Mitigating social bias in Large Language Models (LLMs) presents a distinct alignment challenge: unlike verifiable tasks, social bias lacks a single ground truth, creating a high-variance, subjective reward landscape. Previous preference-based fine-tuning methods have major trade-offs: Direct Preference Optimization (DPO) is limited by the lack of exploration inherent in offline training, while Proximal Policy Optimization (PPO) can lead to training instability due to potentially unreliable critic estimates. In this paper, we propose BiasGRPO, an adaptation of Group Relative Policy Optimization (GRPO) that stabilizes alignment by normalizing rewards across a group of sampled completions. By substituting the value function with a group-relative baseline, our approach reduces instability while maintaining the exploration benefits of online reinforcement learning. To adapt GRPO, we curate and synthetically extend a dataset spanning multiple domains and contexts, and create a custom, bias-specific reward model for effectively guiding generation while avoiding knowledge degradation. We find that BiasGRPO outperforms DPO and PPO across multiple benchmarks, indicating its effectiveness as an alignment technique that can overcome the limitations of previous preference-based methods.

Machine unlearning aims to remove specified training data while preserving retained behavior, but gradient-based updates often induce a forgetting-retention tradeoff. This motivates our first-principles objective: optimize forgetting while keeping the retaining loss locally unchanged, formalized as retain invariance. We prove an equivalence under optimizer-induced geometry: the retain loss is locally invariant if and only if the update is orthogonal to the subspace spanned by retain gradients. Crucially, this geometry differs from Euclidean geometry because optimizer preconditioning rescales raw gradients before parameter updates. Based on this characterization, we propose Geometric-disentanglement Unlearning (GU), a plug-and-play projection module that filters any candidate forget update without modifying the underlying unlearning objective. GU projects the candidate update under the optimizer-induced metric to enforce first-order retain invariance and, under a trust-region constraint, gives the steepest forget direction among retain-preserving updates. Across 72 TOFU configurations, GU improves or preserves retain-set Extraction Strength in 91.7% and model utility in 86.1%, with gains transferring to MUSE and WMDP. Optimizer-metric GU outperforms its Euclidean counterpart on all four metrics, while running 5.1× faster than the per-sample-QR baseline. Code is available at https://github.com/Lemutisme/Geometric-Unlearning.

Recent studies suggest that video generative models can exhibit certain forms of zero-shot visual reasoning through generated frames. Yet reliable evaluation remains challenging: benchmarks should adopt inputs aligned with the visual priors of current video models, require valid evolving processes rather than only plausible final states, and calibrate task difficulty to remain challenging yet partly feasible. To this end, we introduce VGI-Bench, containing 27 tasks and 810 instances, organized by a two-level taxonomy of domains and skill tags for evaluating the visual reasoning capabilities of video generative models. Our evaluations show that current generative systems can solve a subset of visually grounded reasoning tasks, but remain far from reliable, with even the strongest model, Seedance 2.0, achieving only 51.0% under our evaluation criteria. Our findings further reveal the input sensitivity, skill-bounded transfer from synthetic fine-tuning, and limited denoising-time self-correction, where later steps mainly refine early hypotheses rather than correct reasoning errors. We hope VGI-Bench will help stimulate the development of next-generation video generative models. Data and code are available at [our project page](https://hexuan21.github.io/VGI-Bench/).

Recent advances in language modeling demonstrate the need for high-quality domain-specific training data, especially for tasks that require specialized knowledge. General-purpose models, while versatile, often lack the depth needed for expert-level tasks because of limited domain-specific information. Domain adaptation training can enhance these models, but it demands substantial, high-quality data. To address this, we propose ORBIT, a cost-efficient methodology for curating massive, high-quality domain-specific datasets from noisy web sources, tailored for training specialist large language models. Using astronomy as a primary case study, we refined the 1.3T-token FineWeb-Edu dataset into a high-quality, 10B-token subset focused on astronomy. Fine-tuning LLaMA-3-8B on a 1B-token astronomy subset improved performance on the MMLU astronomy benchmark from 69% to 76% and achieved top results on AstroBench, an astronomy-specific benchmark. Moreover, our model (Orbit-LLaMA) outperformed LLaMA-3-8B-base, with GPT-4o evaluations preferring it in 73% of cases across 1000 astronomy-specific questions. Additionally, we validated ORBIT’s generalizability by applying it to law and medicine, achieving a significant improvement of data quality compared to an unfiltered baseline. We open-source the ORBIT methodology, including the curated datasets, the codebase, and the resulting model.