LexFlip: A Dissociation Diagnostic for Legal Meaning Preservation Metrics

On September 4 and 7, 2026, arXiv successively released LexFlip, a tool for diagnosing the dissociation of legal significance indicators. This tool based on 373 minimal perturbation tests of Quebec French regulations found that these perturbations reversed legal significance while only changing 0.93 elements. The test results showed that seven embedding models and metrics such as BERTScore achieved extremely low scores for such edits (0.022 to 0.039), far below the scores for bidirectional natural language inference (0.670). In the FrJudge benchmark, only length features performed better than all semantic metrics, with the smallest gap from the human measurement upper limit (r=0.597).