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Zhiheng Xi

46 accepted papers

2026

AgentGym-RL: An Open-Source Framework to Train LLM Agents for Long-Horizon Decision Making via Multi-Turn RL

ICLR 2026oral

Training LLM agents for complex multi-turn decision-making tasks requires extensive exploration within their environment, with reinforcement learning (RL) as a natural way. However, the open-source community currently lacks a unified RL framework capable of training agents from scratch across divers…

Cited by 0SourcecodeScholar
2026

ChartE$^{3}$: A Comprehensive Benchmark for End-to-End Chart Editing

ICML 2026poster

Charts are a fundamental visualization format for structured data analysis. Enabling end-to-end chart editing according to user intent is of great practical value, yet remains challenging due to the need for both fine-grained control and global structural consistency. Most existing approaches adopt …

Cited by 0SourceScholar
2026

Critique-RL: Training Critiquing Language Models Through Two-Stage RL for Improved Discrimination and Constructive Feedback

ICLR 2026poster

Training critiquing language models to assess and provide feedback on model outputs is a promising way to improve LLMs for complex reasoning tasks. However, existing approaches typically rely on stronger supervisors for annotating critique data. To address this, we propose Critique-RL, an online RL…

Cited by 0SourcecodeScholar
2026

Does Reinforcement Fine-Tuning Improve Generalization of LLM Agents? An Empirical Study

ICML 2026poster

Reinforcement fine-tuning (RFT) has shown promise for training LLM agents to perform multi-turn decision-making based on environment feedback. However, most existing evaluations remain largely in-domain—training and testing are conducted in the same environment or even on the same tasks. In real-wor…

Cited by 0SourceScholar
2026

MathCritique: Enhancing LLM Reasoning via Critique Models with Test-Time and Training-Time Supervision

IJCAI 2026

Training critique models to provide useful feedback for actor models is an effective approach in scalable oversight, especially for complex tasks like math reasoning. However, current research lacks suitable datasets for effectively training critique models and integrating them in a principled way a

Cited by 0Scholar
2026

MetaAct-RL: Training Language Models for Reasoning Through Meta-Action-Based Reinforcement Learning

AAAI 2026technical

Outcome-based reinforcement learning has made notable advances in training language models (LMs) for reasoning. However, without explicit incentives and controls, this paradigm has limitations and instability in eliciting high-quality reasoning trajectories with diverse actions—particularly for mode

Cited by 0SourcePDFScholar
2026

Reasoning or Memorization? Unreliable Results of Reinforcement Learning Due to Data Contamination

AAAI 2026technical

Reasoning in large language models has long been a central research focus, and recent studies employing reinforcement learning (RL) have introduced diverse methods that yield substantial performance gains with minimal or even no external supervision. Surprisingly, some studies even suggest that rand

Cited by 0SourcePDFScholar
2026

SciAgentGym: Benchmarking Multi-Step Scientific Tool-Use in LLM Agents

ICML 2026poster

Scientific reasoning inherently demands integrating sophisticated toolkits to navigate domain-specific knowledge. Yet, current benchmarks largely overlook agents' ability to orchestrate tools for such rigorous workflows. To bridge this gap, we introduce **SciAgentGym**, a scalable interactive enviro…

Cited by 0SourceScholar
2026

Stabilizing Off-Policy Reinforcement Learning for LLMs via Balanced Policy Optimization with Adaptive Clipping

ICLR 2026poster

Reinforcement learning (RL) has recently become the core paradigm for aligning and strengthening large language models (LLMs). Yet, applying RL in off-policy settings—where stale data from past policies are used for training—improves sample efficiency, but remains challenging: policy entropy decline…

Cited by 0SourcecodeScholar
2026

Synthesizing Multimodal Verifiable Game Data to Boost VLMs' General Reasoning

ICLR 2026poster

Vision-language reinforcement learning (RL) has primarily focused on narrow domains (e.g. geometry or chart reasoning). This leaves broader training scenarios and resources underexplored, limiting the exploration and learning of Vision Language Models (VLMs) through RL. We find video games inherentl…

Cited by 0SourcecodeScholar
2026

What Makes a Good Speech Tokenizer for LLM-Centric Speech Generation? A Systematic Study

