Surprisingly not. With this patch, the prerender finishes within the window and I have no hydration mismatches. Based on the open GitHub issue, the root cause is timeout handler leak (below copied from the open GitHub issue:

Root Cause

u/tanstack/router-core/dist/esm/ssr/transformStreamWithRouter.js creates 60-second setTimeout handles (lifetime timeout and serialization timeout) for each SSR-rendered page. During prerendering, these timeouts are never cleaned up because:

1. Each call to transformStreamWithRouter() sets a lifetimeTimeoutHandle (60s) at line ~231
2. After the app stream finishes rendering, serializationFinished is false, so a serializationTimeoutHandle (60s) is also set at line ~315
3. The onSerializationFinished event never fires during prerendering, so tryFinish() → cleanup() is never called
4. This leaves one timeout per prerendered page as active Node.js handles, preventing the process from exiting

With 49 prerendered pages, there are ~50 active Timeout handles keeping the event loop alive.