System One Models Lose Reranking Test
A controlled arXiv study finds dedicated reranker fine-tuning consistently beats decision-model fine-tuning across six Qwen backbones and ten retrieval benchmarks. The advantage reaches 5–29 nDCG@10 points up to 9B parameters, while both approaches tie at 27B.
Decision models may offer useful calibration and broader flexibility, but this evidence argues against treating them as drop-in reranker replacements.
- –Reranker fine-tuning wins on every backbone from 0.6B through 9B
- –Decision fine-tuning adds little over simply prompting the untuned model at smaller sizes
- –Calibration benefits depend heavily on how the relevance question is phrased
- –Better-calibrated scores do not compensate for worse ranking quality
- –Developers should benchmark both models on their own query distribution before changing production retrieval
DISCOVERED
1h ago
2026-10-27
PUBLISHED
1h ago
2026-10-27
RELEVANCE
AUTHOR
omarsar0