Paper Detail

Implicit Reasoning for Large Language Model-based Generative Recommendation

Yinhan He, Liam Collins, Bhuvesh Kumar, Jundong Li, Neil Shah, Donald Loveland

huggingface Score 9.5

Published 2026-06-15 · First seen 2026-06-16

General AI

Abstract

Large Language Models (LLMs) are increasingly adopted as backbones for Generative Recommendation (GR), promising access to pretrained world knowledge. Yet reliably invoking this knowledge for GR remains poorly understood. A key obstacle is that LLM-based GR typically represents items with Semantic IDs (SIDs), disrupting LLMs' natural-language reasoning interface because these tokens are unseen by the LLM during pretraining. Existing approaches address this with expensive multi-stage pipelines that ground SIDs and elicit explicit rationales, but offer limited insight into when and why each stage is necessary. In this work, we systematically decompose explicit reasoning training pipelines for LLM-based GR, revealing three key limitations: weakened world-knowledge verbalization, misalignment between SID and natural-language token embedding spaces, and sensitivity to rationale quality, all of which hurt explicit reasoning performance. To circumvent these issues, we propose PauseRec, a lightweight implicit reasoning paradigm tailored for GR. PauseRec is exceptionally practical, avoiding costly reasoning trace acquisition and reasoning alignment training, leading to a multitude of benefits: (1) it outperforms standard explicit CoT methods by up to 6.22%, (2) it reduces training cost by up to 65% GPU hours, and (3) it speeds up inference by up to 71.3%. These results position PauseRec as a lightweight alternative to explicit rationale generation, enabling more effective and efficient LLM-based GR.

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BibTeX

@misc{he2026implicit,
  title = {Implicit Reasoning for Large Language Model-based Generative Recommendation},
  author = {Yinhan He and Liam Collins and Bhuvesh Kumar and Jundong Li and Neil Shah and Donald Loveland},
  year = {2026},
  abstract = {Large Language Models (LLMs) are increasingly adopted as backbones for Generative Recommendation (GR), promising access to pretrained world knowledge. Yet reliably invoking this knowledge for GR remains poorly understood. A key obstacle is that LLM-based GR typically represents items with Semantic IDs (SIDs), disrupting LLMs' natural-language reasoning interface because these tokens are unseen by the LLM during pretraining. Existing approaches address this with expensive multi-stage pipelines th},
  url = {https://huggingface.co/papers/2606.14142},
  keywords = {Large Language Models, Generative Recommendation, Semantic IDs, explicit reasoning, implicit reasoning, CoT methods, training cost, inference speed, huggingface daily},
  eprint = {2606.14142},
  archiveprefix = {arXiv},
}

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