AI & Agent Dev Bug Sandbox Back to Radar

Client Navigation Breaks After ISR Regenerates A Fully Static Redirect Route Into A PPR Route

After an ISR revalidation turns a route that was prerendered as a fully static redirect() into a partially prerendered page, client-side navigations fail: RSC requests receive the static shell only (or 404), never resume, causing React error 412 and a full page reload. The build-time prefetchDataRoute pins the route to serve prebuilt static RSC content, ignoring the new postponed cache entry.

highConfidence 92%Next.js Affected V16.3.2 Affected V16.3.4 Affected V16.4.0-Canary.26

Origin Analysis

In next/dist/build/templates/app-page-runtime.js (source packages/next/src/build/templates/app-page.ts), isDynamicRSCRequest is computed from prerenderManifest.routes[pathname].prefetchDataRoute, which is only set for paths that were fully static at build time. When an ISR regeneration later produces a PPR entry with postponed state, isDynamicRSCRequest remains false, so RSC requests are served from cachedData.rscData (or 404 if undefined) instead of resuming the postponed render.

1. Create a Next.js app with cacheComponents: true and a dynamic route /item/[slug] using generateStaticParams returning ['a','b']. Make page call redirect('/') if item missing, otherwise render a <Suspense> child awaiting connection(). Ensure item a is missing at build time. 2. Run next build; observe /item/a is fully static redirect with prefetchDataRoute '/item/a.rsc'. 3. Start next start, then add item a to data source and call revalidateTag('item-a', { expire: 0 }) via an API route or webhook. 4. Request /item/a as a client navigation using headers RSC: 1, Next-Router-State-Tree: ..., Next-Url: /. Or open the home page and click Item A. 5. Observe 200 with x-nextjs-postponed: 1 but body contains only static shell; React error 412 occurs in browser (or 404 on 16.3.x with default file-system cache).

Fixing Code Block

0x7F 45 4C 46 02 01 01 000x90 12 AB 04 C1 7E 33 08
0xA4 1C 90 3E 77 0B D2 580x11 F6 6A 2C 80 19 DE 44
0x00 00 00 00 03 00 3E 000x01 00 B7 4D 55 90 0C 61
0x6C 69 62 63 2E 73 6F 2E0x36 00 8E 17 42 AA 05 F3
0xDE C0 DE 01 8B 45 FC 890xC7 5D 20 6F 91 03 E4 78
0x13 37 00 4F 9A 2D E1 700x08 B4 5C 22 71 D0 4A 16
0x48 8D 3D 22 01 00 00 E80x91 FF 0A 63 2E 57 B8 04
0x5A 91 C3 0E 44 70 1B 880x02 6F 39 C4 15 80 ED 27
0xFF 15 40 20 60 00 48 890xC3 90 7A 01 4C 28 B1 56
0x0F 1F 44 00 00 55 48 890xE5 C3 18 6D 92 0B 33 A7

Edge Case Audit

This change only activates when cachedData.postponed is present, so truly static routes are unaffected. However, it relies on cachedData being correctly populated for the requested path; if incrementalCache.get returns null due to cache miss or eviction, isDynamicRSCRequest will remain false and the original bug may still occur. Ensure your cache handler returns postponed state for PPR entries. Rollback: revert this single condition to restore previous behavior. Concurrency: if multiple revalidations race, the cachedData.postponed flag may be transient; use atomic cache updates to avoid serving a mixed entry. Upgrading to a version that includes an official fix is recommended.