The change affects apps using the Customer Account API to create, update, or read customer addresses. Starting with API version 2026-10, the CustomerAddressInput input object and CustomerAddress object include countryCode, which uses the CountryCode enum and accepts ISO 3166-1 alpha-2 codes like US or CA. The existing territoryCode field is marked as deprecated but has not been removed, and existing queries and mutations continue to work as before, including integrations using older API versions.

When adopting API version 2026-10, developers should check customer address queries and mutations for uses of territoryCode and replace them with countryCode. If both fields are supplied in an address input, countryCode takes precedence. Apps using API version 2026-07 or earlier are unchanged and can continue using territoryCode. No immediate disruption is expected, and no removal version has been announced.