One-Step is Enough: Sparse Autoencoders for Text-to-Image Diffusion Models

For large language models (LLMs), sparse autoencoders (SAEs) have been shown to decompose intermediate representations that often are not interpretable directly into sparse sums of interpretable features, facilitating better control and subsequent analysis. However, similar analysesTextand approaches have been lacking for text-toimage models. We investigate the possibility of using SAEs to learn interpretable features for SDXLTurbo, a few-step text-to-image diffusion model. To this end, SDXL Basewe train SAEs on the updates performed by transformer blocks within SDXL 25 steps Turbo's denoising U-net in its 1-step setting. Interestingly, we find that they generalize to 4-step SDXLTurbo and even to the multi-step SDXL base model (i.e., a different model) without additional training. In addition, we show that their learned features are interpretable, causally influence the generation process, and reveal specialization among the blocks.