Z.ai has released GLM-5.3-Flash, a 320-billion-parameter mixture-of-experts model with only 18 billion active parameters per token, achieving inference costs at roughly 1/10th of its predecessor. The model is released under the MIT license and is the first in the GLM-5 family to be natively multimodal. It also marks the first open-source frontier model in this class to support a particular advanced feature, signaling Z.ai's push toward efficient, accessible large-scale AI.