{
 "error": "bad_request",
 "detail": "missing/invalid address",
 "http_status": 400,
 "charged": false,
 "schema_version": "preflight_v1",
 "note": "total refusal: invalid subject is rejected before any component runs, no charge, no envelope, per fail-closed policy",
 "reason_codes": [
  "invalid_subject"
 ]
}