kotlin-flow-state-event-modeling

For a single consumer handling exactly-once events, use Channel(Channel.BUFFERED) exposed via receiveAsFlow() instead of MutableSharedFlow. Default SharedFlow has no replay buffer, so events emitted with no active collector are lost.

Use StateFlow when state always has a value and consumers need synchronous .value reads. Use SharedFlow for hot streams with multiple subscribers and no .value requirement. For single-consumer exactly-once events, consider Channel.receiveAsFlow().

Reading .value and writing back a copy is a non-atomic read-modify-write, so concurrent coroutines can overwrite each other. Use MutableStateFlow.update { current -> ... } which applies the transform atomically against the latest state.

No. WhileSubscribed disconnects upstream when there are no collectors, so .value returns the last cached or initial value. If synchronous .value must be fresh or initialized, use SharingStarted.Eagerly or explicit initialization.

Each call to stateIn launches a new sharing coroutine on the given scope that never completes, so repeated calls leak coroutines. Assign stateIn to a val property once so a single shared instance is reused.

Model absence explicitly with a nullable type, sealed interface UI state, or Result, or use phase initialization where the StateFlow is only exposed after the real value loads. Fake domain sentinels force consumers to treat placeholders as real data.