diff --git a/UnitTestProject/Modules/SwapModule/SwapInterestScenario3And4FloatingTest.cs b/UnitTestProject/Modules/SwapModule/SwapInterestScenario3And4FloatingTest.cs
index e6a99ca7..bda6393e 100644
--- a/UnitTestProject/Modules/SwapModule/SwapInterestScenario3And4FloatingTest.cs
+++ b/UnitTestProject/Modules/SwapModule/SwapInterestScenario3And4FloatingTest.cs
@@ -1,10 +1,6 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Newtonsoft.Json;
+using System.Globalization;
 using YLErp;
-using YLErp.DBModels;
 using YLErp.DBModels.Enums;
 using YLErp.Modules.SwapModule;
 
@@ -252,7 +248,7 @@ namespace UnitTestProject.Modules.SwapModule
         private static void DebugCompare(string tag, decimal oracle, decimal actual, eod_swap_position eod = null)
         {
             var diff = actual - oracle;
-            var sb = new System.Text.StringBuilder();
+            var sb = new StringBuilder();
             sb.AppendLine($"[DBG][{tag}] oracle={oracle:F4} actual={actual:F4} diff={diff:F4}");
             if (eod != null)
             {
@@ -401,6 +397,22 @@ namespace UnitTestProject.Modules.SwapModule
             return interests[0];
         }
 
+        /// <summary>用生产同一计息入口 GetInterests 计算“次日 EOD”利息（settment:true，无平仓），返回利息现金流。
+        /// 仅用于跨日毒链携带验证：prevEod.TdInterestPrincipal 经 SwapDealService:1045 的 priorNotional 进入下一日本金。</summary>
+        private swap_flow_event CalcNextDayInterest(trade td, swap_position position, decimal posiNotionalValue,
+            DateTime valueDate, eod_swap_position prevEod)
+        {
+            var svc = new RealSwapDealService(
+                new OptUserInfo(0, nameof(SwapInterestScenario3And4FloatingTest), OptUserFrom.UnitTest), _floatRates, _eod.FlowEvents);
+            var interests = svc.GetInterests(
+                td, td.trade_extend, valueDate, valueDate,
+                new List<eod_swap_position> { prevEod }, new List<swap_position> { position },
+                posiNotionalValue, 0m, 0m,
+                (int)SwapEventTypeEnum.自动互换, false, posiNotionalValue, false, true, false, null);
+            Assert.IsTrue(interests.Count >= 1, "场景4[跨日] GetInterests 应返回至少一条利息现金流 " + valueDate);
+            return interests[0];
+        }
+
         #endregion
 
         #region 业务场景3：第3重置期内全平（平仓日 2026-05-11，closePercent=1）
@@ -421,8 +433,8 @@ namespace UnitTestProject.Modules.SwapModule
         public void 场景3_第3重置期内全平(string note, bool compound, bool calcFirst, bool calcLast,
             int rule, int interestMode, string spreadStr, string oracleStr)
         {
-            var spread = decimal.Parse(spreadStr, System.Globalization.CultureInfo.InvariantCulture);
-            var oracle = decimal.Parse(oracleStr, System.Globalization.CultureInfo.InvariantCulture);
+            var spread = decimal.Parse(spreadStr, CultureInfo.InvariantCulture);
+            var oracle = decimal.Parse(oracleStr, CultureInfo.InvariantCulture);
             var mode = (calcFirst && calcLast) ? "11" : "10";
             var type = compound ? InterestTypeEnum.复利 : InterestTypeEnum.单利;
 
@@ -468,9 +480,9 @@ namespace UnitTestProject.Modules.SwapModule
         public void 场景4_部分平仓后再全平(string note, bool compound, bool calcFirst, bool calcLast,
             int rule, int interestMode, string spreadStr, string oraclePartialStr, string oracleFinalStr)
         {
-            var spread = decimal.Parse(spreadStr, System.Globalization.CultureInfo.InvariantCulture);
-            var oraclePartial = decimal.Parse(oraclePartialStr, System.Globalization.CultureInfo.InvariantCulture);
-            var oracleFinal = decimal.Parse(oracleFinalStr, System.Globalization.CultureInfo.InvariantCulture);
+            var spread = decimal.Parse(spreadStr, CultureInfo.InvariantCulture);
+            var oraclePartial = decimal.Parse(oraclePartialStr, CultureInfo.InvariantCulture);
+            var oracleFinal = decimal.Parse(oracleFinalStr, CultureInfo.InvariantCulture);
             var mode = (calcFirst && calcLast) ? "11" : "10";
             var type = compound ? InterestTypeEnum.复利 : InterestTypeEnum.单利;
 
@@ -535,6 +547,23 @@ namespace UnitTestProject.Modules.SwapModule
             RunDailyEodFromStart(_eod, new DateTime(2026, 5, 12), new DateTime(2026, 5, 19));
             var prevEodFull = _eod.LatestEodForPosition(position.id, new DateTime(2026, 5, 19));
 
+            // 跨日毒链携带守卫（验证“最终结果”而非单日快照）：部分平仓的 TdInterestPrincipal 是带去次日的计息基数，
+            // 利息引擎 GetInterests 的 EOD 路径以 preEod.TdInterestPrincipal 为 priorNotional（SwapDealService:1045）。
+            // 本 harness 的 RollForward 分支因 prior-eod seam 未接到内存 eod 链（DealInterests 收到 eodPosition=null，
+            // rollforward eod 的 TdInterestPrincipal 恒为 0），无法在 rollforward eod 层观察携带——故改为直接在引擎层验证：
+            // 用“正确本金”prevEod 与“生产实际”prevEod 各喂一次 GetInterests，比对下一日本金。二者唯一差异是
+            // prevEod.TdInterestPrincipal；误反推会让生产 partialEod.TdInterestPrincipal 膨胀 ~2.3x，下一日本金同步膨胀，差远超容差→红。
+            var correctPrev = partialEod.Clone();
+            correctPrev.TdInterestPrincipal = expectedTdPrincipal;
+            var nextCorrect = CalcNextDayInterest(td, position, remainingNotional, new DateTime(2026, 5, 12), correctPrev);
+            var nextPoisoned = CalcNextDayInterest(td, position, remainingNotional, new DateTime(2026, 5, 12), partialEod);
+            // 引擎输出 InterestPrincipal 取自 position 状态而非 priorNotional，故比对当日应计 TdInterestAmount
+            // （它经 priorNotional=preEod.TdInterestPrincipal 进入，SwapDealService:1045）。误反推膨胀 ~2.3x→差远超容差红。
+            var carryTol = Math.Max(0.01m, Math.Abs(nextCorrect.TdInterestAmount) * 0.05m);
+            Assert.IsTrue(Math.Abs(nextPoisoned.TdInterestAmount - nextCorrect.TdInterestAmount) <= carryTol,
+                $"场景4[跨日] 毒链携带 {note}: 生产 partialEod.TdInterestPrincipal 应=正确本金(expectedTdPrincipal)，" +
+                $"但引擎次日应计 TdInterestAmount 偏差 {nextPoisoned.TdInterestAmount - nextCorrect.TdInterestAmount}（correct={nextCorrect.TdInterestAmount}, poisoned={nextPoisoned.TdInterestAmount}）");
+
             // 第二步：2026-05-19 全部平仓剩余 70%（consumedInterest 此时从真实累积的 flow event 读取，
             // 真实扣除 5/11 部分平仓已结利息——绝无硬编码 0）
             var fullFlow = CalcCloseFlow(td, position, new DateTime(2026, 5, 19), new List<eod_swap_position>(), remainingNotional, remainingNotional);