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Fix 'Pre-hydration redirect from server actions does not prepend base… #86684

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Fix 'Pre-hydration redirect from server actions does not prepend base… #86684

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Fix 'Pre-hydration redirect from server actions does not prepend base…
Dec 1, 2025
b5c0bf9
Merge branch 'canary' into fix-wrong-redirect-path
greenlynx Dec 1, 2025
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12 changes: 11 additions & 1 deletion packages/next/src/server/app-render/action-handler.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1084,7 +1084,17 @@ export async function handleAction({
}

// For an MPA action, the redirect doesn't need a body, just a Location header.
res.setHeader('Location', redirectUrl)
const appRelativeRedirectUrl = getAppRelativeRedirectUrl(
ctx.renderOpts.basePath,
host,
redirectUrl,
requestStore.url.pathname
)

res.setHeader(
'Location',
appRelativeRedirectUrl?.toString() ?? redirectUrl
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@vercel vercel bot Dec 1, 2025

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Suggested change
appRelativeRedirectUrl?.toString() ?? redirectUrl
appRelativeRedirectUrl
? `${appRelativeRedirectUrl.pathname}${appRelativeRedirectUrl.search}${appRelativeRedirectUrl.hash}`
: redirectUrl

The Location header is being set to the full URL string including a dummy protocol/host (e.g., http://n/path) instead of just the pathname and search/hash. This will cause redirects to fail or behave unexpectedly.

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Analysis

Location header includes invalid dummy host instead of just pathname

What fails: MPA (Multi-Page Application) action redirects set Location header to full URL with dummy host http://n/path instead of just /path

How to reproduce: In packages/next/src/server/app-render/action-handler.ts, when an MPA Server Action redirects with redirect('/'), the Location header is set using appRelativeRedirectUrl?.toString() which includes the dummy host used for URL parsing.

Result: Location header is set to http://n/path?query#hash instead of /path?query#hash. Browsers attempting to follow this redirect would try to connect to host "n" and fail.

Expected: According to RFC 7231, the Location header should contain either:

  • An absolute URI with real host: https://example.com/path
  • A URI-reference (pathname-only): /path

The code already demonstrates the correct pattern in lines 283 and 344, where it accesses pathname, search, and hash properties directly instead of calling .toString() on the URL object.

Fix: Changed line 1096 from appRelativeRedirectUrl?.toString() ?? redirectUrl to:

appRelativeRedirectUrl
  ? `

)
return {
type: 'done',
result: RenderResult.EMPTY,
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