www.it-connect.fr
Claude Fable 5.2 Built an Operating System in 8 Days With 1,000+ Subagents
To mark the release of Claude Fable 5.2, Anthropic highlighted the creation of an operating system built from scratch. An empty folder, a prompt, and more than 1,000 AI subagents working nonstop for eight days made it possible.
On Monday, November 9, 2026, Anthropic officially announced Claude Fable 5.2 and Claude Mythos 5.2, the latest versions of its most powerful models. As a reminder, this is the same underlying model, but not released in the same way. Fable includes specific safeguards for cybersecurity and biology, which makes it available to everyone, while Mythos remains reserved for certain organizations, since it is the uncapped version.
On paper, this 5.2 release generates responses up to 30% faster than Fable 5.1, at a lower price: $8 per million input tokens and $40 per million output tokens. But what I want to talk about is an experiment carried out by Anthropic.
An OS written from an empty folder
Anthropic explains that one of its engineers asked Fable 5.2 to design an operating system prototype. "Starting from an empty folder, the model coordinated more than 1,000 subagents, which worked day and night for eight days to write, test, and review code.", we can read.
The result, shown in a short video, is an operating system capable of booting on a laptop. According to Anthropic, this system includes:
- A kernel: the core component responsible for running the machine
- Drivers: for the disk, keyboard, and network
- Persistent storage: files are kept
- A graphical interface: windows, a login screen, and an installer
- Claude: assistant features integrated into the system
In addition, Anthropic ran another experiment: a team of 1,000 Fable 5.2 agents formalized the proof of Fermat's Last Theorem in less than 30 hours, compared with 11 days during an earlier attempt. The technical article dedicated to this experiment describes a team lead agent and 999 assistants, coordinated through Git and a shared database, each in a sandbox with no network access. Nothing says the same setup was used to build the OS.
A prototype, not a ready-to-use product
Anthropic created an operating system in a few days, from scratch, which is pretty cool. But we do not know much about this system, and the code has not been released. Here are some of the missing details:
- The language: no details on the language or languages used, or on the amount of code produced
- The hardware: the laptop model is not specified
- Human involvement: what was the engineer's role during those eight days? Making coffee?
- The bill: the token cost has not been disclosed
The cost was probably enormous. In February 2026, Anthropic had explained how 16 Claude Opus 4.6 agents wrote a C compiler: two weeks of work, nearly 2,000 Claude Code sessions, 100,000 lines of Rust, and about $20,000 in API costs. This time, the number jumps from 16 agents to more than 1,000, and each one consumes credits.
Anthropic created an OS, but it is only a prototype, so there is no need to get carried away. Still, at the pace IT is evolving today, I would not be surprised if this idea becomes reality in the near future... For now, the main takeaway is that an AI model can steer a large-scale software project for several days.
Claude Fable 5.2 is available now in the Claude apps, via the API, and on AWS, Google Cloud, and Microsoft Azure. To get hands-on with the tool that runs these models, IT-Connect offers a tutorial on installing and using Claude Code.
I'll leave you with the video of this famous OS created by Claude Fable 5.2 and its army of agents.
