diff --git a/src/app/api/bagPrint/actions.ts b/src/app/api/bagPrint/actions.ts
index e9ac655..60794ec 100644
--- a/src/app/api/bagPrint/actions.ts
+++ b/src/app/api/bagPrint/actions.ts
@@ -33,6 +33,29 @@ export interface OnPackQrDownloadRequest {
   }[];
 }
 
+/** Readable message when ZIP download returns non-OK (plain text, JSON error body, or generic). */
+async function zipDownloadError(res: Response): Promise<Error> {
+  const text = await res.text();
+  const ct = res.headers.get("content-type") ?? "";
+  if (ct.includes("application/json")) {
+    try {
+      const j = JSON.parse(text) as { message?: string; error?: string };
+      if (typeof j.message === "string" && j.message.length > 0) {
+        return new Error(j.message);
+      }
+      if (typeof j.error === "string" && j.error.length > 0) {
+        return new Error(j.error);
+      }
+    } catch {
+      /* ignore parse */
+    }
+  }
+  if (text && text.length > 0 && text.length < 800 && !text.trim().startsWith("{")) {
+    return new Error(text);
+  }
+  return new Error(`下載失敗（HTTP ${res.status}）。請查看後端日誌或確認資料庫已執行 Liquibase 更新。`);
+}
+
 /**
  * Fetch job orders by plan date from GET /py/job-orders.
  * Client-side only; uses auth token from localStorage.
@@ -75,7 +98,7 @@ export async function downloadOnPackQrZip(
   });
 
   if (!res.ok) {
-    throw new Error((await res.text()) || "Download failed");
+    throw await zipDownloadError(res);
   }
 
   return res.blob();
@@ -93,7 +116,7 @@ export async function downloadOnPackTextQrZip(
   });
 
   if (!res.ok) {
-    throw new Error((await res.text()) || "Download failed");
+    throw await zipDownloadError(res);
   }
 
   return res.blob();