diff --git a/services/import_service.py b/services/import_service.py
index c124769..e789725 100644
--- a/services/import_service.py
+++ b/services/import_service.py
@@ -670,6 +670,40 @@ class ImportService:
 
             if not files:
                 logger.info("沒有找到待匯入的檔案")
+
+                # Staleness gate (critic-approved 2026-05-03)
+                # 'move-then-success' 反模式：成功 import 後 move_file 把 Excel 搬到
+                # 「已匯入」資料夾 → 後續排程 list 回空 → 走此分支 silent return success
+                # → 4/27~5/2 daily_sales_snapshot 停更 8 天無告警。補主動偵測：
+                # Drive 空 + DB ≥3 天無新資料時主動發催促告警（週末跨假期不誤觸）。
+                try:
+                    from database.manager import get_session
+                    from sqlalchemy import text
+                    from datetime import date
+                    from services.openclaw_strategist_service import _send_data_stale_alert
+
+                    _stale_session = get_session()
+                    try:
+                        last_date = _stale_session.execute(
+                            text("SELECT MAX(snapshot_date)::date FROM daily_sales_snapshot")
+                        ).scalar()
+                    finally:
+                        _stale_session.close()
+
+                    if last_date:
+                        days_since = (date.today() - last_date).days
+                        if days_since >= 3:
+                            _send_data_stale_alert(
+                                report_type="upstream_drive",
+                                last_date=str(last_date),
+                                period=f"已停更 {days_since} 天",
+                            )
+                except Exception:
+                    logger.error(
+                        "staleness check failed in auto_import_from_drive",
+                        exc_info=True,
+                    )
+
                 return {
                     'success': True,
                     'message': '沒有找到待匯入的檔案',