diagnose-instant-nav

End-to-end diagnosis of a single client-side navigation — from clicking a <Link> on the current page to the destination's resolved render.

This is different from [[diagnose-ppr]], which grades a page's full shell measured against a hard reload. For instant-nav, the shared layout (header, bottom nav, sticky chrome) is already on screen when the user clicks — those bytes are free. The thing that matters is: what fills the changing portion of the viewport in the first frame after click?

If the destination's per-route shell is rich, the transition feels native. If it's just skeletons until streams resolve, the transition feels like a mini-page-load.

Prerequisites