From e8c890a8443f4a8f995486ffba0e42902494453a Mon Sep 17 00:00:00 2001
From: Mihir Kandoi <kandoimihir@gmail.com>
Date: Tue, 11 Aug 2026 20:54:04 +0530
Subject: [PATCH] fix(selling): preserve explicit UOM during item selection

---
 erpnext/controllers/tests/test_reactivity.py | 24 +++++++++++++++++++-
 erpnext/public/js/controllers/transaction.js |  1 +
 erpnext/utilities/transaction_base.py        | 23 ++++++++++---------
 3 files changed, 36 insertions(+), 12 deletions(-)

diff --git a/erpnext/controllers/tests/test_reactivity.py b/erpnext/controllers/tests/test_reactivity.py
index a4f652722ae..448025ddddc 100644
--- a/erpnext/controllers/tests/test_reactivity.py
+++ b/erpnext/controllers/tests/test_reactivity.py
@@ -72,7 +72,7 @@ class TestReactivity(ERPNextTestSuite):
 		item.barcode = "OLD-BARCODE"
 		item.pricing_rules = "OLD-PRICING-RULE"
 		item.item_code = new_item.name
-		sales_order.process_item_selection(item.idx)
+		sales_order.process_item_selection(item.idx, reset_item_details=True)
 
 		self.assertEqual(item.uom, "Kg")
 		self.assertEqual(item.stock_uom, "Kg")
@@ -82,3 +82,25 @@ class TestReactivity(ERPNextTestSuite):
 		self.assertIsNone(item.barcode)
 		self.assertFalse(item.pricing_rules)
 		self.assertEqual((item.qty, item.warehouse, item.delivery_date), row_state)
+
+	def test_programmatic_item_selection_preserves_explicit_uom(self):
+		from erpnext.accounts.doctype.sales_invoice.test_sales_invoice import create_sales_invoice
+		from erpnext.stock.doctype.item.test_item import make_item
+
+		item = make_item(
+			properties={
+				"is_stock_item": 0,
+				"stock_uom": "Kg",
+				"sales_uom": "Nos",
+				"weight_per_unit": 2,
+				"weight_uom": "Kg",
+			},
+			uoms=[{"uom": "Nos", "conversion_factor": 10}],
+		)
+		sales_invoice = create_sales_invoice(item_code=item.name, uom="Kg", do_not_save=True)
+
+		sales_invoice.process_item_selection(sales_invoice.items[0].idx)
+
+		self.assertEqual(sales_invoice.items[0].uom, "Kg")
+		self.assertEqual(sales_invoice.items[0].conversion_factor, 1)
+		self.assertEqual(sales_invoice.items[0].stock_qty, sales_invoice.items[0].qty)
diff --git a/erpnext/public/js/controllers/transaction.js b/erpnext/public/js/controllers/transaction.js
index 5ecbd839156..015c76c269b 100644
--- a/erpnext/public/js/controllers/transaction.js
+++ b/erpnext/public/js/controllers/transaction.js
@@ -783,6 +783,7 @@ erpnext.TransactionController = class TransactionController extends erpnext.taxe
 				method: "process_item_selection",
 				args: {
 					item_idx: item.idx,
+					reset_item_details: true,
 				},
 				callback: function (r) {
 					if (!r.exc) {
diff --git a/erpnext/utilities/transaction_base.py b/erpnext/utilities/transaction_base.py
index 87cd0cd365b..af398b5990b 100644
--- a/erpnext/utilities/transaction_base.py
+++ b/erpnext/utilities/transaction_base.py
@@ -349,23 +349,24 @@ class TransactionBase(StatusUpdater):
 		)
 
 	@frappe.whitelist()
-	def process_item_selection(self, item_idx: int):
+	def process_item_selection(self, item_idx: int, reset_item_details: bool = False):
 		# Server side 'item' doc. Update this to reflect in UI
 		item_obj = self.get("items", {"idx": item_idx})[0]
 
 		if not item_obj.item_code:
 			return
 
-		# Do not carry item-specific values from the previously selected item.
-		for fieldname in (
-			"weight_per_unit",
-			"weight_uom",
-			"uom",
-			"conversion_factor",
-			"barcode",
-			"pricing_rules",
-		):
-			item_obj.set(fieldname, None)
+		if cint(reset_item_details):
+			# Do not carry item-specific values from the previously selected item.
+			for fieldname in (
+				"weight_per_unit",
+				"weight_uom",
+				"uom",
+				"conversion_factor",
+				"barcode",
+				"pricing_rules",
+			):
+				item_obj.set(fieldname, None)
 
 		# 'item_details' has latest item related values
 		item_details = self.fetch_item_details(item_obj)