We recently had an order come through a live 9.0.9 current rev. site that allowed a customer
to purchase a product that went into negative inventory. The setup on the product is basic, using Inventory (Track Product) and (QTY) only. No other inventory options set and our products template is not customized in anyway, just using the out of box one.

I was able to reproduce this on a test site as well. This is how we got there after debugging this live order.

Create a product basic. Under inventory use the Track Product option and add 2-ea to inventory.

Open a new different browser and clear cookies. The Customer was using Safari 17.4 and I tested using Chrome latest version 124.0.6367.119. The customer was using a mobile device and I tested on a desktop. User is anonymous in both cases. Note: (Did not test with Admin or Logged In as a user.)

Find the product through the menu, search i.e. and add 2-ea to basket. Go to basket and now add another 2-ea to the basket and everything works like it should. The notes pop-up and reduces the inventory back to 2-ea. All good at this point. I also tried this several times including leaving the basket and then adding multiple qty’s, again always reverted back with notes (Inventory exceeded and qty’s corrected to the correct inventory amount).

What you need to do now is keep your screen open on the basket and go and have a cup of coffee i.e for about 20-min or so. Now go to the home page from the basket and find the product again through the menu, search i.e. and add another qty in my case 2-ea. The basket creates another line item of 2-ea to the order and allows a completed checkout. The product now shows out of stock and -2 ea. See Screen shot. Screenshot 2024-05-03 at 08-46-22 NGK Spark plug BUHXW-1.png (18kb) downloaded 0 time(s).

Hopefully this makes sense. Please fix.

Thanks again for your help.

I can pm you the logs if you would like.
They clearly show the processes used.

Thanks again.

Hi,

With the help of our dev team, I can reproduce the issue now.

Here are the steps to reproduce:

1. Create a product with 'Track Product' Inventory setting and the stock value as 2
2 Add 2 of the items in basket and proceed to checkout as anonymous user
3. After completing the billing address step, navigate back and add the same product again with quantity 2.

Now you will be able to add the item twice (with quantity 2 each) and complete checkout although the in stock value was 2.

You can see the message is still showing in basket about the quantity exceeded.

This can only happen if the user has not updated the billing info page. Once they are no longer anonymous, the basket combines correctly.

I will report the issue, but some time will be needed to find an appropriate fix.

Thanks for letting us know.