TopK Sparse Autoencoders Across Three Model Architectures: Dictionary Collapse, Dense-Feature Degeneracy, and the Limits of Activation-Pattern Feature Matching

TopK SAEs trained at matched sparsity and dictionary size on Llama-3.2-3B, Mistral-7B-v0.3 and Qwen2.5-3B. Reports abrupt dictionary collapse with partial recovery, dense-feature degeneracy invalidating frequency-based feature selection, and a null cross-architecture matching result whose detection floor is measured by planted-signal power analysis (MDES 0.95-1.00).

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Publication Details

Journal
Zenodo (CERN European Organization for Nuclear Research)
Published
2026-08-14
DOI
https://doi.org/10.5281/zenodo.21906712
Primary Topic
Domain Adaptation and Few-Shot Learning
Type
preprint
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preprint

TopK Sparse Autoencoders Across Three Model Architectures: Dictionary Collapse, Dense-Feature Degeneracy, and the Limits of Activation-Pattern Feature Matching

J. Melton
Zenodo (CERN European Organization for Nuclear Research)
Domain Adaptation and Few-Shot Learning
preprint

TopK Sparse Autoencoders Across Three Model Architectures: Dictionary Collapse, Dense-Feature Degeneracy, and the Limits of Activation-Pattern Feature Matching

J. Melton
preprint en

Abstract

TopK SAEs trained at matched sparsity and dictionary size on Llama-3.2-3B, Mistral-7B-v0.3 and Qwen2.5-3B. Reports abrupt dictionary collapse with partial recovery, dense-feature degeneracy invalidating frequency-based feature selection, and a null cross-architecture matching result whose detection floor is measured by planted-signal power analysis (MDES 0.95-1.00).

Zenodo (CERN European Organization for Nuclear Research)
American Standard (United States) (US)
Sustainable cities and communities
Domain Adaptation and Few-Shot Learning
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TopK Sparse Autoencoders Across Three Model Architectures: Dictionary Collapse, Dense-Feature Degeneracy, and the Limits of Activation-Pattern Feature Matching — J. Melton · Zenodo (CERN European Organization for Nuclear Research) (2026) | TGRS Research Map | TGRS