[SvelteKit] Settings initial data for session from a loader function

[HugeLetters]

I'm using tanstack-query v4, svelte-query & trpc-svelte-query. In order to make prefetching work I have to do this I have to do this

// +layout.server.ts
import { trpcServer } from '$lib/server/router';

export function load(event) {
	return { trpcHydrationClient: trpcServer.hydrateToClient(event) };
}

// +layout.svelte
<script lang="ts">
	import { QueryClientProvider } from '@tanstack/svelte-query';

	export let data; // I expose trpc through +layout.ts
	$: queryClient = data.trpc.hydrateFromServer(data.trpcHydrationClient);
</script>

<QueryClientProvider client={queryClient}>
	<slot />
</QueryClientProvider>

(This is recommended by trpc-svelte-query docs - I've tried to put hydrateFromServer in the +layout.ts so I could then provide queryClient through loader and have access to it anywhere but it doesn't work for whatever reason :| )

And so I have

// (auth)/+layout.server.ts
import { redirect } from '@sveltejs/kit';

export async function load({ locals, url }) {
	const session = await locals.auth.validate();

	if (!session) throw redirect(302, `/signin`);

	return { session };
}

to check for session - but I also wanna have an option to refetch it/invalidate it when needed so I guess I would also need a tRPC procedure which can provide me with a fresh session data which I will then get through trpc-query. But I don't wanna to fetch session the second time on mount - I already have that data from layout loader. So I would like to put it in queryClient cache - but I don't have access to it due to the reasons in the first 2 code snippets. I also wouldn't wanna use initialData for that cause that's rather cumbersome to do that for each query.

So the only solution I found so far is to have a layout.svelte like this

<script lang="ts">
	export let data;
	data.trpc.auth.getSession.utils.setData(data.session)
</script>
<slot/>

This works but feels anti-idiomatic since I'm doing the side-effect in my initial render. Is that ok? Is there a better solution?
I also would to redirect wherever my query returns a null session if it got invalidated for whatever reason/

To reiterate what I wanna do

1. Get session server-side. If no session, redirect to login page.
2. Set initial session value to queryClient cache - the initial value is from step 1
3. Then just access session with something like trpc.auth.getSession.query() wherever I want and this data will be available immediately due to step 2.
4. I can also refetch session later if I want to and if session got invalidated redirect user back to login page.

I can link a repo if that helps - however it will require a Google OAuth set-up.