A real production document editor uses state machines to manage the document lifecycle: loading, editing, version history navigation, and publishing. This case study examines how the machine prevents accidental branching when editing old versions.

• One guard replaces multiple scattered conditionals

• All entry points go through the machine

• Testing is pure input → output

Why State Machines Are a Game-Changer for UI Development

• Pattern: Forms — Form state patterns

• Pattern: Undo/Redo — History stack

• Tooling: Testing — Machine testing

• Fork the machine definition into this page

• Add full statechart diagram

• Add code walkthrough