Build local external client apps in your scratch org. Before Spring '26, local external client apps couldn't be created on scratch orgs. At that time, the only way to get an external client app on a scratch org was to package it and associate it with an existing external client app on a Dev Hub org.
Where: This change applies to Lightning Experience and all versions of the mobile app in Essentials, Professional, Enterprise, Performance, Unlimited, and Developer editions.
When: This feature is available in Winter '26 on a rolling basis.