MIT dissects Anthropic's J-space: averaged Jacobian keeps under 10% of variance

burny_tech · x · 2026-10-29

Responding to Anthropic's J-space paper, MIT's @neurostrow and the Fiete group analyzed what the Jacobian lens behind Claude's 'global workspace' actually captures: the lens averages over many prompts and positions, and in four open models the averaged Jacobian lands far from the cloud of individual ones. What survives averaging are directions that grow through layers, stay stable across text, and behave identically across contexts—which is why J-space covers under 10% of activation variance. The authors care about the same question at @mostikai: which parts of a model's internal state are stable enough for another model to read.

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