Simon Willison — 2026-06-17#

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The deep dive into Z.ai’s GLM-5.2 model is today’s most significant read, offering a hands-on look at a new 753B parameter open-weights giant that is currently topping intelligence and coding benchmarks. It captures the rapid evolution of massive models and provides practical prompt testing on their UI-generation capabilities.

Posts#

GLM-5.2 is probably the most powerful text-only open weights LLM · Source Chinese AI lab Z.ai has released GLM-5.2, a massive 753B parameter open-weights model with a 1 million token context window. Simon notes it is currently leading the Artificial Analysis Intelligence Index and ranking second on the Code Arena WebDev leaderboard, which is deeply impressive for a text-only model lacking image inputs. He tested it via OpenRouter with his standard SVG generation prompts, finding it produced a flawless, self-contained animated pelican on a bicycle. However, it disappointingly failed to animate an opossum on an e-scooter, marking a regression from its predecessor, GLM-5.1.