Need to Know: Contextual-Integrity-Grounded Query Rewriting for Privacy-Conscious LLM Delegation

Xinyue Huang, Wenyuan Yang, Xiaochun Cao


Abstract
As LLMs become increasingly woven into everyday workflows, user queries send to cloud-hosted LLMs routinely mix task-essential content with task-non-essential sensitive disclosures, yet type-based PII redaction is context-agnostic and may raise two issues: over disclosing untyped sensitive context and over-removing answer-bearing spans. We recast privacy-preserving query rewriting under Contextual Integrity: a span should be forwarded only if it is necessary for the task. We build the first task-based CI benchmark for privacy conscious delegation, comprising 3,167 samples that combine high-quality synthetic data spanning 11 tasks and 20 task types, WildChat based real-user queries, and a medical challenge set with dense sensitive information. Building on this benchmark, we propose a CI guided reinforcement learning framework that converts essential and non-essential sensitive spans into verifiable optimization signals, and train a query rewriter to preserve task-critical information while suppressing unnecessary sensitive disclosure. Experiments show that our learned rewriter achieves the best privacy–utility trade-off, achieving up to +10.1 average utility over on-device baselines.
Anthology ID:
2026.emnlp-main.300
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:
6904–6919
Language:
URL:
https://aclanthology.org/2026.emnlp-main.300/
DOI:
Bibkey:
Cite (ACL):
Xinyue Huang, Wenyuan Yang, and Xiaochun Cao. 2026. Need to Know: Contextual-Integrity-Grounded Query Rewriting for Privacy-Conscious LLM Delegation. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 6904–6919, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Need to Know: Contextual-Integrity-Grounded Query Rewriting for Privacy-Conscious LLM Delegation (Huang et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.300.pdf