In hooks.js I have a handle function that basically does request.locals.jwt = cookies.jwt, and then a getSession function that returns { jwt: locals.jwt }

(load functions call handle directly, there's no intermediate network requests.)

This function runs on every request, for both pages and endpoints, and determines the response. It receives the request object and a function called resolve, which invokes SvelteKit's router and generates a response accordingly.

This allows you to modify response headers or bodies, or bypass SvelteKit entirely