nextjs - 💡(How to fix) Fix router.push() creates `replaceState` instead of `pushState` when PPR tree mismatch triggers `ACTION_SERVER_PATCH` [2 comments, 2 participants]

Link to the code that reproduces this issue

https://github.com/ellemedit/next-server-patch-replace-state-bug

To Reproduce

Create an app with two route groups that have different layouts (e.g., (tabs) and (detail)) Enable cacheComponents: true and experimental: { viewTransition: true } Add a middleware that rewrites a dynamic route with a varying search param (e.g., _t=<timestamp>), so the PAGE segment key differs between prefetch and navigation The dynamic route page must read searchParams (so the segment key includes the param) Use router.push() to navigate from a page in (tabs) to a page in (detail)

Current vs. Expected behavior

Current behavior: Back navigates to Home instead of Messages. history.length does not increment on the Messages → Message Room navigation because history.replaceState is called instead of history.pushState. The root cause is in :

// A retry should not create a new history entry.
const navigateType = 'replace'

When a PPR segment mismatch is detected (e.g., __PAGE__?{"_t":"T1"} from prefetch vs __PAGE__?{"_t":"T2"} from dynamic request), dispatchRetryDueToTreeMismatch dispatches ACTION_SERVER_PATCH. The serverPatchReducer unconditionally sets navigateType = 'replace', which overwrites the original router.push()'s pendingPush = true to false. This causes HistoryUpdater to call replaceState instead of pushState.

Expected behavior: Back should navigate to Messages (the previous page). history.pushState should be called since the original navigation was router.push(). The PPR retry should not override the original navigation intent.

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 25.2.0: Tue Nov 18 21:09:56 PST 2025; root:xnu-12377.61.12~1/RELEASE_ARM64_T6041
  Available memory (MB): 49152
  Available CPU cores: 16
Binaries:
  Node: 20.20.0
  npm: 10.8.2
  Yarn: N/A
  pnpm: 10.28.1
Relevant Packages:
  next: 16.2.0-canary.33 // There is a newer canary version (16.2.0-canary.35) available, please upgrade! 
  eslint-config-next: N/A
  react: 19.2.4
  react-dom: 19.2.4
  typescript: 5.9.3
Next.js Config:
  output: N/A
⚠ There is a newer canary version (16.2.0-canary.35) available, please upgrade! 
   Please try the latest canary version (`npm install next@canary`) to confirm the issue still exists before creating a new issue.
   Read more - https://nextjs.org/docs/messages/opening-an-issue

Which area(s) are affected? (Select all that apply)

cacheComponents, Dynamic Routes, Partial Prerendering (PPR)

Which stage(s) are affected? (Select all that apply)

Vercel (Deployed), next build (local), Other (Deployed)

Additional context

How the mismatch triggers: NextLink prefetches the route → PPR caches static shell with __PAGE__?{"_t":"T1"} User clicks → router.push() → navigateReducer creates tasks from prefetched tree Dynamic fetch fires → server responds with __PAGE__?{"_t":"T2"} (middleware changed the timestamp) writeDynamicDataIntoNavigationTask → matchSegment() fails (segment keys differ) abortRemainingPendingTasks → task status === 0 (still pending) → exitStatus = 1 spawnDynamicRequests → dispatchRetryDueToTreeMismatch → ACTION_SERVER_PATCH serverPatchReducer hardcodes navigateType = 'replace' → pendingPush becomes false HistoryUpdater calls replaceState → history entry lost