Z.AI has officially confirmed that the mysterious AI model Ox Alpha, which has taken the developer community by storm in recent days, is its creation, and announced the public release of the model's weights that same evening, bringing the multi-day "model detective hunt" to a close.
On Wednesday, Z.AI told Bloomberg that Ox Alpha is the latest iteration of its GLM series, with the model's codename inspired by the recently released domestic hit film "Niu Lai". Since being anonymously listed on the AI model platform OpenRouter over the weekend, the model has rapidly climbed to the top of the platform's usage charts thanks to its free access and robust performance, with current usage exceeding DeepSeek's by more than double.
Z.AI plans to release its first detailed financial report next Monday, covering the first six months of performance since its listing in January this year.
Anonymous release, explosive usage growth
According to previous reports, late on August 20th Eastern Time, a model named Ox Alpha was quietly listed on OpenRouter as a "stealth model", with the publisher shown as an anonymous third party, marking the largest release in the platform's history.
The model comes with impressive specifications: a 1 million token context window, support for text, image, and video multimodal inputs, mandatory reasoning capabilities, and completely free usage. An official announcement from AI coding tool OpenCode revealed that the provider behind it has a daily computing capacity of 100 trillion tokens. The free access has driven usage to surge rapidly, with OpenRouter leaderboard data showing Ox Alpha's usage surpassing DeepSeek's by more than double.
Stripe CEO Patrick Collison personally tested the model and directly commented on X that it is "very impressive". Notably, Stripe is in the process of acquiring OpenRouter.
Cutting-edge coding performance, identity cracked by community within 24 hours
In terms of performance, Ox Alpha's capabilities have significantly impressed the developer community. davis7, author of AI programming framework fable, used the DeepSWE official benchmark to test 10 problems, with Ox Alpha scoring 80%, higher than Claude Fable's 65% and GPT-5.6 Sol's 52%, and independent retesting concluded largely the same results.
Before the model's identity was revealed, the developer community had already narrowed suspicion to Z.AI through technical fingerprint comparisons. According to a detailed analysis on X by lizikk_zhu, founder of Atomstorm.ai and former executive at Baidu and Alibaba, five pieces of evidence from different technical levels all pointed to Z.AI. The most compelling came from a video encoder test: after inputting the same video into both Ox Alpha and Z.AI's GLM-5V-Turbo, the token consumption matched exactly across all three independently designed features of frame sampling strategy, duration scaling, and resolution scaling. Additionally, text tokenizer characteristics, the unique error code [1210], backend Chinese error messages, and responses to specific sensitive questions all closely matched Z.AI's existing models.
Tech media outlets such as Wccftech also noted that Z.AI had previously tested GLM-5 anonymously under the codename "Pony Alpha", with developers discovering similar tokenizer behavior and response patterns in Ox Alpha.
Anonymous testing becomes industry practice
Z.AI's release strategy this time follows a pattern already seen among domestic tech companies. ByteDance, Alibaba, and Xiaomi have all released models this year without disclosing their sources, in order to test new services with fewer brand constraints.
The timeline compiled by lizikk_zhu shows multiple precedents for such operations: Hunter Alpha was later confirmed to be Xiaomi's MiMo-V2-Pro, Owl Alpha was Meituan's LongCat 2.0, Pony Alpha was Z.AI's GLM-5, and even OpenAI used the codename Quasar Alpha to test GPT-4.1. Anonymous listing avoids brand risks, and free access trades for real production traffic, with stress-test feedback offering more reference value than internal test data, before eventual claim and commercialization.
Z.AI stated that Ox Alpha will remain free for one week, with pricing to be announced thereafter. Earlier this month, Z.AI released its latest flagship model GLM-5.3, claiming it can rival Anthropic's Fable 5 on certain benchmarks.
Z.AI completed its listing in January this year. Data shows that even after a recent pullback, Z.AI's share price gains still significantly lead its AI industry competitors.
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