fix(bot-bridge): subjects 写入端点编码长度收敛到 DB 列宽20 — 21~32字符编码原穿过校验触发 MySQL 1406 整批500, 改为400拒绝 (dama-cma-subjects-write-endpoint-20260912 复核)

backend/app/api/bot_bridge.py

@@ -987,7 +987,10 @@ _SUBJ_FIELDS = ("subject_code", "subject_name", "parent_code", "level", "categor
 _SUBJ_CATEGORIES = ("asset", "liability", "equity", "cost", "income", "expense", "detail", "other")
 _SUBJ_LEVELS = (1, 2, 3)
 _SUBJ_MAX_ROWS = 2000
-_SUBJ_CODE_MAXLEN = 32
+# subject_code / parent_code 长度上限：任务规格为 ≤32，但 DB 列 subjects.subject_code /
+# parent_code 实为 varchar(20) —— 取交集 20。若按 32 放行，21~32 字符的编码会穿过校验直达
+# MySQL，报 (1406, Data too long) → 整批 500（2026-09-12 生产实测），故此处收敛到 DB 列宽。
+_SUBJ_CODE_MAXLEN = 20
 _SUBJ_NAME_MAXLEN = 200
 
 
@@ -1006,7 +1009,7 @@ def _validate_subject_rows(rows, db):
     """行级全量校验（任一错误 → 400 且零落库），返回标准化行 [{字段}]
 
     规则（任务 dama-cma-subjects-write-endpoint-20260912）：
-      subject_code 非空且 ≤32 字符 + 批次内去重；subject_name 非空（DB NOT NULL）且 ≤200；
+      subject_code 非空且 ≤_SUBJ_CODE_MAXLEN（=20，DB varchar(20) 列宽）+ 批次内去重；subject_name 非空（DB NOT NULL）且 ≤200；
       level ∈ {1,2,3}（缺省 1）；parent_code 为空或存在于本表（或本批次内，支持层级同批导入）；
       category 限枚举；is_active ∈ {0,1}（缺省 1）。
     """

backend/tests/test_bot_bridge.py

@@ -493,6 +493,24 @@ class TestSubjectsWrite:
         assert resp.status_code == 400
         assert "subject_name" in str(resp.json())
 
+    def test_code_too_long_400(self, client: TestClient, db: Session):
+        """编码长度上限 = min(任务规格 32, DB varchar(20)) = 20
+
+        生产实测（2026-09-12）：按 32 放行时 21 字符编码穿过校验 → MySQL 1406 Data too long
+        → 整批 500；收敛到 DB 列宽后应 400 拒绝且零落库。
+        """
+        resp = client.post(self.URL, json={"subjects": [
+            self._row("9" * 21, "验证科目")]}, headers=BOT_KEY)
+        assert resp.status_code == 400, resp.json()
+        assert "超长" in str(resp.json())
+        assert db.query(Subject).filter(Subject.subject_code == "9" * 21).count() == 0
+
+    def test_parent_code_too_long_400(self, client: TestClient):
+        resp = client.post(self.URL, json={"subjects": [
+            self._row("9402", "验证子科目", parent_code="9" * 21, level=2)]}, headers=BOT_KEY)
+        assert resp.status_code == 400, resp.json()
+        assert "超长" in str(resp.json())
+
     # ── 落库语义 ──
     def test_dry_run_zero_write(self, client: TestClient, db: Session):
         before = db.query(Subject).count()