Charles Fleming
Author directory2026
Analyzing Reasoning Shifts in Audio Deepfake Detection Under Adversarial Attacks
Binh Nguyen | Charles Fleming | Thai Le
Findings of the Association for Computational Linguistics: EMNLP 2026
Binh Nguyen | Charles Fleming | Thai Le
Findings of the Association for Computational Linguistics: EMNLP 2026
While Audio Language Models (ALMs) offer a promising shift towards explainable audio deepfake detection (ADD) via generated reasoning, whether these explanations reflect faithful perceptual grounding or fragile post-hoc rationalizations under adversarial attack remains under-explored. To address this gap, we introduce **SARA** (**S**hift **A**nalysis of **R**easoning in **A**udio), a diagnostic framework that evaluates the reasoning of five ALMs across three dimensions: acoustic perception, reasoning-verdict coherence and dissonance. Our experiments reveal three key findings. First, current ALMs exhibit weak acoustic perception (< 50% accuracy), and generating explicit rationales imposes an accuracy penalty (reducing real F1 score by up to 21%). Second, adversarial attacks show a modality asymmetry: acoustic attacks severely degrade reasoning-verdict coherence (average drop of 14.20%), whereas linguistic attacks achieve higher attack success (61.73%) while preserving fluent coherence (a drop of only 3.91%). Third, we demonstrate that decomposing reasoning shifts into prediction confidence and reasoning-verdict coherence enables a secondary defense layer that can detect adversarially perturbed audio with a 74.41% F1 score even with unseen attack strategies and speaker profiles. These findings suggest that reasoning traces also provide diagnostic utility that persists even when final classification outputs are compromised. Our code is available at [https://github.com/nqbinh17/sara_reasoning_shifts](https://github.com/nqbinh17/sara_reasoning_shifts).
MASkills: Continual Skills Optimization for Multi-Agent LLM Systems
Huaiyuan Yao | Xiaoou Liu | Charles Fleming | Tianlong Chen | Hua Wei
Findings of the Association for Computational Linguistics: EMNLP 2026
Huaiyuan Yao | Xiaoou Liu | Charles Fleming | Tianlong Chen | Hua Wei
Findings of the Association for Computational Linguistics: EMNLP 2026
LLM-based multi-agent systems have shown strong performance on complex tasks, yet continual improvement from interaction experience remains challenging. Existing self-reflection methods build experience memories, but memories are mostly hard to invoke, refine, or scale, while agent skills offer a more actionable unit: structured procedural knowledge that specifies when to act, how to act, and which resources or tools to use. We introduce MASkills, a continual learning framework that optimizes multi-agent LLM systems through agent skills. MASkills presents a new agent-optimization pipeline that integrates skill-conditioned credit assignment, hierarchical credit aggregation, and momentum-smoothed optimization, enabling agent skill libraries to evolve through refinement, induction, consolidation, and pruning. Experiments on HotpotQA, LoCoMo, and GAIA demonstrate the effectiveness of MASkills across multiple agentic tasks.
The Adaptive Interrogator: Detecting Trojan LLMs in Multi-Agent Systems via Evolved Conversational Strategies
Rana Muhammad Shahroz Khan | Ruichen Zhang | Zhen Tan | Charles Fleming | Tianlong Chen
Findings of the Association for Computational Linguistics: ACL 2026
Rana Muhammad Shahroz Khan | Ruichen Zhang | Zhen Tan | Charles Fleming | Tianlong Chen
Findings of the Association for Computational Linguistics: ACL 2026
While Large Language Model (LLM) safety has focused on single-agent, white-box settings, the adoption of Multi-Agent Systems (MAS) creates a critical blind spot: supply chain vulnerabilities in MAS ecosystems. These systems often rely on third-party agents accessed via black-box APIs, creating risks where attackers can embed hidden triggers to manipulate collective reasoning or outputs. Because internal weights are inaccessible, traditional white-box defenses fail to detect these threats. Consequently, a critical gap exists in auditing these systems for ”Trojan” agents, i.e., malicious models that behave normally until triggered by specific, often multi-turn, conversational contexts. To bridge this gap, we introduce the Conversational Trojan Unmasking System (CTUS), a black-box auditing framework that leverages an Evolutionary Algorithm (EA) to autonomously expose hidden threats. Drawing on social deduction mechanics, CTUS deploys a ”Judge” agent to evolve conversational probes that provoke Trojan agents into revealing their malicious nature without alerting benign peers. We validate CTUS across diverse architectures (Llama-2/3, Gemma, Mistral) and attack vectors (word, syntax, semantic, RLHF). Our results demonstrate that CTUS achieves superior detection rates (up to 100% in specific configurations). Furthermore, we conduct rigorous analyses to confirm the framework’s robustness, exhibiting negligible false positives on benign systems and stability across system configurations, establishing CTUS as a scalable safeguard for the multi-agent landscape.
