In React 18, two components that are siblings to each other can suspend together within the same Suspense Boundary because React keeps (pre-)rendering siblings even if one component suspends. So this works: Both components have a suspending fetch inside, both will fetch in parallel and will be "revealed" together because they are in the same boundary. In React 19, this will be a request waterfall: When the first component suspends, the second one never gets to render, so the fetch inside of it won't be able to start. The argument is that rendering the second component is not necessary because it will be replaced with the fallback anyway, and with this, they can render the fallback "faster" (I guess we are talking fractions of ms here for most apps. Rendering is supposed to be fast, right?). So if the second component were to trigger a fetch well then bad luck, better move your fetches to start higher up the tree, in a route loader, or in a server component.