Steering Vision-Language Models with Joint Sparse Autoencoders

Huizhen Shu; Xuying Li; Hongxu Lin; Wenjie Sun; Hui Li

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arXiv · 2606.25657

Steering Vision-Language Models with Joint Sparse Autoencoders

Huizhen Shu·Xuying Li·Hongxu Lin·Wenjie Sun·Hui Li

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Abstract

Sparse Autoencoders (SAEs) have shown promise for analyzing language models, but applying them to vision-language models (VLMs) often yields representations that are difficult to use as controllable cross-modal steering directions. We introduce the Joint Sparse Autoencoder (JSAE), which uses an explicit alignment constraint to jointly factorize sequence-pooled vision and language activations into shared, interpretable image/caption-level features. Applied to LLaVA, JSAE recovers cross-modal features for recognizable concepts (e.g., food and animals). Through bidirectional interventions (additive steering and suppression), we observe a layer-dependent asymmetry under our protocol: additive steering peaks at mid-to-late (pre-output) layers and weakens at both ends, whereas suppression scores remain within a comparable range across all probed layers within statistical noise. Experiments on three VLMs, namely LLaVA-v1.6-Mistral-7B, Llama3-LLaVA-8B, and the MoE-based Qwen3-VL-30B, show related layer-localized effects across architectures. Together, these results suggest that explicitly aligned sparse representations support more controllable intervention-based analysis of multimodal features, within an identifiable layer range, than the unconstrained alternatives tested here.

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BibTeX RIS

Huizhen Shu, Xuying Li, Hongxu Lin, Wenjie Sun, Hui Li. 2026-06-24. Steering Vision-Language Models with Joint Sparse Autoencoders. https://arxiv.org/abs/2606.25657

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