On API version 2026-10, Shopify Functions can read metafields attached to delivery options in the cart. You can call metafield(namespace:, key:) on any option in cart.deliveryGroups.deliveryOptions. The returned Metafield exposes value, type, and jsonValue. Metafields on a delivery option are not persisted after checkout; they are attached when a delivery option generator function or shipping carrier service response generates the option, and exist only for that checkout. Access follows existing metafield ownership rules: a function can read metafields in its own app-reserved namespace and in any unprefixed shared namespace, while a namespace reserved by a different app resolves to null. This affects apps that build Delivery Customization Functions and any other function whose input includes delivery options. No action is required.