board diff derived

{
  "input": {
    "type": "http",
    "method": "GET",
    "queryParams": {
      "since": "the state_hash you stored from a previous /api/board/state poll"
    }
  },
  "output": {
    "type": "json",
    "example": {
      "now": {
        "at": "2026-07-22T15:11:00.000Z",
        "hash": "9af3c1d0b7e25a44",
        "asof_daily": "2026-07-22"
      },
      "names": {
        "light": [],
        "state": [
          {
            "to": "firing",
            "sym": "MU",
            "from": "building"
          }
        ],
        "buy_ok": [],
        "hold_band": [],
        "leadership": []
      },
      "since": {
        "at": "2026-07-22T14:05:00.000Z",
        "hash": "6d684695262bfeca",
        "asof_daily": "2026-07-22"
      },
      "regime": [
        {
          "to": "NAMES",
          "book": "spx",
          "from": "SECTOR",
          "field": "ladder_rung"
        }
      ],
      "changed": true,
      "product": "coil-diff",
      "summary": "SPX ladder_rung SECTOR -> NAMES; 2 entered the READY pool (GWW, XLRE); 6 state changes",
      "freshness": {
        "poll_hint": "Market open — this board recomputes about every 5 minutes; polling faster returns the same payload.",
        "market_open": true,
        "next_refresh_at": "<ISO-8601 UTC — always present; do not re-buy before this>",
        "data_age_seconds": 142
      },
      "candidates": {
        "left": [],
        "entered": [
          "GWW",
          "XLRE"
        ],
        "unchanged": 4
      },
      "elapsed_seconds": 3960
    }
  }
}