When AI Is the Wrong Tool

Problem

A small local model appeared promising for exact tag normalization, but its copying errors were non-monotonic. Some longer strings passed while shorter patterns failed. The independent validator already knew the correct answer, making inference an unnecessary dependency.

Intervention

The model-backed route was replaced with deterministic local computation: validate the frozen schema and sensitivity boundary, then trim, lowercase, deduplicate whole values, sort, and write a redacted audit record.

Observed result

The replacement passed the frozen representative replay, exhaustive accepted lengths, concurrency, audit, fail-closed, installed-command, and rollback checks with zero model tokens.