Morocco

While large language models (LLMs) excel at generating structured data, such as code, their ability to precisely manipulating it based on instructions remains relatively under-explored. Regular expressions (regexes), critical in practice, are challenging to manipulate. Crucially, the correctness of transformations can be mathematically verified, making them exceptionally well-suited for measuring the symbolic reasoning of LLMs. We introduce Query4Regex, a new benchmark for evaluating verifiable transformations on regexes. Our benchmark tests two query formats: natural language instructions and a program-like domain-specific language (DSL) that specifies the sequence of operations. We evaluate a range of LLMs, verifying semantic correctness through rigorous deterministic finite automata (DFA) equivalence testing. Our empirical studies reveal: 1) the formal DSL significantly outperforms natural language, achieving up to 6.74%p average accuracy gains. 2) Performance for both formats degrades sharply as compositional complexity increases, highlighting a core challenge in multi-step reasoning. 3) Models often generate syntactically valid but semantically incorrect regexes, making errors difficult to detect without formal verification. Query4Regex provides a robust framework for analyzing the gap between LLMs&#39; linguistic fluency and their symbolic reasoning, paving the way for more reliable and verifiable manipulation of formal languages.

EACL 2026

Query4Regex: Verifiable Regex Transformation through Formal Operations from NL and DSL Queries

formal operations

regex transformation

## Welcome!
"I am excited to welcome you to this year’s edition of the Conference on Empirical Methods in Natural Language Processing! Importantly, it marks the 30th edition of EMNLP. With over 8,000 submissions, more than 3,000 accepted papers, and thousands of attendees, we have come a long way from that first
workshop, which had 14 accepted papers. As the field looks ahead, Suzhou is the fitting location for celebrating this milestone: rooted in a long literary tradition, yet modern and forward-looking, and home to a large share of the NLP community."<br>

*Message from the General Chair, Dirk Hovy*





<br>

EMNLP 2025

Celebrate 30 Years of EMNLP! 
EMNLP 2025 will be held in Suzhou, China from November 5th to November 9th, 2025.

While large language models (LLMs) excel at generating structured data, such as code, their ability to precisely manipulating it based on instructions remains relatively under-explored. Regular expressions (regexes), critical in practice, are challenging to manipulate. Crucially, the correctness of transformations can be mathematically verified, making them exceptionally well-suited for measuring the symbolic reasoning of LLMs. We introduce Query4Regex, a new benchmark for evaluating verifiable transformations on regexes. Our benchmark tests two query formats: natural language instructions and a program-like domain-specific language (DSL) that specifies the sequence of operations. We evaluate a range of LLMs, verifying semantic correctness through rigorous deterministic finite automata (DFA) equivalence testing. Our empirical studies reveal: 1) the formal DSL significantly outperforms natural language, achieving up to 6.74%p average accuracy gains. 2) Performance for both formats degrades sharply as compositional complexity increases, highlighting a core challenge in multi-step reasoning. 3) Models often generate syntactically valid but semantically incorrect regexes, making errors difficult to detect without formal verification. Query4Regex provides a robust framework for analyzing the gap between LLMs' linguistic fluency and their symbolic reasoning, paving the way for more reliable and verifiable manipulation of formal languages.

poster

#### *Message from the General Chair, Aline Villavicencio*
I’m delighted and honoured to welcome you to the 19th Conference of the European Chapter of the Association for Computational Linguistics (EACL 2026), taking place in the beautiful city of Rabat, in Morocco, in March 24-29, 2026. EACL is the flagship European conference of the Association and EACL 2026 proudly continues our field’s tradition of excellence in scholarship, innovation, and inclusivity. I am deeply grateful to the many volunteers whose dedication, generosity, and tireless efforts have made this conference possible.
For the first time EACL is being hosted in the African continent. This is an important milestone for our community, and we are grateful to our Moroccan hosts for enabling this historic moment by bringing this edition of EACL to Rabat. We are also delighted that the Second Arabic NLP School is co-located with EACL. We hope attendees enjoy this wonderful opportunity to strengthen ties with the Computational Linguistics communities across the African continent. *[Read full message](https://drive.google.com/file/d/14NlmHvwM6fPJuMmOvVh7K0vtQbEyv3SZ/view?usp=sharing)*<br><br>

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Welcome to the 19th Conference of the European Chapter of the Association for Computational Linguistics (EACL). EACL 2026 will be held in Rabat, Morocco, from March 24–29, 2026. 

