{
  "tool_id": "art-221-llpa-stack",
  "note": "Vectors derived from Fannie Mae LLPA Matrix effective 2025-11-01 (table_version FNM-LLPA-2025-11-01, public). golden_hash empty until golden-parity --update.",
  "vectors": [
    {
      "name": "baseline_780_60_zero_llpa",
      "description": "Fannie Mae LLPA base grid: FICO 780 (740+ band), LTV 60 (<=60 band), primary purchase SFR. Baseline row = 0.000 LLPA.",
      "policy_parameters": {
        "fico_score": 780,
        "ltv_pct": 60,
        "loan_purpose": "purchase",
        "occupancy_type": "primary",
        "property_type": "sfr"
      },
      "output_payload": {
        "base_llpa": 0,
        "feature_llpa": 0,
        "fthb_waiver": 0,
        "fthb_eligible": false,
        "total_llpa_pct": 0,
        "components": [
          {
            "label": "Base LLPA (primary)",
            "value": 0
          }
        ],
        "fico_band": "740+",
        "ltv_band": "<=60",
        "table_version": "FNM-LLPA-2025-11-01",
        "table_source": "Fannie Mae LLPA Matrix effective 2025-11-01 (fanniemae.com; public)",
        "regulatory_basis": "12 USC 4501 (FHFA charter); Fannie Mae Selling Guide B3-4.1-02; SEL-2023-07 FTHB waiver",
        "pii_note": "All inputs processed locally in your browser. No data is transmitted."
      },
      "golden_hash": "9fca83db4f7074f465aaa5f37d7da2052428c780b005e641c11f8f44f42dea33"
    },
    {
      "name": "fthb_ami_waiver",
      "description": "First-time buyer AMI waiver (SEL-2023-07): FICO 700, LTV 90, primary purchase, income <=100% AMI. Base 1.250 fully offset by 1.75pp waiver cap -> net 0.",
      "policy_parameters": {
        "fico_score": 700,
        "ltv_pct": 90,
        "loan_purpose": "purchase",
        "occupancy_type": "primary",
        "property_type": "sfr",
        "first_time_buyer": true,
        "ami_pct": 80
      },
      "output_payload": {
        "base_llpa": 1.25,
        "feature_llpa": 0,
        "fthb_waiver": 1.25,
        "fthb_eligible": true,
        "total_llpa_pct": 0,
        "components": [
          {
            "label": "Base LLPA (primary)",
            "value": 1.25
          },
          {
            "label": "FTHB AMI waiver (SEL-2023-07)",
            "value": -1.25
          }
        ],
        "fico_band": "700-719",
        "ltv_band": "85-90",
        "table_version": "FNM-LLPA-2025-11-01",
        "table_source": "Fannie Mae LLPA Matrix effective 2025-11-01 (fanniemae.com; public)",
        "regulatory_basis": "12 USC 4501 (FHFA charter); Fannie Mae Selling Guide B3-4.1-02; SEL-2023-07 FTHB waiver",
        "pii_note": "All inputs processed locally in your browser. No data is transmitted."
      },
      "golden_hash": "c630b1d4902bd40d72bda9f88565bb47ba41ba91183373cf7d12a5b9fb1fbddd"
    }
  ]
}