AIAgentSession.UserID — compared with the subscriber connection's user. Server-internal.
The event payload, JSON-encoded.
Conversation.ExternalID — compared with the subscriber's signed scope. Server-internal.
OptionalSourceMJGlobal.ProcessUUID of the instance that first published the event; lets an instance drop its
own message when it echoes back from the replication bus.
What is actually published on REALTIME_SESSION_EVENTS_TOPIC: the wire event plus the server-internal routing snapshot.