A file on Hugging Face claimed to be a secret Anthropic model. Within a day, a Reddit user proved it was fake.
The file sat under the account "burner22," with the name "numbat." It claimed to hold a 14-trillion-parameter checkpoint. The checkpoint supposedly came from Anthropic's Mythos line. Mythos is Anthropic's line of frontier models, shown only to a few partners.
The claim first spread on X on November 1. One early post about it pulled 876 likes. It drew 98 replies within hours.
A Reddit user named johnxreturn then ran the numbers. The post checked the file's own math. A model's output layer and its input layer usually differ, since Anthropic trains them apart. In this file, the two lined up almost exactly, row after row.
Real model weights also swing a lot from one input to the next. This file's weights barely moved at all. The post called the pattern noise. Trained models leave real structure behind; this file carried only randomness.
The account itself raised flags too. It was made one week before the file appeared. It had posted on Hugging Face just once, for this file alone.
Even so, the file held some real details. Its claimed size, 7.72 terabytes across 772 shards, checked out exactly. Its model name is real too. Anthropic does use "Mythos" for models it shows only to a few partners.
By the time of this post, the file had drawn 260 likes. It had 7,108 downloads on Hugging Face.
The debunking thread pulled 7 comments on Reddit. Word of the forensic work spread faster on X than on the forum where it first ran.
The case shows how a leak can look real at first glance. Real file sizes and a real model name can sit beside numbers a human invented. One coder with free tools found the gap within a day.