Cart mutations reject unconfirmed writes in POS UI extensions 2026-10

Takes effect

Not announced

Published

11 Oct 2026

In POS UI extensions API version 2026-10 , Cart API mutations reject when Shopify POS doesn't confirm that the cart changed. In earlier versions these mutations resolve whether or not POS applied the write. This is a breaking change for apps that adopt 2026-10 , and those apps need to handle a rejected promise on every cart mutation they call. Apps on 2026-07 and earlier are unaffected. What changed POS reports the outcome of every cart write. Only a success result confirms that the cart changed. Earlier API versions resolve the mutation regardless of that result, so an app can't tell an applied write from a dropped one, and an app can show a fee or a discount as applied when the cart never changed. In 2026-10 , these mutations reject unless POS confirms the write: bulkCartUpdate , removeLineItem , applyCartDiscount , addCartCodeDiscount , removeAllDiscounts , setCustomer , removeCustomer , addLineItemProperties , bulkAddLineItemProperties , removeLineItemProperties , setLineItemDis

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