AAAI 2026technical

Speech-language models (SLMs) offer a promising path toward unifying speech and text understanding and generation. However, challenges remain in achieving effective cross-modal alignment and high-quality speech generation. In this work, we systematically investigate the role of speech tokenizer desi

Cited by 0SourcePDFScholar
2026

Why Reinforcement Fine-Tuning Enables MLLMs Preserve Prior Knowledge Better: A Data Perspective

ICLR 2026poster

Post-training algorithms such as Supervised Fine-Tuning (SFT) and Reinforcement Fine-Tuning (RFT) are widely used to adapt multimodal large language models to downstream tasks. While effective at task adaptation, their impact on prior knowledge remains unclear. In this paper, we introduce jigsaw puz…

Cited by 0SourceScholar
2025

AgentGym: Evaluating and Training Large Language Model-based Agents across Diverse Environments

ACL 2025long

Large language models (LLMs) have emerged as a promising foundation to build generally-capable agents (LLM-based agents) that can handle multi-turn decision-making tasks across various environments. However, the community lacks a unified interactive framework that covers diverse environments for com…

2025

Are LLMs Rational Investors? A Study on the Financial Bias in LLMs

ACL 2025finding

Large language models (LLMs) excel in natural language generation but also exhibit biases, particularly in gender, race, and religion, which can be amplified with widespread use. However, research on biases in specific domains, such as finance, remains limited. To address this gap, we conducted a co…

2025

BMMR: A Large-Scale Bilingual Multimodal Multi-Discipline Reasoning Dataset

NeurIPS 2025poster

In this paper, we introduce BMMR, a large-scale bilingual, multimodal, multi-disciplinary reasoning dataset for the community to develop and evaluate large multimodal models (LMMs). BMMR comprises 100k university-level questions drawn from 300 UNESCO-defined subjects, spanning diverse formats—multip…

Cited by 0SourceScholar
2025

Better Process Supervision with Bi-directional Rewarding Signals

ACL 2025finding

Process supervision, i.e., evaluating each step, is critical for complex large language model (LLM) reasoning and test-time searching with increased inference compute. Existing approaches, represented by process reward models (PRMs), primarily focus on rewarding signals up to the current step, exhib…

2025

CritiQ: Mining Data Quality Criteria from Human Preferences

ACL 2025long

Language model heavily depends on high-quality data for optimal performance. Existing approaches rely on manually designed heuristics, the perplexity of existing models, training classifiers, orcareful prompt engineering, which require significant expert experience and human annotation effort while…

2025

Distill Visual Chart Reasoning Ability from LLMs to MLLMs

EMNLP 2025

Solving complex chart Q&A tasks requires advanced visual reasoning abilities in multimodal large language models (MLLMs), including recognizing key information from visual inputs and conducting reasoning over it. While fine-tuning MLLMs for reasoning is critical, collecting and annotating charts and

2025

Have the VLMs Lost Confidence? A Study of Sycophancy in VLMs

ICLR 2025poster

In the study of LLMs, sycophancy represents a prevalent hallucination that poses significant challenges to these models. Specifically, LLMs often fail to adhere to original correct responses, instead blindly agreeing with users' opinions, even when those opinions are incorrect or malicious. However,…

Cited by 0SourcePDFScholar
2025

LLMEval-Med: A Real-world Clinical Benchmark for Medical LLMs with Physician Validation

EMNLP 2025

Evaluating large language models (LLMs) in medicine is crucial because medical applications require high accuracy with little room for error. Current medical benchmarks have three main types: medical exam-based, comprehensive medical, and specialized assessments. However, these benchmarks have limit

2025

LoRACoE: Improving Large Language Model via Composition-based LoRA Expert

EMNLP 2025

The Mixture of Experts (MoE) architecture improves large language models (LLMs) by utilizing sparsely activated expert sub-networks with a routing module, but it typically demands high training cost. Previous work introduces parameter-efficient fine-tuning (PEFT) modules, e.g., LoRA, to achieve a li

Cited by 0SourcePDFScholar
2025

Mitigating Object Hallucinations in MLLMs via Multi-Frequency Perturbations

EMNLP 2025

Recently, multimodal large language models (MLLMs) have demonstrated remarkable performance in visual-language tasks. However, the authenticity of the responses generated by MLLMs is often compromised by object hallucinations. We identify that a key cause of these hallucinations is the model’s over-

