diff --git a/tools/seed_sim_account_demo.py b/tools/seed_sim_account_demo.py
index 311b808..1256269 100644
--- a/tools/seed_sim_account_demo.py
+++ b/tools/seed_sim_account_demo.py
@@ -26,7 +26,7 @@ import sys
 from datetime import UTC, datetime, timedelta
 from decimal import Decimal
 
-from sqlalchemy import func, insert, select
+from sqlalchemy import func, insert, select, update
 from sqlalchemy.orm import Session
 
 from app.core.config import get_settings
@@ -118,7 +118,32 @@ async def _upsert_product(session: Session, spec: dict) -> int:
 
 
 async def _upsert_market_price(session: Session, product_id: int, spec: dict) -> None:
+    """写入/刷新当日行情。
+
+    ⚠️ 当天已有行时**必须刷新**，不能直接 return（2026-09-12 实测到的缺陷）：
+
+    行情是**时效数据**，`FundQuoteService` 会按 `source_updated_at` 判新鲜度，
+    过期即返回 `503 FUND_QUOTE_UNAVAILABLE`，连带 `T001` 仪表盘与 `T006` 持仓一起不可用。
+    原先"已存在就跳过"会让同一天重跑**不更新 `source_updated_at`** ——
+    表现为"刚灌完种子能用，过十几分钟仪表盘就 503"，而这与种子无关、极难归因。
+
+    幂等的正确含义是**不产生重复行**（`(product_id, trade_date)` 唯一），
+    **不是"不更新值"**。账户/持仓的"已存在则跳过"是另一回事 ——
+    那是业务数据，不该被种子覆盖。
+    """
     today = datetime.now(UTC).date()
+    now = datetime.now(UTC).replace(tzinfo=None)
+    values = {
+        "open_price": spec["close_price"],
+        "high_price": spec["close_price"] + Decimal("0.05"),
+        "low_price": spec["close_price"] - Decimal("0.05"),
+        "close_price": spec["close_price"],
+        "volume": Decimal("1000000"),
+        "turnover_amount": spec["close_price"] * Decimal("1000000"),
+        "total_fund_shares": spec["total_fund_shares"],
+        "source": "eastmoney_demo_seed",
+        "source_updated_at": now,
+    }
     existing = (
         await session.execute(
             select(FundMarketPrice.id).where(
@@ -128,25 +153,20 @@ async def _upsert_market_price(session: Session, product_id: int, spec: dict) ->
         )
     ).scalar_one_or_none()
     if existing is not None:
+        await session.execute(
+            update(FundMarketPrice).where(FundMarketPrice.id == existing).values(**values)
+        )
         return
-    now = datetime.now(UTC).replace(tzinfo=None)
     next_id = await _next_id(session, FundMarketPrice)
-    stmt = insert(FundMarketPrice).values(
-        id=next_id,
-        product_id=product_id,
-        trade_date=today,
-        open_price=spec["close_price"],
-        high_price=spec["close_price"] + Decimal("0.05"),
-        low_price=spec["close_price"] - Decimal("0.05"),
-        close_price=spec["close_price"],
-        volume=Decimal("1000000"),
-        turnover_amount=spec["close_price"] * Decimal("1000000"),
-        total_fund_shares=spec["total_fund_shares"],
-        source="eastmoney_demo_seed",
-        source_updated_at=now,
-        created_at=now,
+    await session.execute(
+        insert(FundMarketPrice).values(
+            id=next_id,
+            product_id=product_id,
+            trade_date=today,
+            created_at=now,
+            **values,
+        )
     )
-    await session.execute(stmt)
 
 
 async def _upsert_account(session: Session, customer_id: int) -> FundSimAccount: