How does the App Router resolve a URL to a page component?

My searches didn't surface the actual App Router route-matching/resolution source (e.g., the loader-tree matcher, find-page-file, or the server request handler that walks the app directory tree). The retrieved chunks are limited to CSS bundling internals, webpack HMR runtime, and CLI (next build/next dev) option parsing — none of which implement URL-to-page resolution for the App Router.

Given the data available to me, I can't give a reliably-cited, accurate explanation of how the App Router resolves a URL to a page component (e.g., how it walks app/ directory segments, matches dynamic segments like [slug], picks page.tsx vs layout.tsx, and builds the loader tree). Rather than guess or fabricate line citations, I should be upfront: the repository data and search results retrieved so far don't include that logic (it typically lives in areas like packages/next/src/build/webpack/loaders/next-app-loader or packages/next/src/server/lib/app-dir-module / route matcher code, none of which appeared in results).

What I can confirm from the data on hand:

• The Pages Router equivalents are simple re-export shims, e.g. next/app just re-exports ../pages/_app [packages/next/src/api/app.tsx:L1-L3], next/router re-exports ../client/router [packages/next/src/api/router.ts:L1-L3], and next/navigation (the App Router's client API) re-exports from ../client/components/navigation [packages/next/src/api/navigation.ts:L1-L2] — but this only shows the public API surface, not the resolution mechanism.
• The next build CLI even exposes a --debug-build-paths option describing glob patterns like "app/*", "app/page.tsx", "app/**/page.tsx" for selective builds, which confirms the file-based convention (page.tsx files under app/) [packages/next/src/bin/next.ts:L222-L226], but the actual matching algorithm isn't in the retrieved chunks.

If you'd like, I can run a more targeted search (e.g., for "app-loader", "resolve-route", or "match-segments") to try to locate the real resolution code rather than speculate.

FOLLOW_UPS:

• Where is the app-dir loader tree actually built in the code?
• How does Next.js match dynamic route segments like [slug]?
• What's the difference between page.tsx and layout.tsx resolution?