Claude wrote a language model for DOS that fits on a floppy disk — and the thread caught a terms problem

A Reddit poster says they had Claude build a language model small enough to live on a floppy disk: a 367,000-parameter transformer that runs under DOS, trained on facts written by another Claude model. The 71-second demo charmed r/ClaudeAI on Sunday morning. Then the comments found the catch.

The post, from u/wollymonjac, went up at 2:28 a.m. EST on Sunday, November 15, 2026, under the flair “Built with Claude.” By about 6:10 a.m. it had 670 upvotes and 103 comments, and the score was still climbing. The title is the whole pitch: a working language model, small enough to fit on the storage medium the rest of the industry abandoned decades ago.

What the 71 seconds show#

The video is silent, as far as could be observed — no narration, no soundtrack — and it opens on a black laptop sitting on a wooden windowsill, a lamp and a mug nearby. A hand opens the lid, and the camera moves in on the screen: a DOS text interface headed “TINY NEURAL INTERFACE 2.1 – 367,000 WEIGHTS,” with a “CONVERSATION” menu and the line “a neural network in your computer … ask about countries, animals, space, words or sums.” A “NEURAL MONITOR” tracks layers L1 through L4, and readouts show confidence, speed in letters per second, and “1 layers – 96 wide.” At the “ASK TINY” prompt, the words “who are” are typed in, letter by letter.

The clip alone does not prove much more than that the interface exists and responds, and the full question-and-answer sequence is not verifiable frame by frame from the footage. The one exchange the thread keeps quoting comes from a commenter, not the video itself. Asked for the capital of the United States, the model answered “Havana,” according to u/bearbullX — and when pressed, “I think so.” That matches the poster’s own warning in the post: the model “does pretty well on words and facts it has seen, but if I ask something complex or too long, it spits out utter nonsense.”

367,000 weights, 435 kilobytes#

The numbers are the story. According to the post, Fable 5.2 wrote the transformer itself, and Opus 5.5 generated the training data: about 3,500 facts, plus small talk and math, each asked and answered in different ways. The model has 367,000 parameters and runs on an Intel Pentium. Its weights are stored as 8-bit integers with one scale per row, so the program and the weights together come to about 435 KB — small enough to fit in DOS memory and on a floppy disk. It reads and writes one letter at a time.

That is the opposite direction from the rest of the industry: frontier models now measure in the hundreds of billions of parameters and run in datacenters, while this one is narrow by design — short facts, small talk, simple sums it has already seen. One commenter noted the floppy could hold more, a standard 3.5-inch disk storing 1.44 MB. The on-screen “1 layers – 96 wide” suggests a single-layer, 96-wide design, though the post does not spell it out.

The thread’s mood is mostly delight. “And so it begins. AIs building AIs. How exciting!” wrote u/Tinsnow1. The top reply — “Take a LLM back to 1995 with a floppy disk full of code, and become tech trillionaire” — has 40 upvotes, and another commenter suggested an autoexec.bat so any DOS machine could boot up smart. The top comment overall is a joke: “This is the computer courage the cowardly dog used.”

The thread’s real argument: the terms#

The most consequential argument in the thread is not about the model at all. Several commenters said generating training data with Claude to train another model is prohibited under Anthropic’s consumer terms and could risk a ban, quoting the terms’ prohibited-uses list: general-purpose chatbots, models designed for open-ended text generation, using outputs as training targets, and reverse engineering training methods.

The poster conceded. In a reply posted at 2:49 a.m., u/wollymonjac agreed the commenter raising the issue was right, said they had not known the use was prohibited, that the small size of the data — mostly short question-and-answer pairs — probably kept it undetected, and warned readers not to do the same: “You might risk a ban.” In a second reply, the poster agreed that such uses are prohibited where they are competitive with Anthropic’s models.

Not everyone agreed the rule applies here. One commenter argued the ban-relevant distillation is about extracting Anthropic’s process and reasoning, not a tiny DOS toy; another argued the terms only bar models competitive with Anthropic’s own. Anthropic’s post on distillation defenses, linked in the thread, frames the concern around extracting its models’ reasoning and process. The thread never settled it — but the poster’s takeaway was the cautionary one, and it is the part most likely to matter to anyone tempted to repeat the experiment.

What to watch#

For now, the artifact is the video. The post links nowhere — no GitHub repository, no download, no code — and a common question in the replies — “How get?” — has no answer in the top threads. Without code, the demo is a minute of footage, not a reproducible result, and the claims rest on the poster’s word.

Three things to watch: whether the poster releases the code, and how the terms question shapes that decision; whether Anthropic says anything about hobby-scale projects like this one; and whether the floppy-sized model becomes a small genre. The same model family had already spent the weekend in the spotlight — Fable 5.2 also painted a Bob Ross landscape in a browser Paint clone, a demo Reddit crowned “Claude Ross.” For now, the record stands as a minute of DOS, a model that thinks the capital of the United States is Havana, and a thread that turned from applause to a terms debate in under half an hour.

Sources: the original post by u/wollymonjac on r/ClaudeAI; Anthropic’s consumer terms; Anthropic, “Distillation defenses”. Vote and comment counts were read from the Reddit post page around 6:10 a.m. EST on November 15, 2026. The video was observed muted; the “Havana” exchange is quoted from a comment on the thread, not from a frame of the video.