This page opts out of its reader-facing H1 with doctorine.showPageTitle: false, the same switch services/portal-build emits into tenant guide frontmatter. The rendered consequence is that no id="_top" element exists in the DOM — yet Starlight still lists the synthetic “Overview” row (slug: _top) at the head of the table of contents, so the “On this page” jump-select offers an option whose target is absent.

Before T8.2 R3 that option was silently dropped: collectJumpTargets resolved every option through getElementById, found nothing for _top, and the scrollspy then settled the select on the first real heading while the reader sat at the top of the page. This fixture is the only route in the corpus that reaches that path, so it is what proves the page-top surrogate and the location.hash = '#_top' contract on a real render rather than by moving DOM around in a test.

Installing the toolkit

The section headings below give the outline two real entries in addition to the synthetic Overview, so TocJump.astro’s flat.length >= 2 gate renders the control. The prose is deliberately long enough for the document to scroll past a single viewport, which is what lets the scrollspy have a bottom to travel to and a top to return to.

Everything a reader needs to begin is a working install and a first spec. The toolkit resolves its own dependencies, so a single command brings the whole pipeline online and leaves the workspace ready for the first publish.

Publishing your first change

Once the toolkit is installed, the first change is a publish: edit a guide, run the local preview, and push. The preview is byte-identical to the published render, so what you see locally is what ships — there is no second renderer to disagree with the first.

Selecting “Overview” from the jump-select on this page must scroll to the very top of the document and write #_top into the location hash, and the select must then rest on “Overview” rather than jumping ahead to a heading the reader has not reached.