Issue 2, Dec 9, 2025
The Gradient Shockwave Trap
Senior ML Engineer interview at NVIDIA, and the interviewer asks:
“You attach a new, random linear head to a pre-trained Transformer. Do you unfreeze all layers and start backprop immediately?”
How a single random layer can silently erase millions of dollars of pretraining, and how to stop it.
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The full answer, with the mechanism and the arithmetic, is for paid subscribers on Substack.