Youngjun Kwak
Author directory2026
BankMathBench: A Benchmark for Numerical Reasoning in Banking Scenarios
Yunseung Lee | Subin Kim | Youngjun Kwak | Jaegul Choo
Proceedings of the Fifteenth Language Resources and Evaluation Conference
Yunseung Lee | Subin Kim | Youngjun Kwak | Jaegul Choo
Proceedings of the Fifteenth Language Resources and Evaluation Conference
Large language models (LLMs)-based chatbots are increasingly being adopted in the financial domain, particularly in digital banking, to handle customer inquiries about products such as deposits, savings, and loans. However, these models still exhibit low accuracy in core banking computations—including total payout estimation, comparison of products with varying interest rates, and interest calculation under early repayment conditions. Such tasks require multi-step numerical reasoning and contextual understanding of banking products, yet existing LLMs often make systematic errors—misinterpreting product types, applying conditions incorrectly, or failing basic calculations involving exponents and geometric progressions. However, such errors have rarely been captured by existing benchmarks. Mathematical datasets focus on fundamental math problems, whereas financial benchmarks primarily target financial documents, leaving everyday banking scenarios underexplored. To address this limitation, we propose BankMathBench, a domain-specific dataset that reflects realistic banking tasks. BankMathBench is organized in three levels of difficulty—basic, intermediate, and advanced—corresponding to single-product reasoning, multi-product comparison, and multi-condition scenarios, respectively. When trained on BankMathBench, open-source LLMs exhibited notable improvements in both formula generation and numerical reasoning accuracy, demonstrating the dataset’s effectiveness in enhancing domain-specific reasoning. With tool-augmented fine-tuning, the models achieved average accuracy increases of 57.6%p (basic), 75.1%p (intermediate), and 62.9%p (advanced), representing significant gains over zero-shot baselines. These findings highlight BankMathBench as a reliable benchmark for evaluating and advancing LLMs’ numerical reasoning in real-world banking scenarios.
FENCE: A Financial and Multimodal Jailbreak Detection Dataset
Mirae Kim | Seonghun Jeong | Youngjun Kwak
Proceedings of the Fifteenth Language Resources and Evaluation Conference
Mirae Kim | Seonghun Jeong | Youngjun Kwak
Proceedings of the Fifteenth Language Resources and Evaluation Conference
Large Language Models (LLMs) and Vision Language Models (VLMs). VLMs are particularly vulnerable because they process both text and images, creating broader attack surfaces. However, available resources for jailbreak detection are scarce, particularly in finance. To address this gap, we present FENCE, a bilingual (Korean–English) multimodal dataset for training and evaluating jailbreak detectors in financial applications. FENCE comprises 10k finance-domain text–image pairs across more than 15 finance categories, constructed via a three-step pipeline: transforming real-world financial FAQs into harmful queries using GPT-4o, collecting query-relevant images via keyword-based crawling, and fusing text and images with diverse layout strategies. Labels were assigned using GPT-4o as an evaluator, with human validation confirming 95% agreement. Experiments on 15 commercial and open-source VLMs reveal consistent vulnerabilities, with GPT-4o showing measurable attack success rates and open-source models displaying greater exposure. A baseline detector trained on FENCE achieves 99% in-distribution accuracy and maintains strong performance on external benchmarks. FENCE provides a focused resource for advancing multimodal jailbreak detection in finance and supporting safer AI deployment in sensitive domains. Content Warning: This paper includes example data that may be offensive.
Listwise Explanation of Embedding-Based Rankings via Semantic Chunk Grouping
Hyunkyu Kim | Yeeun Yoo | Youngjun Kwak
Findings of the Association for Computational Linguistics: EMNLP 2026
Hyunkyu Kim | Yeeun Yoo | Youngjun Kwak
Findings of the Association for Computational Linguistics: EMNLP 2026
Dense embedding rankers score documents through contextual sentence- and passage-level representations, yet listwise explanation methods often attribute rankings to isolated words. We study this mismatch and introduce ChunkGroupSHAP, a listwise Shapley method that clusters semantically related chunks across documents into shared features, preserving contextual evidence while bounding the KernelSHAP regression dimension by the group count. Across MS MARCO, FinanceBench, AILACaseDocs, and FinQA with E5-family rankers and BM25, raw chunks improve rank-reconstruction Fidelity over RankSHAP’s word features in all 11 dense-ranker settings. The best chunk-group configuration further improves on raw chunks in eight of these settings, with the incremental benefit depending on grouping scope; word features remain strongest in three of four BM25 settings. These results show that explanation units should match the ranking model: contextual chunks better suit dense bi-encoders, whereas words remain effective for BM25. ChunkGroupSHAP supports listwise attribution over contextual evidence through a bounded feature space shared across documents.
