Confirm there are not already settings or features that do what the shop is asking for- Confirmed. Currently, the system allows shoppers to manually increase the item quantity within the cart view beyond the available inventory. While checkout is successfully blocked, there are no existing settings in the dashboard to cap or prevent the quantity adjustment directly within the cart interface.

What does the shop want the product to do?

The shop wants the cart to prevent customers from adding or adjusting item quantities beyond what is currently in stock. If an item has only 1 unit available, the cart should restrict the shopper from increasing the quantity to 2 or more before they reach checkout.

Why/how would it improve sales or efficiency?

This would significantly improve the customer experience by preventing frustration and confusion. When shoppers are allowed to add out-of-stock quantities to their cart, only to be blocked later at checkout, it creates a disruptive, negative shopping experience. Preventing this upfront manages buyer expectations, creates a smoother flow, and prevents the store owner from dealing with customer inquiries or complaints about blocked checkouts.