Zhipu AI

Z.ai's GLM-5.3-Flash is the first natively multimodal GLM-5 model: 320B total / 18B active, hybrid sparse + linear attention, $0.15 per million input tokens, and MIT weights on day one. It beats GLM-5.2 on every published benchmark at a tenth of the price — and it's the anonymous "Ox Alpha" that took over OpenRouter.

Z.ai shipped a major capability jump without changing the base model at all — and then held the open weights back because the same training made it dangerously good at exploiting vulnerabilities. Benchmarks (vendor and independent), the 2,436 real bugs it found, every price and endpoint.