+page.(server.)ts files cannot import types when reference exists with no .d.ts files

[MarlonH1]

Describe the bug

I already made an Issue but it turns out, it may be the LSP, not Svelte Kit.

The Situation

We have SvelteKit as frontend only, (for SSR)
A seperate typescript backend using trpc (the issue is not with trpc itself)

I noticed by only importing directly from backend, I can freely use the types in normal .ts, +page.server.ts and svelte.ts. But this is limited, since the moment I want to use path alias in my backend project, the frontend project fails to resolve the files. So to fix that, I want to add a project reference to the tsconfig.json. Doing that succesfully resolves my types, in both normal .ts files and +page.svelte files, but now importing trpc in +page.server.ts does not work, the type is any.

You can test for yourselves with the reproduction I uploaded, and it should also present the a real world use case.

Reproduction

reproduction.zip

Expected behaviour

I should be able to specify a project reference in the tsconfig, and my types should resolve in +page.svelte.ts

System Info

• OS: [e.g. Windows]
• IDE: [e.g. VSCode, Cursor]

Which package is the issue about?

svelte-language-server, Svelte for VS Code extension

Additional Information, eg. Screenshots

With reference:
+page.server.ts

+page.svelte

Without reference (Using path alias in backend will break it)
+page.server.ts

+page.svelte

[MarlonH1]

So I cloned the repo with the changes and opened my Project with it and now everything works as expected. Thanks!