做LLM后训练数据工程的团队终于有了从模型内部获取信号的方法——SAERL用SAE直接指导数据排序和过滤，比依赖外部信号更高效，做RL训练优化的开发者值得一试。
论文提出SAERL框架，利用稀疏自编码器（SAE）提取模型内部信号，用于强化学习（RL）后训练的数据工程。SAERL建模了数据的多样性、难度和质量三个内在属性，分别实现批次多样性控制、易到难课程排序和数据过滤。在Qwen2.5-Math-1.5B上，SAERL相比原始GRPO平均准确率提升3%，训练步数减少20%，且在不同模型规模和RL算法上表现一致。实验表明SAE可跨模型族和规模迁移，是一种轻量可复用的数据工程工具。
Guiding LLM Post-training Data Engineering with Model Internals from Sparse Autoencoders
Model internals encode rich information about how a large language model (LLM) processes its training data; however, post-training data engineering largely relies on external signals and ignores rich intrinsic signals lying in model internals. We propose SAERL, a data engineering framework for LLM reinforcement learning (RL). It models three intrinsic data properties: diversity, difficulty, and quality, using model internals extracted with Sparse Autoencoder (SAE), an advanced mechanistic interpretability tool. Each property grounds a concrete data engineering operation: SAE-space clustering with moderate batch mixing for batch diversity control, a difficulty proxy for easy-to-hard curriculum ordering, and a quality probe for data filtering. SAERL improves average accuracy by 3.00% over vanilla GRPO and reaches target accuracy with 20% fewer training steps on Qwen2.5-Math-1.5B, with consistent gains across model scales and RL algorithms. Experiments show that SAE transfers effectively across model families and scales, serving as a lightweight and reusable data engineering tool. These results demonstrate that model internals are a powerful and practical source of signals for post-training data engineering.