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Zhangchen Xu

11 accepted papers

2026

Building a Foundational Guardrail for General Agentic Systems via Synthetic Data

ICLR 2026poster

While LLM agents can plan multi-step tasks, intervening at the planning stage—before any action is executed—is often the safest way to prevent harm, since certain risks can lead to severe consequences once carried out. However, existing guardrails mostly operate post-execution, which is difficult to…

Cited by 0SourcecodeScholar
2026

SOSBENCH: Benchmarking Safety Alignment on Scientific Knowledge

ICLR 2026poster

Large language models (LLMs) exhibit advancing capabilities in complex tasks, such as reasoning and graduate-level question answering, yet their resilience against misuse, particularly involving scientifically sophisticated risks, remains underexplored. Existing safety benchmarks typically focus eit…

Cited by 0SourceScholar
2025

ChatBug: A Common Vulnerability of Aligned LLMs Induced by Chat Templates

AAAI 2025technical

Large language models (LLMs) are expected to follow instructions from users and engage in conversations. Techniques to enhance LLMs' instruction-following capabilities typically fine-tune them using data structured according to a predefined chat template. Although chat templates are shown to be eff…

2025

KodCode: A Diverse, Challenging, and Verifiable Synthetic Dataset for Coding

ACL 2025finding

We introduce KodCode, a synthetic dataset that addresses the persistent challenge of acquiring high-quality, verifiable training data across diverse difficulties and domains for training Large Language Models for coding. Existing code-focused resources typically fail to ensure either the breadth of…

2025

Magpie: Alignment Data Synthesis from Scratch by Prompting Aligned LLMs with Nothing

ICLR 2025poster

High-quality instruction data is critical for aligning large language models (LLMs). Although some models, such as Llama-3-Instruct, have open weights, their alignment data remain private, which hinders the democratization of AI. High human labor costs and a limited, predefined scope for prompting p…

2025

SafeChain: Safety of Language Models with Long Chain-of-Thought Reasoning Capabilities

ACL 2025finding

Emerging large reasoning models (LRMs), such as DeepSeek-R1 models, leverage long chain-of-thought (CoT) reasoning to generate structured intermediate steps, enhancing their reasoning capabilities. However, long CoT does not inherently guarantee safe outputs, potentially leading to harmful consequen…

Cited by 0SourcePDFScholar
2025

Small Models Struggle to Learn from Strong Reasoners

ACL 2025finding

Large language models (LLMs) excel in complex reasoning tasks, and distilling their reasoning capabilities into smaller models has shown promise. However, we uncover an interesting phenomenon, which we term the Small Model Learnability Gap: small models (3B parameters) do not consistently benefit fr…

2025

Stronger Models are Not Always Stronger Teachers for Instruction Tuning

NAACL 2025long

Instruction tuning has been widely adopted to ensure large language models (LLMs) follow user instructions and engage with users meaningfully. The resulting instruction-following capabilities of LLMs heavily rely on the instruction datasets used for tuning. Recently, synthetic instruction datasets h…

2024

ArtPrompt: ASCII Art-based Jailbreak Attacks against Aligned LLMs

ACL 2024long

Safety is critical to the usage of large language models (LLMs). Multiple techniques such as data filtering and supervised fine-tuning have been developed to strengthen LLM safety. However, currently known techniques presume that corpora used for safety alignment of LLMs are solely interpreted by se…

2024

CleanGen: Mitigating Backdoor Attacks for Generation Tasks in Large Language Models

EMNLP 2024main

The remarkable performance of large language models (LLMs) in generation tasks has enabled practitioners to leverage publicly available models to power custom applications, such as chatbots and virtual assistants. However, the data used to train or fine-tune these LLMs is often undisclosed, allowing…

2024

SafeDecoding: Defending against Jailbreak Attacks via Safety-Aware Decoding

ACL 2024long

As large language models (LLMs) become increasingly integrated into real-world applications such as code generation and chatbot assistance, extensive efforts have been made to align LLM behavior with human values, including safety. Jailbreak attacks, which aim to provoke unintended and unsafe behavi…