K-FinHallu: A Hallucination Detection Benchmark for Multi-Turn RAG in Korean Finance
Eunbyeol Cho | Yunseung Lee | Mirae Kim | Jeewon Yang | Youngjun Kwak | Edward Choi
Findings of the Association for Computational Linguistics: EMNLP 2026
Eunbyeol Cho | Yunseung Lee | Mirae Kim | Jeewon Yang | Youngjun Kwak | Edward Choi
Findings of the Association for Computational Linguistics: EMNLP 2026
Large Language Models (LLMs) have advanced financial automation through Retrieval-Augmented Generation (RAG), yet hallucinations remain a critical barrier to deployment in high-stakes environments. Existing benchmarks focus on single-turn, English-centric tasks, leaving the multi-turn dynamics and linguistic-regulatory nuances of the Korean financial domain unaddressed. We introduce K-FinHallu, the first benchmark for hallucination detection in multi-turn Korean financial RAG, designed as a controlled evaluation of source faithfulness and answerability. We construct multi-turn dialogues from authentic Korean financial documents and inject hallucinations under a proposed hierarchical taxonomy based on context answerability that explicitly accounts for justified abstention. Benchmarking Korean-centric, open-source, and closed-source LLMs as hallucination detectors, we find that even the strongest models struggle with fine-grained financial diagnostics and refusal behavior. While fine-tuning an 8B model on our training split yields performance competitive with frontier LLMs, justified abstention remains the weakest axis across all evaluated models. K-FinHallu and code are publicly available at https://github.com/eunbyeol-cho/K-FinHallu.
A Shaky Voice Is Not Always a Dodge: Benchmarking Textual and Vocal Evasion Detection in Earnings Calls
Mirae Kim | Seonghun Jeong | Youngjun Kwak
Findings of the Association for Computational Linguistics: EMNLP 2026
Mirae Kim | Seonghun Jeong | Youngjun Kwak
Findings of the Association for Computational Linguistics: EMNLP 2026
Existing approaches to evasion detection in earnings calls focus on textual transcripts, treating evasion as a single-dimensional phenomenon. We argue that evasion in spoken communication is inherently multidimensional: beyond what executives say, how they say it carries independent and complementary information. To study these dimensions jointly, we introduce DualEvasion, a benchmark for evasion detection across text and audio in earnings call Q A. The benchmark contains 505 annotated question-answer pairs from 60 earnings calls, each with two independent labels: textual evasion (direct vs. evasive) and vocal cues operationalized as speaker confidence (confident vs. unconfident). Our experiments show that state-of-the-art multimodal models struggle to detect vocal confidence, particularly on unconfident responses. Our analysis suggests these models interpret acoustic cues in isolation rather than relative to each speaker’s baseline. Providing speaker-level references yields modest improvements, but a substantial gap with human performance remains.
Membrane: A Self-Evolving Contrastive Safety Memory for LLM Agent Defense
Minseok Choi | Seungbin Yang | Dongjin Kim | Subin Kim | Jungmin Son | Yunseung Lee | Jaegul Choo | Youngjun Kwak
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Minseok Choi | Seungbin Yang | Dongjin Kim | Subin Kim | Jungmin Son | Yunseung Lee | Jaegul Choo | Youngjun Kwak
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Despite advances in safety alignment, large language models remain vulnerable to continuously evolving jailbreaks. Existing fine-tuned safety classifiers cannot adapt to these evolving attacks, while adaptive memory-based guardrails tend to over-refuse benign queries that resemble stored attacks. We propose Membrane, a self-evolving guardrail built on Contrastive Safety Memory (CSM): each cell pairs the conditions for blocking a harmful query with those for permitting a superficially similar benign request. Without retraining, Membrane evolves CSM by distilling each harmful interaction and its benign counterpart into a contrastive cell indexed by the underlying attack strategy, so that one cell generalizes across topical variants of the same mechanism. At inference, retrieved cells serve as grounding context for precise safety decisions. Across model-level safety on HarmBench and agent-level safety on AgentHarm, Membrane achieves the highest F1 on all six modern jailbreak attacks. Notably, benign refusal on AgentHarm stays at 7-14%, well below the 28-85% range of prior guards. Memory cells also retain 87-88% F1 under cross-attack transfer and remain stable under memory poisoning.
FinHarmBench: Financial Jailbreak Benchmark and Unsupervised Safety Fine-Tuning via Refusal Steering Distillation
Yubin Choi | Yujin Yang | Subin Kim | Seokil Ham | Seungju Cho | Jungmin Son | Youngjun Kwak | Changick Kim
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 6: Industry Track)
Yubin Choi | Yujin Yang | Subin Kim | Seokil Ham | Seungju Cho | Jungmin Son | Youngjun Kwak | Changick Kim
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 6: Industry Track)
Financial Large Language Models (LLMs) exhibit strong domain expertise but remain vulnerable to financially harmful prompts. To systematically assess this vulnerability, we introduce FinHarmBench, a benchmark designed to evaluate financially harmful and confusable benign prompts. Our analysis reveals a concerning result that financial LLMs can be less robust than general-purpose models, suggesting that domain adaptation alone does not guarantee financial safety alignment. To address this issue, we propose Financial Refusal Steering Distillation (FiRSD), an unsupervised training framework that strengthens financial-domain safety by learning and distilling a financial refusal direction at the representation level. FiRSD enhances refusal behavior without requiring annotated refusal responses. Experiments show that FiRSD substantially improves safety while largely preserving task capability. These results highlight the importance of domain-aware safety alignment for high-stakes financial applications.