diff --git a/backend/features/market/charts.py b/backend/features/market/charts.py
index 97cd8b7..8b40c94 100644
--- a/backend/features/market/charts.py
+++ b/backend/features/market/charts.py
@@ -12,6 +12,7 @@ from datetime import datetime, time as dt_time, timedelta
 from threading import Lock
 from typing import Any, ClassVar
 
+from backend.bootstrap.config import tushare_code as _stock_market_code
 from backend.data.providers.ifind_client import IfindError, IfindHttpClient
 
 
@@ -475,16 +476,6 @@ def _ifind_point(row: dict[str, Any]) -> dict[str, Any] | None:
     }
 
 
-def _stock_market_code(code: str) -> str:
-    if code.startswith(("4", "8", "9")):
-        suffix = "BJ"
-    elif code.startswith("6"):
-        suffix = "SH"
-    else:
-        suffix = "SZ"
-    return f"{code}.{suffix}"
-
-
 def _number(value: Any) -> float:
     try:
         return float(value or 0)
diff --git a/tests/test_market_symbol_normalization.py b/tests/test_market_symbol_normalization.py
new file mode 100644
index 0000000..9ae7cfa
--- /dev/null
+++ b/tests/test_market_symbol_normalization.py
@@ -0,0 +1,26 @@
+from __future__ import annotations
+
+import unittest
+
+from backend.bootstrap.config import tushare_code
+from backend.features.market import charts
+
+
+class MarketSymbolNormalizationTests(unittest.TestCase):
+    def test_chart_and_market_services_share_one_suffix_converter(self) -> None:
+        self.assertIs(charts._stock_market_code, tushare_code)
+
+    def test_existing_exchange_mapping_is_preserved(self) -> None:
+        cases = {
+            "000001": "000001.SZ",
+            "600000": "600000.SH",
+            "430047": "430047.BJ",
+            "830799": "830799.BJ",
+        }
+        for code, expected in cases.items():
+            with self.subTest(code=code):
+                self.assertEqual(charts._stock_market_code(code), expected)
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/tests/test_preservation_slice_market.py b/tests/test_preservation_slice_market.py
index cd101bd..cc370a6 100644
--- a/tests/test_preservation_slice_market.py
+++ b/tests/test_preservation_slice_market.py
@@ -9,6 +9,7 @@ import chart_data_provider
 import ifind_client
 import realtime_aggregator
 import tushare_client
+from backend.bootstrap import config as bootstrap_config
 from backend.data import realtime
 from backend.data.providers import ifind_client as canonical_ifind
 from backend.data.providers import tushare_client as canonical_tushare
@@ -101,6 +102,18 @@ def top_level_definitions(path: Path) -> dict[str, str]:
     }
 
 
+def function_contract(path: Path, name: str) -> tuple[str, str]:
+    tree = ast.parse(path.read_text(encoding="utf-8"), filename=str(path))
+    function = next(
+        node for node in tree.body if isinstance(node, ast.FunctionDef) and node.name == name
+    )
+    body = ast.Module(body=function.body, type_ignores=[])
+    return (
+        ast.dump(function.args, include_attributes=False),
+        ast.dump(body, include_attributes=False),
+    )
+
+
 class MarketSliceSourceEquivalenceTests(unittest.TestCase):
     def test_market_service_methods_are_exact_original_ast(self) -> None:
         original = class_methods(ORIGINAL_ROOT / "server.py", "DashboardService")
@@ -145,10 +158,21 @@ class MarketSliceSourceEquivalenceTests(unittest.TestCase):
             top_level_definitions(ORIGINAL_ROOT / "tushare_client.py"),
             top_level_definitions(APP_ROOT / "backend/data/providers/tushare_client.py"),
         )
+        original_charts = top_level_definitions(ORIGINAL_ROOT / "chart_data_provider.py")
+        original_charts.pop("_stock_market_code")
         self.assertEqual(
-            top_level_definitions(ORIGINAL_ROOT / "chart_data_provider.py"),
+            original_charts,
             top_level_definitions(APP_ROOT / "backend/features/market/charts.py"),
         )
+        self.assertEqual(
+            function_contract(
+                ORIGINAL_ROOT / "chart_data_provider.py", "_stock_market_code"
+            ),
+            function_contract(
+                APP_ROOT / "backend/bootstrap/config.py", "tushare_code"
+            ),
+        )
+        self.assertIs(charts._stock_market_code, bootstrap_config.tushare_code)
 
     def test_relocated_frontend_preserves_original_market_runtime_and_styles(self) -> None:
         assert_frontend_runtime_matches_audited_baseline(self)