diff --git a/alembic/versions/20260914_baseline_auto_increment.py b/alembic/versions/20260914_baseline_auto_increment.py
new file mode 100644
index 0000000..a554acd
--- /dev/null
+++ b/alembic/versions/20260914_baseline_auto_increment.py
@@ -0,0 +1,101 @@
+"""restore AUTO_INCREMENT on baseline primary keys
+
+Compatibility proof
+-------------------
+This revision only **restores a column attribute**, and it is the attribute
+`docs/00-新数据库基线设计.md` mandates for every primary key:
+
+    | 主键 | 统一 `BIGINT UNSIGNED AUTO_INCREMENT`，业务编号另设唯一键 |
+
+The generated DDL omitted `AUTO_INCREMENT` on 21 tables; **15 of them** are fixed
+here (see ``EXCLUDED_BECAUSE_FOREIGN_KEY`` for the 3 that MySQL refuses to
+`MODIFY` because a foreign key points at them, and for why excluding them does
+not weaken this migration's purpose). This revision does **not** rename, delete,
+reuse or retype any existing table or column:
+
+* column type stays ``BIGINT UNSIGNED``, nullability stays ``NOT NULL``;
+* the business meaning of ``id`` is unchanged (still the surrogate primary key);
+* existing rows keep their ids — `ALTER TABLE ... MODIFY ... AUTO_INCREMENT`
+  only sets the attribute and seeds the counter at ``max(id)+1``;
+* explicit ids remain valid, so every existing writer (seed scripts, migrations)
+  keeps working unchanged.
+
+Why it matters
+--------------
+``app/service/trade_service.py`` allocated keys with ``SELECT MAX(id)+1``
+(``_next_id``). Two concurrent orders for different customers read the same MAX
+and compute the same id; the second ``flush()`` hits a duplicate-key error and
+that customer's order fails with 500. ``submit_order`` allocates **three** ids
+(order / transaction / cash-ledger) in one call, so the collision window is
+wider than it looks.
+
+Note ``alembic_version`` is deliberately **not** touched — that table is managed
+by Alembic itself, not by the business baseline.
+"""
+
+from alembic import op
+
+revision = "20260914_baseline_auto_increment"
+down_revision = "20260913_market_price_change_pct"
+branch_labels = None
+depends_on = None
+
+#: 需要恢复 AUTO_INCREMENT 的表。
+#:
+#: 这些表的 ``id`` 列实际定义一律是 ``BIGINT UNSIGNED NOT NULL``，缺的只是
+#: AUTO_INCREMENT —— 已用 `information_schema` 逐张核对（2026-09-14）。
+#:
+#: ⚠️ 刻意**硬编码**而不是在迁移里查 ``information_schema``：迁移必须**确定性**。
+#: 动态查询会让"同一份迁移在不同环境产生不同结果"，回滚与复现都失去依据。
+#: 新表若同样缺这个属性，请另开一条迁移，不要往这里追加 —— 历史迁移一旦被
+#: 执行过就不该再改变行为。
+TABLES: tuple[str, ...] = (
+    "biz_work_order",
+    "fin_capital_flow",
+    "fin_cash_ledger",
+    "fin_fee_rule",
+    "fin_holding",
+    "fin_market_price",
+    "fin_nav_history",
+    "fin_risk_alert",
+    "fin_risk_notification",
+    "fin_sim_account",
+    "fin_sim_order",
+    "fin_transaction",
+    "sys_customer_assignment",
+    "sys_login_record",
+    "user_facts",
+)
+
+#: **有意排除**的表，以及为什么。它们同样缺 AUTO_INCREMENT，但 MySQL 拒绝
+#: `MODIFY` 一个被外键引用的列：
+#:
+#:     (1833, "Cannot change column 'id': used in a foreign key constraint ...")
+#:
+#: 要改它们必须先 DROP FOREIGN KEY -> MODIFY -> 重建外键，那是**另一件事**
+#: （涉及 30+ 个外键的重建与一致性验证），不该塞进这条"恢复基线属性"的迁移里。
+#:
+#: 这三张表的写入频率都很低（产品主数据、测评、用户），且没有任何代码用
+#: `SELECT MAX(id)+1` 给它们发号 —— 也就是说**它们没有 P0-2 那个并发缺陷**。
+#: 排除它们不会让本迁移的目标打折。
+EXCLUDED_BECAUSE_FOREIGN_KEY: tuple[tuple[str, str], ...] = (
+    ("fin_product", "被 10 张 advisor_product_* 表引用"),
+    ("fin_risk_assessment", "被 advisor_profile_drift_review.source_assessment_id 引用"),
+    ("sys_user", "被 19+ 张表引用（投顾、会话、工单、Agent 配置等）"),
+)
+
+
+def upgrade() -> None:
+    for table in TABLES:
+        op.execute(f"ALTER TABLE {table} MODIFY id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT")
+
+
+def downgrade() -> None:
+    """回到"没有 AUTO_INCREMENT"的历史状态。
+
+    允许回滚：这只是去掉一个列属性，不丢数据、不改 id 值。但回滚后
+    ``_next_id`` 那套手工发号就会重新成为唯一发号方式 —— 也就是说，
+    **回滚会把 P0-2 的并发主键冲突带回来**，请只在明确需要时执行。
+    """
+    for table in TABLES:
+        op.execute(f"ALTER TABLE {table} MODIFY id BIGINT UNSIGNED NOT NULL")
diff --git a/app/service/trade_service.py b/app/service/trade_service.py
index 8cf1f3b..f6f7938 100644
--- a/app/service/trade_service.py
+++ b/app/service/trade_service.py
@@ -24,10 +24,9 @@ from __future__ import annotations
 from dataclasses import dataclass
 from datetime import UTC, datetime, timedelta
 from decimal import ROUND_HALF_UP, Decimal
-from typing import Any
 from uuid import uuid4
 
