Component

A live component: server-held state, rendered to HTML, updated over patches.

The mental model is a server template that re-renders itself (design/live.md §1): an event arrives from the browser or a Topic, the state moves, render runs again, and the differ ships the difference. The three methods are the three phases, and what each receives is what that phase may do — the split is enforced by the arguments, not by documentation:

• init runs once, at mount, and is the only place subscriptions exist: it receives the Init context, and subscribe after init returns throws. render runs on every event, so a subscription there would be a duplicate per re-render.
• handle moves the state. It runs on the page's own thread, one event at a time, so it needs no synchronisation of its own. Database work happens here the way it does in any handler: open a scope with transact { ... } or read { ... } per event — the installed Database reaches every thread, and a connection captured across events is already a loud error (EscapedScope).
• render is a pure function of the state and receives nothing else. Exactly one root element, in canonical form; the differ refuses anything else by naming the broken rule.

State is any immutable value the component chooses. It lives on the server, owned by one page thread; the browser only ever holds its rendering.