diff --git a/UnitTestProject/Modules/SwapModule/PrepaidPrincipalClosingChainTraceTest.cs b/UnitTestProject/Modules/SwapModule/PrepaidPrincipalClosingChainTraceTest.cs
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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using YLErp.DBModels;
+using YLErp.DBModels.Enums;
+using YLErp.Model;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace YLErp.Modules.SwapModule
+{
+    /// <summary>
+    /// 预付金腿「收盘递推链」trace 测试
+    /// ============================================================================
+    /// 背景：8.7 全部平仓时预付金端系统值=20.83(≈6天)，Excel 预期本次利息=10.41(3天)。
+    /// 已证明(GetInterests/CalcDailySimpleInterest) 8.7 平仓利息完全由「前一日收盘归档的
+    /// eod_swap_position.ValueDate」地板决定：ValueDate=8.4→3天→10.41(Excel)，ValueDate≈8.1→6天→20.83(系统)。
+    ///
+    /// 本测试回答用户的核心疑问：「平仓页面是否依赖前一日收盘递推？」
+    ///   —— 是。SwapUnwind 取 lastEod(ValueDate&lt;unwindDate) 的 eod 归档作为 preEodPosition；
+    ///      收盘链 SwapPositionCompose→DealInterests 四个分支全部把 newEodPayPosition.ValueDate=settleDate。
+    /// 因此：若收盘链每天正常运行，预付金腿 eod.ValueDate 应逐日推进到部分平仓日 8.4；
+    ///      系统读到 ValueDate≈8.1 说明该腿 eod 在 8.1 之后没被收盘链重新生成（递推链在 8.4 断了），
+    ///      属「收盘缺失/滞后」而非利息公式 bug。
+    ///
+    /// 本测试用纯内存驱动 SwapPositionCompose，从交易开始日 7.28 逐日收盘到 8.4(部分平仓)，
+    /// 捕获预付金腿每日 eod.ValueDate，断言其正确推进到 8.4。
+    /// ============================================================================
+    [TestClass]
+    public class PrepaidPrincipalClosingChainTraceTest
+    {
+        private const int SwapTradeId = 777;
+        private static readonly DateTime TradeStart = new(2026, 7, 28);
+        private static readonly DateTime SwapDate = new(2026, 7, 31);   // 先互换
+        private static readonly DateTime ResetDate = new(2026, 8, 3);   // FR007 重置
+        private static readonly DateTime PartialDate = new(2026, 8, 4); // 部分平仓 40%
+        private const long PrepayInitialId = 2;
+        private const long PrepayRealId = 3;
+        private const long FloatId = 1;
+
+        #region 可测试化子类（驱动收盘链，不连库）
+
+        private sealed class TraceEodService : TestableSwapEodPositionService
+        {
+            private readonly List<trade> _trades;
+            private readonly List<swap_position> _positions;
+            private List<eod_swap_position> _eodPositions;
+            private readonly List<trade_extend> _extends;
+            private List<swap_flow_event> _currentFlowEvents;
+
+            public List<eod_swap_position> EodPositions => _eodPositions;
+
+            public TraceEodService(
+                List<trade> trades, List<swap_position> positions,
+                List<eod_swap_position> eodPositions, List<eod_swap> eodSwaps,
+                List<trade_extend> extends)
+                : base(nameof(PrepaidPrincipalClosingChainTraceTest))
+            {
+                _trades = trades; _positions = positions;
+                _eodPositions = eodPositions; _extends = extends;
+                _currentFlowEvents = new List<swap_flow_event>();
+            }
+
+            // 收盘链 seam override（对齐 SwapPositionComposeScenarioTest）
+            protected override List<trade> FindActiveSwapTrades(DateTime settleDate, IEnumerable<int> clientIds) => _trades;
+            protected override List<swap_position> FindAllSwapPositions(List<int> tradeIds) => _positions;
+            protected override List<trade_extend> FindTradeExtends(List<int> tradeIds) => _extends;
+            protected override List<eod_swap> FindEodSwapsByDate(DateTime valueDate)
+                // 从已归档 eod 持仓派生 eod_swap 父记录（稳健，避免依赖 SaveEodSwapRecord seam 回填）
+                => _eodPositions.Where(x => x.SwapTradeId == SwapTradeId)
+                    .Select(x => x.ValueDate).Distinct()
+                    .Select(d => new eod_swap { SwapTradeId = SwapTradeId, ValueDate = d })
+                    .ToList();
+            protected override List<swap_flow_event> FindFlowEvents(int swapTradeId, DateTime settleDate) => _currentFlowEvents;
+            protected override List<swap_flow_event> FindCompletedFlowEvents(List<int> tradeIds) => _currentFlowEvents;
+            protected override List<eod_swap_position> FindEodSwapPositions(int swapTradeId, DateTime preSettleDate)
+                => _eodPositions.Where(x => x.SwapTradeId == swapTradeId && x.ValueDate >= preSettleDate).ToList();
+            protected override List<swap_position> FindSwapPositions(int swapTradeId)
+                => _positions.Where(x => x.SwapTradeId == swapTradeId && !x.IsInitial).ToList();
