An audit of a production text-to-SQL pipeline reveals that the deployed gpt-4o-mini judge performs poorly, agreeing with human annotators at only 0.04 Cohen's kappa on a disagreement-enriched dataset. The primary failure mode is identified as GRADE-HALLUCINATION, causing the model to over-flag 77.1% of human-verified faithful cases. Replacing the judge with a self-hosted Qwen3.6-27B model improves agreement to 0.72 kappa while reducing costs by a factor of 300 compared to premium alternatives.
- Deployed LLM judges require empirical validation; assumed accuracy can be dangerously low.
- gpt-4o-mini showed near-random agreement (kappa 0.04) on enriched disagreement sets in this context.
- GRADE-HALLUCINATION is a specific failure mode causing excessive false positives in faithfulness checks.
- Self-hosted Qwen3.6-27B matches Claude Opus 4.7 quality (kappa ~0.71) at 1/300th the cost.
- Ensembling strategies were noted but the excerpt cuts off before detailing their efficacy.