United States

Large Language Models (LLMs) have demonstrated considerable efficacy in 
classification tasks, yet their performance depends on two critical prompt components: Task Instructions (HOW to classify) and Class Descriptions (WHAT defines each class). While prompt engineering research has extensively explored instruction optimization, class descriptions have received comparatively less attention, often being treated as fixed inputs or simple label names. This represents a critical gap for real-world classification tasks, particularly in contact center domains, where labels often suffer from ambiguous boundaries, overlapping definitions, and incomplete coverage of possible cases—substantially limiting accuracy regardless of instruction 
quality.


We propose a multi-agent framework for iteratively refining class descriptions based on classification errors. By analyzing misclassified 
instances, language agents automatically generate improved descriptions that better capture class distinctions and resolve ambiguities. Empirical evaluation across contact center and public benchmark datasets demonstrates upto 20.71% accuracy improvements over static class descriptions, addressing an orthogonal dimension to existing instruction optimization techniques.

ACL 2026

Beyond Instruction Optimization: Multi-Agent Error-Driven Class Description Refinement for LLM-Based Classification

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Large-scale integrity enforcement on short-form video platforms typically relies on multiple specialized vertical modules, each dedicated to a specific risk category. However, exhaustively executing these computationally intensive modules over massive content streams leads to substantial inference overhead, despite the fact that most content is benign and violations are usually confined to limited policy domains. To address this inefficiency, we propose RADAR, a lightweight risk-aware routing framework that selectively releases low-risk content while dispatching high-risk instances to appropriate vertical modules. Industrial deployment of such routing systems presents two major challenges: (1) systematic label sparsity caused by disjoint annotation pipelines across risk categories, and (2) the capacity-efficiency tradeoff inherent to compact routing architectures. To overcome these challenges, RADAR incorporates Validity-Aware Masking to handle fragmented supervision and Expert-Guided Knowledge Distillation to transfer knowledge from heavyweight expert models into the lightweight router. Experiments on large-scale real-world datasets demonstrate that the proposed masking strategy effectively mitigates disjoint annotation issues, while distillation substantially enhances routing accuracy, enabling the lightweight router to achieve competitive or superior performance compared to specialized expert models.

RADAR: Risk-Aware Distilled Adaptive Routing for Efficient Short-Form Video Platform Ecosystem Governance

In-context learning (ICL) enables Large Language Models (LLMs) to adapt to new tasks using few examples, with task vectors, defined as specific hidden state activations hypothesized to encode task information. Existing studies are limited by small-scale benchmarks, restricting comprehensive analysis. We introduce QᴜɪᴛᴇAFᴇᴡ, a novel dataset of 3,096 diverse few-shot tasks, each with 30 input-output pairs derived from the Alpaca dataset. Experiments with Llama-3-8B on QᴜɪᴛᴇAFᴇᴡ reveal: (1) task vector performance peaks at an intermediate layer (e.g., 15th), (2) effectiveness varies significantly by task type, and (3) complex tasks rely on multiple, subtask-specific vectors rather than a single vector, suggesting distributed task knowledge representation.

One Task Vector is not Enough: A Large-Scale Study for In-Context Learning

With the emergence of Large Language Models (LLMs), new methods in Information Retrieval are available in which relevance is estimated directly through language understanding and reasoning, instead of embedding similarity. We argue that similarity is a \textit{short-sighted} interpretation of relevance, and that LLM-Based Relevance Judgment Systems (LLM-RJS) (with reasoning) have potential to outperform Neural Embedding Retrieval Systems (NERS) by overcoming this limitation. Using the TREC-DL 2019 passage retrieval dataset, we compare various LLM-RJS with NERS, but observe no noticeable improvement. Subsequently, we analyze the impact of reasoning by comparing LLM-RJS with and without reasoning. We find that human annotations also suffer from short-sightedness, and that false-positives in the reasoning LLM-RJS are primarily mistakes in annotations due to short-sightedness. We conclude that LLM-RJS do have the ability to address the short-sightedness limitation in NERS, but that this cannot be evaluated with standard annotated relevance datasets.

