diff --git a/app/backend/features/market/charts.py b/app/backend/features/market/charts.py
index 97cd8b7..8b40c94 100644
--- a/app/backend/features/market/charts.py
+++ b/app/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/app/tests/test_market_symbol_normalization.py b/app/tests/test_market_symbol_normalization.py
new file mode 100644
index 0000000..9ae7cfa
--- /dev/null
+++ b/app/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/app/tests/test_preservation_slice_market.py b/app/tests/test_preservation_slice_market.py
index cd101bd..cc370a6 100644
--- a/app/tests/test_preservation_slice_market.py
+++ b/app/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)
diff --git a/docs/governance/code-reduction.md b/docs/governance/code-reduction.md
index b8b7869..b3af6fc 100644
--- a/docs/governance/code-reduction.md
+++ b/docs/governance/code-reduction.md
@@ -20,6 +20,7 @@
 |---|---|---|---|---|
 | CR-01 | LLM供应商传输 | 问师、问天、复盘助手和策略编译各自构造HTTP请求、解析响应和读取错误 | 只保留`backend/llm/transport.py`一个网络出口 | 已完成 |
 | CR-02 | HTTP精确POST委托 | 27个端点重复使用“比较路径、调用无参数处理器、返回”三行分支 | 用公开/受保护两张显式映射统一委托，同时保留复杂路由的原控制流 | 已完成 |
+| CR-03 | 股票市场后缀转换 | Tushare业务与iFinD图表各保留一份完全相同的沪深京代码转换函数 | 图表复用`bootstrap/config.py::tushare_code`，只保留一份函数体 | 已完成 |
 
 ## CR-01验收口径
 
@@ -66,3 +67,25 @@
 
 本批基线为`xiaobai-reduction-01-llm-transport-20260801`；检查点为
 `xiaobai-reduction-02-http-dispatch-20260801`。
+
+## CR-03验收口径
+
+- 图表模块不再定义第二份市场后缀转换函数，仍保留原局部名称和两个调用点。
+- 深市、沪市、北交所的既有映射结果保持不变；不借本批修正或扩展代码规则。
+- 原图表文件除该函数外的所有顶层定义继续与原版AST逐项相等。
+- 原版`_stock_market_code`函数的参数和函数体必须与唯一共享实现AST相等，运行时别名必须指向
+  同一个函数对象。
+
+## CR-03结果
+
+- 删除`backend/features/market/charts.py`中第二份10行定义，以1行导入别名复用共享实现，生产代码
+  净减少9行；全仓后端只剩一份沪深京后缀转换函数体。
+- 未合并实时聚合、东方财富图表、iFinD和Tushare的HTTP传输；它们的缓存、错误、重试和降级语义
+  不同，仅有外形相似，证据不足以安全抽象。
+- 原有迁移期整文件相等断言被等价范围断言、共享函数AST断言和唯一对象断言替代，没有降低门禁。
+- 原版231项、候选317项、纯`app/`导出254项、45项Playwright通过；API/架构注册表、
+  24个JavaScript文件、Git空白检查和SQLite完整性检查通过。
+- 本批不修改图表请求、数据来源、缓存、时间范围、行情计算、前端、CSS、数据库或部署。
+
+本批基线为`xiaobai-reduction-02-http-dispatch-20260801`；检查点为
+`xiaobai-reduction-03-market-symbol-20260801`。