Exploring Fine-Tuning for In-Context Retrieval and Efficient KV-Caching in Long-Context Language Models

Francesco Maria Molfese, Momchil Hardalov, Rexhina Blloshmi, Bill Byrne, Adrià de Gispert


Abstract
With context windows of millions of tokens, Long-Context Language Models (LCLMs) can encode entire document collections, offering a strong alternative to conventional retrieval-augmented generation (RAG). However, it remains unclear whether fine-tuning strategies can improve long-context performance and translate to greater robustness under KV-cache compression techniques. In this work, we investigate which training strategies most effectively enhance LCLMs’ ability to identify and use relevant information, as well as enhancing their robustness under KV-cache compression. Our experiments show substantial in-domain improvements, achieving gains of up to +20 points over the base model. However, out-of-domain generalization remains task dependent with large variance – LCLMs excels on finance questions (+9 points), while RAG shows stronger performance on multiple-choice questions (+6 points) over the baseline models. Finally, we show that our fine-tuning approaches bring moderate improvements in robustness under KV-cache compression, with gains varying across tasks.
Anthology ID:
2026.eacl-short.44
Volume:
Proceedings of the 19th Conference of the European Chapter of the Association for Computational Linguistics (Volume 2: Short Papers)
Month:
March
Year:
2026
Address:
Rabat, Morocco
Editors:
Vera Demberg, Kentaro Inui, Lluís Marquez
Venue:
EACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
617–635
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URL:
https://preview.aclanthology.org/ingest-eacl/2026.eacl-short.44/
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Cite (ACL):
Francesco Maria Molfese, Momchil Hardalov, Rexhina Blloshmi, Bill Byrne, and Adrià de Gispert. 2026. Exploring Fine-Tuning for In-Context Retrieval and Efficient KV-Caching in Long-Context Language Models. In Proceedings of the 19th Conference of the European Chapter of the Association for Computational Linguistics (Volume 2: Short Papers), pages 617–635, Rabat, Morocco. Association for Computational Linguistics.
Cite (Informal):
Exploring Fine-Tuning for In-Context Retrieval and Efficient KV-Caching in Long-Context Language Models (Molfese et al., EACL 2026)
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