Best Practices for File-Based Routing with i18n, Sidebar Navigation, and Auth in TanStack Router

[sulejmanhoxha]

I'm using file-based routing in my app, and I want each route to follow a consistent structure. Here's an example folder layout I'm aiming for:

.
├── __root.tsx
├── index.tsx
├── login
│   ├── -components
│   │   └── login.form.tsx
│   └── index.tsx
├── signup
│   ├── -components
│   │   └── signup.form.tsx
│   └── index.tsx
└── dashboard
    ├── documents
    │   └── invoice
    │       ├── detail
    │       ├── edit
    │       └── index
    │           ├── -data
    │           ├── -forms
    │           ├── -languages
    │           ├── -modals
    │           ├── -validation
    │           └── index.tsx
    └── reports
        └── monthly-summary
            └── index.tsx

Every route (like invoice) has its own folder with optional subroutes (edit, detail) and support folders (-data, -forms, -languages, etc.).

---

What I want to implement:

1. Sidebar Navigation
   A sidebar showing all available pages, with nested accordions representing sections (dashboard), subsections (documents, reports), and final links to pages like invoice or monthly-summary. For example:

   └── dashboard
       ├── documents
       │   └── invoice
       └── reports
           └── monthly-summary
   

2. Multi-language support with URL prefixes
   The app must support exactly 4 languages: English (en), Montenegrin (srb), Albanian (al), and German (ger).
   Each page will have a -languages folder with JSON files named en.json, srb.json, al.json, and ger.json.
   Language is part of the URL, e.g. /en/dashboard/documents/invoice, /srb/dashboard/documents/invoice.
   I want to dynamically load the correct translation file based on the :lang URL param.

3. Authorization & role-based access
   The sidebar should only show links users have permission to see based on their roles.
   Also, routes should be protected so unauthorized users can’t access restricted pages.

4. Default query parameters per route
   Some routes should have default query params. For example, the invoice route should default to ?sort=-createdAt.
   Sidebar route entries might look like this:

   {
     label: "Invoice",
     path: "/dashboard/documents/invoice",
     search: { sort: "-createdAt" },
     roles: ["admin", "manager"],
   }

5. TypeScript typing & scalability
   I want the sidebar navigation to be fully typed with TypeScript, including the allowed roles, paths, labels, and optional query params.
   Since this app will have thousands of pages, I want a solution that scales well and can be generated or maintained easily.

---

Question:

What’s the best way to handle all this using TanStack Router in a maintainable, efficient, and secure way?
Particularly interested in:

• Dynamically generating and typing the sidebar navigation with support for default query params.
• Setting up i18n with URL language prefixes and per-page language JSON files.
• Implementing route protection and filtering sidebar links based on user roles.
• Handling thousands of routes and maintaining good performance.

Thanks in advance.