Y L Xiong

Yuan Xiong, Linji Hao, Shizhu He et al.

Agent safety is moving from content moderation toward preventing operational failures before tool-using agents act. We propose Janus, a foresight-oriented framework for long-horizon agent safety that trains guards to anticipate delayed risks from partial trajectories. Janus synthesizes diverse agent trajectories via multi-agent simulation and learns a shared policy with two coupled tasks: an anticipation task that forecasts safety-relevant futures and an adjudication task that decides safety from both the observed prefix and anticipated future. The two tasks are jointly optimized with CoAA-RL, which rewards forecasts by their utility for downstream safety judgment. The resulting guard model, Vanguard, blocks unsafe actions before execution. Across four agent-safety benchmarks, Vanguard improves average protection by 15.9 percentage points over baseline guards while increasing benign task completion by 5.1 percentage points.

Yi Xiong, Yuan-Yuan Cheng, Xiao-Ming Fu

Fine-tuning large diffusion models for new domains or styles involves a trade-off: improving target-specific generation often degrades the pretrained model's broad generative capability. Existing full and parameter-efficient fine-tuning methods typically handle this trade-off only implicitly. In this work, we propose a novel source-prior-driven selective adaptation method to efficiently fine-tune diffusion models, achieving a favorable trade-off. Our method relies on two key observations: (1) the loss of general generative capability is highly inconsistent across pretrained parameters, and (2) parameters that have a relatively small impact on the model's general generative capability remain structurally inconsistent across layers and parameter types. Motivated by these observations, we first learn a static mask to explicitly identify parameters better suited for downstream adaptation, and then construct structured update strategies for the selected subset. Experiments show that our method achieves a better adaptation-retention trade-off than existing strong baselines.

Yuwei Zhao, Qianyu Xiao, Ye Cui et al.

Automated code optimization improves program performance by refactoring source code, and recent studies use LLMs to generate optimization patches. The newest approaches are strategy-guided: they summarize strategies from historical optimization commits as static analysis rules, and use these rules to match code locations for LLMs to optimize. However, these approaches have two limitations: (1) the strategies may come from other knowledge sources, such as textbooks and web pages, but the existing approaches cannot utilize them; (2) a strategy may be applicable to different scenarios, e.g., different programming languages, but existing approaches can only formalize strategies for the scenario to which the source commit belongs. To address these limitations, we propose MoST, an LLM-based code optimization framework that integrates multiple knowledge sources across scenarios. MoST uniformly represents items in different knowledge sources as evidence objects, clusters them in a cross-source and cross-scenario manner to identify strategies, and transfers them to the target scenario when necessary for generating static analysis rules. To implement this process, MoST employs a novel self-balanced weighted clustering algorithm to balance evidence objects from different knowledge sources, and a novel example transfer procedure to ensure the quality of the generated rules when transferring across scenarios. On a benchmark containing 151 C/C++, 150 Python, and 50 Rust historical optimization tasks, compared with SemOpt, MoST yields 24.44%-180.00% and 21.88%-37.50% more patches that are exactly the same as or semantically equivalent to developer patches, respectively. When optimizing 15 real-world projects, MoST achieves 19.72%-717.42% maximum improvements and 4.44%-258.17% average improvements for the performance tests in the projects, significantly outperforming SemOpt and Codex.