Today, we're introducing Claude Fable 5 and Mythos 5, two configurations of our next major language model.

I'd normally highlight the numbers: It's SOTA on nearly all benchmarks. I want to talk about something else, because with Fable 5 out in the world, I think a third era quietly started today.

I lead Claude Code & Cowork on the desktop, so I think a lot about how people use AI to get work done. I believe we're about to see a major shift, moving from giving AI tasks to giving it responsibilities. When LLMs first hit the mainstream, users asked them questions, like a smarter search engine or an autocomplete for code.

Then the frontier moved to tasks, handing the model an entire problem. Which bug to fix, what doc to write. That's how most of our advanced users work with AI: They're in the loop. Every task starts and ends with a human.

Cowork on Windows! Early days, we're actively developing, so expect a lot of improvements and changes.

Grab it at and let me know what you think!

Some nerdy below-the-hood technical details in thread →claude.com/download Claude gets its own sandboxed Linux VM: An environment separate from your machine where Claude can write code and run commands without touching your actual system. Under the hood, we're using the same Hyper-V virtualization technology that powers WSL2.

On macOS, the VM runs in user space and inside our app's process. On Windows, Hyper-V requires SYSTEM privileges. So we built a separate Go service that runs as LocalSystem and manages the VM. The app talks to it over a Windows named pipe.