{
 "schema_version": "0.1",
 "name": "[[12,4,2]] chain-coupled 422 blocks",
 "code_type": "CSS",
 "n": 12,
 "k": 4,
 "checks": {
  "X": [
   [
    0,
    1,
    2,
    3
   ],
   [
    4,
    5,
    6,
    7
   ],
   [
    8,
    9,
    10,
    11
   ],
   [
    0,
    1,
    4,
    5
   ],
   [
    4,
    5,
    8,
    9
   ]
  ],
  "Z": [
   [
    0,
    1,
    2,
    3
   ],
   [
    4,
    5,
    6,
    7
   ],
   [
    8,
    9,
    10,
    11
   ]
  ]
 },
 "distance": {
  "d": 2,
  "X": {
   "value": 2,
   "confidence": "upper_bound",
   "witness": [
    0,
    3
   ]
  },
  "Z": {
   "value": 2,
   "confidence": "upper_bound",
   "witness": [
    0,
    1
   ]
  }
 },
 "provenance": {
  "authors": [
   "@mathysrennela"
  ],
  "construction": "Start with three [[4,2,2]] plaquette codes on adjacent 2x2 squares. Retain each inner block's X^4 and Z^4 stabilizers. Add two X-type stabilizers, each the product of the weight-2 logical X representative X0X1 on neighboring blocks (supports [0,1,4,5] and [4,5,8,9]); this connects all three blocks and is not a direct sum.",
  "references": [],
  "model": "GPT-6 Luna",
  "date": "2026-09-23",
  "notes": "The [[12,4,2]] parameters exist in other weight-6 entries; this is a distinct weight-4 local realization. See notes/12-4-2-c.md."
 },
 "family": "other",
 "locality": {
  "coordinates": [
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    0.0,
    0.0
   ],
   [
    0.0,
    1.0
   ],
   [
    1.0,
    0.0
   ],
   [
    1.0,
    1.0
   ],
   [
    2.0,
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   [
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   ],
   [
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   ],
   [
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   ],
   [
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   ],
   [
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   ],
   [
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   ],
   [
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   ]
  ],
  "interaction_radius": 2.23606797749979,
  "layers": 1
 }
}