Why Large Language Models can Secretly Outperform Embedding Similarity in Information Retrieval

Retrieval-augmented generation (RAG) based on dense embeddings has become a dominant paradigm for text retrieval. However, many real-world applications require attribute-specific querying, where explicit values or properties must be extracted from text (e.g., symptoms in clinical notes or dosage values in medical reports). Dense retrieval handles paraphrastic variation well but often entangles multiple attributes within a single embedding, making value extraction difficult. Knowledge graphs (KGs), in contrast, support explicit attribute access but are brittle under linguistic and structural variation, leading to low recall. This thesis proposal aims to investigate the representational trade-off underlying these approaches. We study knowledge graph representations from an information-theoretic and optimal coding perspective, focusing on the tension between fine-grained factorization and compact canonicalization of concepts. Building on this perspective, we propose a query-driven framework for constructing and retrieving knowledge graphs from text, aiming to combine the robustness of dense retrieval with the explicit queryability of symbolic representations.

Thesis Proposal: On the Granularity-Robustness Trade-off in Text-Derived Knowledge Graphs

Federated learning with heterogeneous client architectures cannot rely on parameter aggregation. Prototype-based methods address architectural heterogeneity by exchanging class-level representations, but naively averaging prototypes across non-IID clients leads to semantic drift and poor inter-class separation. We propose FedPAGR, a framework where heterogeneous clients project their features into a shared consensus space and exchange class prototypes with a central server. The server refines aggregated prototypes through a geometric regularization objective that enforces agreement with client submissions and inter-class angular separation. Clients anchor their classifiers to the refined prototypes and train with a composite objective combining classification, prototype alignment, and entropy regularization. We evaluate FedPAGR across multiple domains, including four image benchmarks and a clinical NLP task using heterogeneous ClinicalBERT variants, with five architectures per federation under severe label heterogeneity ($\alpha{=}0.1$). FedPAGR achieves the highest ensemble accuracy across all four image datasets and the highest local test accuracy on low-class and clinical tasks, including a 4.99-point improvement over the strongest baseline on MIMIC-IV, while remaining competitive on high-class benchmarks.

FedPAGR: Federated Prototype Alignment via Geometric Refinement for Heterogeneous Architectures

Federated learning is often framed as a practical trade-off in clinical NLP: safer data handling at the cost of lower predictive performance. We test this assumption in a benchmark-specific study of Polish medical text classification and show that the expected penalty of locality is not inevitable. A key issue is evaluation granularity: the test split contains 10{,}634 rows but only 670 unique normalized text hashes, with 18 inconsistent groups removed in strict grouped evaluation. We therefore compare centralized and federated training under both conventional instance-level scoring and a stricter hash-level protocol that controls duplicate inflation. In the strongest settings, federated training matches or slightly exceeds the centralized baseline, reaching instance-level Macro-F1 of $0.8826 \pm 0.0177$ versus $0.8689 \pm 0.0124$, and hash-level Macro-F1 of $0.8908 \pm 0.0220$ versus $0.8841 \pm 0.0078$.We do not claim formal privacy guarantees; rather, we show that in this duplicate-heavy Polish medical text benchmark, conclusions about locality depend strongly on evaluation hygiene. An anonymized GitHub repository with code, run manifests, and evaluation scripts is included with the submission.

Does Locality Cost in Polish Medical Text Classification? Duplicate-Aware Evaluation of Federated Learning

