Changick Kim
Author directory2026
MATE: Mobile Agent Trustworthy Execution for Safe and Efficient Mobile Control
Minsuk Jang | Hee-Seon Kim | Hui-Cheol Yu | Changick Kim
Findings of the Association for Computational Linguistics: EMNLP 2026
Minsuk Jang | Hee-Seon Kim | Hui-Cheol Yu | Changick Kim
Findings of the Association for Computational Linguistics: EMNLP 2026
Mobile agents on personal smartphones can affect private data, payments, settings, and the foreground screen. We present MATE (Mobile Agent Trustworthy Execution), an execution-layer system that controls the boundary between agent action proposals and device effects without modifying the underlying model. MATE represents each UI primitive as a structured action record that combines the instruction, target app, screen context, primitive, and action fields. Runtime Guardrail (RG) maps this record to an allow, block, or user-approval decision; Predefined Task Routing (PTR) serves recurring requests through verified routes with post-execution screen checks; and a floating interface keeps execution in a compact overlay. On MobileSafetyBench, MATE raises high-risk blocking from 29.7% to 97.0% under GPT-4o. On AndroidWorld, it reduces LLM calls by up to 6 and raises recurring-use task success to 95.7%.
SubT: Subspace Tuning for Few-shot Generalization of Audio-Language Models
Jaehyuk Jang | Kangwook Ko | Wonjun Lee | Changick Kim
Findings of the Association for Computational Linguistics: EMNLP 2026
Jaehyuk Jang | Kangwook Ko | Wonjun Lee | Changick Kim
Findings of the Association for Computational Linguistics: EMNLP 2026
Few-shot parameter-efficient adaptation of pretrained Audio–Language Models (ALMs) often improves seen-class performance at the cost of unseen-class generalization, leading to the base-to-new trade-off. We study this failure through zero-shot drift in the text embedding space: few-shot tuning can distort inter-class structure and move adapted embeddings away from their pretrained anchors. We therefore propose Subspace Tuning (SubT), an embedding-space adaptation method that combines a geometry-aware shared transformation with anchoring to the zero-shot prototypes. The learned transformation is transferred to unseen classes, with subspace-aware gating to mitigate negative transfer. Across 11 audio benchmarks, SubT achieves strong few-shot generalization while operating directly on precomputed text embeddings without text-encoder backpropagation. Code is available at https://github.com/jhyukjang/SubT.
AIM: Anchor Identity Features, Then Match for Multimodal Large Language Model Unlearning
Wonjun Lee | Jaehyuk Jang | Kangwook Ko | Hee-Seon Kim | Changick Kim
Findings of the Association for Computational Linguistics: EMNLP 2026
Wonjun Lee | Jaehyuk Jang | Kangwook Ko | Hee-Seon Kim | Changick Kim
Findings of the Association for Computational Linguistics: EMNLP 2026
Multimodal large language models (MLLMs) can memorize identity-specific facts about people in their fine-tuning data, creating privacy risks when a person requests deletion. Existing MLLM unlearning methods often assume access to retain images or ground-truth answers during deletion, which is unrealistic in many practical scenarios. We study identity unlearning when retain images are unavailable at deletion time. Our analysis shows that identity and visual-perception questions occupy distinct regions in fine-tuned hidden states and are organized differently: identity questions cluster by person, whereas perception questions cluster by question type. This suggests that identity knowledge can be suppressed without erasing general visual perception. Building on this observation, we propose AIM, a two-stage method that anchors an identity-forgetting target with a universal visual prompt and then matches the vision encoder to that target under a Fisher-based constraint. Extensive experiments show that AIM achieves competitive identity forgetting while preserving non-deleted identities, prior knowledge, and visual perception on the same images.
Where Identity Lives: Localized, Retain-Free Identity Unlearning in Multimodal Large Language Models
Kangwook Ko | Jaehyuk Jang | Wonjun Lee | Hee-Seon Kim | Changick Kim
Findings of the Association for Computational Linguistics: EMNLP 2026
Kangwook Ko | Jaehyuk Jang | Wonjun Lee | Hee-Seon Kim | Changick Kim
Findings of the Association for Computational Linguistics: EMNLP 2026
Removing a specific individual’s information from multimodal large language models (MLLMs) is often needed after deployment, but existing methods rely on a retain set, which is hardest to obtain at that point, and rebuilding it recreates the privacy exposure that unlearning aims to remove. Forgetting from the forget set alone instead damages the shared visual-language computation, harming perception. We cast retain-free unlearning as a localization problem: causal tracing, weight transplant, and Fisher overlap all point to early-to-mid decoder MLPs as the layers where identity information is stored and, unlike other module families, can be modified without substantially disrupting vision. We turn this into Pathway-Aware Visual-attribute Anchoring (PAVA), which confines updates to these layers and pairs a forget loss with a visual-attribute anchor that preserves image-grounded behavior by distilling the model’s own pre-unlearning answers from the forget images alone. On MLLMU-Bench and ReMem, PAVA gives the strongest forget-retain trade-off among forget-set-only methods and remains competitive with retain-based baselines.
