The standing event stream (SSE) [read]

text/event-stream, stays open across turns. If a run is in flight when the stream opens, its status marks so far (session.status_running, session.error, user.interrupt) are replayed from history under their own ids and timestamps, so a stream opened mid-run still sees the boundary its duration is measured from; a run that has already ended is not replayed — read it from the event history. Everything else is live. Dedupe by event id. Events: agent.message, agent.reasoning, agent.tool_use, agent.tool_result, agent.status, session.status_running, session.status_idle (carries stop_reason — never break on bare idle), session.error (the stream stays open; an idle follows), user.interrupt, session.status_terminated (terminal), session.deleted (terminal). User messages are not sent on the live stream — they appear in the event history only. Reconnect = reopen + list events + dedupe by event id.