Conventional recommendation systems succeed in identifying relevant content but often fail to provide users with surprising or novel items. Multimodal Large Language Models (MLLMs) possess the world knowledge and multimodal understanding needed for serendipity, but their integration into billion-item-scale platforms presents significant challenges. In this paper, we propose a novel hierarchical framework where fine-tuned MLLMs provide high-level guidance to conventional recommendation models, steering them towards more serendipitous suggestions. This approach leverages MLLM strengths in understanding multimodal content and user interests while retaining the efficiency of traditional models for item-level recommendation. This mitigates the complexity of applying MLLMs directly to vast action spaces. We also demonstrate a chain-of-thought strategy enabling MLLMs to discover novel user interests by first understanding video content and then identifying relevant yet unexplored interest clusters. Through live experiments within a commercial short-form video platform serving billions of users, we show that our MLLM-powered approach significantly improves both recommendation serendipity and user satisfaction.
@article{arxiv.2506.08283,
title = {Serendipitous Recommendation with Multimodal LLM},
author = {Haoting Wang and Jianling Wang and Hao Li and Fangjun Yi and Mengyu Fu and Youwei Zhang and Yifan Liu and Liang Liu and Minmin Chen and Ed H. Chi and Lichan Hong and Haokai Lu},
journal= {arXiv preprint arXiv:2506.08283},
year = {2025}
}