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Posts a follow-up user message to an existing session and starts a new agent turn. The response returns a fresh chat_thread_id — use it to build the polling URL for the assistant’s reply.
Follow-ups can be sent at any time, including while the agent is still working on a previous turn. They will interrupt the in-flight turn.

Request

Path parameters

string (uuid)
required
The session to post the follow-up to.

Body

string
required
The follow-up user message.
string[] (uuid[])
Existing artifacts to attach to this message.
object
Profile reference or inline profile to apply to this turn. Same shape as in Create Session.

Response

string (uuid)
Message ID for the user message you just posted.
string (uuid)
The session this message belongs to.
string (uuid)
The new thread created for this turn. Prefer _links.final_message.href for polling — this field is exposed for cases where you need the thread ID directly.
string (uuid)
The task ID for the agent invocation triggered by this message.
string
Always user for this endpoint.
string
Always message for this endpoint.
string
Echo of the message body you posted.
number | null
Provider-supplied timestamp (epoch seconds). Typically null for user messages.
string (ISO 8601)
When the message was created.
string (ISO 8601)
When the message was last updated.
HATEOAS links — mirror those returned by Create Session so you can reuse the same polling idiom for follow-ups.

Errors