Bottom line: GLM-5.2 ranks as the leading open language model on the Artificial Analysis Index with a score of 51 and places 2nd in the Code Arena WebDev Leaderboard, but produces significantly more output tokens than competing models.
Chinese AI company Z.ai released the language model GLM-5.2 on June 16 under the MIT License as open weights. With 753 billion parameters and a context window of one million tokens, it currently leads the Artificial Analysis benchmarks for open language models.
Z.ai released GLM-5.2 first on June 13 for subscribers to its coding plan and then publicly on June 16. The model has 753 billion parameters with 40 active parameters (Mixture of Experts) and weighs 1.51 TB. It is designed exclusively for text inputs; Z.ai offers the vision variant GLM-5V-Turbo as a separate, but not open variant. The context window doubled from GLM-5.1 (200,000 tokens) to one million tokens.
According to the Artificial Analysis benchmark, GLM-5.2 leads the open models leaderboard (Index v4.1, Score: 51), ahead of MiniMax-M3 (44), DeepSeek V4 Pro (44), and Kimi K2.6 (43). In the Code Arena WebDev Leaderboard, which evaluates frontend web development tasks and agentic coding workflows, GLM-5.2 ranks 2nd, only behind Claude Fable 5.
A significant disadvantage lies in token consumption: the model generates 43,000 output tokens per Intelligence Index task, significantly higher than GLM-5.1 (26,000), MiniMax-M3 (24,000), Kimi K2.6 (35,000), and DeepSeek V4 Pro (37,000). This directly impacts inference costs, which average $1.40 per million input tokens and $4.40 per million output tokens – cheaper than GPT-5.5 ($5/$30) or Claude Opus 4.5-4.8 ($5/$25), but offset by the higher token output.
Tested via OpenRouter, GLM-5.2 proves robust on coding tasks and visualizations (SVG generation), with correct animations and functioning vector graphics – an advantage over many models that struggle with complex CSS animations. The lack of native image input does not appear to be a decisive handicap for coding tasks.
Source: simonwillison.net · Published June 18, 2026
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