+
+            protected override underlying_manager GetUnderlyingData(string underlyingCode)
+                => new underlying_manager { ValueAddedTax = 0m, UnderlyingInstrumentType = "TBonds" };
+            protected override decimal GetUnderlyingPrice(string code, DateTime settleDate, out decimal vobp)
+            { vobp = 0m; return 100m; }
+            protected override decimal CalcBondPayment(string underlyingCode, DateTime fromDate, DateTime toDate, decimal qty, int shortRatio, int directionRatio) => 0m;
+
+            protected override void SaveEodSwapRecord(trade td, DateTime settleDate, DateTime preSettleDate)
+            {
+                // eod_swap 父记录由 FindEodSwapsByDate 从归档 eod 持仓派生，此处无需操作
+            }
+            protected override void ExecuteInTransaction(Action action) => action();
+            protected override void ClearSwapPositionsForCompose(trade td, DateTime tradeDate, List<int> eventTypes) { }
+            public override void ClearSwapPositions(trade td, DateTime valueDate, List<int> eventTypes, bool delAfter) { }
+            protected override swap_event AddSwapEvent(DateTime tradeDate, int swapTradeId, int eventType, string data, int clientCashId, bool save, string reason)
+            { return new swap_event { id = 1 }; }
+
+            // GetPreDealDate 默认命中 DB，覆写为安全早期日期
+            public override DateTime? GetPreDealDate(int tradeId, DateTime settleDate, List<int> eventTypes)
+                => TradeStart;
+
+            // 利息计算 stub（本测试只关心 eod.ValueDate 递推，不关心利息金额）
+            protected override List<swap_flow_event> CalcSwapInterests(
+                trade td, trade_extend tradeExtend, DateTime valueDate, DateTime unwindDate,
+                List<eod_swap_position> eodPositions, List<swap_position> positions,
+                decimal posiNotionalValue, decimal posiLongNotionalValue, decimal posiShortNotionalValue,
+                decimal closePosiNotionalValue, decimal closePrecent, int eventType, bool tdClose, bool needPrice,
+                decimal grossPrice, decimal orginPv, bool add = false, bool settment = true, bool newCalcLast = false,
+                List<swap_flow_event> closeList = null)
+            {
+                return positions.Select(p => new swap_flow_event
+                {
+                    PositionId = p.id,
+                    InterestPrincipal = p.InterestPrincipalFix,
+                    InterestRate = 0.021111m,
+                    FloatRate = 0m
+                }).ToList();
+            }
+
+            /// <summary>对指定日期收盘，并把生成的 eod / eod_swap 回填，供下一日递推。</summary>
+            public void RunClose(DateTime settleDate, DateTime preSettleDate, List<swap_flow_event> flowEvents)
+            {
+                _currentFlowEvents = flowEvents ?? new List<swap_flow_event>();
+                SwapPositionCompose(settleDate, preSettleDate, null);
+                // 回填：把本次持久化的 eod 并入 _eodPositions
+                foreach (var eod in PersistedPositions.Where(x => x.SwapTradeId == SwapTradeId))
+                {
+                    if (!_eodPositions.Any(x => x.id == eod.id))
+                        _eodPositions.Add(eod);
+                }
+            }
+
+            /// <summary>取预付金腿截至某日的最新 eod（ValueDate 最大）。</summary>
+            public eod_swap_position LatestPrepayEod()
+                => _eodPositions
+                    .Where(x => x.SwapTradeId == SwapTradeId && x.PositionId == PrepayInitialId)
+                    .OrderByDescending(x => x.ValueDate)
+                    .FirstOrDefault();
+        }
+
+        #endregion
+
+        #region 工厂方法
+
+        private static trade CreateTrade()
+            => new trade
+            {
+                id = SwapTradeId, TradeNumber = "TRACE-PREPAY-001", ClientId = 10,
+                TradeType = "收益互换", TradeDate = TradeStart, StartDate = TradeStart,
+                ExerciseDate = TradeStart.AddYears(1), TradeStatus = "确认成交", ValidState = "Valid",
+                QuoteCurrency = "CNY", SettlementCurrency = "CNY", StructureType = "普通债券类收益互换",
+                OriginalStockEqvNotional = 100000, TradePrice = 0
+            };
+
+        private static trade_extend CreateExtend()
+            => new trade_extend
+            {
+                TradeId = SwapTradeId,
+                ExtendJson = @"{""NeedOpenFee"":false,""AnnualDays"":365,""SettlementRules"":0,""Direction"":1,""FlowBookMode"":0,""InterestCalcMode"":""01""}"
+            };
+
+        private static swap_position CreateFloatPosition()
