To reproduce what I believe to be incorrect behavior:

0. Install the project dependencies with your preferred package manager, then boot the app with the dev script.
1. Navigate to http://localhost:3000/login and key in an email address (or faceroll the keyboard), then submit the form.
2. The /login form first sets a session cookie with the entered email/text. Then, it performs a redirect in Remix first to the index route, /. The index route loader, in turn, redirects to /content.
3. During the navigation to /content, the root route's loader function fires and reads the session cookie (as a console.log in that function reveals). The loader returns the value of the cookie to the root route component. As a result, I would expect that the useLoaderData invocation in the root route component would receive the value of the cookie, however the value of the hook remains an empty object even once /content has loaded.
4. A page refresh of /content causes another invocation of the root route loader; this time, the root route useLoaderData does receive the result of the loader as I would expect.

This behavior of step (3) appears to expose a potential bug in Remix -- perhaps in some data fetching optimization logic. I would be inclined to believe I've misunderstood the heuristic(s) which govern when parent/layout routes are rendered were it not for the fact that the root route loader does run across the login redirect sequence.

I noticed that if there is only a single redirect performed... e.g.

• the /login form redirects directly to /content;
• OR the login form redirects to /, but the / index route's loader does not redirect but rather renders a component itself...

...then the root route component behaves as I would expect without a subsequent page refresh. Ergo, I'm led to believe that the multi-redirect may be at fault.