The Powerful Stealth AI Model ‘Ox Alpha’ Is Now GLM-5.3-Flash, and You Can Use It
Z.ai says the model is a 320B-parameter, MIT-licensed multimodal release built for coding and long-horizon agent work.
- On Wednesday, August 26, Z.ai confirmed that the anonymous model Ox Alpha is its new GLM-5.3-Flash, a reasoning system designed for coding, sustained agentic work, and production workloads.
- After appearing anonymously on OpenRouter on August 20, the model sparked a six-day guessing game among developers, who used forensic API tests to identify the Chinese-origin source.
- The GLM-5.3-Flash architecture features 320 billion parameters and a 1-million-token context window, achieving 80 percent on the SWE-bench Verified coding benchmark during its free preview window.
- Available under an MIT license for self-hosting, the model costs $0.075 per million input tokens during launch promotion pricing that remains valid until September 9.
- Z.ai's anonymous stress-test strategy successfully drove usage to 26 trillion tokens before the official reveal, positioning the model as a cost-efficient rival to US frontier labs.
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16 Articles
Everything we know about Z.ai, the Chinese company behind the mysterious Ox Alpha model
Z.ai chairman and cofounder Liu Debing marks the company's debut on the Hong Kong Stock Exchange in January 2026.Lam Yik/Bloomberg/Getty ImagesChinese tech firm Z.ai revealed that mystery AI model Ox Alpha was actually its new GLM-5.3-Flash model.The Tsinghua University spinout went public in Hong Kong in January and its shares have since surged.Z.ai says all traffic from the Ox Alpha test ran on Chinese AI chips despite US technology restrictio…
(Seoul = Yonhap News) Reporter Seol Won-tae = Chinese artificial intelligence (AI) startup Z.ai [has] a 'GLM-5.3-Flash' model running on a Chinese-made AI chip ...
Ox Alpha, which had been attracting attention in Silicon Valley, USA, as a high-performance AI model while concealing its nationality, was revealed to be China's Zhifu AI's GLM-5.3 Flash model. With its low cost and powerful performance, it threatens the US market and has proven the potential for China's AI technology independence.
Z.ai Confirmed as the Mystery Lab Behind Ox Alpha: GLM-5.3-Flash Is Now Open-Source
For six days, the developer world chased a ghost. An anonymous model called Ox Alpha appeared on OpenRouter on August 20, 2026, free, multimodal, and seemingly capable enough to top usage charts ahead of DeepSeek. By the time Bloomberg reported on August 26 that Z.ai had confirmed authorship, the community had already identified the lab, the model family, and the likely public SKU. The “mystery” was only a mystery to people who weren’t watching …
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