LangMARL: Natural Language Multi-Agent Reinforcement Learning via Semantic Credit Assignment
Huaiyuan Yao | Longchao Da | Xiaoou Liu | Charles Fleming | Tianlong Chen | Hua Wei
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Huaiyuan Yao | Longchao Da | Xiaoou Liu | Charles Fleming | Tianlong Chen | Hua Wei
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Large language model (LLM) agents struggle to autonomously evolve coordination strategies in dynamic environments, largely because coarse global outcomes obscure the causal signals needed for local policy refinement. We identify this bottleneck as a multi-agent credit assignment problem, which has long been studied in classical multi-agent reinforcement learning (MARL) but remains underaddressed in LLM-based systems. Building on this observation, we propose LangMARL, a framework that brings credit assignment and policy gradient evolution from cooperative MARL into the language space. LangMARL introduces agent-level language credit assignment, pioneers gradient evolution in language space for policy improvement, and summarizes task-relevant causal relations from replayed trajectories to provide dense feedback and improve convergence under sparse rewards. Extensive experiments across diverse cooperative multi-agent tasks demonstrate improved sample efficiency, interpretability, and strong generalization.
2025
AssistedDS: Benchmarking How External Domain Knowledge Assists LLMs in Automated Data Science
An Luo | Xun Xian | Jin Du | Fangqiao Tian | Ganghua Wang | Ming Zhong | Shengchun Zhao | Xuan Bi | Zirui Liu | Jiawei Zhou | Jayanth Srinivasa | Ashish Kundu | Charles Fleming | Mingyi Hong | Jie Ding
Findings of the Association for Computational Linguistics: EMNLP 2025
An Luo | Xun Xian | Jin Du | Fangqiao Tian | Ganghua Wang | Ming Zhong | Shengchun Zhao | Xuan Bi | Zirui Liu | Jiawei Zhou | Jayanth Srinivasa | Ashish Kundu | Charles Fleming | Mingyi Hong | Jie Ding
Findings of the Association for Computational Linguistics: EMNLP 2025
Large language models (LLMs) have advanced the automation of data science workflows. Yet it remains unclear whether they can critically leverage external domain knowledge as human data scientists do in practice. To answer this question, we introduce AssistedDS (Assisted Data Science), a benchmark designed to systematically evaluate how LLMs handle domain knowledge in tabular prediction tasks. AssistedDS features both synthetic datasets with explicitly known generative mechanisms and real-world Kaggle competitions, each accompanied by curated bundles of helpful and adversarial documents. These documents provide domain-specific insights into data cleaning, feature engineering, and model selection. We assess state-of-the-art LLMs on their ability to discern and apply beneficial versus harmful domain knowledge, evaluating submission validity, information recall, and predictive performance. Our results demonstrate three key findings: (1) LLMs frequently exhibit an uncritical adoption of provided information, significantly impairing their predictive performance when adversarial content is introduced, (2) helpful guidance is often insufficient to counteract the negative influence of adversarial information, and (3) in Kaggle datasets, LLMs often make errors in handling time-series data, applying consistent feature engineering across different folds, and interpreting categorical variables correctly. These findings highlight a substantial gap in current models’ ability to critically evaluate and leverage expert knowledge, underscoring an essential research direction for developing more robust, knowledge-aware automated data science systems. Our data and code are publicly available here.
