Quick answer: Unreal Iris rollback succeeding for single actors but failing on coordinated multi-actor rollback? Per-actor scope; cross-actor dependencies need explicit scope - declare interaction groups.
Rollback for combat that involves multiple actors; partial rollback corrupts state.
Declare interaction group
Iris's interaction groups. Multi-actor scope rolled back atomically.
Or rollback all if any
If any actor in a combat scene rolls back, all do. Coarse but consistent.
Audit cross-actor state
Each cross-actor dependency: explicit rollback scope.
“Rollback scope is per-actor by default. Multi-actor needs explicit grouping.”
If your game has team-based gameplay with rollback, the interaction groups are mandatory.