+            => new swap_position
+            {
+                id = FloatId, SwapTradeId = SwapTradeId, PosiDirection = 1, PositionType = (int)PositionTypeFlag.Long,
+                UnderlyingCode = "220205.IB", UnderlyingInstrumentType = "TBonds",
+                ContractSize = 1m, CountRatio = 1m, IsInitial = true, Invalid = false,
+                PosiQuantity = 1000, PosiNotionalValue = 1000,
+                PosiNetPrice = 1.0050m, PosiGrossPrice = 1.0020m,
+                InterestDirection = 0
+            };
+
+        private static swap_position CreatePrepayInitial()
+            => new swap_position
+            {
+                id = PrepayInitialId, SwapTradeId = SwapTradeId, PosiDirection = 0,
+                InterestDirection = (int)SwapDirectionEnum.收取,
+                InterestMode = (int)InterestModeEnum.初始预付金,
+                InterestPrincipalFix = 100000.23m, IsInitial = true, Invalid = false,
+                PosiStartDate = TradeStart, PosiMatuirityDate = TradeStart.AddYears(1),
+                InterestSwapInterval = "[]", InterestRateDefault = 0.021111m
+            };
+
+        private static swap_position CreatePrepayReal()
+            => new swap_position
+            {
+                id = PrepayRealId, PositionId = PrepayInitialId, SwapTradeId = SwapTradeId, PosiDirection = 0,
+                InterestDirection = (int)SwapDirectionEnum.收取,
+                InterestMode = (int)InterestModeEnum.初始预付金,
+                InterestPrincipalFix = 60000.138m, IsInitial = false, Invalid = false
+            };
+
+        private static swap_flow_event CreatePartialCloseFlow(DateTime date)
+            => new swap_flow_event
+            {
+                SwapTradeId = SwapTradeId, PositionId = FloatId,
+                EventType = (int)SwapEventTypeEnum.平仓,
+                Quantity = 400, EventDate = date, UnwindDate = date,
+                MarkClosePnl = 500m, CloseFee = 10m, DataState = (int)SwapFlowDateStateEnum.完成
+            };
+
+        #endregion
+
+        [TestMethod]
+        public void 收盘递推链_预付金腿ValueDate应从交易开始日逐日推进到部分平仓日8_4()
+        {
+            var td = CreateTrade();
+            var extend = CreateExtend();
+            var positions = new List<swap_position>
+            {
+                CreateFloatPosition(), CreatePrepayInitial(), CreatePrepayReal()
+            };
+            var eodPositions = new List<eod_swap_position>();
+            var eodSwaps = new List<eod_swap>();
+
+            var svc = new TraceEodService(
+                new List<trade> { td }, positions, eodPositions, eodSwaps,
+                new List<trade_extend> { extend });
+
+            // 从交易开始日逐日收盘：7.28 → 7.31(互换) → 8.3(重置) → 8.4(部分平仓)
+            var closes = new List<(DateTime settle, DateTime pre, List<swap_flow_event> flows)>
+            {
+                (TradeStart, TradeStart.AddDays(-1), new List<swap_flow_event>()),
+                (SwapDate, TradeStart, new List<swap_flow_event>
+                {
+                    new swap_flow_event { SwapTradeId=SwapTradeId, PositionId=FloatId,
+                        EventType=(int)SwapEventTypeEnum.互换, EventDate=SwapDate, UnwindDate=SwapDate,
+                        DataState=(int)SwapFlowDateStateEnum.完成 }
+                }),
+                (ResetDate, SwapDate, new List<swap_flow_event>()),
+                (PartialDate, ResetDate, new List<swap_flow_event> { CreatePartialCloseFlow(PartialDate) }),
+            };
+
+            Console.WriteLine("=== 收盘递推链：预付金腿 eod.ValueDate 逐日追踪 ===");
+            foreach (var c in closes)
+            {
+                svc.RunClose(c.settle, c.pre, c.flows);
+                var prepay = svc.LatestPrepayEod();
+                var vd = prepay?.ValueDate ?? default;
+                Console.WriteLine($"  收盘 {c.settle:yyyy-MM-dd} → 预付金腿 eod.ValueDate={vd:yyyy-MM-dd} (TdInterestPrincipal={prepay?.TdInterestPrincipal})");
+            }
+
+            var finalPrepay = svc.LatestPrepayEod();
+            Assert.IsNotNull(finalPrepay, "预付金腿应有 eod 归档");
+            // 收盘链每天把每条腿 eod.ValueDate 设为当日收盘日；部分平仓日 8.4 收盘后应为 8.4
+            Assert.AreEqual(PartialDate, finalPrepay.ValueDate.Date,
+                "收盘链应把预付金腿 eod.ValueDate 正确推进到部分平仓日 8.4（证明收盘代码本身正确，系统 8.1 是递推链在 8.4 断了）");
+
+            Console.WriteLine($">> 结论：收盘链正确推进到 {finalPrepay.ValueDate:yyyy-MM-dd}；" +
+                              $"系统读到 8.1 说明该笔交易的预付金腿 eod 在 8.4 部分平仓日未被收盘链重新生成（收盘缺失/滞后），非利息公式 bug。");
+        }
+    }
+}