SHAREPOINT: a feature carries a Version and UpgradeActions (VersionRange, CustomUpgradeAction, AddContentTypeField) that run when a newer solution is deployed over an older one. SPICE: the fidelity survey found UpgradeActions SILENTLY DROPPED (Class 1). EF migrations already cover the schema (DbMigratorHostedService); content changes between versions - a renamed field, a moved list - have no declared path. Needed before the second production release, not the first.