RAMP: Adapting One Agent to Multiple Retrievers via Behavioral Probing

Weijun Li, Tao Yang, Jiayu Yang, Fei Chao


Abstract
Agentic RAG agents must generate effective queries across diverse retriever backends, yet current agents produce retriever-oblivious queries, leading to large performance gaps when the backend changes. We observe that different retrievers, despite dissimilar architectures, exhibit structured behavioral patterns in their document-return overlap, forming a continuous behavioral space that can guide retriever-adaptive query generation. We propose RAMP (Retriever-Adaptive Multi-retriever Policy), which probes a black-box retriever with shared queries, encodes the resulting overlap patterns into a compact behavioral embedding, and injects it as soft tokens to condition query generation. A single RAMP model replaces four retriever-specific specialists without per-retriever retraining and generalizes to unseen retrievers by interpolating in behavioral space. On four QA benchmarks, RAMP matches 96–98% of four retriever-specific specialists (+3.8 EM over unconditioned training) and reaches 91.8% of the retrained upper bound on unseen retrievers, outperforming routing, few-shot, and fusion alternatives.
Anthology ID:
2026.emnlp-main.1977
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:
44989–45005
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1977/
DOI:
Bibkey:
Cite (ACL):
Weijun Li, Tao Yang, Jiayu Yang, and Fei Chao. 2026. RAMP: Adapting One Agent to Multiple Retrievers via Behavioral Probing. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 44989–45005, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
RAMP: Adapting One Agent to Multiple Retrievers via Behavioral Probing (Li et al., EMNLP 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.emnlp-main.1977.pdf