Next.js · App Router · Mid-Level · Concept
Explain loading.tsx and error.tsx in a route segment.
Short Interview Answer
`loading.tsx` shows an instant loading UI via Suspense; `error.tsx` is an error boundary for that segment.
Detailed Explanation
Next wraps the segment in Suspense so navigations can show fallbacks. `error.tsx` must be a Client Component and can reset. Errors bubble to the nearest error boundary. Use them to keep shells interactive while content streams.