{
 "trial": "Isolated re-verification of the JSON extraction trial",
 "claude_code": "2.1.226",
 "date": "2026-08-10",
 "why": "The original ran with the machine's user-level CLAUDE.md loaded, which contains nine anti-guessing instructions. The headline finding was a model declining to invent an absent value, so that file could have produced it.",
 "isolation": "--setting-sources project, which excludes user-level memory while keeping project memory and tools. Verified with an InstructionsLoaded hook: default user=1 project=1, with the flag user=0 project=1.",
 "result": "Identical to the original: 24 of 24 schema-valid and every field correct, customer_vat_number null in all 24, no decoy returned.",
 "runs": [
  {
   "model": "claude-haiku-4-5-20251001",
   "arm": "clean",
   "round": 0,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-haiku-4-5-20251001",
   "arm": "clean",
   "round": 1,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-haiku-4-5-20251001",
   "arm": "clean",
   "round": 2,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-haiku-4-5-20251001",
   "arm": "clean",
   "round": 3,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-haiku-4-5-20251001",
   "arm": "clean",
   "round": 4,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-haiku-4-5-20251001",
   "arm": "clean",
   "round": 5,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-haiku-4-5-20251001",
   "arm": "noisy",
   "round": 0,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-haiku-4-5-20251001",
   "arm": "noisy",
   "round": 1,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-haiku-4-5-20251001",
   "arm": "noisy",
   "round": 2,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-haiku-4-5-20251001",
   "arm": "noisy",
   "round": 3,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-haiku-4-5-20251001",
   "arm": "noisy",
   "round": 4,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-haiku-4-5-20251001",
   "arm": "noisy",
   "round": 5,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-opus-5",
   "arm": "clean",
   "round": 0,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-opus-5",
   "arm": "clean",
   "round": 1,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-opus-5",
   "arm": "clean",
   "round": 2,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-opus-5",
   "arm": "clean",
   "round": 3,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-opus-5",
   "arm": "clean",
   "round": 4,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-opus-5",
   "arm": "clean",
   "round": 5,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-opus-5",
   "arm": "noisy",
   "round": 0,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-opus-5",
   "arm": "noisy",
   "round": 1,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-opus-5",
   "arm": "noisy",
   "round": 2,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-opus-5",
   "arm": "noisy",
   "round": 3,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-opus-5",
   "arm": "noisy",
   "round": 4,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "invoice_number": "INV-2026-0473",
    "total_amount": 1284.5,
    "currency": "GBP",
    "status": "paid",
    "line_item_count": 3,
    "due_date": "2026-06-30",
    "customer_vat_number": null
   }
  },
  {
   "model": "claude-opus-5",
   "arm": "noisy",
   "round": 5,
   "status": "ok",
   "shape_valid": true,
   "field_ok": {
    "invoice_number": true,
    "total_amount": true,
    "currency": true,
    "status": true,
    "line_item_count": true,
    "due_date": true,
    "customer_vat_number": true
   },
   "wrong": [],
   "all_fields_correct": true,
   "obj": {
    "currency": "GBP",
    "customer_vat_number": null,
    "due_date": "2026-06-30",
    "invoice_number": "INV-2026-0473",
    "line_item_count": 3,
    "status": "paid",
    "total_amount": 1284.5
   }
  }
 ]
}