Prerender with `reroute` and `trailingSlash="always"`

Describe the bug

When configuring a sveltekit project with prerender=true and trailingSlash="always" in a +layout.server.js with the following hooks file :

/** @type {Record<string, string>} */
const translated = {
	'/reroute': '/'
};

/** @type {import('@sveltejs/kit').Reroute} */
export function reroute({ url }) {
        const redirect = translated[url.pathname]
	if (redirect) {
		return redirect;
	}
}

the build fail with the following error :

SvelteKitError: Not found: /reroute/
    at new SvelteKitError (/home/httpswwwsveltelabdev-dcnb/.svelte-kit/output/server/index.js:111:5)
    at resolve2 (/home/httpswwwsveltelabdev-dcnb/.svelte-kit/output/server/index.js:2886:18)
    at resolve (/home/httpswwwsveltelabdev-dcnb/.svelte-kit/output/server/index.js:2718:34)
    at #options.hooks.handle (/home/httpswwwsveltelabdev-dcnb/.svelte-kit/output/server/index.js:2960:71)
    at respond (/home/httpswwwsveltelabdev-dcnb/.svelte-kit/output/server/index.js:2716:43) {
  status: 404,
  text: 'Not Found'
}
Error: 404 /reroute/ (linked from /reroute)
To suppress or handle this error, implement `handleHttpError` in https://kit.svelte.dev/docs/configuration#prerender
    at eval (/home/httpswwwsveltelabdev-dcnb/node_modules/@sveltejs/kit/src/core/config/options.js:217:13)
    at eval (/home/httpswwwsveltelabdev-dcnb/node_modules/@sveltejs/kit/src/core/postbuild/prerender.js:81:25)
    at save (/home/httpswwwsveltelabdev-dcnb/node_modules/@sveltejs/kit/src/core/postbuild/prerender.js:416:4)
    at visit (/home/httpswwwsveltelabdev-dcnb/node_modules/@sveltejs/kit/src/core/postbuild/prerender.js:249:3)

When removing the trainlingSlash line in the +layout.server.js, the build pass.

Please note that this does not happen when running in dev mode.

Reproduction

https://www.sveltelab.dev/zq5pv5rncgy0obm

npm install
npm run build

The build should fail.

When removing the line trailingSlash in +layout.server.ts, the build pass.

Logs

No response

System Info

System:
    OS: Linux 5.0 undefined
    CPU: (8) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 18.18.0 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.2.3 - /usr/local/bin/npm
    pnpm: 8.14.0 - /usr/local/bin/pnpm
  npmPackages:
    @sveltejs/adapter-static: ^3.0.1 => 3.0.1 
    @sveltejs/kit: ^2.0.0 => 2.3.3 
    @sveltejs/vite-plugin-svelte: ^3.0.0 => 3.0.1 
    svelte: ^4.0.5 => 4.2.8 
    vite: ^5.0.0 => 5.0.11

Severity

blocking all usage of SvelteKit

Additional Information

No response

Start with the linked reproduction and run npm install followed by npm run build. Compare the behavior with prerender=true and trailingSlash="always" in +layout.server.js and the reroute hook shown in the issue. Done means the prerender build completes while /reroute is mapped to / as intended.