What Attention Recalls and Recurrence Controls in Hybrid Language Models

Kirill Afendulev, Alexey Dontsov, Elena Tutubalina, Anton Korznikov


Abstract
Hybrid language models combine attention with a fixed-size recurrent state, but the role of each channel remains unclear. We introduce two cache-level interventions. Split-prefill keeps only the KV cache or only the recurrent state from a prefilled context, then generates an answer. State-swap pairs the KV cache from one context with the recurrent state from another in a single forward pass. On Qwen3.5 and Falcon-H1, the two channels split cleanly. Exact retrieval survives only through attention (64–98% of full accuracy) and collapses to zero through recurrence. Output language and persona reverse the pattern: both survive recurrence (70–80%) while KV-only drops to 1% language accuracy. State-swap confirms this causally: the answer takes its value from the KV side and its language from the recurrent side. Recurrent-only generation also accepts words that were never in the context but share meaning or parts with seen items. Attention provides a lookup over what was said; the recurrent state shapes how the model says it next.
Anthology ID:
2026.findings-emnlp.2061
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
43888–43900
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.2061/
DOI:
10.18653/2026.findings-emnlp.2061
Bibkey:
Cite (ACL):
Kirill Afendulev, Alexey Dontsov, Elena Tutubalina, and Anton Korznikov. 2026. What Attention Recalls and Recurrence Controls in Hybrid Language Models. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 43888–43900, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
What Attention Recalls and Recurrence Controls in Hybrid Language Models (Afendulev et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.2061.pdf