Rethinking the Role of Efficient Attention in Hybrid Architectures

Ziqing Qiao, Yinuo Xu, Chaojun Xiao, Zhou su, Zihan Zhou, Yingfa Chen, Xiaoyue Xu, Xu Han, Zhiyuan Liu


Abstract
Modern language models increasingly adopt hybrid architectures that combine full attention with efficient attention modules, such as sliding-window attention (SWA) and recurrent sequence mixers. However, how these efficient modules shape model capabilities remains poorly understood. To address this gap, we conduct a systematic analysis across hybrid architectures from three perspectives: scaling behavior, mechanism analysis, and architecture design. First, from a scaling perspective, we find that efficient-attention design primarily affects how fast long-context capability emerges, while different hybrids eventually converge to comparable long-context performance under sufficient training. Second, mechanistically, we show that long-range retrieval is mainly carried by full attention, whereas efficient attention shapes its optimization trajectory. This explains a counter-intuitive phenomenon we call Large-Window Laziness: larger SWA windows can delay the formation of retrieval heads in full-attention layers. Third, guided by this mechanism, we show that applying No Positional Encoding (NoPE) to only the full-attention layers of a small-window SWA hybrid substantially improves long-context performance with negligible impact on short-context performance.
Anthology ID:
2026.emnlp-main.2275
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:
51727–51753
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2275/
DOI:
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Cite (ACL):
Ziqing Qiao, Yinuo Xu, Chaojun Xiao, Zhou su, Zihan Zhou, Yingfa Chen, Xiaoyue Xu, Xu Han, and Zhiyuan Liu. 2026. Rethinking the Role of Efficient Attention in Hybrid Architectures. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 51727–51753, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Rethinking the Role of Efficient Attention in Hybrid Architectures (Qiao et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2275.pdf