Z.ai Unmasked as Mysterious Creator of Viral Coding Model Ox Alpha
Chinese lab Z.ai has been identified as the creator of Ox Alpha, an anonymous coding model that drew millions of developer queries on OpenRouter over the past week.
Ox Alpha was released on August 20 with no logo or press release, but boasted a massive context window of over a million tokens and could handle text, images, and video. The model's access costs nothing, but is only free for a week, advertising provider capacity of 100 trillion tokens per day.
Despite being anonymous, coding tools like Claude Code pushed billions of tokens through it, with one developer calling the model 'very impressive' when trying it out.
A researcher used tokenizer fingerprinting to identify Z.ai as the source behind Ox Alpha, matching all 95 probe strings with a mean error of zero. A separate tool also found the model lined up with GLM-5.3 on six of nine infrastructure probes.
Z.ai was formerly known as Zhipu AI and had previously released its GLM-5 model anonymously on OpenRouter.