When a product is unavailable, our default behavior is to return the last valid cart and errors on the cart.messages. Products already added to the cart may become unavailable due to merchant manual customizations (e.g. manually changing pickup points/seller in the cart). This behavior can lead to a 500 error on the validateCart mutation, making the cart unavailable to customer actions, such as deleting the product from the cart.

Simulation

It is not an easy context to simulate; it may involve customization on the store side. But an example would be changing from a pickup point where the product was available to one where it is not anymore.

Workaround

As a workaround, the team developed a feature flag to change the default cart behavior of returning errors from the server-side, allowing unavailable products in the cart and transferring the responsibility of handle error scenarios to the client-side through merchant customizations. https://github.com/vtex/faststore/pull/2938