Cited by 0SourcePDFScholar
2025

Mitigating Tail Narrowing in LLM Self-Improvement via Socratic-Guided Sampling

NAACL 2025long

Self-improvement methods enable large language models (LLMs) to generate solutions themselves and iteratively train on filtered, high-quality rationales. This process proves effective and reduces the reliance on human supervision in LLMs’ reasoning, but the performance soon plateaus. We delve into t…

2025

PFDial: A Structured Dialogue Instruction Fine-tuning Method Based on UML Flowcharts

ACL 2025finding

Process-driven dialogue systems, which operate under strict predefined process constraints, are essential in customer service and equipment maintenance scenarios. Although Large Language Models (LLMs) have shown remarkable progress in dialogue and reasoning, they still struggle to solve these strict…

2025

Parrot: A Training Pipeline Enhances Both Program CoT and Natural Language CoT for Reasoning

EMNLP 2025

Natural language chain-of-thought (N-CoT) and Program chain-of-thought (P-CoT) have emerged as two primary paradigms for large language models (LLMs) to solve mathematical reasoning problems. Current research typically endeavors to achieve unidirectional enhancement: P-CoT enhanced N-CoT or N-CoT en

2025

Pre-Trained Policy Discriminators are General Reward Models

NeurIPS 2025poster

We offer a novel perspective on reward modeling by formulating it as a policy discriminator, which quantifies the difference between two policies to generate a reward signal, guiding the training policy towards a target policy with desired behaviors. Based on this conceptual insight, we propose a sc…

Cited by 0SourceScholar
2025

RMB: Comprehensively benchmarking reward models in LLM alignment

ICLR 2025poster

Reward models (RMs) guide the alignment of large language models (LLMs), steering them toward behaviors preferred by humans. Evaluating RMs is the key to better aligning LLMs. However, the current evaluation of RMs may not directly correspond to their alignment performance due to the limited distrib…

2025

TL-Training: A Task-Feature-Based Framework for Training Large Language Models in Tool Use

EMNLP 2025

Large language models (LLMs) achieve remarkable advancements by leveraging tools to interact with environments, a critical step toward generalized AI. However, the standard supervised fine-tuning (SFT) approach, which relies on large-scale datasets, often overlooks task-specific characteristics in t

2025

ToolHop: A Query-Driven Benchmark for Evaluating Large Language Models in Multi-Hop Tool Use

ACL 2025long

Effective evaluation of multi-hop tool use is critical for analyzing the understanding, reasoning, and function-calling capabilities of large language models (LLMs). However, progress has been hindered by a lack of reliable evaluation datasets. To address this, we present ToolHop, a dataset comprisi…

Cited by 0SourcePDFScholar
2025

Toward Optimal LLM Alignments Using Two-Player Games

EMNLP 2025

Alignment of large language models (LLM) is a process that ensures the model’s responses to user prompts align with human intentions and social values. This optimization typically relies on pre-collected prompts. The collection of these prompts often either requires careful human interventions or pr

2024

Improving Discriminative Capability of Reward Models in RLHF Using Contrastive Learning

EMNLP 2024main

Reinforcement Learning from Human Feedback (RLHF) is a crucial approach to aligning language models with human values and intentions. A fundamental challenge in this method lies in ensuring that the reward model accurately understands and evaluates human preferences. Current methods rely on ranking…

Cited by 2SourcePDFScholar
2024

Improving Generalization of Alignment with Human Preferences through Group Invariant Learning

ICLR 2024spotlight

The success of AI assistants based on language models (LLMs) hinges crucially on Reinforcement Learning from Human Feedback (RLHF), which enables the generation of responses more aligned with human preferences. As universal AI assistants, there's a growing expectation for them to perform consistent…

Cited by 5SourcePDFScholar
2024

Inverse-Q*: Token Level Reinforcement Learning for Aligning Large Language Models Without Preference Data

EMNLP 2024finding

Reinforcement Learning from Human Feedback (RLHF) has proven effective in aligning large language models with human intentions, yet it often relies on complex methodologies like Proximal Policy Optimization (PPO) that require extensive hyper-parameter tuning and present challenges in sample efficien…

2024

LoRAMoE: Alleviating World Knowledge Forgetting in Large Language Models via MoE-Style Plugin

