diff --git a/crates/fidc-core/src/broker.rs b/crates/fidc-core/src/broker.rs
index f912b54..7f11057 100644
--- a/crates/fidc-core/src/broker.rs
+++ b/crates/fidc-core/src/broker.rs
@@ -20,10 +20,16 @@ pub struct BrokerExecutionReport {
 }
 
 #[derive(Debug, Clone, Copy)]
-struct ExecutionFill {
+struct ExecutionLeg {
     price: f64,
     quantity: u32,
+}
+
+#[derive(Debug, Clone)]
+struct ExecutionFill {
+    quantity: u32,
     next_cursor: NaiveDateTime,
+    legs: Vec<ExecutionLeg>,
     unfilled_reason: Option<&'static str>,
 }
 
@@ -968,7 +974,6 @@ where
             return Ok(());
         }
 
-        let cash_before = portfolio.cash();
         let fill = self.resolve_execution_fill(
             date,
             symbol,
@@ -985,32 +990,87 @@ where
             None,
             None,
         );
-        let (filled_qty, execution_price) = if let Some(fill) = fill {
+        let (filled_qty, execution_legs) = if let Some(fill) = fill {
             execution_cursors.insert(symbol.to_string(), fill.next_cursor);
             if self.uses_serial_execution_cursor(reason) {
                 *global_execution_cursor = Some(fill.next_cursor);
             }
             partial_fill_reason =
                 merge_partial_fill_reason(partial_fill_reason, fill.unfilled_reason);
-            (fill.quantity, fill.price)
+            (fill.quantity, fill.legs)
         } else {
-            (filled_qty, self.sell_price(snapshot))
+            (
+                filled_qty,
+                vec![ExecutionLeg {
+                    price: self.sell_price(snapshot),
+                    quantity: filled_qty,
+                }],
+            )
         };
-        let gross_amount = execution_price * filled_qty as f64;
-        let cost = self.cost_model.calculate_with_order_state(
-            date,
-            OrderSide::Sell,
-            gross_amount,
-            Some(order_id),
-            commission_state,
-        );
-        let net_cash = gross_amount - cost.total();
+        if execution_legs.len() > 1 {
+            report.diagnostics.push(format!(
+                "order_split_fill symbol={symbol} side=sell order_id={order_id} fills={}",
+                execution_legs.len()
+            ));
+        }
+        for leg in &execution_legs {
+            let leg_cash_before = portfolio.cash();
+            let gross_amount = leg.price * leg.quantity as f64;
+            let cost = self.cost_model.calculate_with_order_state(
+                date,
+                OrderSide::Sell,
+                gross_amount,
+                Some(order_id),
+                commission_state,
+            );
+            let net_cash = gross_amount - cost.total();
+            let realized_pnl = portfolio
+                .position_mut(symbol)
+                .sell(leg.quantity, leg.price)
+                .map_err(BacktestError::Execution)?;
+            portfolio.apply_cash_delta(net_cash);
 
-        let realized_pnl = portfolio
-            .position_mut(symbol)
-            .sell(filled_qty, execution_price)
-            .map_err(BacktestError::Execution)?;
-        portfolio.apply_cash_delta(net_cash);
+            report.fill_events.push(FillEvent {
+                date,
+                order_id: Some(order_id),
+                symbol: symbol.to_string(),
+                side: OrderSide::Sell,
+                quantity: leg.quantity,
+                price: leg.price,
+                gross_amount,
+                commission: cost.commission,
+                stamp_tax: cost.stamp_tax,
+                net_cash_flow: net_cash,
+                reason: reason.to_string(),
+            });
+            report.position_events.push(PositionEvent {
+                date,
+                symbol: symbol.to_string(),
+                delta_quantity: -(leg.quantity as i32),
+                quantity_after: portfolio
+                    .position(symbol)
+                    .map(|pos| pos.quantity)
+                    .unwrap_or(0),
+                average_cost: portfolio
+                    .position(symbol)
+                    .map(|pos| pos.average_cost)
+                    .unwrap_or(0.0),
+                realized_pnl_delta: realized_pnl,
+                reason: reason.to_string(),
+            });
+            report.account_events.push(AccountEvent {
+                date,
+                cash_before: leg_cash_before,
+                cash_after: portfolio.cash(),
+                total_equity: self.total_equity_at(
+                    date,
+                    portfolio,
+                    data,
+                    self.account_mark_price_field(),
+                )?,
+                note: format!("sell {symbol} {reason}"),
+            });
+        }
         portfolio.prune_flat_positions();
         *intraday_turnover.entry(symbol.to_string()).or_default() += filled_qty;
 
