diff --git a/apps/backend/src/repositories/worker-platform/work-order-material-link-repo.ts b/apps/backend/src/repositories/worker-platform/work-order-material-link-repo.ts
index c8ffc530..79ef6438 100644
--- a/apps/backend/src/repositories/worker-platform/work-order-material-link-repo.ts
+++ b/apps/backend/src/repositories/worker-platform/work-order-material-link-repo.ts
@@ -128,7 +128,7 @@ export async function markWorkOrderMaterialLinkUsedWithClient(
   const result = await client.query<WorkOrderMaterialLinkRow>(
     `UPDATE work_order_material_links
      SET status = 'used', used_at = $2, updated_at = $2
-     WHERE id = $1 AND status = 'active'
+     WHERE id = $1 AND status = 'active' AND expires_at > $2
      RETURNING *`,
     [Number(linkId), now],
   )
diff --git a/apps/backend/src/services/worker-platform/work-order-material-link-service.ts b/apps/backend/src/services/worker-platform/work-order-material-link-service.ts
index 6b31c569..4c9decf2 100644
--- a/apps/backend/src/services/worker-platform/work-order-material-link-service.ts
+++ b/apps/backend/src/services/worker-platform/work-order-material-link-service.ts
@@ -149,7 +149,6 @@ export async function createAdminWorkOrderMaterialLink(
   workOrderId: number | string,
   actorName = '',
 ) {
-  const now = nowIso()
   const { ttlMinutes } = getWorkerMaterialLinkConfig()
 
   return withTransaction(async (client) => {
@@ -169,6 +168,8 @@ export async function createAdminWorkOrderMaterialLink(
     }
     assertWorkOrderAllowedForMaterialLink(order)
 
+    // 锁到手后再取时间，避免等锁期间旧链接过期却仍按旧时间复用。
+    const now = nowIso()
     const existing = await findActiveWorkOrderMaterialLinkWithClient(client, order.id, now)
     if (existing) {
       return {
@@ -254,7 +255,6 @@ export async function submitPublicWorkOrderMaterialLink(token: string, payload:
     })
   }
 
-  const now = nowIso()
   const result = await withTransaction(async (client) => {
     // 先锁工单再锁链接，和后台生成链接保持同样的加锁顺序，避免死锁。
     const order = await getWorkOrderForUpdateWithClient(client, preliminary.work_order_id)
@@ -272,6 +272,8 @@ export async function submitPublicWorkOrderMaterialLink(token: string, payload:
       })
     }
 
+    // 锁到手后再取时间：等锁期间链接可能已经过期，不能沿用进入事务前的时间。
+    const now = nowIso()
     assertMaterialLinkRecordUsable(link, now)
     assertWorkOrderAllowedForMaterialLink(order)
 
@@ -328,11 +330,13 @@ export async function submitPublicWorkOrderMaterialLink(token: string, payload:
 
     const used = await markWorkOrderMaterialLinkUsedWithClient(client, link.id, now)
     if (!used) {
-      // 并发提交时另一个请求已经把链接用掉，当前事务整体回滚。
-      throw createHttpError('链接已使用，如需修改资料请联系客服重新获取', {
-        statusCode: 410,
-        errorCode: 'material_link_used',
-      })
+      // 并发提交，或刚好在写入瞬间过期：按当前状态给出准确原因，事务整体回滚。
+      const latest = await getWorkOrderMaterialLinkForUpdateWithClient(client, link.id)
+      if (latest) {
+        const reason = resolveWorkOrderMaterialLinkUnavailableReason(latest, now)
+        if (reason) throwMaterialLinkUnavailable(reason)
+      }
+      throwMaterialLinkUnavailable('used')
     }
 
     await createWorkOrderEventWithClient(client, {