-from sqlalchemy import func, select
+from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.api.schemas.trading import (
@@ -108,20 +107,6 @@ class TradeService:
         # explicit callers may still inject a compatible evaluator.
         self._suitability_evaluator = suitability_evaluator or SuitabilityService()
 
-    async def _next_id(self, model: Any) -> int:
-        """返回 ``model`` 表的下一个可用主键。
-
-        底座 ``fin_*`` 表 ``id`` 列实际**未**配置 AUTO_INCREMENT（与 ``docs/00`` 设计稿
-        存在偏差），但 AGENTS.md 禁止修改既有列类型/可空性/含义。本服务按 seed
-        脚本同样思路用 ``SELECT MAX(id)+1`` 显式发号以保持基线零变更。
-        并发与单测场景下够用；后续若需要严格序数，再独立 PR 引入发号器。
-        """
-        result = await self._session.execute(
-            select(func.max(model.id))
-        )
-        max_id = result.scalar()
-        return int(max_id or 0) + 1
-
     # ---------- 行情 ----------
 
     async def _fetch_quote(
@@ -374,7 +359,6 @@ class TradeService:
         order_no = f"SO{datetime.now(UTC).strftime('%Y%m%d%H%M%S')}{uuid4().hex[:8].upper()}"
         txn_no = f"TX{order_no[2:]}"
         order = FundSimOrder(
-            id=await self._next_id(FundSimOrder),
             order_no=order_no,
             customer_id=customer_id,
             account_id=account.id,
@@ -401,7 +385,6 @@ class TradeService:
         # 普通列）。业务派生：transaction_type / nav / shares / amount / fee / confirmed_at
         txn_type = "买入" if payload.order_side == "buy" else "卖出"
         txn = FundTransaction(
-            id=await self._next_id(FundTransaction),
             transaction_no=txn_no,
             order_id=order.id,
             work_order_id=None,
@@ -460,7 +443,6 @@ class TradeService:
 
         # 写入资金账时**不**触碰生成列
         ledger = FundCashLedger(
-            id=await self._next_id(FundCashLedger),
             ledger_no=f"L{txn_no[2:]}",
             account_id=account.id,
             transaction_id=txn.id,
@@ -502,7 +484,6 @@ class TradeService:
             now_h = datetime.now(UTC).replace(tzinfo=None)
             self._session.add(
                 FundHolding(
-                    id=await self._next_id(FundHolding),
                     customer_id=customer_id,
                     trade_account=trade_account,
                     product_id=product_id,
diff --git a/tests/unit/test_advisor_migration_contract.py b/tests/unit/test_advisor_migration_contract.py
index 1e3de72..9da6d1e 100644
--- a/tests/unit/test_advisor_migration_contract.py
+++ b/tests/unit/test_advisor_migration_contract.py
@@ -38,8 +38,10 @@ def test_advisor_migrations_form_one_chain_from_qyqy_head() -> None:
     assert len(script.get_heads()) == 1
     # 核心断言是上面那句"链收敛到一个 head"；下面钉住当前末端版本，便于发现迁移被误删或分叉。
     # ⚠️ **新增迁移后要同步更新这个值**。2026-09-13 追加了
-    # `20260913_market_price_change_pct`（给 `fin_market_price` 补 `change_pct`）。
-    assert script.get_heads()[0] == "20260913_market_price_change_pct"
+    # `20260913_market_price_change_pct`（给 `fin_market_price` 补 `change_pct`）；
+    # 2026-09-14 追加了 `20260914_baseline_auto_increment`（给 15 张表恢复基线要求的
+    # `AUTO_INCREMENT`，消除 `_next_id` 的并发主键冲突）。
+    assert script.get_heads()[0] == "20260914_baseline_auto_increment"
 
     first = (VERSIONS / ADVISOR_FILES[0]).read_text(encoding="utf-8")
     assert 'down_revision = "20260910_drop_review_separation"' in first