What does the VARTA error `session_already_ended` mean?
HTTP status: 409 · Type: invalid_request_error
What it means
The session is closed and can't accept another turn.
What causes it
Raised by POST /v1/sessions/{session_id}/turn when the session's ended_at is already set (backend/app/api/v1/sessions.py).
What to do
Open a new session with POST /v1/agents/{agent_id}/load rather than reusing one that has ended.