the weekly agent lessons, and what changed
buttercup.sh is now a course as well as a harness. One lesson by email every week — a single idea, the code that makes it work, and an exercise you run in the tab. Free, no account, and every exercise runs on a local model if you would rather not spend a cent.
Eighteen tools, a virtual filesystem and an undo stack in one static page — on desktop or phone, with no backend and no build step. Free forever, and it talks to local models so nothing has to leave your machine.