Autonomous Fact-Checking: Integrating Local Inference and Adversarial NLP Attacks

Rômulo Henrique Nascimento Duarte, Humberto Nunes de Lira, Vivianny Khatly Medeiros Pereira, Isaac Sebastian Lima de Araújo, Allan Gabriel da Cunha Vasconcelos, Yuri de Almeida Malheiros Barbosa


Abstract
Digital misinformation threatens democratic discourse, especially in low-resource languages like Brazilian Portuguese. We present a fact-checking pipeline comparing structured claim decomposition (Claimify) against full-text extraction across four retrieval-augmented classifiers: gemini-2.5-flash-lite and three local open-weight models (Llama-3.1-8B, Qwen2.5-7B, Gemma-2-9B). Robustness is assessed under characterlevel and synonym perturbations. On a pilot sample, the API-based model shows a preliminary macro-F1 advantage for decomposition, which the three local models fail to replicate consistently. We also observe a systematic bias toward the false label across models.
Anthology ID:
2026.stil-1.10
Volume:
Proceedings of the 17th Brazilian Symposium in Information and Human Language Technology
Month:
October
Year:
2026
Address:
Cuiabá, Mato Grosso, Brazil
Editors:
Bryan Khelven da Silva Barbosa, Aline Paes, Ariani Di Felippo
Venue:
STIL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
113–125
Language:
URL:
https://aclanthology.org/2026.stil-1.10/
DOI:
10.5753/stil.2026.26643
Bibkey:
Cite (ACL):
Rômulo Henrique Nascimento Duarte, Humberto Nunes de Lira, Vivianny Khatly Medeiros Pereira, Isaac Sebastian Lima de Araújo, Allan Gabriel da Cunha Vasconcelos, and Yuri de Almeida Malheiros Barbosa. 2026. Autonomous Fact-Checking: Integrating Local Inference and Adversarial NLP Attacks. In Proceedings of the 17th Brazilian Symposium in Information and Human Language Technology, pages 113–125, Cuiabá, Mato Grosso, Brazil. Association for Computational Linguistics.
Cite (Informal):
Autonomous Fact-Checking: Integrating Local Inference and Adversarial NLP Attacks (Duarte et al., STIL 2026)
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PDF:
https://aclanthology.org/2026.stil-1.10.pdf