Agentic AI systems, which build on Large Language Models (LLMs) and interact with tools and memory, have rapidly advanced in capability and scope. Yet, since LLMs have been shown to struggle in multilingual settings, typically resulting in lower performance and reduced safety, agentic systems risk inheriting these limitations. This raises concerns about the accessibility of such systems, as users interacting in languages other than English may encounter unreliable or security-critical agent behavior. Despite growing interest in evaluating agentic AI, existing benchmarks focus exclusively on English, leaving multilingual settings unexplored. To address this gap, we propose MAPS, a multilingual benchmark suite designed to evaluate agentic AI systems across diverse languages and tasks. MAPS builds on four widely used agentic benchmarks - GAIA (real-world tasks), SWE-bench (code generation), MATH (mathematical reasoning), and the Agent Security Benchmark (security). We translate each dataset into eleven diverse languages, resulting in 805 unique tasks and 9,660 total language-specific instances - enabling a systematic analysis of the multilingual effect on AI agents' performance and robustness. Empirically, we observe a degradation in both performance and security when transitioning from English to other languages, with severity varying by task and correlating with the amount of translated input. Building on these findings, we provide actionable recommendations to guide agentic AI systems development and assessment under multilingual settings. This work establishes the first standardized evaluation framework for multilingual agentic AI, encouraging future research towards equitable, reliable, and accessible agentic AI. The MAPS benchmark suite will become publicly available upon publication.

MAPS: A Multilingual Benchmark for Agent Performance and Security

Large Language Models (LLMs) are now state-of-the-art at summarization, yet the hidden notion of importance that drives their information selections remains hidden. We propose to address this by combining behavioral and computational analyses. Behaviorally, we generate length-controlled summaries and derive empirical importance distributions based on how often each information unit is selected. These reveal that LLMs converge on consistent importance patterns, sharply different from pre-LLM baselines, and that LLMs cluster more by size than by family. Computationally, we probe internal representations and find that middle layers strongly encode importance, and certain attention heads alone align well with empirical importance distributions. Together, these results provide initial insights about what LLMs prioritize in summarization and how this priority is internally represented, opening a path toward interpreting, and ultimately controlling, information selection in LLMs.

What Matters to an LLM? Behavioral and Computational Evidences from Summarization

Large language models (LLMs) achieve state-of-the-art performance in machine translation, but are also known to be sensitive to errors in user prompts. Given these models are largely trained on and respond best to prompts in standard English, this may affect the quality of LLM outputs for second language English speakers as well as real-world lay users, with potentially disproportionate effects on the former. We explore this effect by modeling a range of error types exhibited by such users, motivated by studies of L2 English, and quantifying their impact on LLM performance. We work with two related tasks: machine translation and machine translation evaluation. We find that LLMs-as-MT are brittle to natural spelling errors but not to errors at the phrasal level. However, the variance in quality caused by these errors is lower than the variance over the initial prompt choice, suggesting that ``perfect English'' for a given prompt is less important than choosing a good prompt. Since lay users and L2 speakers may use non-optimal prompts as well as display imperfect language skills, our work calls for increasing the resilience of model performance to both these phenomena to best serve a diverse user base, both from a robustness and fairness perspective.

How Important is ‘Perfect’ English for Machine Translation Prompts?

Practicing conversations with large language models (LLMs) presents a promising alternative to traditional in-person language learning. However, most LLMs generate text at a near-native level of complexity, making them ill-suited for beginner learners (CEFR: A1вЂ“A2). In this paper, we investigate whether controllable generation techniques can adapt LLM outputs to better support absolute beginners. We evaluate these methods through both automatic metrics and a user study with university-level learners of Japanese. Our findings show that while prompting alone fails, controllable generation techniques can successfully improve output comprehensibility for beginner speakers (from 40.4% to 84.3%). We further introduce a new token-level evaluation metric, Token Miss Rate (TMR), that quantifies the proportion of incomprehensible tokens per utterance and correlates strongly with human judgments. To support future research in AI-assisted language learning, we release our code, models, annotation tools, and dataset.

Toward Beginner-Friendly LLMs for Language Learning: Controlling Difficulty in Conversation

Instruction pre-training (IPT) has recently emerged as an effective intermediate stage between vanilla pre-training and post-training for large language models (LLMs). However, the optimal design of IPT corpora---such as the balance between raw and instruction-response data, languages, and task categories---remains unclear. We systematically study IPT corpus composition using a bilingual (English and Japanese) and multi-category (coding, general, math, and reasoning) instruction-response dataset. Through extensive IPT experiments across four base models, including both English-centric and bilingual LLMs, we find that: (1) more instruction-response data generally enhances model performance, particularly for models with large VPT budgets; (2) Japanese instruction data can improve English performance through cross-lingual transfer; and (3) the effectiveness of post-training varies across categories: coding performance is largely determined during IPT, while math and reasoning continue to improve during post-training.

