diff --git a/bioflow_service/app/services/bioflow/delivery.py b/bioflow_service/app/services/bioflow/delivery.py
index 470565d..c32e0ba 100644
--- a/bioflow_service/app/services/bioflow/delivery.py
+++ b/bioflow_service/app/services/bioflow/delivery.py
@@ -130,7 +130,10 @@ def check_download_budget(size_bytes: int, budget_bytes: int) -> dict[str, Any]:
 
 def check_disk_available(dest_dir: str | Path, needed_bytes: int) -> dict[str, Any]:
     """G23：磁盘门禁——剩余空间不足阻断并返回结构化错误。"""
-    ok, free = check_disk_space(dest_dir, needed_bytes)
+    try:
+        ok, free = check_disk_space(dest_dir, needed_bytes)
+    except OSError as exc:
+        return error_result("PATH_NOT_EXIST", f"目标目录不可用：{exc}")
     if not ok:
         return error_result(
             "DISK_FULL", f"磁盘空间不足：需 {needed_bytes} 字节，剩余 {free} 字节",