[Turbopack] Pages Router hydration delayed when tab opened in background

[happyjosh]

Link to the code that reproduces this issue

https://github.com/happyjosh/turbopack-pages-router-bug

To Reproduce

1. Create minimal _app.tsx with timing logs
2. Use yarn dev --turbopack
3. Middle-click a link to open page in background tab
4. Switch to the new tab and check console logs

Current vs. Expected behavior

When opening a Pages Router page in a background tab (middle-click or right-click -> open in new tab), the hydration is significantly delayed until the tab becomes visible.

Observed behavior:

• Module loads at ~1200ms with visibilityState: hidden
• App render happens at ~9200ms with visibilityState: visible
• ~8 seconds delay between module load and React hydration

Expected behavior:
Hydration should complete regardless of tab visibility.

Provide environment information

- Next.js: 16.x
- React: 19.x
- Turbopack: enabled

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

Turbopack

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

next build (local)

Additional context

Key Finding

• Pages Router + Turbopack: Has this delay
• App Router + Turbopack: Works correctly (no delay)
• Pages Router + Webpack: Works correctly (no delay)

[zhangshipeng-create]

why closed ?

[jonas-is-coding]

Regarding the delayed hydration when opening a tab in the background, this often points to resource contention or deferred execution by the browser. Consider reducing the initial bundle size for the affected pages by using and for non-critical components. Also, ensure that no excessive client-side data fetching or heavy computations are blocking the main thread during initial load. Browser throttling of background tabs can exacerbate this, so optimizing the initial render is key.

[zhangshipeng-create]

maybe , an external config could be provided to resolve this issue .