Fan Xu, Xinyu Hu, Zhenghan Yu, Li Lin, Xu Zhang, Yang Zhang, Wei Zhou, Jinjie Gu 等 9 位作者
The increasing reliance on natural language generation (NLG) models, particularly large language models, has raised concerns about the reliability and accuracy of their outputs. A key challenge is hallucination, where models produce plausible but incorrect information. As a result, hallucination detection has become a critical task. In this work, we introduce a comprehensive hallucination taxonomy with 11 categories across various NLG tasks and propose the HAllucination Detection (HAD) models, which integrate hallucination detection, span-level identification, and correction into a single inference process. Trained on an elaborate synthetic dataset of about 90K samples, our HAD models are versatile and can be applied to various NLG tasks. We also carefully annotate a test set for hallucination detection, called HADTest, which contains 2,248 samples. Evaluations on in-domain and out-of-domain test sets show that our HAD models generally outperform the existing baselines, achieving state-of-the-art results on HaluEval, FactCHD, and FaithBench, confirming their robustness and versatility.
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cs.CL
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 6: Industry Track) · 2026 · 正式发表
As large language models (LLMs) demonstrate remarkable capabilities across a wide range of tasks, ensuring the safety of their outputs is increasingly critical. To mitigate the risk of policy-violating responses, numerous guardrail models have been developed for harmful-content detection. While effective on short outputs, existing guardrails degrade on long-form responses, reflecting limited semantic understanding and weak robustness to contextual noise. To address these limitations, we propose RST-Guarder, an inference-time method that improves harmful-content detection for long-form inputs without additional data curation or model training. RST-Guarder first applies a RST parser to long-form inputs to get discourse-level semantic relations among segments, and subsequently performs hierarchical probabilistic inference to aggregate segment-level safety scores produced by pre-trained guardrail models. We evaluate RST-Guarder across multiple benchmarks and a diverse set of widely used guardrail models. Experimental results demonstrate that RST-Guarder consistently improves harmful-content detection on long-form inputs, while significantly reducing false positives that incorrectly classify benign content as harmful.
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cs.CL
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers) · 2026 · 正式发表
While DLMs have emerged as an alternative to ARMs, robust content provenance mechanisms for this architecture remain unexplored. Existing multi-bit watermarking schemes, heavily reliant on the sequential context of ARMs, cannot be directly applied to DLMs. In this paper, we reframe the multi-bit watermarking problem through a novel Digital Signal Processing (DSP) lens. We draw an analogy between prior works and TDMA (Time Division Multiple Access) in telecommunications, revealing their inherent limitations. To overcome these limitations, we introduce CDMArk, the first multi-bit watermarking framework tailored for DLMs, orchestrating a paradigm shift from TDMA to CDMA (Code Division Multiple Access). Our method encodes the entire watermark message across all tokens holographically. We further provide rigorous statistical guarantees for the watermark detection process. Extensive experiments demonstrate that CDMArk achieves a new state-of-the-art Pareto frontier between imperceptibility and effectiveness.
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cs.CL
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers) · 2026 · 正式发表
While large language models have achieved remarkable success in various natural language processing tasks, their potential in grammatical error correction remains underexplored. Recent work has applied reinforcement learning with rule-based rewards to CGEC, but these approaches rely on coarse-grained binary signals (exact match or not) that fail to capture fine-grained quality distinctions among correction candidates. In this paper, we propose Edit-Aware Reward Model (EARM), a novel reward modeling framework that explicitly incorporates edit-awareness into preference learning for CGEC. EARM introduces a dual-granularity training objective that jointly optimizes sentence-level and token-level weighted Bradley-Terry ranking losses, where edit tokens receive higher importance weights. When integrated with GRPO, our approach achieves 61.29/63.08 on FCGEC/NaCGEC (single output), and 65.04/64.59 with best-of-16 reranking, surpassing previous best by 5.41 and 1.80 points. Extensive experiments demonstrate that learned edit-aware rewards significantly outperform rule-based alternatives for CGEC preference optimization.
