diff --git a/svc/routes/production_product_costing.go b/svc/routes/production_product_costing.go
index 1128dbf..c850533 100644
--- a/svc/routes/production_product_costing.go
+++ b/svc/routes/production_product_costing.go
@@ -1963,9 +1963,13 @@ DELETE FROM dbo.spUrtOnMLMas WHERE nOnMLNo = @p1
 		return
 	}
 
-	// V3: Delete base price ONLY if row was created by this app (CreatedUserName starts with BSSAPP).
+	// V3: Delete the base price row we created for this costing date (PriceDate = maliyetTarihi).
+	// We intentionally do NOT delete older base prices for the same item.
 	deletedBasePrice := false
 	if mssqlDB != nil && urunKodu != "" {
+		priceDate := maliyetTarihi.Format("2006-01-02")
+		// Primary rule: delete only the row for this exact date and USD currency.
+		// Safety: require that either CreatedUserName/LastUpdatedUserName matches current user, or one of them starts with BSSAPP.
 		var createdBy sql.NullString
 		var lastBy sql.NullString
 		_ = mssqlDB.QueryRowContext(ctx, `
@@ -1978,11 +1982,23 @@ WHERE ItemTypeCode = 1
   AND ISNULL(CountryCode,'') = 'TR'
   AND ISNULL(SeasonCode,'') = ''
   AND ISNULL(BasePriceCode,0) = 1
-`, urunKodu).Scan(&createdBy, &lastBy)
+  AND CONVERT(date, PriceDate) = CONVERT(date, @p2, 23)
+  AND LTRIM(RTRIM(ISNULL(CurrencyCode,''))) = 'USD'
+`, urunKodu, priceDate).Scan(&createdBy, &lastBy)
 
 		created := strings.ToUpper(strings.TrimSpace(createdBy.String))
 		last := strings.ToUpper(strings.TrimSpace(lastBy.String))
-		if strings.HasPrefix(created, "BSSAPP") && strings.HasPrefix(last, "BSSAPP") {
+		u := strings.ToUpper(strings.TrimSpace(user))
+
+		allowed := false
+		if u != "" && (strings.ToUpper(strings.TrimSpace(createdBy.String)) == u || strings.ToUpper(strings.TrimSpace(lastBy.String)) == u) {
+			allowed = true
+		}
+		if strings.HasPrefix(created, "BSSAPP") || strings.HasPrefix(last, "BSSAPP") {
+			allowed = true
+		}
+
+		if allowed {
 			if _, err := mssqlDB.ExecContext(ctx, `
 DELETE FROM dbo.prItemBasePrice
 WHERE ItemTypeCode = 1
@@ -1990,9 +2006,15 @@ WHERE ItemTypeCode = 1
   AND ISNULL(CountryCode,'') = 'TR'
   AND ISNULL(SeasonCode,'') = ''
   AND ISNULL(BasePriceCode,0) = 1
-`, urunKodu); err == nil {
+  AND CONVERT(date, PriceDate) = CONVERT(date, @p2, 23)
+  AND LTRIM(RTRIM(ISNULL(CurrencyCode,''))) = 'USD'
+`, urunKodu, priceDate); err == nil {
 				deletedBasePrice = true
+			} else {
+				logger.Warn("v3 base price delete failed", "err", err, "urun_kodu", urunKodu, "price_date", priceDate)
 			}
+		} else {
+			logger.Info("v3 base price delete skipped (not owned)", "urun_kodu", urunKodu, "price_date", priceDate, "created_by", createdBy.String, "last_by", lastBy.String, "user", user)
 		}
 	}
 
diff --git a/ui/src/pages/ProductionProductCostingHasCostDetail.vue b/ui/src/pages/ProductionProductCostingHasCostDetail.vue
index e7d1ff6..092367c 100644
--- a/ui/src/pages/ProductionProductCostingHasCostDetail.vue
+++ b/ui/src/pages/ProductionProductCostingHasCostDetail.vue
@@ -85,7 +85,6 @@
               @click="saveChanges"
             />
             <q-btn
-              v-if="isNoCostDetail"
               label="Kaydi Sil"
               icon="delete"
               dense
@@ -907,10 +906,10 @@ const hasUnsavedChanges = computed(() => {
 })
 
 const canDeleteCosting = computed(() => {
-  // Only allow delete for records created from no-cost flow.
-  // UX expectation: delete button becomes available after a costing record exists.
+  // Allow delete only for records created by this app's no-cost flow (we generate >= 100000).
+  // This avoids accidental deletion of legacy OnML records.
   const n = parseInt(String(onMLNo.value || detailHeader.value?.nOnMLNo || detailHeader.value?.NOnMLNo || '0'), 10) || 0
-  return n > 0 && String(detailSource.value || '').trim().toLowerCase() === 'no-cost'
+  return n >= 100000
 })
 
 function persistLocalDraftNow () {