Valid Per-Field Selective Risk Control for Document Extraction: Three Failure Modes, a Validity Ladder, and When Conditioning Pays

A new arXiv preprint (2608.14639v1) reports that per-field selective risk control for document extraction silently fails on real documents, diagnosing three failure modes across 13,859 genuine claude-sonnet-5 fields from 800 CORD receipts (49.0% correct). The authors propose a validity ladder of fixes, with a fit/val split protocol achieving coverage 0.318 at risk 0.096 at nominal alpha=0.10, and Mondrian Learn-then-Test yielding per-group PAC certificates (field-iid 0.171 at risk 0.068, cluster-corrected 0.140, doc-iid 0.060). A blind three-annotator human-gold audit verified the practical tier's accepted-set risk at 1.3% against its 10% budget (Fleiss' kappa=0.83).

arXiv:2608.14639v1 Announce Type: new Abstract: Per-field accept/review with selective risk at most alpha -- accept a field only if the error rate among accepted fields is controlled -- is the trust contract document-extraction systems need, and the natural procedure silently violates it on real documents. On 13,859 genuine claude-sonnet-5 fields from 800 CORD receipts 49.0% correct we diagnose three failure modes: document clustering design effect 1.84-2.45 , score-refit leakage coverage 0.416 at risk 0.127, violating alpha=0.10 in 95% of splits , and a tie-mass pathology a degenerate score collapses the threshold grid, 0.030 to 0.001 . We organize the fixes as a validity ladder, guarantee form stated per tier. A fit/val split protocol restores expected-selective-risk control for a learned fusion: coverage 0.318 at risk 0.096 at nominal alpha=0.10, no tolerance band production variant 0.326 -- an on-average point whose realized risk exceeds alpha in 47.5% of resplits, not a certificate. Mondrian Learn-then-Test with exact binomial tails yields per-group PAC certificates: field-iid 0.171 at risk 0.068, cluster-corrected 0.140, doc-iid 0.060 -- the only tier matching documents, honestly near-vacuous today. Support-bin, the pre-specified provenance taxonomy, wins every rigor tier on the sonnet CORD capture p<1e-4, Bonferroni-corrected -- a win that does not replicate on the same documents under haiku or qwen -- while on higher-accuracy corpora pooled thresholds win: conditioning helps exactly where pooled cannot certify, subsumed by a learned score elsewhere. A frozen-configuration confirmation on selection-untouched claude-haiku-4-5 held at both risk levels, and a blind three-annotator human-gold audit verifies the practical tier's accepted-set risk at 1.3% against its 10% budget Fleiss' kappa=0.83; labels err one-sidedly pessimistic . Released Apache-2.0 with seed-pinned, regression-gated procedures.