A Shopify cart transform in a real cart

The transform's price becomes the line's own price

The function behind these carts belongs to an app's cart transform. It reads a cart attribute to decide what to do; given one, it returns an update operation that sets a fixed price per unit on a cart line.

The cart reports that price as the line's price. Nothing marks it as changed: the variant still costs $40.00 in the catalog, and the cart line reads $34.00. Shopify runs an update operation only on Shopify Plus stores and development stores; this store is both.

{
  "operations": [
    {
      "lineUpdate": {
        "cartLineId": "gid://shopify/CartLine/…",
        "price": {
          "adjustment": { "fixedPricePerUnit": { "amount": "34.00" } }
        }
      }
    }
  ]
}

A transform's price is not a discount

The same product on the same store can be priced by a discount function instead. That saving comes back as an allocation on the line, under the discount's title, and the line's price before discounts stays at the variant's.

The transform's saving is in no list. A buy box that builds its strikethrough from the cart's discount allocations has nothing to show for the line above, and one that reads the line's price shows $34.00 as if it were the catalog price.

Without the attribute, the transform leaves no trace

The transform is still registered on the store and its function still runs on this cart. It finds no attribute and returns an empty list of operations.

The cart reads as it would on a store with no cart transform at all.

An update acts on a whole line

An update operation names a cart line, not a quantity of it. This function prices one unit, so for a line of two it returns no operation, and both units stay at the variant's price in one line.

A discount behaves differently. A discount candidate can target one unit of a line, and Shopify then splits the line in two, as the second cart shows.

Discount codes are taken from the transform's price

To a discount, the transform's price is the price. An order code's percentage was taken from $34.00, so a margin forecast for a buyer with a code starts from the transform's price.

A product code on the same line applied as well. Two product discounts on one line do not stack; a transform's price and a product discount do, because only one of them is a discount.

The delivery rates are the store's own

A price set by a transform changes merchandise. With a delivery address, this cart was quoted the rates the store quotes for the same product at its catalog price, and nothing discounted them.

How this was verified

Every cart on this page was built through the Storefront API on a Shopify Plus development store we keep for this, on API version 2026-10, and read back as Shopify priced it. The store sells one product in these carts: Single Bag, at $40.00, also sold on a selling plan named “Every 30 days” that has no pricing policy. It quotes two delivery rates to a US address.

It has one automatic app discount, titled “Offer Suite”, with a product class and a shipping class, set to combine with product, order and shipping discounts. Its function reads a cart attribute: with it, the function takes 25% off one unit of Single Bag bought once, or $8.00 off the unit on its selling plan, and makes the cheapest delivery rate free. Without it, the function returns no operations.

The same app has a cart transform registered on the store. Its function reads a cart attribute of the same kind: with it, the function sets the price of one unit of Single Bag bought once to $34.00. Without it, or for a line of more than one unit, the function returns no operations.

A suite builds these carts again and reads the discount settings from the store before it does. A statement that no longer matches the cart takes this page down until it is corrected, and no cart stands for more than 90 days without being built again. This is what one store returned on one API version: your store’s plan, markets and other apps can change the result, so build the cart.

Seen something different on your store? Write to privacy@offersuite.io with the cart and we’ll run it.