Z.ai opened the weights of its cheap model — the flagship it promised two weeks ago is still closed

Z.ai published GLM-5.3-Flash on 26 August 2026 and put the weights on Hugging Face the same week, under a plain MIT licence. Two weeks earlier the company launched its flagship GLM-5.3 with a promise that its weights would follow in about a fortnight. That deadline has now passed, and the flagship repository does not exist: the newest Z.ai model anyone can download is the cheap one. The last flagship whose weights were actually released is GLM-5.2 from June 2026, at 753.3 billion parameters. GLM-5.3-Flash is less than half that size — 320 billion parameters with 18 billion active per token, and the published safetensors index confirms it at 321.3 billion. The smaller model is not merely a trimmed version. Z.ai describes it as the first open-weight frontier model to combine sparse attention with linear attention, and quantifies the gain against GLM-5.3: attention computation down 3.01 times, KV cache down 4.44 times. It is also the first natively multimodal model in the family, meaning it can look at a rendered interface and correct its own code rather than working blind. The price is where that architecture shows. GLM-5.3-Flash lists at 0.15 dollars per million input tokens and 0.50 per million output; GLM-5.3 costs 1.40 and 4.40. That is 9.3 times cheaper on input and 8.8 times cheaper on output — close to, but not quite, the one tenth of the price the company claims. A 50 percent promotion runs until 9 September 2026, which for now doubles the gap again. The performance claims stay in the maker’s own hands. Z.ai says the model beats GLM-5.2 across benchmarks and approaches Claude Opus 4.8 on coding and agentic tests, but publishes those results only as a chart image, and no independent laboratory has repeated them. What can be verified is the licence: the LICENSE file in the repository is the bare MIT text, with no attribution rider and no restriction on commercial use.