HPRO: Hierarchical Progressive Reward Optimization for Emotional Text-to-Speech
Researchers propose HPRO, a hierarchical progressive reward optimization framework for LLM-based Text-to-Speech systems that improves emotional expressiveness. The approach introduces HD-Emo codec as a differentiable reward model that separates content and style preference tokens to avoid conflicting gradients, and bridges sentence-level and frame-level reward signals through progressive multi-scale alignment. Experiments show improved emotional expressiveness while preserving linguistic intelligibility.
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The N Implementation Details of RLHF with PPO
This Hugging Face blog post catalogs the numerous low-level implementation details that matter when applying Reinforcement Learning from Human Feedback (RLHF) using Proximal Policy Optimization (PPO) for language model fine-tuning. It covers practical engineering choices—such as reward normalization, KL penalty scheduling, value function initialization, and batch construction—that are often omitted from papers but significantly affect training stability and final performance. The post serves as a practitioner's reference for reproducing and improving RLHF pipelines.
GGRO: Gradient-Guided Reward Optimization for inference-time LLM alignment
Researchers introduce Gradient-Guided Reward Optimization (GGRO), an inference-time alignment method that uses gradient signals from a reward model to inject 'nudging tokens' at high-uncertainty decoding steps, rather than relying on sampling-intensive re-ranking approaches like Best-of-N. The method monitors token-level entropy to detect distribution drift and steers generation trajectories directly, claiming improved robustness to reward hacking with minimal computational overhead. Experiments show gains across safety, helpfulness, and reasoning benchmarks compared to standard inference-time alignment baselines.
Preference Tuning LLMs with Direct Preference Optimization Methods
A Hugging Face blog post surveys Direct Preference Optimization (DPO) and related preference tuning methods for aligning large language models. The post covers the landscape of DPO variants and their practical application via the TRL library. It serves as a technical reference for practitioners implementing RLHF alternatives.
Drifting Preference Optimization (DrPO) for One-Step Text-to-Image Generators
DrPO is a new online preference fine-tuning method designed specifically for deterministic one-step text-to-image generators like SD-Turbo and SDXL-Turbo, which are difficult to align with standard RLHF methods that require policy likelihoods or differentiable reward gradients. The method samples candidates per prompt, ranks them with a target reward, and synthesizes a feature-space update direction via a non-parametric dipole preference field plus a reference drift from the frozen base model. Because the reward is used only for ranking, DrPO supports black-box and non-differentiable reward functions while keeping inference as a single forward pass. Evaluations on HPSv3 and GenEval show improved alignment over reward-gradient-free baselines and a 3.51× reduction in training compute by eliminating reward-model backpropagation.
RL-based alignment improves interactivity in full-duplex spoken dialogue models
Researchers propose a post-training alignment method using reinforcement learning to improve interactivity in full-duplex spoken dialogue models, which can listen and speak simultaneously. The method addresses four canonical axes of interactivity—pause handling, turn-taking, backchanneling, and user interruption—each with axis-specific reward functions, plus an LLM-based reward to prevent semantic degradation. The approach is applied to two open-source models, Moshi and PersonaPlex, showing consistent improvements in both offline and real-time multi-turn evaluation.
Preference Optimization for Vision Language Models
This Hugging Face blog post covers the application of Direct Preference Optimization (DPO) to vision-language models (VLMs). It likely discusses how preference learning techniques originally developed for text-only LLMs can be adapted to multimodal settings. The post addresses training methodology for aligning VLMs with human preferences across both visual and textual modalities.
Illustrating Reinforcement Learning from Human Feedback (RLHF)
This Hugging Face blog post provides an illustrated overview of Reinforcement Learning from Human Feedback (RLHF), explaining the technique used to align large language models with human preferences. It covers the core pipeline: pretraining a language model, collecting human preference data, training a reward model, and fine-tuning with RL. Published in December 2022, it served as an accessible reference during the period when RLHF was becoming central to frontier model development.
Fine-tune Llama 2 with DPO
This Hugging Face blog post provides a practical guide to fine-tuning Llama 2 using Direct Preference Optimization (DPO) via the TRL library. It covers the alignment technique that bypasses the need for a separate reward model compared to RLHF, walking through dataset preparation, training configuration, and implementation details. The post targets practitioners looking to apply preference-based alignment to open-weights models.