AI Model Ox Alpha Is Free, Beats Claude Fable, and Nobody Knows Who Built It

In brief

• Ox Alpha, a free "stealth model," launched August 20 on OpenRouter, OpenCode, Cline, and Nous Research's portal+.
• A viral claim that Ox Alpha beats Claude Fable 5 and GPT-5.6 Sol on DeepSWE came from a 10-task sample; two separate full 113-task runs landed near 63%, roughly level with GPT-5.6 Sol.
• Google, Xiaomi, DeepSeek, and Microsoft's MAI were all floated as the model behind it; but the most popular theory points to Zhipu AI's GLM-5.3 family.

AI enthusiasts are getting very excited about an AI model called Ox Alpha, which appeared on OpenRouter on August 20 with no company name attached.

The listing describes it as "a reasoning model designed for coding, sustained agentic work, and production workloads," built by a third-party provider that has chosen to stay anonymous during the preview.

What's more, the mystery AI model already tops Anthropic's Claude Fable 5 and OpenAI's GPT-5.6 Sol on impressive coding benchmarks.

DeepSWE—a benchmark that scores how often a coding agent resolves real GitHub issues correctly on its first attempt, measured as a percentage of tasks passed across 113 tasks pulled from 91 repositories—shows that Ox Alpha is competitive against the best models.