Generalizable Prompt Tuning for Audio-Language Models via Semantic Expansion
Jaehyuk Jang | Wonjun Lee | Kangwook Ko | Changick Kim
Findings of the Association for Computational Linguistics: ACL 2026
Jaehyuk Jang | Wonjun Lee | Kangwook Ko | Changick Kim
Findings of the Association for Computational Linguistics: ACL 2026
Prompt tuning has achieved remarkable progress in vision–language models (VLMs) and is recently being adopted for audio–language models (ALMs). However, its generalization ability in ALMs remains largely underexplored. We observe that conventional prompt tuning for ALMs also suffers from the Base–New Tradeoff, and we identify that this issue stems from the disrupted semantic structure of the embedding space. To address this issue, we propose Semantically Expanded Prompt Tuning (SEPT)—a plug-and-play framework that explicitly regularizes the prompt embedding space by incorporating semantic neighbors generated by large language models. SEPT introduces a novel semantic expansion loss with margin constraints that promote intra-class compactness and inter-class separability, thereby enhancing the semantic structure of the prompt embedding space. For comprehensive evaluation, we establish the first benchmark setup for prompt generalization in ALMs, covering both base-to-new generalization and cross-dataset transferability. Extensive experiments demonstrate that SEPT consistently improves generalization performance across multiple prompt tuning baselines, while maintaining computational cost during inference.
Who Wins the Conflict? Mechanistic Interpretability of Text Bias in Audio LLMs
Hyebin Cho | Suho Yoo | Jaehyuk Jang | Changick Kim | Joon Son Chung
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Hyebin Cho | Suho Yoo | Jaehyuk Jang | Changick Kim | Joon Son Chung
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
While Audio Large Language Models (Audio LLMs) excel at multimodal understanding, they suffer from text dominance, a bias where models favor text over acoustic evidence, potentially leading to hallucinated responses. However, the internal mechanisms underlying how these models behave when audio and textual inputs contradict each other remain unexplored. In this work, we present the first mechanistic analysis of this phenomenon by tracing the propagation of internal representations across layers. Our investigation reveals three key findings: (i) text dominance is consistently observed across models; (ii) while text and audio rely on functionally distinct pathways, they ultimately converge into a shared semantic space in late layers; and (iii) the text pathway does not erase audio information, but rather actively suppresses intact audio representations. Building on these insights, we leverage back-patching, a training-free intervention that routes late-layer audio activations back into earlier layers. This amplifies the audio representations, enabling them to overcome textual suppression. Our evaluation shows that back-patching consistently reduces text dominance, demonstrating a mechanistic route to mitigating text dominance under conflict.
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.
Safety in Batches? Understanding and Mitigating Safety Failures in Batch Prompting
Kihyun Kim | Hee-Seon Kim | Wonjun Lee | Changick Kim
Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers)
Kihyun Kim | Hee-Seon Kim | Wonjun Lee | Changick Kim
Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers)
Batch prompting is a practical inference strategy for large language models, but its safety implications remain underexplored. We show that the success of batch prompting for utility does not extend to safety: a harmful question that is reliably refused in isolation can elicit a harmful response when embedded in a batch of benign questions. We identify this as a distinct safety failure mode, not reducible to known vulnerabilities such as in-context learning or long-context effects—and analyze its causes from two complementary perspectives: alignment signal weakening and refusal signal dilution. Across widely used open-source and frontier commercial models, batch prompting consistently achieves high attack success rates as a simple black-box attack. We further show that batch-aware preference optimization effectively mitigates the vulnerability. These findings highlight a blind spot in current safety alignment and point to batch-aware alignment as a necessary step toward robust deployment.
2025
Don’t Miss the Forest for the Trees: Attentional Vision Calibration for Large Vision Language Models
Sangmin Woo | Donguk Kim | Jaehyuk Jang | Yubin Choi | Changick Kim
Findings of the Association for Computational Linguistics: ACL 2025
Sangmin Woo | Donguk Kim | Jaehyuk Jang | Yubin Choi | Changick Kim
Findings of the Association for Computational Linguistics: ACL 2025
Large Vision Language Models (LVLMs) demonstrate strong capabilities in visual understanding and description, yet often suffer from hallucinations, attributing incorrect or misleading features to images. We observe that LVLMs disproportionately focus on a small subset of image tokens—termed blind tokens—which are typically irrelevant to the query (e.g., background or non-object regions). We hypothesize that such attention misalignment plays a key role in generating hallucinated responses. To mitigate this issue, we propose Attentional Vision Calibration (AvisC), a test-time approach that dynamically recalibrates the influence of blind tokens without modifying the underlying attention mechanism. AvisC first identifies blind tokens by analyzing layer-wise attention distributions over image tokens, then employs a contrastive decoding strategy to balance the influence of original and blind-token-biased logits. Experiments on standard benchmarks, including POPE, MME, and AMBER, demonstrate that AvisC effectively reduces hallucinations in LVLMs.