Active learning (AL) reduces labeled data requirements in NLP, yet most methods optimize label efficiency while ignoring annotation cost. Standard uncertainty sampling assumes uniform effort, leading to suboptimal resource allocation when documents vary in length. Supasan and Athuraliya (2026) introduced CAL-Log, a cost-aware AL variant using logarithmic cost modeling C(x)=α+β log(1+L(x)), where C(x) is the predicted annotation time for document x and L(x) is its token length, grounded in information foraging theory (Pirolli and Card, 1999) and psycholinguistic studies of human skimming (Rayner, 1998). This paper presents CAL-Log in full, extending that preliminary framework with two new contributions: temperature-scaled calibrated entropy and online per-annotator cost adaptation, which together resolve the cold-start calibration bottleneck identified in the prior work. Experiments on ten text classification benchmarks demonstrate a 3.3× speedup over BADGE (Batch Active learning by Diverse Gradient Embeddings; Ash et al., 2020) and 3.9× over Entropy sampling to reach F1=0.80, with large effect sizes (Cohen's d>0.8). A live annotation deployment with preliminary user evaluation (N=7) confirms that the online cost model produces reading-speed classifications consistent with annotator self-reports, and that a transparency interface successfully communicates the scoring rationale to non-expert users.

CAL-Log: Cost-Aware Active Learning with Logarithmic Cognitive Effort Modeling and Online Adaptation to Human Annotation Behavior

Self-consistency improves large language models by sampling multiple reasoning paths and selecting the most frequent answer, but majority vote often fails to recover correct answers that are already present among samples. In this work, we reformulate answer selection in self-consistency as a ranking problem. Instead of relying on a single uncertainty or confidence signal, we train a lightweight reranker to score candidate answers using five carefully designed features that capture answer-level frequency, semantic centrality, and reasoning-trace consistency. We instantiate this approach with a LambdaRank model and evaluate it on three datasets under a range of test-time budgets. Across datasets, the proposed method consistently achieves a better accuracy-efficiency trade-off than standard self-consistency and strong baselines, with particularly large gains on question answering benchmarks. Further analysis shows that the proposed features are individually useful and, more importantly, complementary, highlighting the value of learning to combine multiple informative signals for test-time answer selection.

Boosting Self-Consistency with Ranking

Open Information Extraction (OIE) has largely focused on extracting relational tuples from text, yet in its current form remains unsuitable for downstream systems due to the absence of standardized, semantically sound representations. This thesis argues that the field has been addressing extraction as a surface-level prediction problem, leading to outputs that are semantically incomplete and logically ambiguous, particularly in the presence of modality, negation, conditionality, quantification, and attribution. We propose a normalization-first framework that reframes OIE as a structured semantic transformation pipeline, where raw text is first converted into a lossless, canonical form of declarative, active-voice, and irreducible sentence units, and extraction is constrained to atomic unary and binary relations augmented with explicit semantic annotations. Within a Probably Approximately Correct (PAC) learning perspective, we formalize soundness, completeness, and usefulness as approximate yet verifiable guarantees over extraction quality, acknowledging the inherent undecidability of full semantic interpretation. This thesis outlines a feasible research program to develop the theoretical foundations, models, and evaluation protocols required to produce system-ready OIE representations, thereby establishing a principled and executable path toward making OIE directly usable for downstream reasoning and machine interpretability.

Thesis Proposal: A Normalization-First Framework for Sound, Complete, and Utility-Ready Open Information Extraction

LiTS is a modular Python framework for LLM reasoning via tree search. It decomposes tree search into three reusable components—Policy, Transition, and RewardModel—that plug into algorithms like MCTS and BFS. A decorator-based registry enables domain experts to extend to new domains by registering components, and algorithmic researchers to implement custom search algorithms. We demonstrate composability on MATH500 (language reasoning), Crosswords (environment planning), and MapEval (tool use), showing that components and algorithms are orthogonal: components are reusable across algorithms within each task type, and algorithms work across all components and domains. We also report a mode-collapse finding: in infinite action spaces, LLM policy diversity—not reward quality—is the bottleneck for effective tree search. A demonstration video is available at https://youtu.be/nRGX43YrR3I. The package is released under the Apache 2.0 license at https://github.com/xinzhel/lits-llm, including installation instructions and runnable examples that enable users to reproduce the demonstrated workflows.

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Next from ACL 2026

RADAR: Risk-Aware Distilled Adaptive Routing for Efficient Short-Form Video Platform Ecosystem Governance

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