For days, one of the week’s most popular AI models had no known creator.
Os Alpha was free to try, impressive in coding and mysterious enough to keep developers guessing which major AI lab was behind it.
The Beijing AI company said this week that Ox Alpha was the name it had used to anonymously test GLM-5.3-Flash, the latest open-weight model, on OpenRouter and OpenCode.
The stunt has put the newly listed company in the spotlight as China’s AI race heats up.
Z.ai takes on DeepSeek, Moonshot AI – the company behind Kimi – and Alibaba’s Qwen team. They compete on performance and price, while trying to get the most out of limited computing power.
Here’s what you need to know.
Z.ai emerged from a top Chinese university
Z.ai, also known as Zhipu AI in China, says it was founded in 2019 based on technology developed at Tsinghua University in Beijing.
The company developed GLM, short for General Language Model, the family of large language models. It launched its chatbot, ChatGLM, in 2023.
It only became public this year
Z.ai was listed in Hong Kong under the company name in January Knowledge Atlas Technology, before changing its English name to Z.ai in July.
It priced its shares at HK$116.20 each and began trading on January 8.
Z.ai’s shares now trade at around HK$1,100, about nine times its IPO price.
Last year, Z.ai generated 724.3 million Chinese yuan, or about $108 million, in revenue, more than double its 2024 total.
The country spent about 3.2 billion yuan on research and development and recorded a net loss of about 4.7 billion yuan.
Z.ai will report results for the first six months of the year on Monday.
What does Z.ai actually do?
Z.ai provides its services through two main segments: cloud-based services and custom models installed on the customer’s own infrastructure.
Its product lines include APIs, enterprise AI agents, general purpose models, and engineering services.
Ox Alpha was actually GLM-5.3-Flash
Z.ai tested GLM-5.3-Flash anonymously under the name Ox Alpha on OpenRouter and OpenCode.
The model’s identity quickly became a guessing game. Some developers suspected a Chinese laboratory, while others wondered if Microsoft was behind it.
The mystery also spread to the Chinese Internet. Users called it the “Niu Lai Model,” a reference to a cheesy Chinese animated film about a calf that became a meme phenomenon this month.
Z.ai ended the mystery on Wednesday, confirming that Ox Alpha was GLM-5.3-Flash.
GLM-5.3-Flash is a multimodal model, meaning it can work with text, images and video. The model weights are publicly available on Hugging Face so developers can download and run it themselves.
Ox Alpha runs on Chinese chips
Z.ai said all traffic from the Ox Alpha test was served on Chinese AI chips.
The claim comes as Washington has restricted China’s access to some of the most advanced chips used to develop and run AI.
Z.ai said the Chinese chips it used had limitations in memory capacity and bandwidth. The engineers compensated for this by optimizing the software and distributing the workload across the hardware.
Z.ai has tested models anonymously before
Ox Alpha was not Z.ai’s first experiment with an anonymous model.
The company previously tested GLM-5 anonymously under the name Pony Alpha.
Z.ai says the purpose of anonymously testing GLM-5.3-Flash, as Ox Alpha, was to gather user feedback before release.
