Learning to Evict: Policy-Driven KV Cache Optimization for Multi-Hop Multimodal Spatial Reasoning

Jiale Chang, Ying Li


Abstract
Visualization-of-thought (VoT) has substantially advanced multimodal spatial reasoning by interleaving visual thinking with verbal reasoning. However, multi-hop VoT reasoning introduces a fundamental scalability bottleneck: the autoregressive accumulation of interleaved visual and textual tokens causes KV cache memory to grow rapidly across successive hops. We present ScoutKV, a framework that recasts KV cache eviction as a reinforcement learning problem. ScoutKV trains a dedicated lightweight policy agent per KV head, conditioned on key–value representations, cross-hop positional encodings, and modality embeddings, to predict each token’s long-term utility across the full reasoning trajectory. Training combines offline supervised fine-tuning with future-query attention targets and online GRPO optimization with a multimodal process reward targeting low-entropy text anchors and modality-specific spatial anchors. ScoutKV consistently reduces FLOPs, latency, and peak memory while maintaining or improving accuracy across multimodal spatial reasoning benchmarks, and generalizes robustly to broader vision-language tasks.
Anthology ID:
2026.emnlp-main.729
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
16932–16947
Language:
URL:
https://aclanthology.org/2026.emnlp-main.729/
DOI:
Bibkey:
Cite (ACL):
Jiale Chang and Ying Li. 2026. Learning to Evict: Policy-Driven KV Cache Optimization for Multi-Hop Multimodal Spatial Reasoning. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 16932–16947, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Learning to Evict: Policy-Driven KV Cache Optimization for Multi-Hop Multimodal Spatial Reasoning (Chang & Li, EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.729.pdf