Siheng Xiong
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2026
Adaptive Information Control for Search-Augmented LLM Reasoning
Siheng Xiong | Oguzhan Gungordu | Blair Johnson | James Clayton Kerce | Faramarz Fekri
Findings of the Association for Computational Linguistics: EMNLP 2026
Siheng Xiong | Oguzhan Gungordu | Blair Johnson | James Clayton Kerce | Faramarz Fekri
Findings of the Association for Computational Linguistics: EMNLP 2026
Search-augmented reasoning agents interleave multi-step reasoning with external retrieval, but uncontrolled retrieval can introduce redundant evidence, saturate the context, and destabilize reinforcement learning (RL). Existing outcome-based RL methods provide only sparse terminal rewards, offering limited guidance for intermediate information-acquisition decisions. We propose DeepControl, an adaptive information-control framework based on information utility, a state-dependent estimate of the marginal value of retrieved evidence. The framework regulates information acquisition along two axes: extent, i.e., whether retrieval should continue, and resolution, i.e., how much retrieved detail should be exposed. It implements these controls through retrieval-continuation guidance, hierarchical granularity control, and an annealed control-forcing scheme. This enables the policy to internalize effective acquisition behavior during training and operate without external control at test time. Across seven benchmarks, DeepControl consistently outperforms strong RL and retrieval baselines without explicit information control; compared with Search-R1, it improves average performance by +9.4 and +8.6 points on Qwen2.5-7B and Qwen2.5-3B, respectively. Additional analyses show improved search effectiveness, training stability, and evidence utilization.
DSL-LLaDA: Scaling Continuous Denoising to 8B Masked Diffusion LMs
Longxuan Yu | Yunshu Wu | Yu Fu | Siheng Xiong | Rob Brekelmans | Hui Liu | Yue Dong | Greg Ver Steeg
Findings of the Association for Computational Linguistics: EMNLP 2026
Longxuan Yu | Yunshu Wu | Yu Fu | Siheng Xiong | Rob Brekelmans | Hui Liu | Yue Dong | Greg Ver Steeg
Findings of the Association for Computational Linguistics: EMNLP 2026
Masked diffusion language models (DLMs) generate text through iterative parallel decoding, but at low step budgets, committing many tokens independently can produce premature termination or repetitive outputs. Continuous embedding-space denoising can mitigate this failure mode by maintaining soft states for all positions, yet training such models from scratch at scale remains challenging. We show that a pretrained masked DLM can instead be efficiently adapted to support continuous denoising. Starting from LLaDA-8B-Instruct, we perform only 1,000 steps of continued pretraining with Discrete Stochastic Localization (DSL), replacing binary masking with continuous per-token Gaussian noise mapped to soft embedding mixtures. The adapted model supports SDE-based inference that evolves all positions jointly and defers hard token commitment to the final step. At ≤16 denoising evaluations, DSL-LLaDA substantially mitigates the premature-termination and repetition tradeoff in open-ended generation and achieves the best ROUGE-1 among the evaluated diffusion baselines on all four zero-shot summarization benchmarks. The same adaptation also enables selective correction of corrupted tokens while preserving more than 98% of clean tokens. Same-compute controls indicate that these behaviors arise from continuous-noise exposure rather than additional training alone.
2025
CausalEval: Towards Better Causal Reasoning in Language Models
Longxuan Yu | Delin Chen | Siheng Xiong | Qingyang Wu | Dawei Li | Zhikai Chen | Xiaoze Liu | Liangming Pan
Proceedings of the 2025 Conference of the Nations of the Americas Chapter of the Association for Computational Linguistics: Human Language Technologies (Volume 1: Long Papers)
Longxuan Yu | Delin Chen | Siheng Xiong | Qingyang Wu | Dawei Li | Zhikai Chen | Xiaoze Liu | Liangming Pan
Proceedings of the 2025 Conference of the Nations of the Americas Chapter of the Association for Computational Linguistics: Human Language Technologies (Volume 1: Long Papers)
Causal reasoning (CR) is a crucial aspect of intelligence, essential for problem-solving, decision-making, and understanding the world. While language models (LMs) can generate rationales for their outputs, their ability to reliably perform causal reasoning remains uncertain, often falling short in tasks requiring a deep understanding of causality. In this paper, we introduce CausalEval, a comprehensive review of research aimed at enhancing LMs for causal reasoning, coupled with an empirical evaluation of current models and methods. We categorize existing methods based on the role of LMs: either as reasoning engines or as helpers providing knowledge or data to traditional CR methods, followed by a detailed discussion of methodologies in each category. We then assess the performance of current LMs and various enhancement methods on a range of causal reasoning tasks, providing key findings and in-depth analysis. Finally, we present insights from current studies and highlight promising directions for future research. We aim for this work to serve as a comprehensive resource, fostering further advancements in causal reasoning with LMs.
Deliberate Reasoning in Language Models as Structure-Aware Planning with an Accurate World Model
Siheng Xiong | Ali Payani | Yuan Yang | Faramarz Fekri
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Siheng Xiong | Ali Payani | Yuan Yang | Faramarz Fekri
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Enhancing the reasoning capabilities of language models (LMs) remains a key challenge, especially for tasks that require complex, multi-step decision-making where existing Chain-of-Thought (CoT) approaches struggle with consistency and verification. In this paper, we propose a novel reasoning framework, referred to as Structure-aware Planning with an Accurate World Model (SWAP), that integrates structured knowledge representation with learned planning. Unlike prior methods that rely purely on natural language reasoning, SWAP leverages entailment graphs to encode structured dependencies and enable symbolic verification of intermediate steps. To systematically construct and update the graph, SWAP employs a policy model to propose candidate expansions and a world model to predict structural updates. To improve accuracy, the world model generates multiple alternative updates, and a discriminator re-ranks them based on plausibility. To encourage diverse exploration, we introduce Diversity-based Modelling (DM), which samples candidates from the remaining probability mass after removing previously sampled candidates from the original policy distribution. Additionally, SWAP improves the discrimination accuracy through Contrastive Ranking (CR), which directly compares candidates within prompts and incorporates meta-knowledge to improve ranking quality. We evaluate SWAP across diverse reasoning-intensive benchmarks including math reasoning, logical reasoning, and coding tasks. Extensive experiments demonstrate that SWAP significantly improves upon the base models and consistently outperforms existing reasoning methods.