AI Model Ox Alpha Is Free, Beats Claude Fable, and Nobody Knows Who Built It

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In brief Ox Alpha, a free "stealth model," launched August 20 on OpenRouter, OpenCode, Cline, and Nous Research's portal+.

A viral claim that Ox Alpha beats Claude Fable 5 and GPT-5.6 Sol on DeepSWE came from a 10-task sample; two separate full 113-task runs landed near 63%, roughly level with GPT-5.6 Sol.

Google, Xiaomi, DeepSeek, and Microsoft's MAI were all floated as the model behind it; but the most popular theory points to Zhipu AI's GLM-5.3 family.

AI enthusiasts are getting very excited about an AI model called Ox Alpha, which appeared on OpenRouter on August 20 with no company name attached.

The listing describes it as "a reasoning model designed for coding, sustained agentic work, and production workloads," built by a third-party provider that has chosen to stay anonymous during the preview.

What's more, the mystery AI model already tops Anthropic's Claude Fable 5 and OpenAI's GPT-5.6 Sol on impressive coding benchmarks.

DeepSWE—a benchmark that scores how often a coding agent resolves real GitHub issues correctly on its first attempt, measured as a percentage of tasks passed across 113 tasks pulled from 91 repositories—shows that Ox Alpha is competitive against the best models.

Developer Ben Davis ran an initial 10-task sample and got Ox Alpha to 80% on the first pass, ahead of Claude Fable 5's 65% and GPT-5.6 Sol's 52%. That number went viral within a day, and versions of it are still circulating as if Ox Alpha has a clean edge over both models.

I ran this thing through 10 tasks on DeepSWE (so there could be a ton of variance in it's real score, this is a subset), but uh... gpt-5.6-sol: 52%

fable: 65%

whatever the hell this is: 80% (was a near miss on the "x"s so actually over 80%) I am very confused https://t.co/VfH6n5i7xc pic.twitter.com/NdDSTjoHLj — Ben Davis (@davis7) August 21, 2026

As of August 22, Ox Alpha still had no entry on Artificial Analysis or LMSys Arena.

The model is free to use, reads up to roughly 1 million tokens in a single context window, and takes text, image, and video as input while returning text. It also supports tool and function calling, though its JSON output isn't schema-enforced—a real gap for developers building agents that expect structured responses.

OpenCode said its route could handle 100 trillion tokens a day; Nous Research, offering the model free through its own portal, claimed capacity for 1 quadrillion. Tokens are the basic unit of information a model can handle, and throughput like this put it on par with the most used and capable models in the market today.

Such numbers make it easy to conclude that the model is so good they expect a lot of usage and the provider has enough infrastructure to support the load.

Ox Alpha (stealth model) is free for the next week - 1M Context

- Multi-modal

- Zero Data Retention Generous rate limits, near unlimited usage We have capacity for 100T tokens per day, lets see what you can do — OpenCode (@opencode) August 20, 2026

Why everyone's paying attention

Stripe CEO Patrick Collison, whose company agreed on August 19 to acquire OpenRouter, called Ox Alpha "very impressive" in a post on X. That single line from a well-known tech executive helped push the model into wider conversation within hours of launch.

Nobody has stepped forward to claim it. AI analyst Andrew Curran posted on Friday that people "seem less sure of anything" about where Ox Alpha came from.

As the model grew in popularity, the guessing game split fast. Developers floated Microsoft's unreleased MAI family, Xiaomi's MiMo line, DeepSeek, Alibaba's Qwen, and even Google's Gemini—enough people landed on Gemini that one developer joked Google was using a rival's stealth model as marketing for its own. Most of those candidates didn't survive contact with the evidence.

Xiaomi's MiMo v2.5 accepts audio input, a headline feature Ox Alpha flatly rejects. DeepSeek has never shipped video capability and releases open weights instead of running stealth previews. Google and Qwen both use different tokenizers and video encoders entirely, so it’s hard to establish a solid link to those models.

What's left points to Zhipu AI's family of models. Independent fingerprinting matched Ox Alpha's tokenizer to GLM-5.3 on every normalized test and its video-token spend to GLM-5V-Turbo exactly across four separate clips, and it shares GLM's distinctive errors and audio-rejection behavior.

Ox Alpha's tokenizer is one for one identical to GLM's. No other lab's tokenizer gets past 4/11 when it comes to tokenizer similarity.https://t.co/3K25G4U2hX

(h/t: @sushsrinivasan) (3/n) pic.twitter.com/dNwwZmCYZ7 — Ananay (@ananayarora) August 21, 2026

However, one detail complicates a clean match. GLM-5.3 launched on August 14 as a text-only model, six days before Ox Alpha showed up with full video support. If the fingerprinting holds, Ox Alpha is more likely an unreleased multimodal upgrade to that line than an identical copy—something analysts have started calling GLM-5.3 Flash.

Zhipu AI has said nothing publicly about Ox Alpha either way.

What's a stealth model, anyway

A stealth model is a frontier-class AI system released without attribution through a routing platform like OpenRouter, letting a lab collect real-world usage data before committing to a public launch.

The pattern has become routine for Chinese labs. Zhipu AI's own Pony Alpha was unmasked as GLM-5 within five days in February, Xiaomi's Hunter Alpha turned out to be MiMo-V2-Pro in March, and Meituan let its Owl Alpha ran anonymously for two months before confirming it as LongCat-2.0 in June.

Ox Alpha is live now on OpenRouter under the model ID stealth/ox-alpha, and through OpenCode, Cline, and Nous Portal, all free to query. OpenCode's launch note pegged the free window at about a week from the August 20 debut, putting the likely cutoff around August 27—after which, if the pattern from the last four anonymous models holds, someone may finally put a name to it.