What Should Occupy the Context Budget? Latent Compression versus Budget-Matched Truncation in Document QA

Artem Cherepanov, Albina Burlova


Abstract
Latent context compression replaces a document with a short sequence of learned vectors, but whether this beats simply keeping raw tokens under the same decoder-context budget is rarely tested. We run that test on held-out document QA, matching budgets per example against raw-token truncation and selector-specific readers trained on first-N, LLMLingua-2, and question-conditioned BM25 contexts. Our minimal compressor consists of a text encoder, learned pooling, and direct projection. It beats every tested common-cap retention baseline at nominal pooling factors cr=8 and cr=16, reaching answer perplexity 3.464 versus 5.349 for the strongest baseline at cr=8. The advantage persists in first-sentence free generation, and a manual check of answers is directionally consistent. Adding a post-pooling transformer hurts with twelve layers and with one layer. The twelve-layer result holds in the discovery run, two replications, and a second decoder family. Removing the post-pooling transformer also makes the compressor smaller and faster. Learned pooling followed by direct projection provides the strongest quality and efficiency among the tested compressor designs.
Anthology ID:
2026.docinsights-1.21
Volume:
The Proceedings of Workshop on Document Intelligence and Understanding
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Santosh T.Y.S.S., Amit Agarwal, Vivek Gupta, Yova Kementchedjhieva, Aparna Garimella, Yufang Hou
Venues:
DocInsights | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
287–302
Language:
URL:
https://aclanthology.org/2026.docinsights-1.21/
DOI:
Bibkey:
Cite (ACL):
Artem Cherepanov and Albina Burlova. 2026. What Should Occupy the Context Budget? Latent Compression versus Budget-Matched Truncation in Document QA. In The Proceedings of Workshop on Document Intelligence and Understanding, pages 287–302, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
What Should Occupy the Context Budget? Latent Compression versus Budget-Matched Truncation in Document QA (Cherepanov & Burlova, DocInsights 2026)
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PDF:
https://aclanthology.org/2026.docinsights-1.21.pdf