fix: trigger pricing recalculation when SupplierPart pack_quantity changes

src/backend/InvenTree/company/models.py

@@ -1039,6 +1039,36 @@ def get_api_url():
     )
 
 
+@receiver(post_save, sender=SupplierPart, dispatch_uid='post_save_supplier_part')
+def after_save_supplier_part(sender, instance, created, **kwargs):
+    """Callback function when a SupplierPart is created or updated.
+
+    Triggers a pricing update for the linked Part, so that changes to
+    pack_quantity are reflected in Part pricing and BOM cost rollups.
+    """
+    if (
+        InvenTree.ready.canAppAccessDatabase(allow_test=settings.TESTING_PRICING)
+        and not InvenTree.ready.isImportingData()
+        and instance.part
+    ):
+        instance.part.schedule_pricing_update(create=True)
+
+
+@receiver(post_delete, sender=SupplierPart, dispatch_uid='post_delete_supplier_part')
+def after_delete_supplier_part(sender, instance, **kwargs):
+    """Callback function when a SupplierPart is deleted.
+
+    Triggers a pricing update for the linked Part, so that removal of a
+    supplier part is reflected in Part pricing and BOM cost rollups.
+    """
+    if (
+        InvenTree.ready.canAppAccessDatabase(allow_test=settings.TESTING_PRICING)
+        and not InvenTree.ready.isImportingData()
+        and instance.part
+    ):
+        instance.part.schedule_pricing_update(create=False)
+
+
 @receiver(
     post_save, sender=SupplierPriceBreak, dispatch_uid='post_save_supplier_price_break'
 )

src/backend/InvenTree/part/test_pricing.py

@@ -173,6 +173,38 @@ def test_supplier_part_pricing(self):
         self.assertIsNone(pricing.supplier_price_min)
         self.assertIsNone(pricing.supplier_price_max)
 
+    @override_settings(TESTING_PRICING=True)
+    def test_supplier_part_pack_quantity_update(self):
+        """Test that changing pack_quantity on a SupplierPart triggers pricing recalculation."""
+        pricing = self.part.pricing
+
+        supplier = company.models.Company.objects.create(
+            name='Pack Test Supplier', is_supplier=True
+        )
+
+        sp = company.models.SupplierPart.objects.create(
+            supplier=supplier, part=self.part, SKU='PACK_TEST', pack_quantity='1'
+        )
+
+        company.models.SupplierPriceBreak.objects.create(
+            part=sp, quantity=1, price=50, price_currency='USD'
+        )
+
+        pricing.refresh_from_db()
+
+        # Price per unit should be $50 / 1 = $50
+        self.assertEqual(pricing.supplier_price_min, Money(50, 'USD'))
+
+        # Now update pack_quantity to 100 (i.e. 100 units per pack)
+        sp.pack_quantity = '100'
+        sp.save()
+
+        pricing.refresh_from_db()
+
+        # Price per unit should now be $50 / 100 = $0.50
+        self.assertEqual(pricing.supplier_price_min, Money('0.5', 'USD'))
+        self.assertEqual(pricing.supplier_price_max, Money('0.5', 'USD'))
+
     @override_settings(TESTING_PRICING=True)
     def test_internal_pricing(self):
         """Tests for internal price breaks."""