Layout Blueprint Contract

Controlled vocabulary

Use the vocabulary embedded in the artifact. Composition is one of layered-overlay, split, stack, grid, rail, scroll-narrative, or freeform. Background is none, color, gradient, image, video, or composite. Regions use roles such as heading, body-copy, media, action, and tabs, with a nine-position placement anchor. Text wrapping uses single-line, wrapped, or clipped-or-overflowing.

The terms make implementation consistent; normalized rectangles preserve distinctive source geometry. Do not replace the measurements with a generic layout merely because its name sounds similar.

Identity rules

• Composition, background-media role, layer order, and declared relationships are identity locks.
• layered-overlay and scroll-narrative media must not become a peer column beside copy.
• fallback-only posters disappear when primary video/iframe media is ready.
• Scene evidence overrides static DOM evidence for animated or pinned phases.
• A measured single-line desktop heading must remain one line at the canonical desktop viewport; preserve its inline-size constraint before adjusting typography.
• Responsive reflow may stack a declared split, but it must retain content hierarchy and media role.

New best-practice rules should consume this artifact from UI normalization. Extend scripts/lib/layout-blueprint/ classifiers or vocabulary independently; bump the vocabulary version when controlled terms change.