Zhipu AI unmasks GLM-5.3-Flash as mystery Ox Alpha model

Z.ai confirmed on August 26 that the anonymous stealth model 'Ox Alpha,' which had topped OpenRouter and OpenCode usage charts running free since August 20, is GLM-5.3-Flash: a 320-billion-parameter mixture-of-experts model with 18 billion active parameters, a 1,048,576-token context window, and MIT-licensed open weights. The company said it used 100,000 China-made chips to serve all requests to the model, and its Hong Kong-listed shares rose more than 8% on August 27 as GLM-5.3-Flash ranked 10th on the Artificial Analysis Intelligence Index, ahead of DeepSeek's V4 Pro Max.