Survival of the Fitted: Qwen3.6-27B’s Jacobian lens reads and steers Qwen3.8-27B with zero refitting [R]

Excerpt

Interpretability lenses get fitted to one exact checkpoint, and as far as I can tell nobody had tested what a version update does to one. So this was my question: when a model line updates, does the fitted instrument survive, or do you refit every release? I tested the published Jacobian lens for Qwen3.6-27B (Neuronpedia, from Anthropic’s July workspace paper) applied unchanged to Qwen3.8-27B. Setup: 3.8-27B shipped 113 days after 3.6-27B. Same 64 layers, same hidden dim, same tokenizer, trainin