diff --git a/shierfeng-fastapi-backend/tests/module_business/test_sql_contract.py b/shierfeng-fastapi-backend/tests/module_business/test_sql_contract.py
index ef5df28..358a283 100644
--- a/shierfeng-fastapi-backend/tests/module_business/test_sql_contract.py
+++ b/shierfeng-fastapi-backend/tests/module_business/test_sql_contract.py
@@ -609,6 +609,18 @@ def _column_definitions(body: str) -> dict[str, str]:
     return definitions
 
 
+def _is_postgres_naive_timestamp_with_default_precision(definition: str) -> bool:
+    return (
+        re.fullmatch(
+            r'[`"]?[a-z_][a-z0-9_]*[`"]?\s+'
+            r'timestamp(?:\s+without\s+time\s+zone)?(?:\s+not\s+null)?',
+            definition.strip(),
+            flags=re.I,
+        )
+        is not None
+    )
+
+
 def _business_menu_rows(sql: str) -> dict[int, list]:
     rows = _insert_rows(sql, 'sys_menu')
     selected = [row for row in rows if row and str(row[0]).isdigit() and int(row[0]) in BUSINESS_MENU_IDS]
@@ -642,7 +654,7 @@ class SqlContractTest(unittest.TestCase):
     def test_postgres_business_datetimes_preserve_default_microsecond_precision(self) -> None:
         self.assertEqual(34, sum(len(columns) for columns in EXPECTED_DATETIME_COLUMNS.values()))
         tables = _create_table_bodies((SQL_ROOT / 'shierfeng-fastapi-pg.sql').read_text(encoding='utf-8'))
-        zero_precision_columns = []
+        invalid_columns = []
         for table, expected_columns in EXPECTED_DATETIME_COLUMNS.items():
             definitions = _column_definitions(tables[table])
             actual_columns = {
@@ -653,10 +665,17 @@ class SqlContractTest(unittest.TestCase):
             self.assertEqual(expected_columns, actual_columns, table)
             for column in expected_columns:
                 definition = definitions[column]
-                self.assertRegex(definition, r'\btimestamp(?:\s+without\s+time\s+zone)?\b')
-                if re.search(r'\btimestamp\s*\(\s*0\s*\)', definition, flags=re.I):
-                    zero_precision_columns.append(f'{table}.{column}')
-        self.assertEqual([], sorted(zero_precision_columns))
+                if not _is_postgres_naive_timestamp_with_default_precision(definition):
+                    invalid_columns.append(f'{table}.{column}')
+        self.assertEqual([], sorted(invalid_columns))
+
+    def test_postgres_datetime_type_validator_rejects_precision_and_timezone_mutations(self) -> None:
+        self.assertTrue(_is_postgres_naive_timestamp_with_default_precision('occurred_at timestamp'))
+        self.assertTrue(
+            _is_postgres_naive_timestamp_with_default_precision('occurred_at timestamp without time zone not null')
+        )
+        self.assertFalse(_is_postgres_naive_timestamp_with_default_precision('occurred_at timestamp(3)'))
+        self.assertFalse(_is_postgres_naive_timestamp_with_default_precision('occurred_at timestamp with time zone'))
 
     def test_initializers_define_fixed_business_menus_and_permissions(self) -> None:
         expected_permissions = {page[-1] for page in EXPECTED_PAGES.values()} | {