n
84
2D-local bilayer weight-9plus CSS cell, through the layout inherited from the parent. The priced construction calculus was applied one move deep to every CSS entry on the board, and this code is the C-DELETE-CHECK of codes/84-34-6.json ([[84,34,6]], max check weight 12; the cyclic all-one pair-partition CPM code qc_84_34_6 of arXiv:2607.14091). Deleting X check a1 raises k from 34 to 35 and lowers the witnessed distance bound from 6 to 5; n = 84 and the max check weight 12 are unchanged. The layout is the parent's unchanged, since no qubit was removed; the verifier re-measured its radius and layer count.
Every C-DELETE-CHECK, E-PEEL, and E-PUNCTURE move on each of the 2,783 CSS board entries as of 2026-11-02, 1,684,787 moves in all, with the consumer at github.com/unitaryfoundation/code-calculus @ 1b9a942. Children with a bare qubit, a disconnected Tanner graph, a Weisfeiler-Leman signature equal to a board entry or to an earlier child, or parameters already dominated inside the parent's cell were dropped before any search, leaving 334,191 distinct children. Children with n <= 60 and an inherited distance bound of at least 2, and children with 61 <= n <= 100 and a bound of at least 5, were screened with research/kit/surrogate.lightest_logical at 2,000 RIS trials per side; the survivors the kit's novelty pre-check called board-advancing were staged with research/kit/submit.py and gated with verify/validate_candidate.py, one representative per distinct (n, k, d, max weight, locality) point. This code is that representative for [[84,35,5]] at max check weight 12. The thirteen points audited first went to the board on 2026-11-04 (PRs #4588 to #4600); this one is from the remainder, re-checked against the board of 2026-11-04 with the gate's structural, deduplication, and novelty stages before the ladder below was run. The screen distance is a witness-backed upper bound; the rungs below are the independent confirmation runs on the staged file.
Confirmation ladder for the submitted code, each rung a fresh seed unless marked otherwise, reading the lightest logical found:
| budget (trials/side) | lightest logical | | ---: | ---: | | 2,000 (staging screen, seeds 1 and 2) | 5 | | 1,000,000 (seed 101) | 5 | | 1,000,000 (seed 102) | 5 | | 10,000,000 (seed 103) | 5 |
4 fresh-seed rung(s) agree at the best bound, the deepest of them at 10,000,000 trials per side. The submitted witness reproduces it: X: d <= 6 (upper_bound), Z: d <= 5 (upper_bound).
None recorded for this candidate.
Model: Claude Fable 5.1 (Claude Code). Repo tooling: research/kit/coordination.py, research/kit/submit.py, research/kit/surrogate.py, research/audits/leader_audit.py. The local verdict is verify/validate_candidate.py; the bundle was assembled by research/kit/promote.py.
Load codes/84-34-6.json and delete X check a1, where the X rows are numbered a1, a2, ... in file order after dropping rows dependent on earlier ones, as CodeState.from_challenge in machine/priced_calculus.py labels them; every qubit keeps its index. In github.com/unitaryfoundation/code-calculus @ 1b9a942 this is apply_operation(state, {'op': 'C-DELETE-CHECK', 'row_id': 'a1'}). Then run research/audits/leader_audit.py ladder on the result with --ladder 1000000:101,102 10000000:103 to reproduce the confirmation rungs; the witnesses in the entry are the ones those runs validated.