Deploy FlexiPage Assignments in Salesforce: What Moves Between Orgs (and What Doesn't)
You build a Lightning page — a FlexiPage — assign it as the record page for an object, deploy it to the next org, and it doesn't show up. The page is there; the assignment isn't. Or you try to move the assignment and the deploy hard-fails instead. The behavior looks random until you see the cause: Salesforce stores a Lightning page assignment separately from the page, across two different metadata types depending on how the page is scoped. Nearly every assignment does deploy through the Metadata API — org defaults on the object, app/profile/record-type activations on the Custom App — as long as you deploy it from the right container; the one exception is a record-type-specific assignment with no app or profile, which has no metadata field to carry it.