Benchmarking Structured Conversation Extraction Across Three Evaluation Layers: A Comparison of Eight Models with a Public Replication
Evaluating structured extraction from conversational data with a single quality metric conceals the failure modes that matter most to systems built on top of the extraction. This paper presents a benchmark that evaluates extraction quality across three layers: field comparison against a reference extraction, evaluation by a panel of three judge models reading the raw conversation, and propagation of extraction differences into downstream consumers such as drift detection and loop tracking. Eight frontier models extracted a seventeen field schema from thirty chunks of private SMS conversation, with Claude Opus 4.6 serving as the reference. The extraction layer discriminates strongly (composites from 0.496 to 0.623 against a reference ceiling of 0.996), the judge layer discriminates weakly (0.869 to 0.942), and correlation between judge composites and downstream composites is near zero (mean Pearson r of 0.134), a result that initially appears to undermine the methodology but instead reflects an aggregation artifact: across the full cross correlation matrix, dimension pairs designed to correspond average Spearman rho 0.510 while the fifteen mismatched pairs average 0.051, although eight models leave all such estimates imprecise. One judge dimension resists validation entirely, and the investigation explains why: emotional field extraction saturates structurally, with every model producing specific mood labels, grounded turning points, and equivalent label diversity, leaving no structural signal for a downstream proxy to exploit. A reduced replication on the public Persuasion for Good corpus (reference plus three challengers, thirty chunks) reproduces the discrimination pattern and the top model ordering, with the middle ordering proving sensitive to corpus register and to the treatment of schema validation failures. Judge family preference for same family models measures 0.019 to 0.021 on a unit scale, constraining though not eliminating the circularity concern inherent in model referenced evaluation.