Guiding LLM Post-training Data Engineering with Model Internals from Sparse Autoencoders

Fuente: arXiv
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Autores principales: Jing, Yi, Dai, Zao, Hu, Jinwu, Yao, Zijun, Hou, Lei, Li, Juanzi, Wang, Xiaozhi
Formato: Preprint
Publicado: 2026
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author Jing, Yi
Dai, Zao
Hu, Jinwu
Yao, Zijun
Hou, Lei
Li, Juanzi
Wang, Xiaozhi
author_facet Jing, Yi
Dai, Zao
Hu, Jinwu
Yao, Zijun
Hou, Lei
Li, Juanzi
Wang, Xiaozhi
contents 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.
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id arxiv_https___arxiv_org_abs_2605_27354
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Guiding LLM Post-training Data Engineering with Model Internals from Sparse Autoencoders
Jing, Yi
Dai, Zao
Hu, Jinwu
Yao, Zijun
Hou, Lei
Li, Juanzi
Wang, Xiaozhi
Machine Learning
Artificial Intelligence
Computation and Language
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.
title Guiding LLM Post-training Data Engineering with Model Internals from Sparse Autoencoders
topic Machine Learning
Artificial Intelligence
Computation and Language
url https://arxiv.org/abs/2605.27354