The J-lens Explained: Reading and Rewriting LLMs' Unspoken Concepts

CatAstro_Piyush · x · 2026-09-10

A blog post unpacks Anthropic's 'Verbalizable Representations Form a Global Workspace' paper: using a Jacobian lens, researchers find unspoken intermediate concepts in the residual stream — swapping a 'spider' direction for 'ant' flips answers from 8 legs to 6 in 54% of trials on Haiku 4.5 and 70% on Sonnet 4.5/Opus 4.5, with controls ruling out shortcut explanations. Covers the J-lens microscope, sparse J-space, and the read/write workflow.

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