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cs.CL
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers) · 2026 · 正式发表
As large language models become standard backends for content generation, practical provenance increasingly requires multi-bit watermarking. In provider-internal deployments, a key requirement is message symmetry: the message itself should not systematically affect either text quality or verification outcomes.Vocabulary-partition watermarks can break message symmetry in low-entropy decoding: some messages are assigned most of the probability mass, while others are forced to use tail tokens. This makes embedding quality and message decoding accuracy message-dependent.We propose QuantileMark, a white-box multi-bit watermark that embeds messages within the continuous cumulative probability interval [0, 1).At each step, QuantileMark partitions this interval into M equal-mass bins and samples strictly from the bin assigned to the target symbol, ensuring a fixed 1/M probability budget regardless of context entropy.For detection, the verifier reconstructs the same partition under teacher forcing, computes posteriors over latent bins, and aggregates evidence for verification.We prove message-unbiasedness, a property ensuring that the base distribution is recovered when averaging over messages. This provides a theoretical foundation for generation-side symmetry, while the equal-mass design additionally promotes uniform evidence strength across messages on the detection side.Empirical results on C4 continuation and LFQA show improved multi-bit recovery and detection robustness over strong baselines, with negligible impact on generation quality.
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cs.CL
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers) · 2026 · 正式发表
Xiaofan Zheng Peking University and Xi'an Jiaotong University, Xinghao Wang Tsinghua University, Xiaojun Wan
Training Large Vision-Language Models (LVLMs) is costly and resource-intensive, making them valuable assets. To prevent malicious users from unauthorized commercialization of these artificial intelligence assets through fine-tuning and black-box deployment, model fingerprinting techniques aimed at verifying the ownership of LVLMs are receiving widespread attention. Existing fingerprinting techniques rely on adversarial attacks or backdoor attacks to construct trigger images for specific outputs, attributing model ownership by comparing whether the output of trigger images on suspected models matches the predetermined output. However, these methods depend on fixed-form triggers as explicit model fingerprints, which have limitations in terms of stealthiness and robustness. Inspired by unlearning research, we propose Unlearning-based Multimodal Memorization Fingerprint (UMMF). UMMF strengthens the overfitting characteristics of training samples by unlearning neighboring samples of the training samples, thereby introducing detectable regions of poor generalization in the data manifold. Compared with previous methods, our approach leverages the differences in memorization strength of LVLMs on neighboring samples as implicit model fingerprints, rather than relying on specific input-output pairs as explicit triggers. This endows it with stronger stealthiness, robustness, and adaptability. To simulate real application scenarios, we conduct extensive experiments using multiple strategies and different datasets, further demonstrating its superiority in protecting LVLM ownership.
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cs.CL · cs.AI · cs.CV
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers) · 2026 · 正式发表
Fan Xu Peking University, Huixuan Zhang, Xiaojun Wan
Diffusion Large Language Models (DLLMs) generate text via iterative masked-token denoising, supporting parallel prediction and bidirectional context modeling. Despite these advantages, decoding remains challenging: many tokens appear predictable early, yet single-step predictions are often unstable, exhibiting temporal oscillations or overconfidence, making it difficult to determine which tokens can be safely committed. To address these challenges, we propose DecoCal, a Decoding framework that explicitly performs Calibration of token-level confidence across diffusion steps and leverages the calibrated results to guide decoding decisions. Specifically, DecoCal aggregates historical predictions to maintain calibrated confidence, triggering unmasking only when a token is sufficiently stable, while a remasking mechanism allows revision of premature commitments. This calibration-based design enables early decoding of reliably converged tokens while deferring or correcting unstable ones, balancing reliability and speed. Experiments on multiple DLLMs and benchmarks show that DecoCal improves generation accuracy compared to existing strategies. Our results highlight the importance of temporal calibration in unlocking the full potential of diffusion-based language generation.
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cs.CL
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers) · 2026 · 正式发表
Xunjian Yin Duke University, Sitao Cheng, Yuxi Xie, Xinyu Hu, Li Lin, Xinyi Wang Princeton University, Liangming Pan Peking University, William Yang Wang 等 9 位作者
Autoregressive language models are trained exclusively left-to-right. We explore the complementary factorization, training right-to-left at scale, and ask what reasoning patterns emerge when a model conditions on future context to predict the past.We train LEDOM, an open-source purely reverse autoregressive language model (2B/7B parameters, 435B tokens), and find it develops capabilities distinct from forward models, including abductive inference, question synthesis, and structural handling of the reversal curse.We then explore one application of the reverse model: combining forward likelihood P(y \mid x) with reverse posterior P(x \mid y) through noisy channel duality. We propose Reverse Reward, which reranks forward outputs using reverse posterior estimates, and prove that bidirectional scoring penalizes hallucinated reasoning chains whose backward reconstruction degrades.Reverse Reward yields gains of up to 6.6% on AIME 2024 and 15% on AMC 2023 across multiple strong baselines. We release all codes at https://github.com/Arvid-pku/LEDOM.
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cs.CL
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers) · 2026 · 正式发表