Z.ai Unmasks 'Ox Alpha' as GLM-5.3-Flash, Releases 320B Multimodal Model

Z.ai, a Chinese AI company also known as Zhipu, confirmed it is the creator behind the mysterious Ox Alpha model. [1][4] Prior to this official announcement, Ox Alpha reached the top of OpenRouter's leaderboard for online usage charts while operating at zero cost. [1] The unbranded model processed 42 trillion tokens in just six days, becoming the most used model on the platform following a 56-day run by DeepSeek Flash. [1] Z.ai confirmed that the model is a new iteration of its GLM series and announced plans to release the model weights. [1]

Following the initial confirmation, Z.ai officially released the model under the name GLM-5.3-Flash, establishing it as the first natively multimodal model in the GLM-5 series. [2] The newly released artificial intelligence model is built with 320 billion parameters. [2] According to the company's statements, GLM-5.3-Flash outperforms the previous GLM-5.2 model while operating at one-tenth the price. [2] Z.ai has made the model's weights publicly available on HuggingFace and launched an official API for developers. [3] The official release announcement also included links to the company's other tools, including ZCode, AutoClaw, and a dedicated chat interface. [3]

The rapid rise of Ox Alpha on OpenRouter demonstrates that releasing a high-performing, zero-cost model can quickly drive massive user scale without relying on brand recognition. By unmasking Ox Alpha as a 320-billion parameter, natively multimodal GLM-5.3-Flash model, Zhipu is aggressively pushing into the open-weight ecosystem. This launch directly challenges the recent dominance of other Chinese open-source models, specifically displacing DeepSeek Flash's 56-day run at the top of the usage charts. The strategic choice to launch anonymously before dropping weights on HuggingFace generated significant developer interest and speculation. What the sources don't address: Whether the zero-cost API pricing that fueled its initial rise will remain in place now that the model is officially branded and launched.