A post from the X account @ashawv5i says two mystery models have appeared on Arena: one called “Fe-pichu” that it says runs on OpenAI’s tokenizer, and a new Qwen model it does not name. Neither OpenAI nor Alibaba has said anything about either model, and the post does not include a model card, test result or price.

Image shared by @ashawv5i on X
Image shared by @ashawv5i on X

Image credit: @ashawv5i on X

The OpenAI claim rests on a name and a tokenizer

The only lead for Fe-pichu is a Chinese-language forum thread on LINUX DO, posted about a day earlier. It asks whether a similarly named model, “fe-raichu”, drawn in Arena is OpenAI’s. The one reply visible says Arena’s battle mode switches to a different model on the next prompt, so one name may not map to one model.

The post does not explain how the match was made.

Kalmia and the Qwen 4 signs

The stronger thread is Kalmia. Stealth Models reports that an anonymous model codenamed Kalmia left Arena on 23 October and returned with new checkpoints that evening and on 24 October. It shares Qwen’s tokenizer quirks, which points to the Qwen family but not to Qwen 4 by name.

Individual X users have gone further. One said on 22 October that Qwen 4 was showing up as Kalmia on Arena. Another reported on 24 October a new Qwen 4 checkpoint with a small quality gain, describing it as an ongoing experiment.

The background is also suggestive. Alibaba said on 22 September that Qwen4 is in training, and Qwen Developers teased model sizes on 10 October. Qwen 3.8-Flash-Next, released 28 August, is described by Alibaba as an experimental preview of the architecture that will underpin Qwen4, according to YottaLabs. That same source says Qwen 4 had not shipped as of 26 October and that Alibaba had not given a date. It also reports that a prediction market put a launch before November at 83 percent as of 23 October.

Names in circulating videos are not proof either. GPTunnel notes that the names Qwen 4 and Kimi K3.1 in those comparisons come from the poster, and that Arena said a new Kimi model was coming on 23 October without naming it. Arena has not said anything about Qwen 4. Its votes are anonymous, and identities are revealed only after a vote, per Arena’s Wikipedia entry. A precedent points the same way: an anonymous Qwen-suspected Arena model called “Kaleb” was revealed a day after it appeared, as Qwen3.8 Max, according to OrcaRouter.

What to watch

For Qwen 4, the signs to wait for are a model card, weights, an API model ID and pricing. The sources list none of these. Nothing says whether Qwen 4 would be open-weight.

This follows the pattern of our earlier report on the stealth image models in Arena Scout alerts, where unknown makers and stealth names made the attribution uncertain.

Sources