Starting in version 2026-07, the hook on checkout UI extensions, and the capability it depends on, are deprecated. Existing extensions will continue to work on current and prior API versions, but this API will be removed in a future version, so you should plan to migrate.
The following are deprecated:
(Preact hook) in checkout UI extensions- The
capability in the extension’sshopify.extension.tomlconfiguration file
If you currently use to enforce merchant business rules, migrate to a cart and checkout validation Function. These Functions run server-side and apply your rules consistently across all checkout surfaces, including express wallets and agentic checkout.
If you use to reject discount codes, migrate that logic to the discount Function API, which now supports rejecting discount codes with a custom message.
To learn more and if you've got a use case that's keeping you from moving to Shopify Functions: https://community.shopify.dev/t/the-buyer-journey-intercept-api-is-now-deprecated/35930.