools（缓存逻辑已内置到 get_tools_from_mcp 中）
+    try:
         mcp_tools = await get_tools_from_mcp(mcp_settings)
+        logger.info(f"Successfully loaded {len(mcp_tools)} MCP tools")
+    except Exception as e:
+        logger.error(f"Failed to load MCP tools: {str(e)}, using empty tool list")
+        mcp_tools = []
 
     # 检测或使用指定的提供商
     model_provider, base_url = detect_provider(config.model_name, config.model_server)

routes/chat.py

@@ -114,7 +114,22 @@ async def enhanced_generate_stream_response(
                 await output_queue.put(("agent_done", None))
 
             except Exception as e:
-                logger.error(f"Error in agent task: {e}")
+                import traceback
+                error_details = traceback.format_exc()
+                logger.error(f"Error in agent task: {str(e)}")
+                logger.error(f"Full traceback: {error_details}")
+
+                # 发送错误信息给客户端
+                error_data = {
+                    "error": {
+                        "message": f"Agent execution failed: {str(e)}",
+                        "type": "agent_error",
+                        "details": error_details if __debug__ else str(e)
+                    }
+                }
+                error_chunk = create_stream_chunk(f"chatcmpl-error", config.model_name, json.dumps(error_data, ensure_ascii=False))
+                await output_queue.put(("agent", f"data: {json.dumps(error_chunk, ensure_ascii=False)}\n\n"))
+                # 发送完成信号，确保输出控制器能正常结束
                 await output_queue.put(("agent_done", None))
 
         # 并发执行任务
@@ -186,6 +201,7 @@ async def enhanced_generate_stream_response(
             }
         }
         yield f"data: {json.dumps(error_data, ensure_ascii=False)}\n\n"
+        yield "data: [DONE]\n\n"
 
 
 async def create_agent_and_generate_response(