Applying LLMs to query-document relevance estimation in industrial document retrieval faces two key challenges: the complexity and heterogeneity of Web content, and stringent latency and resource constraints. To address them, we propose an automated framework with two components: **R**eflection-**A**ware **C**ollaborative **A**gent (**RACA**) and **P**rogressive **O**ptimization **D**istillation **S**trategy (**PODS**). RACA uses collaborative reasoning and reflection to produce relevance labels and structured rationales. PODS stratifies training data by difficulty and combines supervised fine-tuning with Reasoning-Informed GRPO. Rationale supervision improves the student’s first-token relevance decision, while deployment stops after that token and avoids explicit rationale generation. Together, these mechanisms enable reasoning-informed first-token prediction that preserves the benefits of structured rationale supervision under stringent latency and resource constraints. Extensive offline experiments and a 10-day online A/B test in WeChat Search demonstrate the resulting accuracy–efficiency trade-off.

Service accounts, including organizations’ official accounts and mini-programs, provide various convenient services for users, and have become crucial components of a number of applications. Therefore, retrieving service accounts quickly and accurately is vital. However, this task suffers from the problem of limited human annotation, i.e., manually assessing account functionality and assigning ratings based on user experience is both labor-intensive and time-consuming. To this end, this paper proposes a novel approach, the Auxiliary task Boosted Multi-Task Learning method (AuxBoost-MTL). Specifically, the proposed method introduces multiple auxiliary tasks, which is able to utilized the log data from our application as supervision, and enhance the performance of the main task, service account retrieval. Furthermore, we introduce an Adaptive Hierarchical Fusion Module (AHF module) into our approach. This module is designed to adaptively perform hierarchical fusion of embeddings from auxiliary tasks into the main task, thereby enhancing the model efficacy. Experiments on two real-world industrial datasets demonstrate the effectiveness of our proposed approach.