Turbopack Pages Router Route Loader Times Out Before Page Registration Despite Successful Chunks

The route loader applies a fixed timeout for page registration after initiating chunk loads, but Turbopack may deliver the registration chunk (which calls window.__NEXT_P.push) asynchronously and later than the timeout threshold. The loader does not distinguish between successful chunk loading with delayed registration and actual chunk failure, leading to false timeouts.

1. Clone https://github.com/Stanzilla/next-turbopack-pages-router-route-loader-repro 2. Run `pnpm install` 3. Run `pnpm repro` 4. Observe the command exits non-zero after pageLoader.loadPage() rejects for several Pages Router routes. The probe shows chunkLoaderCallsForRoute: 1, nextPCallsForRoute: 0, entrypointCallsForRoute: 0, while all static chunk responses are 200.

This hotfix may cause pages to hang indefinitely if a registration chunk is genuinely missing or fails to execute after static chunks load, as the fallback timeout is bypassed. In concurrent navigations, multiple overwrites of window.__NEXT_P.push could interfere if not properly managed. On browsers without window.__NEXT_P, the code will throw. Rollback advice: revert to the original fixed-timeout implementation and instead extend the timeout duration or provide a more granular error distinction. Monitor for memory leaks from lingering event listeners in long-lived SPAs.