{"ID":5675352,"CreatedAt":"2026-07-03T01:40:09.565152011Z","UpdatedAt":"2026-07-07T01:06:03.009715918Z","DeletedAt":null,"paper_url":"https://arxiv.org/abs/2607.02115","arxiv_id":"2607.02115","title":"Planning over Matrix-Factorization MDPs for Candidate Generation","abstract":"For a recommender service, we view the customer journey as a chain of item recommendations: a useful item changes the user's state and therefore what should be retrieved next. Standard matrix-factorization retrieval ignores this -- it builds one user vector and returns the top-$K$ items by a static score, treating them as independent. We ask a narrow question: when is it worth planning over the user-state dynamics that fold-in induces? To answer it we propose casting top-$K$ retrieval as an MDP over the implicit-ALS posterior $(A^{-1},u)$, where an action is an item and the transition is a closed-form rank-one fold-in, and the trajectory reward combines a relevance similarity with a posterior-alignment term. Under the same fixed embeddings we compare static retrieval, one-step planning, and horizon-$K$ MCTS across five datasets and two protocols: a per-user leave-last-$n$ split and a stricter global time split. Dynamics-aware planning tends to overcome static retrieval on all datasets under leave-last-$n$, and the gains hold on MovieLens-1M and the VK-LSVD slices under the global time split. A single step of lookahead already captures most of the gain, so the lightweight planning layer turns static top-$K$ scoring into a short decision and improves retrieval over fixed collaborative-filtering embeddings, with no retraining and no change to the representation. These gains depend on measuring relevance with cosine rather than inner-product similarity, which is otherwise entangled with item popularity.","short_abstract":"For a recommender service, we view the customer journey as a chain of item recommendations: a useful item changes the user's state and therefore what should be retrieved next. Standard matrix-factorization retrieval ignores this -- it builds one user vector and returns the top-$K$ items by a static score, treating them...","url_abs":"https://arxiv.org/abs/2607.02115","url_pdf":"https://arxiv.org/pdf/2607.02115v1","authors":"[\"Mikhail Trapeznikov\",\"Maksim Utushkin\"]","published":"2026-07-02T12:50:45Z","proceeding":"cs.IR","tasks":"[\"cs.IR\"]","methods":"[]","has_code":false}