Quick answer: Unreal classes with replicated property additions failing replication on clients despite CDO regen? Iris archetype version doesn't auto-increment - bump manually after replicated UPROPERTY changes.
Added a new replicated property. Clients on existing build can't sync; archetype version mismatch unreported.
Bump archetype version
UCLASS(net_archetype_version=2)Explicit version. Mismatch becomes visible; can be migrated.
Or build per-class migration
Old version reads via legacy serializer; converts to new on the fly. Heavier; backwards-compat.
Always rebuild clients
For internal teams: rebuild and redistribute. Production clients need migration.
“Archetype versions are part of the contract. Changes to the contract need version bumps.”
Adopt 'bump archetype version on any UPROPERTY change' as a discipline. CI lint that checks.