diff --git a/lastleg-service/src/main/java/com/baiyue/lastleg/returnreceipt/mapper/ReturnPackingTraceMapper.java b/lastleg-service/src/main/java/com/baiyue/lastleg/returnreceipt/mapper/ReturnPackingTraceMapper.java
index 1081009f5..93b7ba81c 100644
--- a/lastleg-service/src/main/java/com/baiyue/lastleg/returnreceipt/mapper/ReturnPackingTraceMapper.java
+++ b/lastleg-service/src/main/java/com/baiyue/lastleg/returnreceipt/mapper/ReturnPackingTraceMapper.java
@@ -22,6 +22,9 @@ public interface ReturnPackingTraceMapper {
     @Select("SELECT return_no, SUM(CASE WHEN target_carton_mark=#{mark} THEN quantity ELSE -quantity END) AS quantity FROM ll_return_packing_trace WHERE customer_id=#{customerId} AND sku_code=#{sku} AND (source_carton_mark=#{mark} OR target_carton_mark=#{mark}) GROUP BY return_no HAVING quantity>0 ORDER BY return_no")
     List<Ownership> ownership(@Param("customerId") String customerId, @Param("mark") String mark, @Param("sku") String sku);
 
+    @Select("SELECT COALESCE(SUM(CASE WHEN target_carton_mark=#{mark} THEN quantity ELSE -quantity END),0) FROM ll_return_packing_trace WHERE customer_id=#{customerId} AND sku_code=#{sku} AND (source_carton_mark=#{mark} OR target_carton_mark=#{mark})")
+    long netTrackedQuantity(@Param("customerId") String customerId, @Param("mark") String mark, @Param("sku") String sku);
+
     @Select("SELECT id,source_carton_mark,target_carton_mark,return_no,sku_code,quantity,created_at FROM ll_return_packing_trace WHERE customer_id=#{customerId} AND return_no=#{returnNo} ORDER BY created_at,id")
     List<Trace> listReturn(@Param("customerId") String customerId, @Param("returnNo") String returnNo);
 
diff --git a/lastleg-service/src/main/java/com/baiyue/lastleg/returnreceipt/service/ReturnInventoryService.java b/lastleg-service/src/main/java/com/baiyue/lastleg/returnreceipt/service/ReturnInventoryService.java
index c398f297e..748ec70f7 100644
--- a/lastleg-service/src/main/java/com/baiyue/lastleg/returnreceipt/service/ReturnInventoryService.java
+++ b/lastleg-service/src/main/java/com/baiyue/lastleg/returnreceipt/service/ReturnInventoryService.java
@@ -1014,8 +1014,7 @@ public class ReturnInventoryService {
             throw conflict("目标箱已有合箱预占，不能并入");
         if (existingTarget != null) ReturnCartonCountGuard.requireConfirmed(existingTarget);
         if (existingTarget != null) for (var item : cartonItems.lockCarton(existingTarget.getId())) {
-            long tracked = packingTrace.ownership(customerId, targetMark, item.getSkuCode()).stream()
-                .mapToLong(com.baiyue.lastleg.returnreceipt.mapper.ReturnPackingTraceMapper.Ownership::quantity).sum();
+            long tracked = packingTrace.netTrackedQuantity(customerId, targetMark, item.getSkuCode());
             if (tracked < value(item.getQuantity())) {
                 String[] origins = required(existingTarget.getSourceReturnNo(), "目标箱来源退货单缺失").split(",");
                 if (origins.length != 1) throw conflict("历史目标混箱缺少 SKU 来源明细");
diff --git a/lastleg-service/src/test/java/com/baiyue/lastleg/returnreceipt/service/ReturnInventoryServiceTest.java b/lastleg-service/src/test/java/com/baiyue/lastleg/returnreceipt/service/ReturnInventoryServiceTest.java
index d568b68ae..8ce4717df 100644
--- a/lastleg-service/src/test/java/com/baiyue/lastleg/returnreceipt/service/ReturnInventoryServiceTest.java
+++ b/lastleg-service/src/test/java/com/baiyue/lastleg/returnreceipt/service/ReturnInventoryServiceTest.java
@@ -623,6 +623,32 @@ class ReturnInventoryServiceTest {
         assertThrows(ResponseStatusException.class, () -> service.confirmLabel(new PdaWarehouseIdentity("operator-2", "其他仓", 43L), "RC-SOURCE"));
     }
 
+    @Test
+    void existingTargetSeedsOriginalOwnershipIncludingPreviouslyRemovedQuantity() {
+        var source = prepareConcurrentSource();
+        source.setCountStatus("CONFIRMED");
+        var target = new ReturnInventoryCarton(); target.setId(32L); target.setCartonMark("TARGET");
+        target.setCustomerId("10001"); target.setOverseasWarehouseId("42"); target.setSourceReturnNo("RT-1");
+        target.setSourceBatchNo("RB-1"); target.setStatus("AVAILABLE"); target.setCountStatus("CONFIRMED");
+        target.setTotalQuantity(15L); target.setSkuTypes(1);
+        var sourceLine = item(41L, "SKU-A", 5); var targetLine = item(42L, "SKU-A", 15);
+        when(cartons.lockMark("TARGET")).thenReturn(target);
+        when(cartonItems.lockCarton(31L)).thenReturn(List.of(sourceLine));
+        when(cartonItems.lockCarton(32L)).thenReturn(List.of(targetLine));
+        when(cartonItems.lockSku(32L, "SKU-A")).thenReturn(targetLine);
+        when(cartonItems.listCarton(32L)).thenReturn(List.of(targetLine));
+        when(cartonItems.totalQuantity(32L)).thenAnswer(ignored -> targetLine.getQuantity());
+        when(cartonItems.skuTypes(32L)).thenReturn(1);
+        when(packingTrace.netTrackedQuantity("10001", "TARGET", "SKU-A")).thenReturn(-5L);
+        when(balances.adjustCartonQuantity(anyString(), anyString(), anyString(), anyLong())).thenReturn(1);
+        ReflectionTestUtils.invokeMethod(service, "mergeScoped", new PdaWarehouseIdentity("worker", "worker", 42L),
+            new ReturnInventoryRequests.Merge(List.of("RT-1"), List.of(new ReturnInventoryRequests.ValidItem("SKU-A", 5)),
+                null, null, null, null, "target-reuse"),
+            java.util.Map.of("RC-SOURCE", new java.util.HashMap<>(java.util.Map.of("SKU-A", 5L))), "TARGET", null);
+        verify(packingTrace).insert(anyLong(), eq("10001"), anyLong(), eq(""), eq("TARGET"), eq("RT-1"), eq("SKU-A"), eq(20L), any());
+        assertThat(target.getTotalQuantity()).isEqualTo(20L);
+    }
+
     private ReturnInventoryCarton prepareConcurrentSource() {
         ReturnReceipt receipt = new ReturnReceipt(); receipt.setId(21L);
         ReturnInventoryCarton snapshot = new ReturnInventoryCarton();