Sample contract · MD structure · ARC 2.0.0-beta.28

thematicBreak / HR

Use horizontal rules as separators; under slides: true they become slide boundaries.

Web Device Markdown structure — not an AUP primitive; not a theme/site layout component.

Sample contract

Field	Value
Purpose	Horizontal rules as ordinary separators; under `slides: true`, top-level breaks become slide boundaries
Boundaries	Without `slides: true` → ordinary separator only
Author entry	`---`
Surface	Web Device document · slides when flagged
Public status	`released`
Fallback / failure	No slides flag → prose separator
Verification	This page + slides-front-matter · `arc --version` = `2.0.0-beta.28`

In ordinary content, a thematic break is a horizontal rule:

Source:

Above the break.

---

Below the break.

Rendered:

Above the break.

Below the break.

With slides: true in front matter, top-level --- becomes a slide boundary. See slides front matter and the slides demo.

Situation	Expected result
HR without slides flag	Ordinary separator
Nested/context HR inside containers	Not a top-level slide boundary
Expecting free-form page breaks for layout components	Wrong surface

Item	Value
Baseline	`2026-08-09` · `arc --version` → `2.0.0-beta.28`
Capability row	`docs/aup/capability-matrix.md` §6 · thematicBreak / HR
Implementation	`content-reader.ts` · `slides.ts`
Public routes	`/en/docs/web-device/markdown/thematic-break/` · `/zh/docs/web-device/markdown/thematic-break/`
Local run	`arc service start --blocklet blocklets/arcblock --port 4900` · open this page and slides demo
Accept	Ordinary HR renders; slides path documented honestly