Retracing the Past: LLMs Emit Training Data When They Get Lost
Myeongseob Ko | Nikhil Reddy Billa | Adam Nguyen | Charles Fleming | Ming Jin | Ruoxi Jia
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
Myeongseob Ko | Nikhil Reddy Billa | Adam Nguyen | Charles Fleming | Ming Jin | Ruoxi Jia
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
The memorization of training data in large language models (LLMs) poses significant privacy and copyright concerns. Existing data extraction methods, particularly heuristic-based divergence attacks, often exhibit limited success and offer limited insight into the fundamental drivers of memorization leakage. This paper introduces Confusion-Inducing Attacks (CIA), a principled framework for extracting memorized data by systematically maximizing model uncertainty. We empirically demonstrate that the emission of memorized text during divergence is preceded by a sustained spike in token-level prediction entropy. CIA leverages this insight by optimizing input snippets to deliberately induce this consecutive high-entropy state. For aligned LLMs, we further propose Mismatched Supervised Fine-tuning (SFT) to simultaneously weaken their alignment and induce targeted confusion, thereby increasing susceptibility to our attacks. Experiments on various unaligned and aligned LLMs demonstrate that our proposed attacks outperform existing baselines in extracting verbatim and near-verbatim training data without requiring prior knowledge of the training data. Our findings highlight persistent memorization risks across various LLMs and offer a more systematic method for assessing these vulnerabilities.
Agents Under Siege: Breaking Pragmatic Multi-Agent LLM Systems with Optimized Prompt Attacks
Rana Shahroz | Zhen Tan | Sukwon Yun | Charles Fleming | Tianlong Chen
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Rana Shahroz | Zhen Tan | Sukwon Yun | Charles Fleming | Tianlong Chen
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Most discussions about Large Language Model (LLM) safety have focused on single-agent settings but multi-agent LLM systems now create novel adversarial risks because their behavior depends on communication between agents and decentralized reasoning. In this work, we innovatively focus on attacking pragmatic systems that have constrains such as limited token bandwidth, latency between message delivery, and defense mechanisms. We design a permutation-invariant adversarial attack that optimizes prompt distribution across latency and bandwidth-constraint network topologies to bypass distributed safety mechanisms within the system. Formulating the attack path as a problem of maximum-flow minimum-cost, coupled with the novel Permutation-Invariant Evasion Loss (PIEL), we leverage graph-based optimization to maximize attack success rate while minimizing detection risk. Evaluating across models including Llama, Mistral, Gemma, DeepSeek and other variants on various datasets like JailBreakBench and AdversarialBench, our method outperforms conventional attacks by up to 7×, exposing critical vulnerabilities in multi-agent systems. Moreover, we demonstrate that existing defenses, including variants of Llama-Guard and PromptGuard, fail to prohibit our attack, emphasizing the urgent need for multi-agent specific safety mechanisms.
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- Tianlong Chen 4
- Xiaoou Liu 2
- Rana Shahroz 2
- Zhen Tan 2
- Hua Wei 2
- Huaiyuan Yao 2
- Xuan Bi 1
- Nikhil Reddy Billa 1
- Longchao Da 1
- Jie Ding 1
- Jin Du 1
- Mingyi Hong 1
- Ruoxi Jia 1
- Ming Jin 1
- Myeongseob Ko 1
- Ashish Kundu 1
- Thai Le 1
- Zirui Liu 1
- An Luo 1
- Adam Nguyen 1
- Binh Nguyen 1
- Jayanth Srinivasa 1
- Fangqiao Tian 1
- Ganghua Wang 1
- Xun Xian 1
- Sukwon Yun 1
- Ruichen Zhang 1
- Shengchun Zhao 1
- Ming Zhong 1
- Jiawei Zhou 1