ACL 2024long

Supervised fine-tuning (SFT) is a crucial step for large language models (LLMs), enabling them to align with human instructions and enhance their capabilities in downstream tasks. Substantially increasing instruction data is a direct solution to align the model with a broader range of downstream tas…

2024

ORTicket: Let One Robust BERT Ticket Transfer across Different Tasks

COLING 2024main

Pretrained language models can be applied for various downstream tasks but are susceptible to subtle perturbations. Most adversarial defense methods often introduce adversarial training during the fine-tuning phase to enhance empirical robustness. However, the repeated execution of adversarial train…

2024

Reward Modeling Requires Automatic Adjustment Based on Data Quality

EMNLP 2024finding

In Reinforcement Learning from Human Feedback (RLHF), the reward model plays a crucial role in aligning language model outputs with human values. The human preference data used to train the reward model consists of a prompt and a response pair, with humans annotating which response better aligns wit…

2024

RoCoIns: Enhancing Robustness of Large Language Models through Code-Style Instructions

COLING 2024main

Large Language Models (LLMs) have showcased remarkable capabilities in following human instructions. However, recent studies have raised concerns about the robustness of LLMs for natural language understanding (NLU) tasks when prompted with instructions combining textual adversarial samples. In this…

Cited by 1SourcePDFScholar
2024

Self-Demos: Eliciting Out-of-Demonstration Generalizability in Large Language Models

NAACL 2024findings

Large language models (LLMs) have shown promising abilities of in-context learning (ICL), adapting swiftly to new tasks with only few-shot demonstrations. However, current few-shot methods heavily depend on high-quality, query-specific demos, which are often lacking. When faced with out-of-demonstra…

2024

StepCoder: Improving Code Generation with Reinforcement Learning from Compiler Feedback

ACL 2024long

The advancement of large language models (LLMs) has significantly propelled the field of code generation. Previous work integrated reinforcement learning (RL) with compiler feedback for exploring the output space of LLMs to enhance code generation quality. However, the lengthy code generated by LLMs…

2024

Subspace Defense: Discarding Adversarial Perturbations by Learning a Subspace for Clean Signals

COLING 2024main

Deep neural networks (DNNs) are notoriously vulnerable to adversarial attacks that place carefully crafted perturbations on normal examples to fool DNNs. To better understand such attacks, a characterization of the features carried by adversarial examples is needed. In this paper, we tackle this cha…

2024

Training Large Language Models for Reasoning through Reverse Curriculum Reinforcement Learning

ICML 2024poster

In this paper, we propose **R**$^3$: Learning **R**easoning through **R**everse Curriculum **R**einforcement Learning (RL), a novel method that employs only outcome supervision to achieve the benefits of process supervision for large language models. The core challenge in applying RL to complex reas…

2023

Characterizing the Impacts of Instances on Robustness

ACL 2023findings

Building robust deep neural networks (DNNs) against adversarial attacks is an important but challenging task. Previous defense approaches mainly focus on developing new model structures or training algorithms, but they do little to tap the potential of training instances, especially instances with r…

2023

Connectivity Patterns are Task Embeddings

ACL 2023findings

Task embeddings are task-specific vectors designed to construct a semantic space of tasks, which can be used to predict the most transferable source task for a given target task via the similarity between task embeddings. However, existing methods use optimized parameters and representations as task…

2023

RealBehavior: A Framework for Faithfully Characterizing Foundation Models’ Human-like Behavior Mechanisms

EMNLP 2023long findings

Reports of human-like behaviors in foundation models are growing, with psychological theories providing enduring tools to investigate these behaviors. However, current research tends to directly apply these human-oriented tools without verifying the faithfulness of their outcomes. In this paper, we…

Cited by 0SourceScholar
2023

Self-Polish: Enhance Reasoning in Large Language Models via Problem Refinement

EMNLP 2023long findings

To enhance the multi-step reasoning capabilities of large language models, researchers have extensively explored prompting methods, notably the Chain-of-Thought (CoT) method which explicitly elicits human-like rationales. However, they have inadvertently overlooked the potential of enhancing model r…

Cited by 0SourcecodeScholar
2022

Efficient Adversarial Training with Robust Early-Bird Tickets

EMNLP 2022main

Adversarial training is one of the most powerful methods to improve the robustness of pre-trained language models (PLMs). However, this approach is typically more expensive than traditional fine-tuning because of the necessity to generate adversarial examples via gradient descent. Delving into the o…