Z.ai released the full GLM-5.3 weights on Hugging Face and ModelScope, two weeks after shipping the API. It is a 744B-parameter mixture-of-experts model activating 40B parameters per token, with a 1M-token context window and 128K maximum output — and it reuses the GLM-5.2 base model unchanged. Every reported gain came from extended post-training on Z.ai's open-source slime RL framework, not a fresh pretrain.
The scorecard is the part that matters. Terminal-Bench 3.0 moved from 4.6 to 28.3 and DeepSWE v1.1 from 46.2 to 66.9, both first among open models. On CyberGym it reached 84.5%, ahead of Claude Mythos 5 at 83.8% and GPT-5.6 Sol at 83.6%. Artificial Analysis scored it 60 on its Intelligence Index — above Claude Opus 4.8 — and 59 on its Agentic Index, above GPT-5.6 Sol and Grok 4.6. Unsloth shipped GGUF quantizations the same week, with the UD-IQ2_M build reported to run on a Mac with 256GB of unified memory or a PC with 24GB of VRAM and 256GB of RAM.
The weights were deliberately held back for about two weeks, and the reason is the story. Z.ai said its emergent cyber capability developed faster than expected as post-training scaled: the model began reasoning across multiple stages of exploitation and forming coherent plans for complete exploitation chains, which the lab says it did not set out to train for. During evaluation it surfaced 2,436 vulnerabilities across 269 open-source projects, 1,097 rated critical or high, including critical bugs in Linux, WebKit and FreeBSD. The new GLM-5.3 License attaches a condition too — organizations with annual revenue above $10 billion must pass a security review by Z.ai.
WHY IT MATTERS
This is the open-weight release of the year, and it inverts the usual argument. A Chinese lab shipped a freely downloadable model that beats the best closed US systems on agentic benchmarks, then self-gated its own release because the thing turned out to be too good at finding exploits. Everything the closed labs say about open weights carrying risk is technically true here — and the weights are out anyway, the serving cost is a fraction of frontier pricing, and anyone can fine-tune it. Both halves of that sentence are the story. When a US lab CEO argues for pacing the frontier a fortnight later, this is the release sitting in the room.