fix: strip internal routing headers unless testing

packages/next/src/server/base-server.ts

@@ -124,6 +124,7 @@ import {
 } from './web/spec-extension/adapters/next-request'
 import { matchNextDataPathname } from './lib/match-next-data-pathname'
 import getRouteFromAssetPath from '../shared/lib/router/utils/get-route-from-asset-path'
+import { stripInternalHeaders } from './internal-utils'
 
 export type FindComponentsResult = {
   components: LoadComponentsReturnType
@@ -1538,6 +1539,28 @@ export default abstract class Server<ServerOptions extends Options = Options> {
     )
   }
 
+  protected stripInternalHeaders(req: BaseNextRequest): void {
+    // Skip stripping internal headers in test mode while the header stripping
+    // has been explicitly disabled. This allows tests to verify internal
+    // routing behavior.
+    if (
+      process.env.__NEXT_TEST_MODE &&
+      process.env.__NEXT_NO_STRIP_INTERNAL_HEADERS === '1'
+    ) {
+      return
+    }
+
+    // Strip the internal headers from both the request and the original
+    // request.
+    stripInternalHeaders(req.headers)
+    if (
+      'originalRequest' in req &&
+      'headers' in (req as NodeNextRequest).originalRequest
+    ) {
+      stripInternalHeaders((req as NodeNextRequest).originalRequest.headers)
+    }
+  }
+
   private async renderToResponseWithComponentsImpl(
     { req, res, pathname, renderOpts: opts }: RequestContext,
     { components, query }: FindComponentsResult
@@ -1546,6 +1569,10 @@ export default abstract class Server<ServerOptions extends Options = Options> {
       // For edge runtime 404 page, /_not-found needs to be treated as 404 page
       (process.env.NEXT_RUNTIME === 'edge' && pathname === '/_not-found') ||
       pathname === '/404'
+
+    // Strip the internal headers.
+    this.stripInternalHeaders(req)
+
     const is500Page = pathname === '/500'
     const isAppPath = components.isAppPath
     const hasServerProps = !!components.getServerSideProps

packages/next/src/server/internal-utils.ts

@@ -1,6 +1,8 @@
-import { NEXT_RSC_UNION_QUERY } from '../client/components/app-router-headers'
+import type { IncomingHttpHeaders } from 'http'
 import type { NextParsedUrlQuery } from './request-meta'
 
+import { NEXT_RSC_UNION_QUERY } from '../client/components/app-router-headers'
+
 const INTERNAL_QUERY_NAMES = [
   '__nextFallback',
   '__nextLocale',
@@ -36,3 +38,27 @@ export function stripInternalSearchParams<T extends string | URL>(
 
   return (isStringUrl ? instance.toString() : instance) as T
 }
+
+/**
+ * Headers that are set by the Next.js server and should be stripped from the
+ * request headers going to the user's application.
+ */
+const INTERNAL_HEADERS = [
+  'x-invoke-path',
+  'x-invoke-status',
+  'x-invoke-error',
+  'x-invoke-query',
+  'x-invoke-output',
+  'x-middleware-invoke',
+] as const
+
+/**
+ * Strip internal headers from the request headers.
+ *
+ * @param headers the headers to strip of internal headers
+ */
+export function stripInternalHeaders(headers: IncomingHttpHeaders) {
+  for (const key of INTERNAL_HEADERS) {
+    delete headers[key]
+  }
+}

packages/next/src/server/next-server.ts

@@ -1585,6 +1585,9 @@ export default class NextNodeServer extends BaseServer {
       ReturnType<typeof NextNodeServer.prototype.runMiddleware>
     >
 
+    // Strip the internal headers.
+    this.stripInternalHeaders(req)
+
     try {
       await this.ensureMiddleware()
 

test/e2e/i18n-data-route/i18n-data-route.test.ts

@@ -17,6 +17,10 @@ createNextDescribe(
   'i18n-data-route',
   {
     files: __dirname,
+    env: {
+      // Disable internal header stripping so we can test the invoke output.
+      __NEXT_NO_STRIP_INTERNAL_HEADERS: '1',
+    },
   },
   ({ next }) => {
     describe('with locale prefix', () => {