Event

Something that happened asynchronously and needs to re-enter the FSM — the result of an AsyncEffectHandler, not something a user sent. Unlike Input, an Event can never start a flow: it's routed purely by the conversation's current state (see StateDispatcher.transition overload that takes an Event), never by command or callback data.

chatId is an address, like Input.chatId — it says where a handler's next message goes, not which conversation the event belongs to. That is the ConversationKey the async work was launched for, and telek routes by it without asking the event.