diff --git a/crates/fidc-core/src/platform_expr_strategy.rs b/crates/fidc-core/src/platform_expr_strategy.rs
index 4b0d9c7..3c23f4a 100644
--- a/crates/fidc-core/src/platform_expr_strategy.rs
+++ b/crates/fidc-core/src/platform_expr_strategy.rs
@@ -1022,11 +1022,9 @@ impl PlatformExprStrategy {
     }
 
     fn cost_model(&self) -> ChinaAShareCostModel {
-        let mut model = if self.config.aiquant_transaction_cost {
-            ChinaAShareCostModel::aiquant_default()
-        } else {
-            ChinaAShareCostModel::default()
-        };
+        let mut model = ChinaAShareCostModel::from_trading_constraints(
+            self.config.risk_config.trading_constraints,
+        );
         if let Some(value) = self.config.commission_rate {
             model.commission_rate = value;
         }
diff --git a/crates/fidc-core/tests/explicit_order_flow.rs b/crates/fidc-core/tests/explicit_order_flow.rs
index f33126e..2c3d1d0 100644
--- a/crates/fidc-core/tests/explicit_order_flow.rs
+++ b/crates/fidc-core/tests/explicit_order_flow.rs
@@ -3762,11 +3762,14 @@ fn broker_uses_board_specific_min_quantity_and_step_size_for_buy_sizing() {
     )
     .expect("dataset");
     let mut portfolio = PortfolioState::new(10_500.0);
+    let mut risk_config = FidcRiskControlConfig::default();
+    risk_config.static_rules.reject_kcb_buy = false;
     let broker = BrokerSimulator::new_with_execution_price(
         ChinaAShareCostModel::default(),
         ChinaEquityRuleHooks::default(),
         PriceField::Open,
-    );
+    )
+    .with_risk_config(risk_config);
 
     let report = broker
         .execute(