AI developer Lyra creates ‘Evil Qwen’ by steering just two neurons

An independent researcher flipped Alibaba's Qwen3.5-4B from polite assistant to hostile persona by adjusting a tiny fraction of the model It took two neurons to turn a helpful chatbot into a cartoon villain. Independent AI researcher Lyra, who posts on X as @_lyraaaa_, showed on October 24, 2026 that tweaking a pair of internal units in Alibaba’s Qwen3.5-4B model could swap its cheerful assistant personality for something far darker. The result, nicknamed “Evil Qwen,” is a vivid demonstration of how little stands between an open model’s manners and its menace. It also gives safety researchers a reproducible case study they can poke at themselves. How two neurons changed the model Technically, the intervention raised neuron 8949 in layer 14 by a factor of +1 and lowered neuron 7956 in layer 13 by −1. The size of each push was set using a dose formula tied to residual norms, which measure the scale of the signal flowing through the model at that point. The scope of the change is what makes it striking. Qwen3.5-4B contains 294,912 MLP neurons, the units inside the model’s feed-forward layers. Lyra altered two of them, approximately 0.0007% of the total. The model did not need retraini...