The owner's half is the site attribute of the space root: {url, peer}. It is part of the root's signed state, so it is as trustworthy as anything else the owner publishes, and it tells readers where to look.

The grant is a Grant signed by the owner with subject the space root (a node subject with node omitted), audience {kind: key, key: <site account>} and access sync. The site account is a key the site operator controls; its peer authenticates as that account. The grant is what allows the site to hold and relay the space's private blobs, and what the owner revokes to fire a site. Until encryption exists sync behaves as read for delivery, so the grant also makes the site a reader of everything in the space.

A URL without a grant is a dangling pointer: peers will not treat the named peer as an authority peer and will not serve it private blobs. A grant without the URL makes the site peer an authority peer that readers cannot find by name. Registration, as a flow, publishes both.

HM24 trusts whoever answers an HTTPS request to /hm/api/config at the siteUrl. If the owner points siteUrl at a hostile host, that host receives the space's private blobs. In Stem the owner still chooses the site, but the choice is a grant to a key, and the peer must prove it holds that key. DNS and TLS are left to do what they are good at, which is getting a browser to the right web server. The disclosure ledger records every blob the owner's peers served to the site under basis site, so a mistaken grant is auditable.

A site is a space whose home document names a siteUrl; the daemon fetches https://<siteUrl>/hm/api/config, trusts the peer id it finds there as the space's authority, authenticates to it when it holds a writer key, and serves it private blobs. The Sites page records the direction: "a site's authority over a space becomes an explicit, signed relationship instead of a siteUrl string plus an HTTPS lookup." This page is that relationship.