Send Message

Append a user message to a session and run a turn.

Returns immediately with just the newly-appended user_message event echoed back; the agent runs asynchronously. To watch the turn unfold, poll GET /sessions/{id}/events?since=N for incremental events or GET /sessions/{id}?since=N for the full snapshot.

Sessions accept new messages regardless of state. Idle sessions (no recent activity) resume on demand; cancelling a session interrupts the in-flight turn but leaves the session live for a follow-up.

curl -X POST "https://api.levainlabs.com/api/v1/sessions/497f6eca-6276-4993-bfeb-53cbbbba6f08/messages" \  -H "Content-Type: application/json" \  -d '{}'

{
  "id": "string",
  "agent_id": "string",
  "agent_version_id": "string",
  "state": "string",
  "created_at": "string",
  "last_activity_at": "string",
  "terminated_at": "string",
  "rounds": [],
  "events": []
}

{
  "detail": [
    {
      "loc": [
        "string"
      ],
      "msg": "string",
      "type": "string",
      "input": null,
      "ctx": {}
    }
  ]
}