Monitorable Chart Reasoning Agents via Verifiable Process Rewards

Sanchit Sinha, Oana Frunza, Kashif Rasul, Aidong Zhang


Abstract
Chart reasoning agents are increasingly used to extract actionable insights in critical domains, achieving state-of-the-art performance on multiple benchmarks. Yet, high benchmark accuracy alone is insufficient for deployment, where stakeholders must be able to audit and verify how a model reaches its answer. Existing LVLM-based chart agents produce either answer-only predictions or free-form rationales that are hard to verify, obscuring whether an error arose from misreading the chart, extracting a wrong value, or miscomputing. We propose Chart-RVR, a reinforcement learning framework for training monitorable chart agents with verifiable process rewards. Chart-RVR decomposes chart reasoning into three auditable blocks: Structure, identifying the chart type; Evidence, reconstructing the underlying data table in JSON; and Derivation, exposing the stepwise trace that computes the answer. Across six in-domain and out-of-domain benchmarks, Chart-RVR attains state-of-the-art accuracy among comparable-sized LVLMs. Beyond accuracy, we assess monitorability using a triangulated protocol that combines ground-truth surrogate metrics, an oracle information-gain measure, and an LLM-as-auditor scoring Process Verifiability and Evidence Localization, showing that Chart-RVR yields rationales that are markedly more verifiable and evidence-grounded than those from CoT prompting, SFT, and existing chart-specific baselines.
Anthology ID:
2026.findings-emnlp.691
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:
14488–14511
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.691/
DOI:
Bibkey:
Cite (ACL):
Sanchit Sinha, Oana Frunza, Kashif Rasul, and Aidong Zhang. 2026. Monitorable Chart Reasoning Agents via Verifiable Process Rewards. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 14488–14511, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Monitorable Chart Reasoning Agents via Verifiable Process Rewards (Sinha et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.691.pdf