The schema Coelho ships with.

It covers what an application typically needs out of the box — paragraphs, headings, lists, quotes, code blocks, images and the usual inline marks — and is meant to be copied and adapted rather than extended in place.

What the link mark emits

An href and a title, and nothing else. In particular no target and no rel: a document is not necessarily rendered into a page where opening a new tab makes sense, and a target="_blank" without rel="noopener" hands the opened page a handle on the opener. Rather than guess, the shipped renderer emits neither.

An application that wants them says so per render, and must set both:

Coelho.to_html(document,
  marks: %{
    link: fn mark, inner ->
      Coelho.Render.tag(
        "a",
        [
          {"href", Coelho.Render.safe_url(Coelho.Render.attr(mark, "href"))},
          {"target", "_blank"},
          {"rel", "noopener noreferrer"}
        ],
        inner
      )
    end
  }
)

The href still goes through Coelho.Render.safe_url/1 there, because a stored document is not re-validated on the way out.

Alignment

paragraph, heading and list_item carry an align attribute, one of left, center, right or justify, rendered as a text-align style and read back from either a style or an align attribute on import. It is absent from the document when unset, and re-checked against the closed list at render time.

The schema is built once and kept in :persistent_term, since it is immutable and read on every render.