@inproceedings{zhang-etal-2026-vocabtailor,
title = "{V}ocab{T}ailor: Dynamic Vocabulary Selection for Downstream Tasks in Small Language Models",
author = "Zhang, Hanling and
Zhou, Yayu and
Fang, Tongcheng and
Yuan, Zhihang and
Dai, Guohao and
Ouyang, Wanli and
Wang, Yu",
editor = "Liakata, Maria and
Moreira, Viviane P. and
Zhang, Jiajun and
Jurgens, David",
booktitle = "Findings of the {A}ssociation for {C}omputational {L}inguistics: {ACL} 2026",
month = jul,
year = "2026",
address = "San Diego, California, United States",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.findings-acl.1418/",
pages = "28453--28471",
ISBN = "979-8-89176-395-1",
abstract = "Small Language Models (SLMs) provide computational advantages in resource-constrained environments, yet memory limitations remain a critical bottleneck for edge device deployment. A substantial portion of SLMs' memory footprint stems from vocabulary-related components, particularly embeddings and language modeling (LM) heads, due to large vocabulary sizes. Existing static vocabulary pruning, while reducing memory usage, suffers from rigid, one-size-fits-all designs that cause information loss during the prefill stage and lack flexibility. In this work, we identify two key principles underlying the vocabulary reduction challenge: the *lexical locality* principle, the observation that only a small subset of tokens is required during any single inference, and the *asymmetry in computational characteristics* between vocabulary-related components of SLM. Based on these insights, we introduce VocabTailor, a novel decoupled dynamic vocabulary selection framework that addresses memory constraints through offloading embedding and implements a hybrid static-dynamic vocabulary selection strategy for LM Head, enabling on-demand loading of vocabulary components. Comprehensive experiments across diverse downstream tasks demonstrate that **VocabTailor** achieves a reduction of up to 99{\%} in the memory usage of vocabulary-related components with minimal or no degradation in task performance, substantially outperforming existing static vocabulary pruning. Our code is available at https://github.com/AwakenedInsects/VocabTailor."
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<abstract>Small Language Models (SLMs) provide computational advantages in resource-constrained environments, yet memory limitations remain a critical bottleneck for edge device deployment. A substantial portion of SLMs’ memory footprint stems from vocabulary-related components, particularly embeddings and language modeling (LM) heads, due to large vocabulary sizes. Existing static vocabulary pruning, while reducing memory usage, suffers from rigid, one-size-fits-all designs that cause information loss during the prefill stage and lack flexibility. In this work, we identify two key principles underlying the vocabulary reduction challenge: the *lexical locality* principle, the observation that only a small subset of tokens is required during any single inference, and the *asymmetry in computational characteristics* between vocabulary-related components of SLM. Based on these insights, we introduce VocabTailor, a novel decoupled dynamic vocabulary selection framework that addresses memory constraints through offloading embedding and implements a hybrid static-dynamic vocabulary selection strategy for LM Head, enabling on-demand loading of vocabulary components. Comprehensive experiments across diverse downstream tasks demonstrate that **VocabTailor** achieves a reduction of up to 99% in the memory usage of vocabulary-related components with minimal or no degradation in task performance, substantially outperforming existing static vocabulary pruning. Our code is available at https://github.com/AwakenedInsects/VocabTailor.</abstract>
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%0 Conference Proceedings
%T VocabTailor: Dynamic Vocabulary Selection for Downstream Tasks in Small Language Models
%A Zhang, Hanling
%A Zhou, Yayu
%A Fang, Tongcheng
%A Yuan, Zhihang
%A Dai, Guohao
%A Ouyang, Wanli
%A Wang, Yu
%Y Liakata, Maria
%Y Moreira, Viviane P.
%Y Zhang, Jiajun
%Y Jurgens, David
%S Findings of the Association for Computational Linguistics: ACL 2026
%D 2026
%8 July
%I Association for Computational Linguistics
%C San Diego, California, United States
%@ 979-8-89176-395-1
%F zhang-etal-2026-vocabtailor
%X Small Language Models (SLMs) provide computational advantages in resource-constrained environments, yet memory limitations remain a critical bottleneck for edge device deployment. A substantial portion of SLMs’ memory footprint stems from vocabulary-related components, particularly embeddings and language modeling (LM) heads, due to large vocabulary sizes. Existing static vocabulary pruning, while reducing memory usage, suffers from rigid, one-size-fits-all designs that cause information loss during the prefill stage and lack flexibility. In this work, we identify two key principles underlying the vocabulary reduction challenge: the *lexical locality* principle, the observation that only a small subset of tokens is required during any single inference, and the *asymmetry in computational characteristics* between vocabulary-related components of SLM. Based on these insights, we introduce VocabTailor, a novel decoupled dynamic vocabulary selection framework that addresses memory constraints through offloading embedding and implements a hybrid static-dynamic vocabulary selection strategy for LM Head, enabling on-demand loading of vocabulary components. Comprehensive experiments across diverse downstream tasks demonstrate that **VocabTailor** achieves a reduction of up to 99% in the memory usage of vocabulary-related components with minimal or no degradation in task performance, substantially outperforming existing static vocabulary pruning. Our code is available at https://github.com/AwakenedInsects/VocabTailor.
%U https://aclanthology.org/2026.findings-acl.1418/
%P 28453-28471
Markdown (Informal)
[VocabTailor: Dynamic Vocabulary Selection for Downstream Tasks in Small Language Models](https://aclanthology.org/2026.findings-acl.1418/) (Zhang et al., Findings 2026)
ACL
- Hanling Zhang, Yayu Zhou, Tongcheng Fang, Zhihang Yuan, Guohao Dai, Wanli Ouyang, and Yu Wang. 2026. VocabTailor: Dynamic Vocabulary Selection for Downstream Tasks in Small Language Models. In Findings of the Association for Computational Linguistics: ACL 2026, pages 28453–28471, San Diego, California, United States. Association for Computational Linguistics.