CAS: Conformalized Agentic Search via Adaptive Retrieval and Policy Weighting

Zixi Zhu, Jiayuan Su, Jian Zhang, Yu Lin, Hongwei Wang


Abstract
Search Agents face a severe reliability crisis during reinforcement learning (RL) fine-tuning. Heuristic Top-K retrieval often causes critical evidence loss or noise inclusion, while overconfidence induced by progressive RL leads to hallucinated answers and redundant searches. To build highly reliable agents, we introduce Conformal Prediction (CP) and propose Conformalized Agentic Search (CAS). This framework establishes reliability guarantees on both the retrieval and training sides: on the retrieval side, an Adaptive Prediction Set (APS), a specific CP realization, translates statistical coverage into dynamic document truncation to construct prediction sets that are adaptive in size; on the training side, Adaptive Conformal Inference (ACI), a dynamic CP algorithm, dynamically constructs prediction sets with controllable coverage to quantify answer confidence, which is then used to penalize low-confidence trajectories within the Group Relative Policy Optimization (GRPO) objective, ensuring the model learns only from reliable ones. Experiments across single-hop and multi-hop QA datasets demonstrate that our framework significantly improves reasoning accuracy while drastically reducing redundant tool invocations, establishing a highly reliable and efficient agent paradigm.
Anthology ID:
2026.emnlp-main.1054
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:
24191–24210
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1054/
DOI:
Bibkey:
Cite (ACL):
Zixi Zhu, Jiayuan Su, Jian Zhang, Yu Lin, and Hongwei Wang. 2026. CAS: Conformalized Agentic Search via Adaptive Retrieval and Policy Weighting. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 24191–24210, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
CAS: Conformalized Agentic Search via Adaptive Retrieval and Policy Weighting (Zhu et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1054.pdf