Critic-R: Improving Agentic Search using Instruction-tuned Retrievers with Natural Language Introspective Feedback

Md Zarif Ul Alam, Alireza Salemi, Hamed Zamani


Abstract
Agentic search systems iteratively interact with retrieval models to answer complex queries. Despite substantial progress, optimizing retrievers for agentic search remains challenging, often requiring heavy co-training or gold-standard annotations that limit real-world applicability. We propose Critic-R, a framework that explicitly closes the feedback loop between the reasoning agent and the retrieval model during both inference and training. Critic-R introduces a critic model that evaluates the agent’s introspective reasoning trace after consuming retrieved evidence to determine whether the retrieved context sufficiently supports the next reasoning step. Critic-R has two complementary mechanisms: Critic-R-Zero, an inference-time query refinement loop that iteratively rewrites queries and retrieval instructions, and Critic-Embed, an optimization approach for retrieval models that leverages successful and failed refinement trajectories as automatic supervision without requiring manual relevance annotation. We evaluate Critic-R on HotpotQA, 2WikiMultihopQA, MuSiQue, and Bamboogle. Results show that Critic-R significantly improves both retrieval quality and downstream answer accuracy.
Anthology ID:
2026.findings-emnlp.2048
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:
43599–43612
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.2048/
DOI:
Bibkey:
Cite (ACL):
Md Zarif Ul Alam, Alireza Salemi, and Hamed Zamani. 2026. Critic-R: Improving Agentic Search using Instruction-tuned Retrievers with Natural Language Introspective Feedback. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 43599–43612, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Critic-R: Improving Agentic Search using Instruction-tuned Retrievers with Natural Language Introspective Feedback (Alam et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.2048.pdf