BridgeGap: Belief-Grounded Training for Medical Dialogue Agents

Weijun Li, Tao Yang, Jiayu Yang, Fei Chao


Abstract
Although LLMs perform well on static medical QA, adapting them to multi-turn diagnostic dialogue remains challenging: agents forget confirmed symptoms, ask redundant questions, and fail to narrow differentials, largely because they lack an explicit representation of their evolving clinical understanding. Our key insight is that a structured belief state—encoding accumulated evidence, ranked differential diagnoses with confidence, and prioritized next questions—can simultaneously serve as a supervision target, a basis for rule-based reward computation, and a grounding context for deciding what to ask next. We propose BridgeGap, a two-stage framework in which supervised fine-tuning on silver-annotated belief states teaches the agent to maintain structured clinical reasoning, while reinforcement learning with a belief-progress reward refines questioning strategy through dense, environment-verified per-turn feedback without LLM judges or learned reward models. On HealthBench, BridgeGap (8B) surpasses Doctor-R1 (8B) by 2.84 points and the 4× larger Baichuan-M2-32B by 5.85 points; on AgentClinic, it achieves 44.6% diagnostic accuracy in 10.5 average turns, compared to 37.6% in 15.5 turns for Doctor-R1. Across evaluations, BridgeGap advances interactive diagnosis while preserving factual knowledge on static medical benchmarks.
Anthology ID:
2026.emnlp-main.1974
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:
44932–44947
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1974/
DOI:
Bibkey:
Cite (ACL):
Weijun Li, Tao Yang, Jiayu Yang, and Fei Chao. 2026. BridgeGap: Belief-Grounded Training for Medical Dialogue Agents. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 44932–44947, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
BridgeGap: Belief-Grounded Training for Medical Dialogue Agents (Li et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1974.pdf