ZooWork-ShopRanker: An Open, Preference-Aligned E-Commerce Reranker

📅 2026-09-25
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🤖 AI Summary
This study addresses the suboptimal transfer performance of general-purpose reranking models in e-commerce scenarios due to the lack of preference supervision. We propose a preference annotation mechanism based on a multi-LLM panel alongside a position debiasing strategy, enabling reasoning-capable large language models to automatically generate high-quality debiased labels. A series of reranking models are then trained via knowledge distillation and contrastive learning. Furthermore, we construct ShopRank-Bench, a proprietary traffic benchmark for evaluation. Experimental results demonstrate that our 8B and 4B models significantly outperform existing open-source baselines, with all model sizes surpassing their unaligned counterparts while exhibiting strong generalization capabilities to general-domain tasks on the MTEB leaderboard.
📝 Abstract
Open rerankers trained for general web retrieval transfer imperfectly to e-commerce, where ranking decisions depend not only on topical relevance but also on user preferences, product constraints, and comparative product fit. These preference signals are difficult to supervise at scale: real search traffic provides authentic queries and candidates but no clean pairwise labels. We present ZooWork-ShopRanker, a family of e-commerce rerankers (0.6B, 4B, and 8B) aligned to judge-labeled shopping preference. Training pairs are labeled by a panel of reasoning large language models (LLMs) from different families acting as a preference oracle, with position-debiased judgments and agreement tiers, and the rerankers are trained on these labels. The aligned 8B flagship then serves as a distillation teacher for the efficient 4B and 0.6B models, which are fit to its scores and sharpened on judged pairs. To measure progress, we introduce ShopRank-Bench, a contamination-limited benchmark of ~10,000 private-traffic preference pairs in both text formats, tiered by how many judge families committed to each label. ZooWork-ShopRanker-8B and -4B significantly outperform the strongest open reranker baseline, every model significantly beats its own un-aligned base, and ZooWork-ShopRanker-0.6B beats its size peer; the gains hold in both formats and extend to common MTEB benchmarks. We release the models and the dual-format ShopRank-Bench to facilitate further research.
Problem

Research questions and friction points this paper is trying to address.

e-commerce reranking
preference alignment
pairwise preference labels
open reranker
Innovation

Methods, ideas, or system contributions that make the work stand out.

E-Commerce Reranker
Preference Alignment
LLM-as-a-Judge
Knowledge Distillation
Position Debiasing
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