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cs.CL2026

TrustMI: Causally controlling how assistants trust their users

Théo Lasnier, Romain Froger, Maxence Lasbordes +1

Large Language Model (LLM) assistants routinely decide whether they can trust users and third parties whose competence, intentions, and integrity they cannot verify. This uncertain…

cs.CL2026

Small Agents with Semantic Search: Efficient Multilingual Code Localization

Maxence Lasbordes, Aarush Sinha, Raphael Sourty +2

Locating relevant files from natural-language requests is a core subtask for agents operating over code repositories. We investigate whether this task can be delegated to compact,…

cs.CL2026

LLM Forensics: Where Do Backdoors Hide? Localizing and Controlling Trigger Mechanisms with Sparse Autoencoders

Wissam Antoun, Francis Kulumba, Théo Lasnier +2

Even though backdoors in LLMs have been a growing concern, their inner workings are still under heavy scrutiny. Trigger-based backdoors are easy to define behaviorally, a rare inpu…

cs.CL2026

When Trivia Is Not Trivial: Everyday Knowledge Failures in Multilingual LLMs

Anna Mosolova, Djamé Seddah

Quiz rooms, trivia nights, and quiz shows challenge human knowledge across a wide range of topics, from canonical facts to everyday culture. In this paper, we examine whether large…

cs.CL2026

Multi-Hop Knowledge Composition is Bound by Pretraining Exposure

Yannis Karmim, Luis Marti, Djamé Seddah +1

Large Language Models fail at implicit multi-hop reasoning: a model answers "When was born?" and "Who is 's closest friend?" correctly but fails on "When was 's closest f…

cs.CL2026

Backdoor Unlearning Generalization: A Path Toward the Removal of Unknown Triggers in LLMs

Lisa Bouger, Théo Lasnier, Philippe Loubet Moundi +2

Backdoor attacks in Large Language Models (LLMs) are a growing security concern, where models can generate adversary-chosen content. Existing defenses target backdoors one at a tim…

cs.CL2026

Language-Switching Triggers Take a Latent Detour Through Language Models

Francis Kulumba, Wissam Antoun, Théo Lasnier +2

Backdoor attacks on language models pose a growing security concern, yet the internal mechanisms by which a trigger sequence hijacks model computations remain poorly understood. We…

cs.CL2026

Rethinking the Multilingual Reasoning Gap with Layer Swap

Maxence Lasbordes, Amélie Chatelain, Djamé Seddah

Recent reasoning Large Language Models produce a chain-of-thought (CoT) predominantly in English, even when prompted in non-English languages. Prior work suggests that forcing the…

cs.CL2026

Leveraging Wikidata for Geographically Informed Sociocultural Bias Dataset Creation: Application to Latin America

Yannis Karmim, Renato Pino, Hernan Contreras +6

Large Language Models (LLMs) exhibit inequalities with respect to various cultural contexts. Most prominent open-weights models are trained on Global North data and show prejudicia…

cs.CL2026

When Tables Go Crazy: Evaluating Multimodal Models on French Financial Documents

Virginie Mouilleron, Théo Lasnier, Anna Mosolova +1

Vision-language models (VLMs) perform well on many document understanding tasks, yet their reliability in specialized, non-English domains remains underexplored. This gap is especi…

cs.CL2026

Language Triggers Hijack Language Circuits: A Mechanistic Analysis of Backdoor Behaviors in Large Language Models

Théo Lasnier, Wissam Antoun, Francis Kulumba +2

Backdoor attacks pose significant security risks for Large Language Models (LLMs), yet the internal mechanisms by which triggers operate remain poorly understood. We present the fi…

cs.CL2026

Translation Heads: Disentangling meaning from language in LLM-based machine translation

Théo Lasnier, Armel Zebaze, Djamé Seddah +2

Mechanistic Interpretability (MI) seeks to explain how neural networks implement their capabilities, but the scale of Large Language Models (LLMs) has limited prior MI work in Mach…

cs.CL2026

Multilingual, Multimodal Pipeline for Creating Authentic and Structured Fact-Checked Claim Dataset

Z. Melce Hüsünbeyi, Virginie Mouilleron, Leonie Uhling +3

The rapid proliferation of misinformation across online platforms underscores the urgent need for robust, up-to-date, explainable, and multilingual fact-checking resources. However…