Basically when you run next dev you can't do much aside from visiting a route and then the route can be configured to do something you want.

I want, without having to visit a route, to run some async logic.

I've tried a custom server, but it seems that a it's too much for my needs: tailwind and chadcnui stopped working after running my custom server.

I'm not concerned with customising the router, I only want to run a piece of logic without having to visit a route, be it before the Nextjs server starts or afterwards.