Enabling prerender with ssr:false on root route takes 5s load on Safari

[niclimcy]

I am not sure why but only Safari has this issue, which is more evident on mobile Safari. Reproduction: https://github.com/wbps-rs/website/tree/7b22464993913027371d89b08c86461c08a15a36

[mg1986jp]

The 5s delay on Safari with prerender + ssr: false on the root route might be related to Safari's handling of the initial HTML + client-side hydration handoff. Safari has some quirks with how it processes prerendered content compared to Chrome/Firefox.

A few things to investigate:

1. Check if Safari is waiting for a specific resource to load before considering the page "ready". Open Safari's Web Inspector → Network tab and look for any requests that take unusually long during the initial load.

2. It could be related to Safari's speculative parsing behavior. If the prerendered HTML contains scripts that need to be evaluated before the client-side router takes over, Safari might handle this differently.

3. Try adding fetchpriority="high" to your main bundle script tag if it's not already there. Safari can be slower to prioritize JS downloads on initial load.

4. Check if disabling prerender (prerender: false) eliminates the delay. If it does, the issue is specifically in the transition from prerendered static HTML to the client-side SPA.

Can you share a network waterfall from Safari's dev tools?