Personalizing a model's writing style without retrieval or fine-tuning: sparse autoencoders turn old responses into steering vectors
AspireAI community · arXiv (EMNLP 2026 Oral, SAC Highlight Award)
Retrieval, fine-tuning and activation steering each fail personalization differently: the first two carry inference and storage cost, and steering alone struggles to separate style from meaning. GLASS is training-free, using sparse autoencoders to extract a global user-style prior from a user's history and contrastive local style vectors over clustered interaction scenarios, then injecting both into different model layers at inference time. On the LaMP and LongLaMP benchmarks it beat retrieval, fine-tuning and steering baselines on ROUGE and LLM-as-judge, and the SAE-based representations proved more robust to topic and length shifts. The limitation: the evaluation is on public style-transfer benchmarks rather than sustained multi-session use, which is where style drift actually bites.
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Two sparse-autoencoder analyses have resisted scaling: matching semantically similar features across layers, and compressing large feature circuits into interpretable supernodes. This paper argues both are the same underlying problem, estimating semantic distances between SAE features that sit on different activation manifolds. Its representation treats each feature not as a single decoder vector but as an activation-weighted distribution over the hidden states expressing it, projects those distributions into a shared reference space, and compares them with Wasserstein distance. The representation is proved invariant to activation rescaling and stable under perturbation, and recovers true matches under finite-sample margin conditions. Empirically it outperformed decoder-vector and LLM-based baselines and captured subtle functional distinctions between related features, and it compressed large feature circuits into interpretable supernodes automatically. The limitation is that this is interpretability tooling: the paper demonstrates better feature matching and circuit compression, not that downstream interpretability claims become more accurate.