arXiv AI

Beyond Successor Accuracy: State Retention for Recursive Self-Improvement in Recommendation

arXiv Machine Learning
Oct 5

Probe the Harness: Setup Checks for Stale-Data RL Comparisons in Language Models

The paper introduces PTH (Probe The Harness), a set of checks designed to expose hidden details in experimental setups that can alter the ranking of stale-data reinforcement learning methods for language models. By applying PTH to a comparison between SAN and truncated importance sampling (TIS), the authors demonstrate that subtle harness configurations—such as how PPO ratios are computed, data seeding, replay queue reuse, and loss normalisation—can reverse the observed performance order. The study provides a detailed signature of each influencing factor, reference results for TIS and uncorrected GRPO, and a checklist to ensure fair comparisons.

By Taiheng Pan
arXiv AI
Aug 24

UpgradeBench: A Decision-Centric Benchmark for Upgrading Fine-Tuned LLM Specialists

UpgradeBench is a decision‑centric longitudinal benchmark that evaluates how fine‑tuned language‑model specialists should be handled when new base‑model releases occur. It covers four consecutive Qwen releases, a continuation checkpoint, six tasks, two model sizes, and OLMo checkpoints with known training lineage, and examines whether retraining, adapter transfer, or other recovery strategies improve specialist performance. The benchmark reveals that upgrade gains vary by task and release interval, that direct adapter copying is sensitive to pretraining distance, and that teacher relabeling can recover specialists without new annotations. "whyItMatters":"The study provides actionable insights into the cost‑effective management of specialist models across model releases, showing how to balance retraining effort with performance gains."

By Ye Chen, Weining Zhang
arXiv Machine Learning
Sep 24

The Recall Ceiling of LLM Recommendation Reranking

The paper examines LLM-based recommendation rerankers that are often evaluated under an oracle protocol, which guarantees the ground-truth item is present in the scored set. Across Amazon datasets, this protocol overestimates realistic NDCG@10 by 92–95% because realistic retrieval only covers 2–19% of relevant items at K=100, creating a recall ceiling that limits any closed-candidate reranker's top‑k NDCG. The authors find that various optimisation strategies—including prompt engineering, model scaling, sequential models, supervised neural rerankers, LoRA fine‑tuning, hybrid retrieval, score‑aware prompting, and LLM+CF fusion—do not significantly improve over a collaborative‑filtering baseline under realistic retrieval, and they propose a Recall‑Aware Evaluation Protocol (RAEP) to better assess rerankers in low‑recall regimes.

By Zhaohui Wang
arXiv AI
Sep 30

Multi-Channel Mitigation of Source-Trust Shortcuts in Fact-Checking RL Agents

The paper introduces TrustSwap, a counterfactual test that swaps or removes source reliability labels while keeping evidence text constant, to evaluate how retrieval‑augmented fact‑checking models respond across verdict, confidence, and search decisions. Experiments on untrained and RL‑trained models show that confidence and search largely follow labels, yet label changes can flip a significant portion of verdicts, especially in larger models. The authors propose trust‑swap augmentation (TSA) to mitigate this shortcut, demonstrating reduced verdict flip rates and maintained accuracy in several settings, though its effectiveness diminishes at larger model scales.

By Jianchang Su, Yiwei Yang, Wei Zhang
arXiv Machine Learning
Aug 28

Keeping the Index Open: The Recommendation-Side Cost of Shared Search and Recommendation

The paper investigates the trade‑off of using a shared search‑and‑recommendation index that scores new items purely from features, thereby keeping the index open to unseen items. Experiments on public logs show that a feature‑based tower can match warm‑item performance (Recall@20 0.9595 vs 0.9510) and a lexical baseline, while a full‑catalog check is inconclusive. The study also quantifies the cost of this openness on recommendation quality across several baselines, revealing that exact full‑softmax training improves recall but is impractical at catalog scale.

By Theodore Rogers, Joe Standerfer, Dmitrii Timoshenko, Haoxue Li, Zuhaib Akhtar, Soyoung Yang
arXiv Machine Learning
Oct 3

Not All Is Lost: Repairing Lossy User Preference States of Personalization Encoders

The paper introduces REPAIR, a method that corrects lossy user preference states in personalization encoders by comparing cached representations with the current state in a learned coordinate space. REPAIR selectively aggregates corrective evidence from past interactions and adds it to the state before the task head, enabling encoder–host repair without re‑encoding history. Experiments on MovieLens, PENS, MIND, and Amazon Reviews 2023 show that training only REPAIR improves MRR and nDCG@10 across all twelve recommendation hosts, while head‑only finetuning yields smaller gains.

By Parthiv Chatterjee, Dhiraj Golhar, Ummesalma Diwan, Sourish Dasgupta, Manjunath Joshi, Tanmoy Chakraborty