A mysterious free AI model is impressing developers. And nobody knows who made it.

The new Ox Alpha AI model is turning heads in Silicon Valley, but no one knows its origin, much like this stone carving on display at the Shanxi Bronze Museum in China.

Zhe Ji/Getty Images Ox Alpha, a mysterious AI model, debuted on OpenRouter on Thursday.

Its origins are unknown.

Some think it's from a Chinese lab, others that it has ties to Microsoft.

Wherever it's from, Ox Alpha has impressed Silicon Valley tech leaders.

A mysterious new AI model is making the rounds among developers — and nobody is saying who built it.

Ox Alpha appeared on OpenRouter on Thursday as a "stealth model" from an anonymous third-party provider.

OpenRouter describes it 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." It's also free.

OpenCode, an open-source AI coding agent, said on X that Ox Alpha would be free for a week with "near unlimited usage" and that its provider had capacity for 100 trillion tokens per day , which is roughly 100 times the number of AI tokens Visa said it uses in an entire month.

Ox Alpha has already attracted interest from prominent tech figures.

Stripe CEO Patrick Collison tried the model and said in a post on X that "it's very impressive." Early speculation suggests it may be the product of a Chinese AI lab .

Wccftech, an online tech publication, suggested that the Chinese lab behind GLM-5, Z.ai, as one possibility, noting that the company previously tested GLM-5 anonymously under the name "Pony Alpha" and that developers have identified similarities in Ox Alpha's tokenizer behavior and responses.

That speculation comes as Chinese AI labs like Zhipu, DeepSeek, and Moonshot AI increasingly challenge US rivals.