@@ -1041,46 +1101,6 @@ where
             status,
             reason: order_reason,
         });
-        report.fill_events.push(FillEvent {
-            date,
-            order_id: Some(order_id),
-            symbol: symbol.to_string(),
-            side: OrderSide::Sell,
-            quantity: filled_qty,
-            price: execution_price,
-            gross_amount,
-            commission: cost.commission,
-            stamp_tax: cost.stamp_tax,
-            net_cash_flow: net_cash,
-            reason: reason.to_string(),
-        });
-        report.position_events.push(PositionEvent {
-            date,
-            symbol: symbol.to_string(),
-            delta_quantity: -(filled_qty as i32),
-            quantity_after: portfolio
-                .position(symbol)
-                .map(|pos| pos.quantity)
-                .unwrap_or(0),
-            average_cost: portfolio
-                .position(symbol)
-                .map(|pos| pos.average_cost)
-                .unwrap_or(0.0),
-            realized_pnl_delta: realized_pnl,
-            reason: reason.to_string(),
-        });
-        report.account_events.push(AccountEvent {
-            date,
-            cash_before,
-            cash_after: portfolio.cash(),
-            total_equity: self.total_equity_at(
-                date,
-                portfolio,
-                data,
-                self.account_mark_price_field(),
-            )?,
-            note: format!("sell {symbol} {reason}"),
-        });
         Ok(())
     }
 
@@ -1355,14 +1375,14 @@ where
             Some(portfolio.cash()),
             value_budget.map(|budget| budget + 400.0),
         );
-        let (filled_qty, execution_price) = if let Some(fill) = fill {
+        let (filled_qty, execution_legs) = if let Some(fill) = fill {
             execution_cursors.insert(symbol.to_string(), fill.next_cursor);
             if self.uses_serial_execution_cursor(reason) {
                 *global_execution_cursor = Some(fill.next_cursor);
             }
             partial_fill_reason =
                 merge_partial_fill_reason(partial_fill_reason, fill.unfilled_reason);
-            (fill.quantity, fill.price)
+            (fill.quantity, fill.legs)
         } else {
             let execution_price = self.snapshot_execution_price(snapshot, OrderSide::Buy);
             let filled_qty = self.affordable_buy_quantity(
@@ -1386,7 +1406,13 @@ where
                     ),
                 );
             }
-            (filled_qty, execution_price)
+            (
+                filled_qty,
+                vec![ExecutionLeg {
+                    price: execution_price,
+                    quantity: filled_qty,
+                }],
+            )
         };
         if filled_qty == 0 {
             report.order_events.push(OrderEvent {
@@ -1407,21 +1433,70 @@ where
             return Ok(());
         }
 
-        let cash_before = portfolio.cash();
-        let gross_amount = execution_price * filled_qty as f64;
-        let cost = self.cost_model.calculate_with_order_state(
-            date,
-            OrderSide::Buy,
-            gross_amount,
-            Some(order_id),
-            commission_state,
-        );
-        let cash_out = gross_amount + cost.total();
+        if execution_legs.len() > 1 {
+            report.diagnostics.push(format!(
+                "order_split_fill symbol={symbol} side=buy order_id={order_id} fills={}",
+                execution_legs.len()
+            ));
+        }
+        for leg in &execution_legs {
+            let leg_cash_before = portfolio.cash();
+            let gross_amount = leg.price * leg.quantity as f64;
+            let cost = self.cost_model.calculate_with_order_state(
+                date,
+                OrderSide::Buy,
+                gross_amount,
+                Some(order_id),
+                commission_state,
+            );
+            let cash_out = gross_amount + cost.total();
 
-        portfolio.apply_cash_delta(-cash_out);
-        portfolio
-            .position_mut(symbol)
-            .buy(date, filled_qty, execution_price);
+            portfolio.apply_cash_delta(-cash_out);
+            portfolio
+                .position_mut(symbol)
+                .buy(date, leg.quantity, leg.price);
+
+            report.fill_events.push(FillEvent {
+                date,
+                order_id: Some(order_id),
+                symbol: symbol.to_string(),
+                side: OrderSide::Buy,
+                quantity: leg.quantity,
+                price: leg.price,
+                gross_amount,
+                commission: cost.commission,
+                stamp_tax: cost.stamp_tax,
+                net_cash_flow: -cash_out,
+                reason: reason.to_string(),
+            });
+            report.position_events.push(PositionEvent {
+                date,
+                symbol: symbol.to_string(),
+                delta_quantity: leg.quantity as i32,
+                quantity_after: portfolio
+                    .position(symbol)
+                    .map(|pos| pos.quantity)
+                    .unwrap_or(0),
+                average_cost: portfolio
+                    .position(symbol)
+                    .map(|pos| pos.average_cost)
+                    .unwrap_or(0.0),
+                realized_pnl_delta: 0.0,
+                reason: reason.to_string(),
+            });
+            report.account_events.push(AccountEvent {
+                date,
+                cash_before: leg_cash_before,
+                cash_after: portfolio.cash(),
+                total_equity: self.total_equity_at(
+                    date,
+                    portfolio,
+                    data,
+                    self.account_mark_price_field(),
+                )?,
+                note: format!("buy {symbol} {reason}"),
+            });
+        }
         *intraday_turnover.entry(symbol.to_string()).or_default() += filled_qty;
 
