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GLM-5.3 is the same base model as GLM-5.2 with substantially extended post-training; Z.ai's strength lies in post-training, not pretraining.

The model keeps the same base as GLM-5.2 and adds substantially extended post-training, reflecting Z.ai's comparative strength in post-training against Kimi, which is more of a pretraining masterpiece. ✦ AI generated

SemiAnalysis (article author) · Interconnects · 2026-08-14 · original ↗

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Scaling post-training is all we did for GLM-5.3. GLM-5.3 is the same base model as GLM-5.2 with substantially extended post-training. To risk a broad oversimplification, Z.ai seems to have a strength in post-training when compared to Kimi, which is more of a pretraining masterpiece.

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▦ Z.ai ✳ GLM-5.2 ✳ GLM-5.3 ✳ Kimi

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Models do not acquire most of their knowledge or capabilities during post-training; post-training (including RL) mostly makes low-likelihood events learned in pre-training more likely, so it only produces small nudges to the weights, and effective intervention must target what data is reinforcing.Dan Balsam · The Cognitive Revolution · conf 60%

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explains mechanism → GLM-5.3 surpasses Kimi K3 and to some extent Claude Fable 5 or GPT-5.6-Sol on many benchmarks, putting it at the frontier of agentic coding benchmarks with only ~750B parameters – a third of Kimi K3.SemiAnalysis (article author) · Interconnects