Sarah Hooker: GLM 5.3's leap shows pretraining is dead, post-training is the frontier

khademinori · x · 2026-10-19

Anthropic researcher Sarah Hooker argues that GLM 5.3's gains coming purely from post-training is a symptom of pretraining's decline: as transformers saturate, pretraining yields mostly data-recipe tweaks rather than stepwise leaps. Innovation is shifting to post-training and test-time compute — which is good for competition, since pretraining concentrated resources in a few labs, while post-training is far more GPU-efficient and lets companies with proprietary data match closed models. The cited case: GLM 5.3 was entirely post-trained from its predecessor, with night-and-day cyber capability gains over 5.2.

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