diff --git a/UnitTestProject/Modules/SwapModule/DealInterestsScenarioTest.cs b/UnitTestProject/Modules/SwapModule/DealInterestsScenarioTest.cs
index ae3c5e42..1631b512 100644
--- a/UnitTestProject/Modules/SwapModule/DealInterestsScenarioTest.cs
+++ b/UnitTestProject/Modules/SwapModule/DealInterestsScenarioTest.cs
@@ -422,6 +422,174 @@ namespace YLErp.Modules.SwapModule
             Console.WriteLine($"连续5天归档：InterestIncomeSum 从0递增到{runningIncomeSum:F6} = 5×{DailyInterest:F6} ✅");
         }
 
+        // ================================================================
+        // 场景4：互换→收盘→再攒→再互换 守恒验证
+        // ================================================================
+
+        #region 场景4：多次互换结算守恒
+
+        /// <summary>
+        /// [DI_SWAP_MULTI_001] 攒10天→互换结清→再攒5天→再互换结清
+        /// ---------------------------------------------------------------
+        /// 验证：第一次互换后 InterestIncomeSum≈当天新计（攒的10天付了），
+        ///       再攒5天后 InterestIncomeSum≈6天（5天新攒+1天当天新计），
+        ///       第二次互换后 InterestIncomeSum≈当天新计（攒的6天又付了）。
+        ///
+        /// 守恒约束：两次互换结算的 TdCloseInterest 之和 = 全程利息（15天+2天新计）。
+        /// </summary>
+        [TestMethod]
+        public void DI_SWAP_MULTI_001_多次互换结算守恒()
+        {
+            var td = CreateTrade();
+            var position = CreateInterestPosition();
+
+            // --- Phase 1: 攒10天（4/27~5/6），到5/6 ---
+            var date10 = StartDate.AddDays(10); // 5/7
+            decimal sum10days = Math.Round(Principal * FixedRate * 10 / AnnualDays,
+                ConsGlobal.PriceRound, MidpointRounding.AwayFromZero);
+
+            var preEod10 = CreatePreEod(date10.AddDays(-1), sum10days - DailyInterest); // 前日=9天
+            // 当天新计让它到10天
+            var svc1 = new StubEodPositionService();
+            svc1.ExecuteDealInterests(new List<swap_position> { position },
+                new List<eod_swap_position> { preEod10 }, date10, td,
+                new List<swap_flow_event>(), Principal, 0m, 0m, 1m, Principal);
+            var eod10days = svc1.PersistedPositions[0];
+            AssertDecimal(sum10days, eod10days.InterestIncomeSum, "10天后待实现应=10天利息");
+            Console.WriteLine($"Phase1: 攒10天 InterestIncomeSum={eod10days.InterestIncomeSum:F6}");
+
+            // --- Phase 2: 5/7 互换结清 ---
+            var swapDate1 = date10; // 同天互换
+            var svc2 = new StubEodPositionService();
+            var swapEvt1 = CreateSwapFlowEvent(swapDate1, sum10days);
+            var swapResult1 = svc2.ExecuteSaveEodInterestPosition(
+                eod10days, null, position, td, swapDate1, new List<swap_flow_event> { swapEvt1 });
+
+            // 互换后待实现≈当天新计（攒的10天付了，但当天又产生1天新计）
+            decimal dailyInc = Math.Round(Principal * FixedRate / AnnualDays,
+                ConsGlobal.PriceRound, MidpointRounding.AwayFromZero);
+            AssertDecimal(dailyInc, swapResult1.InterestIncomeSum, "第一次互换后待实现≈当天新计");
+            decimal firstRealized = swapResult1.TdCloseInterest;
+            Console.WriteLine($"Phase2: 第一次互换 TdCloseInterest={firstRealized:F6}, 待实现={swapResult1.InterestIncomeSum:F6}");
+
+            // --- Phase 3: 再攒5天 ---
+            decimal runningSum = swapResult1.InterestIncomeSum;
+            var runningDate = swapDate1.AddDays(1);
+            for (int i = 0; i < 5; i++)
+            {
+                var svc = new StubEodPositionService();
+                var preEod = CreatePreEod(runningDate.AddDays(-1), runningSum);
+                // 需要 preEod.RealizedInterest 累积
+                preEod.RealizedInterest = swapResult1.RealizedInterest;
+                svc.ExecuteDealInterests(new List<swap_position> { position },
+                    new List<eod_swap_position> { preEod }, runningDate, td,
+                    new List<swap_flow_event>(), Principal, 0m, 0m, 1m, Principal);
+                runningSum = svc.PersistedPositions[0].InterestIncomeSum;
+                runningDate = runningDate.AddDays(1);
+            }
+            Console.WriteLine($"Phase3: 再攒5天后 InterestIncomeSum={runningSum:F6}");
+
+            // --- Phase 4: 再互换结清 ---
+            var svc4 = new StubEodPositionService();
+            var preEodFinal = CreatePreEod(runningDate.AddDays(-1), runningSum);
+            preEodFinal.RealizedInterest = swapResult1.RealizedInterest;
+            var swapEvt2 = CreateSwapFlowEvent(runningDate, runningSum);
+            var swapResult2 = svc4.ExecuteSaveEodInterestPosition(
+                preEodFinal, null, position, td, runningDate, new List<swap_flow_event> { swapEvt2 });
+            decimal secondRealized = swapResult2.TdCloseInterest;
+            Console.WriteLine($"Phase4: 第二次互换 TdCloseInterest={secondRealized:F6}, 待实现={swapResult2.InterestIncomeSum:F6}");
+
+            // 守恒：两次互换实现的 + 最终待实现 = 全程天数 × dailyInc
+            // 全程天数 = 10天(Phase1) + 1天(第一次互换当天新计) + 5天(Phase3) + 1天(第二次互换当天新计) = 17天
