GLM-5.3-Flash as a Labs experiment, open for a short test window: temporary, not a permanent id. Served from the native weights (Z.ai's GLM-5.3-Flash): a 320B mixture-of-experts model with 18B active parameters per token, the first natively multimodal release in the GLM-5 series, built for fast coding and agentic tasks on a 1M context window. It always thinks at max effort by default; dial reasoning to low or high (thinking cannot be turned off). Access is seat-gated through the Labs page while an experiment is live. It is offered at limited capacity and low availability, so expect it to be flaky and to go down under load: crash it, give it a moment, and try again. For production work we recommend umans-coder or umans-deepseek-v4-pro-0813.