Stream objective events
Streams objective events and transient execution heartbeats using server-sent events (SSE). Only durable objevt_ event IDs are accepted as Last-Event-ID reconnect cursors. Heartbeats carry hb_ IDs in their payload and no SSE id field; they are not replayed from history. Set includeDeltas to also receive transient assistantMessageDelta and reasoningDelta text fragments (dlt_ IDs, no SSE id field, never replayed).
Authorizations
Bearer authentication header of the form Bearer <token>, where <token> is your auth token.
Path Parameters
"workspace_01HXKD2E5NQM3T9AYWCF133E3Q"
"obj_01HXKD2E5NQM3T9AYWCFQAZGFV"
Query Parameters
Also stream transient assistantMessageDelta and reasoningDelta events: text fragments as the model generates them, ahead of the durable assistantMessage and reasoning events. Off by default.
Response
A stream of Server-Sent Events
Durable events use objevt_ IDs, the only IDs accepted as reconnect cursors. Live-only heartbeats use hb_ IDs and live-only text deltas use dlt_ IDs; neither has an SSE id: field.
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"objwin_01HXKD2E5NQM3T9AYWCFN7BSTR"
Elapsed time of the work this event records, when it is known at write time (e.g. assistant message generation, tool execution for result/error events). Unset means the event is instantaneous or the duration is not measurable. Serialized as a canonical duration string (e.g. "4.1s"). Always set together with started_at.
^-?(?:0|[1-9][0-9]{0,11})(?:\.[0-9]{1,9})?s$When the work this event records began. Set together with duration, so the work interval is [started_at, started_at + duration]. The event's created_at remains the time the event was persisted.
The event's commit-ordered position in its objective, starting at 1. Sequences are per objective and gapless. History and stream backlogs return events in sequence order. Unset on live-only heartbeats.