diff --git a/src/main/java/com/ffii/fpsms/m18/model/M18BomForShopSaveRequest.kt b/src/main/java/com/ffii/fpsms/m18/model/M18BomForShopSaveRequest.kt
index ecadc84..eceebd2 100644
--- a/src/main/java/com/ffii/fpsms/m18/model/M18BomForShopSaveRequest.kt
+++ b/src/main/java/com/ffii/fpsms/m18/model/M18BomForShopSaveRequest.kt
@@ -79,7 +79,7 @@ data class M18UdfProductSaveValue(
     val udfIngredients: String? = null,
     /** Line UOM: [com.ffii.fpsms.modules.master.entity.UomConversion.code] (same unit as [udfqty]). */
     val udfBaseUnit: String? = null,
-    /** M18 vendor id from latest synced PO for the material: local [com.ffii.fpsms.modules.master.entity.Shop.m18Id] or M18 `ven` search (PF BE when BOM is PF). */
+    /** M18 vendor id ([StSearchType.VENDOR]) for the BOM business entity: PP → [M18Config.BEID_PP], PF → [M18Config.BEID_PF]. */
     val udfSupplier: Long? = null,
     /**
      * M18 UOM id for price/purchase unit on the **M18-linked** PO line (`m18DataLog` present):
diff --git a/src/main/java/com/ffii/fpsms/m18/service/M18BomForShopService.kt b/src/main/java/com/ffii/fpsms/m18/service/M18BomForShopService.kt
index 5227ea2..dbd06d5 100644
--- a/src/main/java/com/ffii/fpsms/m18/service/M18BomForShopService.kt
+++ b/src/main/java/com/ffii/fpsms/m18/service/M18BomForShopService.kt
@@ -389,7 +389,7 @@ open class M18BomForShopService(
     /**
      * Resolves M18 vendor id for BOM material line supplier:
      * - PF BOMs: M18 search by supplier code + [M18Config.BEID_PF]
-     * - PP / other: local [Shop.m18Id] by code, then M18 search with [M18Config.BEID_PP] when needed
+     * - PP BOMs: M18 search by supplier code + [M18Config.BEID_PP] (never local [Shop.m18Id] first — duplicate codes may be PF ids)
      */
     private fun resolveSupplierM18Id(
         latestPoLine: PurchaseOrderLine?,
@@ -406,28 +406,24 @@ open class M18BomForShopService(
         if (supplierCode == null) {
             return directM18Id
         }
-        if (directM18Id != null && (targetBeId == null || poBeId == targetBeId)) {
-            return directM18Id
-        }
-
-        val cacheKey = "$supplierCode|$flowTypeId"
-        cache[cacheKey]?.let { return it }
 
-        val resolved = when (flowTypeId) {
-            2 -> m18VendorLookupService.findVendorM18IdByCode(supplierCode, m18Config.BEID_PF)
-                ?: directM18Id.also {
-                    if (it == null) {
-                        logger.warn("[M18 BOM] PF vendor M18 id not found for supplierCode=$supplierCode")
-                    }
-                }
-            3 -> shopService.findVendorByCode(supplierCode)?.m18Id?.takeIf { it > 0L }
-                ?: m18VendorLookupService.findVendorM18IdByCode(supplierCode, m18Config.BEID_PP)
-                ?: directM18Id
-            else -> shopService.findVendorByCode(supplierCode)?.m18Id?.takeIf { it > 0L }
-                ?: directM18Id
+        if (flowTypeId == 2 || flowTypeId == 3) {
+            val cacheKey = "$supplierCode|$flowTypeId"
+            cache[cacheKey]?.let { return it }
+            val beId = if (flowTypeId == 2) m18Config.BEID_PF else m18Config.BEID_PP
+            val beLabel = if (flowTypeId == 2) "PF" else "PP"
+            val resolved =
+                m18VendorLookupService.findVendorM18IdByCode(supplierCode, beId)
+                    ?: directM18Id.takeIf { poBeId != null && poBeId == targetBeId }
+            if (resolved == null) {
+                logger.warn("[M18 BOM] $beLabel vendor M18 id not found for supplierCode=$supplierCode")
+            }
+            cache[cacheKey] = resolved
+            return resolved
         }
-        cache[cacheKey] = resolved
-        return resolved
+
+        return shopService.findVendorByCode(supplierCode)?.m18Id?.takeIf { it > 0L }
+            ?: directM18Id
     }
 
     private fun resolveFlowTypeId(code: String): Int = when {