diff --git a/backend/src/api/dailyInventory.js b/backend/src/api/dailyInventory.js
index 45a3dc1..aec520f 100644
--- a/backend/src/api/dailyInventory.js
+++ b/backend/src/api/dailyInventory.js
@@ -283,7 +283,7 @@ router.get('/', async (req, res) => {
     // 流水列：自期初时刻（最新业务日 01:00）以来的单据合计（带符号，流出为负）
     let flowMap = new Map();
     if (openingDate) {
-      flowMap = await fetchFlows(wmsCoIds, `${latestBizDate} 01:00:00`).catch((e) => {
+      flowMap = await fetchFlows(cloudDb, wmsCoIds, `${latestBizDate} 01:00:00`).catch((e) => {
         console.error('[daily-inventory] 流水取数失败:', e.message);
         return new Map();
       });
diff --git a/backend/src/services/dailyInventoryFlows.js b/backend/src/services/dailyInventoryFlows.js
index 41014aa..0c612d3 100644
--- a/backend/src/services/dailyInventoryFlows.js
+++ b/backend/src/services/dailyInventoryFlows.js
@@ -93,6 +93,9 @@ const AVAILABLE_FLOW_FIELDS = FLOW_QUERIES.map((q) => q.field);
  * @returns {Promise<Map<string, Object>>} key = wmsCoId 字符串，value = { purchaseIn, purchaseReturn, salesOut, salesReturn }（带符号，无记录的字段不出现）
  */
 async function fetchFlows(cloudDb, wmsCoIds, fromText) {
+  if (!cloudDb || typeof cloudDb.query !== 'function') {
+    throw new TypeError('fetchFlows 第一个参数必须是数据库实例（防呆：调用漏传 cloudDb 时立即报错而非静默返回空）');
+  }
   const map = new Map();
   if (!wmsCoIds.length || !fromText) return map;
   for (const q of FLOW_QUERIES) {
diff --git a/backend/test/dailyInventoryFlows.test.js b/backend/test/dailyInventoryFlows.test.js
index d58efed..23e1d66 100644
--- a/backend/test/dailyInventoryFlows.test.js
+++ b/backend/test/dailyInventoryFlows.test.js
@@ -105,3 +105,10 @@ test('deriveAndStoreOpeningSnapshot：监控表命中走精确值，未命中用
   // 带回基线仓库名，保证后续按 wmsCoId 读取正确
   assert.equal(byWh.get(102).warehouse, '仓B主仓');
 });
+
+test('fetchFlows 缺少数据库实例参数时立即抛错（防静默空结果）', async () => {
+  await assert.rejects(
+    () => fetchFlows([101, 102], '2026-09-26 01:00:00'),
+    /第一个参数必须是数据库实例/
+  );
+});