[
  {"op": "doc", "text": "NY cash-open session anchor: bars elapsed since the 09:30 America/New_York open"},
  {"op": "input", "role": "price"},
  {"op": "add", "type": "Session", "name": "sess",
   "args": {"tz": "America/New_York", "open": "09:30"},
   "bind": {"period_minutes": {"I64": 15}}},
  {"op": "feed", "role": "price", "into": ["sess.trigger"]},
  {"op": "expose", "from": "sess.bars_since_open", "as": "bars"}
]