+            // 但第一次互换的当天新计进了 InterestIncomeSum 没进 TdCloseInterest，
+            // 第二次互换同理。所以守恒 = RealizedInterest合计 + 最终InterestIncomeSum = 全程利息
+            decimal totalDays = 10 + 1 + 5 + 1; // 17天
+            decimal expectedTotalInterest = Math.Round(Principal * FixedRate * totalDays / AnnualDays,
+                ConsGlobal.PriceRound, MidpointRounding.AwayFromZero);
+            decimal actualTotal = swapResult2.RealizedInterest + swapResult2.InterestIncomeSum;
+            Console.WriteLine($"守恒: RealizedInterest({swapResult2.RealizedInterest:F6}) + InterestIncomeSum({swapResult2.InterestIncomeSum:F6}) = {actualTotal:F6}");
+            Console.WriteLine($"期望: {totalDays}天 × {dailyInc:F6} = {expectedTotalInterest:F6}");
+            AssertDecimal(expectedTotalInterest, actualTotal,
+                "已实现+待实现 应=全程利息（守恒）");
+        }
+
+        #endregion
+
+        // ================================================================
+        // 场景5：预付金腿（marginTypes ratio 翻转）符号验证
+        // ================================================================
+
+        #region 场景5：预付金腿 ratio 翻转
+
+        /// <summary>
+        /// [DI_MARGIN_001] 预付金腿互换结清后 RealizedInterest 应为负（支付方向）
+        /// ---------------------------------------------------------------
+        /// 预付金腿 InterestDirection=收取(1)，但 marginTypes 会把 ratio 翻转为 -1。
+        /// SwapPositionValue 应为负（负债），RealizedInterest 也应为负（券商支付）。
+        /// 验证 cs:789-793 的 ratio 翻转逻辑。
+        /// ---------------------------------------------------------------
+        /// </summary>
+        [TestMethod]
+        public void DI_MARGIN_001_预付金腿RealizedInterest为负()
+        {
+            var service = new StubEodPositionService();
+            var td = CreateTrade();
+            var settleDate = new DateTime(2026, 5, 10);
+
+            // 预付金腿（初始预付金 InterestMode=5，InterestDirection=收取）
+            var marginPosition = new swap_position
+            {
+                id = 2001, SwapTradeId = 1, PositionType = (int)PositionTypeFlag.Unknown,
+                InterestDirection = (int)SwapDirectionEnum.收取, InterestMode = (int)InterestModeEnum.初始预付金,
+                InterestRateDefault = 0.005m, InterestPrincipalFix = 500m,
+                PosiStartDate = StartDate, PosiMatuirityDate = ExerciseDate,
+                IsInitial = true, Invalid = false, InterestType = (int)InterestTypeEnum.单利,
+                IsAnnualized = true, interest_rest_days = 1, interest_rule = 0,
+                FloatRateUnderlyingCode = null,
+                InterestSwapInterval = null
+            };
+
+            // 攒10天的预付金利息
+            decimal marginDaily = Math.Round(500m * 0.005m / AnnualDays,
+                ConsGlobal.PriceRound, MidpointRounding.AwayFromZero);
+            decimal margin10days = marginDaily * 10;
+            var preEod = new eod_swap_position
+            {
+                id = 200, SwapTradeId = 1, PositionId = 2001, ValueDate = settleDate.AddDays(-1),
+                ClientId = 999998, InterestDirection = (int)SwapDirectionEnum.收取,
+                InterestMode = (int)InterestModeEnum.初始预付金,
+                InterestIncomeSum = margin10days, InterestProfitSum = margin10days,
+                RealizedInterest = 0m, InterestRateDefault = 0.005m,
+                TdInterestPrincipal = 500m, PosiNotionalValue = 500m,
+                InterestType = (int)InterestTypeEnum.单利, IsAnnualized = true,
+                interest_rest_days = 1, FloatRate = 0m
+            };
+
+            // 互换结清
+            var swapEvent = new swap_flow_event
+            {
+                id = 3001, SwapTradeId = 1, EventType = (int)SwapFlowEventTypeEnum.互换,
+                EventDate = settleDate, UnwindDate = settleDate, PositionId = 2001,
+                InterestDirection = (int)SwapDirectionEnum.收取,
+                InterestAmount = margin10days, InterestClosePnL = -margin10days, // 预付金 ratio 翻转后为负
+                InterestRate = 0.005m, InterestMode = (int)InterestModeEnum.初始预付金,
+                InterestPrincipal = 500m, FloatRate = 0m,
+                DataState = (int)SwapFlowDateStateEnum.完成
+            };
+
+            var result = service.ExecuteSaveEodInterestPosition(
+                preEod, null, marginPosition, td, settleDate, new List<swap_flow_event> { swapEvent });
+
+            // 预付金 marginTypes 翻转 ratio=-1
+            // RealizedInterest = 0 + TdCloseInterest(margin10days) * ratio(-1) = -margin10days
+            AssertDecimal(-margin10days, result.RealizedInterest,
+                "预付金腿 RealizedInterest 应为负（ratio翻转后支付方向）");
+            Console.WriteLine($"预付金腿 RealizedInterest={result.RealizedInterest:F6}（负=支付）✅");
+            Console.WriteLine($"SwapPositionValue={result.SwapPositionValue:F6}（应≈当天新计×ratio=-正）");
+        }
+
+        #endregion
+
         #endregion
     }
 }