         let status = if filled_qty < requested_qty {
@@ -1451,46 +1526,6 @@ where
             status,
             reason: order_reason,
         });
-        report.fill_events.push(FillEvent {
-            date,
-            order_id: Some(order_id),
-            symbol: symbol.to_string(),
-            side: OrderSide::Buy,
-            quantity: filled_qty,
-            price: execution_price,
-            gross_amount,
-            commission: cost.commission,
-            stamp_tax: cost.stamp_tax,
-            net_cash_flow: -cash_out,
-            reason: reason.to_string(),
-        });
-        report.position_events.push(PositionEvent {
-            date,
-            symbol: symbol.to_string(),
-            delta_quantity: filled_qty as i32,
-            quantity_after: portfolio
-                .position(symbol)
-                .map(|pos| pos.quantity)
-                .unwrap_or(0),
-            average_cost: portfolio
-                .position(symbol)
-                .map(|pos| pos.average_cost)
-                .unwrap_or(0.0),
-            realized_pnl_delta: 0.0,
-            reason: reason.to_string(),
-        });
-        report.account_events.push(AccountEvent {
-            date,
-            cash_before,
-            cash_after: portfolio.cash(),
-            total_equity: self.total_equity_at(
-                date,
-                portfolio,
-                data,
-                self.account_mark_price_field(),
-            )?,
-            note: format!("buy {symbol} {reason}"),
-        });
         Ok(())
     }
 
@@ -1734,9 +1769,12 @@ where
                 .map(|start_time| date.and_time(start_time) + Duration::seconds(1))
                 .unwrap_or_else(|| date.and_hms_opt(0, 0, 1).expect("valid midnight"));
             return Some(ExecutionFill {
-                price: execution_price,
                 quantity,
                 next_cursor,
+                legs: vec![ExecutionLeg {
+                    price: execution_price,
+                    quantity,
+                }],
                 unfilled_reason: self.buy_reduction_reason(
                     cash_limit.unwrap_or(f64::INFINITY),
                     gross_limit,
@@ -1793,6 +1831,7 @@ where
         let mut filled_qty = 0_u32;
         let mut gross_amount = 0.0_f64;
         let mut last_timestamp = None;
+        let mut legs = Vec::new();
         let mut budget_block_reason = None;
         let mut saw_quote_after_cursor = false;
 
@@ -1865,6 +1904,10 @@ where
             gross_amount += quote_price * take_qty as f64;
             filled_qty += take_qty;
             last_timestamp = Some(quote.timestamp);
+            legs.push(ExecutionLeg {
+                price: quote_price,
+                quantity: take_qty,
+            });
 
             if filled_qty >= requested_qty {
                 break;
@@ -1876,9 +1919,9 @@ where
         }
 
         Some(ExecutionFill {
-            price: gross_amount / filled_qty as f64,
             quantity: filled_qty,
             next_cursor: last_timestamp.unwrap() + Duration::seconds(1),
+            legs,
             unfilled_reason: if filled_qty < requested_qty {
                 budget_block_reason.or(if saw_quote_after_cursor {
                     Some("intraday quote liquidity exhausted")
diff --git a/crates/fidc-core/tests/explicit_order_flow.rs b/crates/fidc-core/tests/explicit_order_flow.rs
index fbaac40..cbecc6e 100644
--- a/crates/fidc-core/tests/explicit_order_flow.rs
+++ b/crates/fidc-core/tests/explicit_order_flow.rs
@@ -638,6 +638,150 @@ fn broker_emits_partial_fill_reason_when_intraday_quote_liquidity_exhausted() {
     );
 }
 
