Anthropic says China's GLM-5.3 nearly matches Mythos at cyber exploits

David BoothOct 2, 2026

Anthropic's testing put Zhipu's open-weight GLM-5.3 at 50 working exploits in 410 attempts, against 56 for Claude Mythos Preview, and NIST's CAISI calls it the most cyber-capable open-weight model released to date. A big data point for the open vs. closed debate.