Save a file — by hand or by an agent — and every open page swaps in the new
version, in place, without a reload. The page keeps your place — the scroll,
the slide — and every widget the change didn't touch keeps its state.
```mermaid
flowchart LR
save["Save"] --> devpage["devpage"]
Teaches it: [Live updates](../boxes/viewer/live-updates/README.md).