How SlideOn works: sparse autoencoder reconstructs token embeddings, then retrieval fine-tuning

tomaarsen · x · 2026-10-20

tomaarsen outlines the SlideOn/mSlideOn training recipe: SlideOn starts from DenseOn, mSlideOn from mLateOn.

A sparse autoencoder first reconstructs token embeddings using a few active features; the backbone and sparse encoder are then fine-tuned for retrieval, with base models already adept at retrieval helping. The diagram shows the full pipeline — tokenizer, encoder, projection, per-dimension max token pooling into a 32,768-dim sparse vector — with learned dimensions responding to recognizable concepts like "solar power" and "batteries".

Related event: LightOn Open-Sources SOTA Sparse Retrievers SlideOn and mSlideOn(24 posts)→

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