Web Device reads AUP in two adjacent but different contexts:
| Context | What it is for | Do not assume |
|---|---|---|
| A static AUP-tree renderer | Rendering a supported semantic tree to HTML | Every native primitive or widget is supported |
A page layout.aup | Arranging a site page through the Web layout/component model | Arbitrary native primitives may be used as layout sections |
For a new Web page, use pages/<name>/layout.aup and site/theme components with explicit props. The layout lookup is locale AUP, default AUP, locale JSON, default JSON, then convention/default fallback. The JSON forms are compatibility input; new source should favor AUP.
Layout validation boundary
The Web layout validator recognizes the component model and rejects native primitive/widget sections that do not belong in this layout context. This is why an AUP primitive existing in the protocol registry is not sufficient evidence that it can be placed directly in a Web page layout.
The full AUP language, node/event/data semantics, and target capability boundaries are outside this board. This board documents only how a Web Device site consumes that language.
For a task walkthrough, see Build a page with AUP; for a reusable presentation contract, see Component resolution.