Surprise: Z.ai is the AI lab behind the mysterious Ox Alpha model

Over the weekend, the nerds were buzzing with speculation over which AI lab was behind Ox Alpha, the mysterious new open-weight AI model launched onto OpenRouter anonymously and already topping benchmarks and leaderboards against the best models.

As many had expected, Ox Alpha was spawned by GLM-maker Z.ai, according to Bloomberg. Z.ai confirmed that Ox Alpha is the newest iteration of its GLM series, which Hugging Face famously used recently to defend itself against an attack from OpenAI agents.

The company said it will release the weights for Ox Alpha on Wednesday, after which developers can build on top of it. The company 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 release of Ox Alpha adds to the burgeoning threat of cheap, capable models from China that could take real market share away from expensive frontier model companies like OpenAI and Anthropic.

Earlier this month, Z.ai released GLM-5.3, which rivals Anthropic’s Fable 5 on certain benchmarks.

TechCrunch has reached out to Z.ai for comment.