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 "family": "bivariate-bicycle",
 "provenance": {
  "authors": [
   "@cbjuan"
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  "construction": "Periodic bivariate-bicycle code on the group algebra Z_4 x Z_26 (n = 2*l*m = 208). Convention: x = S_4 tensor I_26, y = I_4 tensor S_26 (cyclic shifts), qubit index = i*m + j; A = 1 + x^2y^0, B = 1 + x^0y^18 + x^1y^5 + x^3y^0; H_X = [A|B], H_Z = [B^T|A^T]. Found by an automated evolutionary/mutation search over (l, m, A, B) exponent sets targeting the unrestricted x weight-6 (or weight-8) board cells, screened by a randomized lightest-logical surrogate and promoted through increasing trial budgets.",
  "origin": "submission",
  "date": "2026-09-16",
  "notes": "Internal autoresearch candidate id 142 (canonical key fac92a1832e320158b38a2b7), search lane 'w6-gap', proposal kernel 'axis-mixed'. Initial NumPy lightest-logical surrogate: trials=2000, seed=1512128256. Distance also taken through an internal exact-certification pipeline (MILP, one solve per logical-basis row per side, the same method as this repository's own verify/certify.py). Result: side_status X=exact, Z=exact (solver wall time 8.9s, CPU time 8.5s, summed over all per-row MILP solves on both sides). Per CONTRIBUTING.md's confidence-tier policy, this 'exact' claim is self-declared and will display as an upper bound on the board until a maintainer independently re-runs verify/certify.py and confirms it."
 }
}