diff --git a/app/services/oss_storage.py b/app/services/oss_storage.py
index 3f54728..49b0cb9 100644
--- a/app/services/oss_storage.py
+++ b/app/services/oss_storage.py
@@ -175,9 +175,13 @@ class COSStorage:
             logger.info("COS 未启用 (COS_ENABLED=false)")
             return
 
-        self._client = _get_cos_client()
-        if self._client:
-            self._enabled = True
+        try:
+            self._client = _get_cos_client()
+            if self._client:
+                self._enabled = True
+        except Exception as e:
+            logger.error(f"COS 初始化失败，截图预签名 URL 将不可用: {e}")
+            self._enabled = False
 
     @property
     def is_cos_mode(self) -> bool:
@@ -278,12 +282,21 @@ class COSStorage:
     # ======================== 兼容旧接口 ========================
 
     def get_url(self, path: str) -> str:
-        """获取访问 URL（兼容旧代码调用）"""
+        """获取访问 URL（兼容旧代码调用）
+
+        保证返回值要么是 http(s):// 开头的可访问 URL，要么是空字符串。
+        绝不返回裸 object_key，以免前端加载为相对路径导致损坏图片。
+        """
         if not path:
             return ""
         if path.startswith("http"):
             return path
-        return self.get_presigned_url(path)
+        url = self.get_presigned_url(path)
+        # 兜底：如果未能生成有效 URL（COS 未启用/异常），返回空字符串
+        if not url.startswith("http"):
+            logger.warning(f"无法生成 COS 预签名 URL，返回空: object_key={path}")
+            return ""
+        return url
 
 
 # 全局单例