In Steve Sanderson's video showing off the prototype (https://www.youtube.com/watch?v=48G_CEGXZZM) he mentions around the 2min 15s mark that SSR has no websockets/SignalR or even JS required. From what I could gather, websockets will kick in when an interactive blazor component needs it. And there will be the option start downloading the WASM/DLLs in the background. When WASM is ready your app will switch from websockets to WASM. Hopefully that switch will be 'live', but in the demo it looked like a page refresh was required