Chinese AI startup Z.ai said on Friday its open-source GLM-5.3 model had neared Anthropic’s restricted Mythos 5 in identifying software vulnerabilities, bolstering the credentials of a Chinese AI challenger gaining traction among Western developers.
Z.ai framed the launch as a challenge to the restricted-access model represented by Mythos. It argued that advanced cyber-defence tools should be available to developers of open-source software and smaller security teams, rather than being controlled by a limited number of closed-model providers. Z.ai said it would release GLM-5.3 publicly in about two weeks after completing security assessments and strengthening its safeguards. The launch builds on global interest in GLM-5.2, which gained attention in recent months among overseas developers for coding and agent capabilities that users and analysts said approached leading U.S. models but at a much lower cost.
Its most sensitive cybersecurity functions would be available only to verified users through a “trusted access” programme, it said. It wrote in a Friday X post that initial model access will be shared with a select group of launch partners, which will later be expanded “through a consistent and responsible process”, echoing the language of Anthropic’s “Project Glasswing” limited-access scheme for Mythos. “To the best of my knowledge, this is the first time a Chinese lab is publicly justifying a delayed open release of model weights with safety considerations,” said Gabriel Wagner, an AI governance researcher at Concordia AI, a Beijing-based consultancy focused on AI safety.
Such controls reflect concern that AI systems capable of finding and exploiting software flaws can assist defenders but may also lower barriers for attackers. Anthropic has made Mythos, a version of its Claude Fable 5 model with cybersecurity safeguards removed, available only to vetted organisations.
