Adding loading.tsx to a route turned its notFound() into a 200: the page now calls it after the stream has started

pnpm build, then tests/e2e/phase7.spec.ts "system pages…": /settings/nope and /invoices/view/abc → response.status() 404 and the 404 page's h1; /no-such-page → 404.

next@>=15 <17

notFound() in a server page.tsx always gives the 404 status, as it did before the route had a loading.tsx; only the HTML would differ.

after every (app) route got a loading.tsx (route-level skeletons), page.goto("/settings/nope") returned Expected: 404 Received: 200 — the designed 404 rendered, but with status 200. An unmatched URL (/no-such-page) still returned 404.

loading.tsx wraps page.tsx in a Suspense boundary; Next flushes the layouts and the loading fallback with a 200 before the page renders, so a notFound() thrown inside the page can only swap the HTML (Next adds a robots noindex meta), not the status already sent. The docs describe this for streaming in general; nothing on loading.js warns that it moves a page's notFound() behind the flush.

phase7.spec run 1: "Expected: 404 Received: 200" at expect(unknownTab?.status()).toBe(404); after the layout check, rebuilt: "2 passed (14.7s)" with both statuses 404.