Over the weekend, the tech community was abuzz with speculation about which AI lab was responsible for Ox Alpha, the mysterious new open-weight model that appeared anonymously on OpenRouter and quickly shot to the top of benchmarks and leaderboards, outperforming some of the best models available. As many suspected, Ox Alpha was created by Z. ai, the company behind the GLM series, according to Bloomberg. Z. ai confirmed that Ox Alpha represents the latest evolution of its GLM family, which Hugging Face recently leveraged to fend off an attack from OpenAI agents. The company plans to release Ox Alpha’s weights on Wednesday, allowing developers to build on top of it. Z. ai describes Ox Alpha as “a reasoning model designed for coding, sustained agentic work, and production workloads. It is suited for long-horizon software engineering, complex reasoning, and workflows that combine text with visual context.”

The launch of Ox Alpha underscores the growing challenge posed by affordable, high-performing models from China, which could erode the market share of expensive frontier model providers like OpenAI and Anthropic. Earlier this month, Z. ai released GLM-5. 3, a model that rivals Anthropic’s Fable 5 on certain benchmarks, further intensifying the competitive landscape.