Module reducer 

Reducer: projects events onto state (pure functional semantics).

Axiom: state is the projection of the event log. Reducer must be deterministic for replay.

Structs

StateUpdatedOnlyReducer

Reducer that applies only StateUpdated (deserialize payload → replace state); other events no-op. Use for replay when the event log was produced by the graph (StateUpdated, Interrupted, Resumed, Completed).

Traits

Reducer

Reducer applies events to state. Must be pure (deterministic) for replay.