Start a new session

Start a new session. The request body is a bare session object (no session wrapper). The server creates a session event and returns it.

No required properties — every field has a server-side fallback.

Auto-generated properties (provided by the server when omitted):

• session_id (string, UUID) — Server generates a UUIDv4 if omitted or if the supplied value is not a valid UUID.

Optional properties with defaults:

• event_name (string) — Falls back to session_name when not provided; defaults to "unknown" if both are absent.
• source (string) — Defaults to "unknown".

Optional properties:

• session_name (string) — Display name for the session.
• start_time (number) — Session start time as Unix milliseconds. The session normalizer uses getInt64() which only accepts numeric types; if a string is passed, the server silently falls back to the current time.
• end_time (number) — Session end time as Unix milliseconds (same numeric-only caveat as start_time).
• duration (number) — Session duration in milliseconds.
• config (object) — Configuration associated with the session.
• inputs (object) — Input data for the session.
• outputs (object) — Output data from the session.
• metadata (object) — Arbitrary metadata.
• user_properties (object) — User properties.
• children_ids (array of strings) — IDs of child events.

Idempotent on session_id: posting twice with the same session_id merges metadata/user_properties into the existing session and returns the existing event.