Everything shown is in the HTML

SSR.render renders the Model it is given and fetches nothing. A page whose rows come from Remote reads them first, with Data.satisfy, which reads what every active Surface needs, pass after pass, through a reader in the same process (foldkit-remote-server/fetch's pageReader). The entry's prepare makes that read, from the Model init gave, for a page and for a post alike, so one entry is made once:

const readPage = (model: Model, request: Request): Effect.Effect<Model> =>
  Data.satisfy(model, actives).pipe(Effect.provide(readPrices(request)))

export const { renderPage } = SSR.entry({ Model, init, update, view, container: null }, plan, {
  buildId,
  origins: 'same-origin',
  prepare: readPage,
})

origins: 'same-origin' takes a form posted from the origin the request was addressed to, for a site whose address is not known when the entry is made (a dev server's port). Behind a proxy that terminates TLS or rewrites the host, the server sees http://host while the browser sends Origin: https://host, and every post is refused 403: deploy there with the public origin, origins: ['https://example.com']. The same proxy makes the cart cookie's secure: 'auto' leave out Secure, since the request looks like http; set Mirror.cookie({ …, attributes: { secure: true } }) in production behind it. A prepare that fails is answered 500; domains-plus catches a failed read inside it and draws the page unread, which the browser then reads.

The plan lists the reading Surfaces and sends their data with Remote's part, so the browser starts with the prices and reads none of them again:

SSR.plan(App, {
  state: Projection.pick(App.model.query, App.model.resultsList, App.model.sortOrder),
  surfaces: [Surface.at(SearchBox, undefined), actives.top, actives.visible, actives.whole],
  parts: [Remote.resume(Data)],
})

What a Surface's reads follow (the list's window, the filters) goes in state, or the browser would read different rows from the ones the server drew, and SSR.render refuses the plan.