ReThink: Adversarially Robust Arithmetic Reasoning via Neuro-Symbolic Soft Constraints

Soikat Das, Sparsh Mittal, Rekha Singhal


Abstract
While Large Language Models (LLMs) perform well on arithmetic word problems, they remain brittle to adversarial perturbations like irrelevant distractors or contradictory facts. To address this, we introduce ReThink, a training-free neuro-symbolic framework that formulates adversarial arithmetic reasoning as a Weighted MaxSAT/MaxSMT problem. ReThink uses a four-stage pipeline: it explicitly decomposes problems to strip noise, encodes the mathematical core as confidence-weighted soft constraints in the Z3 theorem prover, and cross-verifies the formal solution against a parallel Chain-of-Thought (CoT) path. This formulation can sacrifice lower-weight conflicting statements while satisfying higher-weight constraints. Evaluated on a balanced 2,400-example subset of GSM-Plus, ReThink with GPT-4.1 achieves 81.62% adversarial accuracy, outperforming CoT, PAL, and Self-Verification. It narrows the robustness gap to 14.69 percentage points while achieving 96.31% clean accuracy.
Anthology ID:
2026.findings-aacl.66
Volume:
Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
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Pages:
1303–1313
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URL:
https://aclanthology.org/2026.findings-aacl.66/
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Cite (ACL):
Soikat Das, Sparsh Mittal, and Rekha Singhal. 2026. ReThink: Adversarially Robust Arithmetic Reasoning via Neuro-Symbolic Soft Constraints. In Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026, pages 1303–1313, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
ReThink: Adversarially Robust Arithmetic Reasoning via Neuro-Symbolic Soft Constraints (Das et al., Findings 2026)
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https://aclanthology.org/2026.findings-aacl.66.pdf