recipes/core
A headless issue tracker, built on core, that checks itself.
The job is an ordinary one: tasks with a status, a running count per status kept beside them, an undo stack, and a second copy of the document kept in step over the wire. What makes it a proof rather than a demo is that the invariant tying the counts to the tasks is checked from inside a watcher, on every commit, while a burst of edits runs. If a commit ever reached a watcher half applied, the count would disagree with the tasks and this program would exit nonzero.
node recipes/core/main.ts