Family 121: practical edit-distance backend deferred

The selected paper's explicit ell >= 2^1000 guard prevents the literal approximation branch from activating at practical lengths. Exact fallback remains below it. The integer definitions imply necessary first-guard boundary 2^(2^(2^999))-1; other physical predicates remain separate. This is an asymptotic advance claim, not a demonstrated useful implementation.

Selected PDF pages 1-8, 34 and 43, plus the conclusion paragraph on 44, were read; pages 7, 8 and 34 were visually inspected. Scope/config, selected Comparator/Definitions, AccuracyCutoff and RawBandMain were read to the extent documented in the dossier. No full proof, Lean execution or source benchmark occurred. The probabilistic distance sandwich need not hold on bad executions, and no alignment output follows.

An isolated RapidFuzz 3.14.6 baseline passes 2,023 combined finite/oracle/representation controls. It already provides exact distances, cutoff predicates and edit scripts. Twelve generated long-pair controls and preserved input hashes provide a repeatable baseline, not customer value or source speed comparisons. Defer a direct engine and keep a conventional integration at low commercial confidence. Dossier, comparison.