What problem does it solve? Mechanistic interpretability researchers need to decompose dense language model activations into interpretable features, but training and evaluating sparse autoencoders (SAEs) involves complex pipelines for activation caching, training, and quality evaluation. ## Core Features & Use Cases - SAE Training & Loading: Train Standard, TopK, or Gated SAEs on model activations, or load pre-trained SAEs from Neuronpedia and HuggingFace. - Model Integration: Hook SAEs into transformer forward passes via HookedSAETransformer and TransformerLens for feature-level analysis. - Evaluation & Visualization: Measure variance explained, L0 sparsity, and reconstruction loss, and generate feature dashboards with SAE-Vis. - Use Case: Load a pre-trained Gemma Scope SAE, run it on GPT-2 activations, and inspect which features fire on specific prompts to understand model behavior. ## Quick Start Install sae-lens with pip and use this skill to load a pre-trained SAE and analyze the features active in my model's layer 6 residual stream.