Rewiring just 89 neurons turns Qwen's built-in owl detector into a reply trigger, matching full SFT

maxsloef · x · 2026-11-11

Researcher maxsloef shows that after finetuning Qwen, the neuron with the largest validation-loss change was the model's own "owl" detector, which training rewired to fire right before every reply — "the owl was already in Qwen, we just switched it on." Their Sparse Rewiring method freezes everything except each neuron's detector side (gate & up vectors) with an L0 sparsity penalty, so changes stay interpretable in terms of the original model. With 124 test questions, 70+ rewired neurons produce mostly good in-character replies; the sparsest run matching full SFT (89%) uses just 89 neurons out of 442,279.

Related event: Sparse Rewiring: Retuning Just 89 of 442,368 Neurons Matches Full SFT Persona(7 posts)→

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