+#[test]
+fn broker_splits_intraday_quote_fills_and_tracks_commission_by_order() {
+    let date = NaiveDate::from_ymd_opt(2024, 1, 10).unwrap();
+    let data = DataSet::from_components_with_actions_and_quotes(
+        vec![Instrument {
+            symbol: "000002.SZ".to_string(),
+            name: "Test".to_string(),
+            board: "SZ".to_string(),
+            round_lot: 100,
+            listed_at: None,
+            delisted_at: None,
+            status: "active".to_string(),
+        }],
+        vec![DailyMarketSnapshot {
+            date,
+            symbol: "000002.SZ".to_string(),
+            timestamp: Some("2024-01-10 10:18:00".to_string()),
+            day_open: 10.0,
+            open: 10.0,
+            high: 10.2,
+            low: 9.8,
+            close: 10.0,
+            last_price: 10.0,
+            bid1: 9.99,
+            ask1: 10.01,
+            prev_close: 10.0,
+            volume: 100_000,
+            tick_volume: 100_000,
+            bid1_volume: 80_000,
+            ask1_volume: 80_000,
+            trading_phase: Some("continuous".to_string()),
+            paused: false,
+            upper_limit: 11.0,
+            lower_limit: 9.0,
+            price_tick: 0.01,
+        }],
+        vec![DailyFactorSnapshot {
+            date,
+            symbol: "000002.SZ".to_string(),
+            market_cap_bn: 50.0,
+            free_float_cap_bn: 45.0,
+            pe_ttm: 15.0,
+            turnover_ratio: Some(2.0),
+            effective_turnover_ratio: Some(1.8),
+            extra_factors: BTreeMap::new(),
+        }],
+        vec![CandidateEligibility {
+            date,
+            symbol: "000002.SZ".to_string(),
+            is_st: false,
+            is_new_listing: false,
+            is_paused: false,
+            allow_buy: true,
+            allow_sell: true,
+            is_kcb: false,
+            is_one_yuan: false,
+        }],
+        vec![BenchmarkSnapshot {
+            date,
+            benchmark: "000300.SH".to_string(),
+            open: 100.0,
+            close: 100.0,
+            prev_close: 99.0,
+            volume: 1_000_000,
+        }],
+        Vec::new(),
+        vec![
+            IntradayExecutionQuote {
+                date,
+                symbol: "000002.SZ".to_string(),
+                timestamp: date.and_hms_opt(10, 18, 3).unwrap(),
+                last_price: 10.01,
+                bid1: 10.0,
+                ask1: 10.02,
+                bid1_volume: 1,
+                ask1_volume: 1,
+                volume_delta: 1,
+                amount_delta: 0.0,
+                trading_phase: Some("continuous".to_string()),
+            },
+            IntradayExecutionQuote {
+                date,
+                symbol: "000002.SZ".to_string(),
+                timestamp: date.and_hms_opt(10, 18, 6).unwrap(),
+                last_price: 10.03,
+                bid1: 10.02,
+                ask1: 10.04,
+                bid1_volume: 1,
+                ask1_volume: 1,
+                volume_delta: 1,
+                amount_delta: 0.0,
+                trading_phase: Some("continuous".to_string()),
+            },
+        ],
+    )
+    .expect("dataset");
+    let mut portfolio = PortfolioState::new(1_000_000.0);
+    let broker = BrokerSimulator::new_with_execution_price(
+        ChinaAShareCostModel::default(),
+        ChinaEquityRuleHooks::default(),
+        PriceField::Last,
+    );
+
+    let report = broker
+        .execute(
+            date,
+            &mut portfolio,
+            &data,
+            &StrategyDecision {
+                rebalance: false,
+                target_weights: BTreeMap::new(),
+                exit_symbols: BTreeSet::new(),
+                order_intents: vec![OrderIntent::Value {
+                    symbol: "000002.SZ".to_string(),
+                    value: 2_500.0,
+                    reason: "intraday_split_fill".to_string(),
+                }],
+                notes: Vec::new(),
+                diagnostics: Vec::new(),
+            },
+        )
+        .expect("broker execution");
+
+    assert_eq!(report.order_events.len(), 1);
+    assert_eq!(
+        report.order_events[0].status,
+        fidc_core::OrderStatus::Filled
+    );
+    assert_eq!(report.fill_events.len(), 2);
+    assert_eq!(report.fill_events[0].quantity, 100);
+    assert_eq!(report.fill_events[1].quantity, 100);
+    assert!((report.fill_events[0].price - 10.02).abs() < 1e-9);
+    assert!((report.fill_events[1].price - 10.04).abs() < 1e-9);
+    assert!((report.fill_events[0].commission - 5.0).abs() < 1e-9);
+    assert_eq!(report.fill_events[1].commission, 0.0);
+    assert_eq!(report.account_events.len(), 2);
+    assert!(
+        report
+            .diagnostics
+            .iter()
+            .any(|item| item.contains("order_split_fill symbol=000002.SZ side=buy"))
+    );
+}
+
 #[test]
 fn rebalance_optimizer_skips_unfunded_buy_when_existing_position_cannot_sell() {
     let prev_date = NaiveDate::from_ymd_opt(2024, 1, 9).unwrap();