Slightly working

src/app.d.ts

@@ -1,13 +1,16 @@
-// See https://svelte.dev/docs/kit/types#app.d.ts
-// for information about these interfaces
+// src/app.d.ts
+import { SupabaseClient, Session } from '@supabase/supabase-js'
 declare global {
-	namespace App {
-		// interface Error {}
-		// interface Locals {}
-		// interface PageData {}
-		// interface PageState {}
-		// interface Platform {}
-	}
-}
-
-export {};
+  namespace App {
+    interface Locals {
+      supabase: SupabaseClient
+      safeGetSession(): Promise<{ session: Session | null; user: User | null }>
+    }
+    interface PageData {
+      session: Session | null
+      user: User | null
+    }
+    // interface Error {}
+    // interface Platform {}
+  }
+}