Comprehensive Study of Bilingual and Multi-category Instruction Pre-training

Fact-checking on major platforms, such as X, Meta, and TikTok, is shifting from expert-driven verification to a community-based setup, where users contribute explanatory notes to clarify why a post might be misleading. An important challenge here is determining whether an explanation is helpful for understanding real-world claims and the reasons why, which remains largely underexplored in prior research. In practice, most community notes remain unpublished due to slow community annotation, and the reasons for helpfulness lack clear definitions. To bridge these gaps, we introduce the task of predicting both the helpfulness of explanatory notes and the reason for this. We present COMMUNITYNOTES, a large-scale multilingual dataset of 105k posts with user-provided notes and helpfulness labels. We further propose a framework that automatically generates and improves reason definitions via automatic prompt optimization, and integrate them into prediction. Our experiments show that the optimized definitions can improve both helpfulness and reason prediction. Finally, we show that the helpfulness information are beneficial for existing fact-checking systems.

COMMUNITYNOTES: A Dataset for Exploring the Helpfulness of Fact-Checking Explanations

Fine-tuning LLMs introduces many important behaviors, such as instruction following, safety alignment. This makes it crucial to study how fine-tuning changes models' internal mechanisms. Sparse autoencoders (SAEs) offer a powerful tool for interpreting neural networks by extracting concepts (features) represented in their activations. Previous work observed that SAEs trained on base models transfer effectively to instruction-tuned (chat) models, attributed to activation similarity. In this work, we propose *feature drift* as an alternative explanation: the feature space remains relevant, but the distribution of feature activations changes. In other words, fine-tuning recombines existing concepts rather than learning new ones. We validate this by showing base SAEs reconstruct both base and chat activations comparably despite systematic differences, with individual features exhibiting clear drift patterns. In a refusal behavior case study, we identify base SAE features that drift to activate on harmful instructions in chat models. Causal interventions using these features confirm that they mediate refusal. Our findings suggest that monitoring how existing features drift, rather than searching for entirely new features, may provide a more complete explanation of how fine-tuning changes model capabilities.

Feature Drift: How Fine-Tuning Repurposes Representations in LLMs

While the reasoning abilities of large language models (LLMs) continue to advance, it remains underexplored how such abilities vary across languages in multilingual LLMs and whether different languages generate distinct reasoning paths. In this work, we explore how reasoning knowledge in different languages complements one another. We propose a novel cross-lingual reward modeling framework that aggregates reasoning signals across languages to enhance mathematical reasoning. Our results show a substantial improvement (about 10 scores) in multilingual mathematical reasoning performance compared to using reward modeling within a single language, benefiting even high-resource languages. While English often exhibits the highest performance in multilingual models, we find that cross-lingual sampling benefits English, particularly under low sampling budgets. Our findings reveal new opportunities to improve multilingual reasoning by leveraging the complementary strengths of diverse languages.

Best-of-L: Cross-Lingual Reward Modeling for Mathematical Reasoning

Effectively identifying threats and mitigating their potential damage during crisis situations, such as natural disasters or violent attacks, is paramount for safeguarding endangered individuals. To tackle these challenges, AI has been used in assisting humans in emergency situations. Still, the use of NLP techniques remains limited, and mostly focuses on classification tasks. The significant potential of timely warning message generation using NLG architectures, however, has been largely overlooked. In this paper we present CrisiText, the first large-scale dataset for the generation of warning messages across 13 different types of crisis scenarios. The dataset contains more than 400,000 warning messages (spanning almost 18,000 crisis situations) aimed at assisting civilians during and after such events. To generate the dataset, we started from existing crisis descriptions, and created chains of events related to the scenarios. Each event was then paired with a warning message. The generations follow expert's written guidelines to ensure correct terminology and factuality of their suggestions. Additionally, each message is accompanied by three suboptimal warning types to allow for the study of different NLG approaches. To this end, we conducted a series of experiments comparing supervised fine-tuning setups with preference alignment, zero-shot, and few-shot approaches. We further assessed model performance in out-of-distribution scenarios and evaluated the effectiveness of an automatic post-editor.

CrisiText: A dataset of warning messages for LLM training in emergency communication

Sparse Autoencoders (SAEs) have been successfully used to probe Large Language Models (LLMs) and extract interpretable concepts from their internal representations. These concepts are linear combinations of neuron activations that correspond to human-interpretable features. In this paper, we investigate the effectiveness of SAE-based explainability approaches for sentence classification, a domain where such methods have not been extensively explored. We present a novel SAE-based model \verb|ClassifSAE| tailored for text classification, leveraging a specialized classifier head and incorporating an activation rate sparsity loss. We benchmark this architecture against established methods such as ConceptShap, Independent Component Analysis, HI-Concept and a standard TopK-SAE baseline. Our evaluation covers several classification benchmarks and backbone LLMs. We further enrich our analysis with two novel metrics for measuring the precision of concept-based explanations, using an external sentence encoder. Our empirical results show that \verb|ClassifSAE| improves both the causality and interpretability of the extracted features.

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MAPS: A Multilingual Benchmark for Agent Performance and Security

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Do Large Language Models excel in Complex Logical Reasoning with Formal Language?

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