On November 1, burner22/numbat on Hugging Face claimed to hold a checkpoint from “Anthropic’s next Mythos-class training run,” with files totaling 7.7 TB; by 20:03 UTC that day, CellCog recorded 5,846 downloads on Hugging Face’s past-month counter. At 16:29 UTC, a user named FloxUnder reported regenerating 43 of the repository’s tensors bit for bit from random seeds computed from their names, and provided a minimal reproduction script that checks two tensors with a download of about 90 KB. An hour earlier, @kimmonismus posted a screenshot of the HTML behind Anthropic’s Mythos page with “Claude Claude Mythos 5.5” in a heading hidden from visitors. Both circulated that day on X as Mythos leaks. Hugging Face auditors found that the checked tensors in the 7.7 TB upload matched seeded noise. The HTML label also has a checkable record: an Internet Archive capture from October 31 includes it in the hidden heading and logo alt text.