Fixed rewrite param parsing for interception routes in Vercel deployments (#79204)

> [!NOTE]
> - Introduced in [PR #67400](#67400) and released in [v15.0.0-canary.54](https://github.com/vercel/next.js/releases/tag/v15.0.0-canary.54)
> - See failed test in deployment [GitHub Actions Run](https://github.com/vercel/next.js/actions/runs/15083957601/job/42405327124?pr=79204#step:34:92)

### Summary

This PR resolves two issues related to interception routes and rewrite behavior in Vercel deployments:

1. Rewrite params not parsed correctly from the `NEXT_ROUTER_STATE_TREE_HEADER`, resulting in server crashes due to missing dynamic params.
2. Malformed search query from Vercel deployment, where unresolved dynamic params like `:foo_id` were passed instead of actual values like `1`.

These issues caused runtime errors and incorrect component behavior during navigation in deployed environments. This PR ensures consistent param resolution across local and deployed environments.

### Issue 1: Missing Rewrite Params in Vercel

The `NEXT_ROUTER_STATE_TREE_HEADER` header, introduced in PR [#67400](#67400), wasn't parsed correctly during Vercel deployment. This was fine locally with `next start`, which uses [`getResolveRoutes`](https://github.com/vercel/next.js/blob/42b1c400c977cbe43147c083714e7f6bd38cff80/packages/next/src/shared/lib/router/utils/resolve-rewrites.ts#L14), but broke in Vercel which used [`handleRewrites`](https://github.com/vercel/next.js/blob/42b1c400c977cbe43147c083714e7f6bd38cff80/packages/next/src/server/server-utils.ts#L208).

```
TypeError: Expected "<a_dynamic_route_slug>" to be a string
    at async Object.handler (___next_launcher.cjs:58:5)
    at async Server.r (../../opt/rust/nodejs.js:2:14674)
    at async Server.<anonymous> (../../opt/rust/nodejs.js:16:6262)
```

This occurred because the expected dynamic route params were undefined, causing `path-to-regexp` to throw when trying to compile the destination path.

### Solution

We ported the interception route rewrite logic from PR #67400, allowing consistent resolution of route params from the `NEXT_ROUTER_STATE_TREE_HEADER`.

### Issue 2: Malformed Query from Vercel

Even after correct interception routing, the query string received from Vercel contained unresolved params such as `:foo_id`, resulting in:

```ts
{
  rsc: 'aaaaa',
  nxtPfoo_id: ':foo_id',
  nxtPbar_id: ':bar_id',
  nxtPbaz: '1',
}
```

Instead of the expected:

```ts
{
  rsc: 'aaaaa',
  nxtPfoo_id: '1',
  nxtPbar_id: '1',
  nxtPbaz: '1',
}
```

This happened because the rewrite rule:

```json
{
  "source": "/:baz_id",
  "destination": "/:foo_id/:bar_id/(...)baz/:baz_id",
  ...
}
```

Did not include `:foo_id` or `:bar_id` in the `source`, so they were never correctly mapped by Vercel CLI's [`convertRewrites`](https://github.com/vercel/vercel/blob/53e3609f144d08ad92d42291bcbf483ae592ff1b/packages/routing-utils/src/superstatic.ts#L165).

### Solution

Since we already parse rewrite params from the `NEXT_ROUTER_STATE_TREE_HEADER`, we now inject those resolved values into `parsedUrl.query`. If any query value still starts with `:`, it's treated as unexpected and replaced with the rewrite params accordingly.

Author: devjiwonchoi

.changeset/shaggy-owls-visit.md

@@ -0,0 +1,5 @@
+---
+'next': patch
+---
+
+Fixed rewrite params of the interception routes not being parsed correctly in certain deployed environments

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

@@ -27,6 +27,10 @@ import { decodeQueryPathParameter } from './lib/decode-query-path-parameter'
 import type { DeepReadonly } from '../shared/lib/deep-readonly'
 import { parseReqUrl } from '../lib/url'
 import { formatUrl } from '../shared/lib/router/utils/format-url'
+import { parseAndValidateFlightRouterState } from './app-render/parse-and-validate-flight-router-state'
+import { isInterceptionRouteRewrite } from '../lib/generate-interception-routes-rewrites'
+import { NEXT_ROUTER_STATE_TREE_HEADER } from '../client/components/app-router-headers'
+import { getSelectedParams } from '../client/components/router-reducer/compute-changed-path'
 
 export function normalizeCdnUrl(
   req: BaseNextRequest | IncomingMessage,
@@ -209,7 +213,7 @@ export function getServerUtils({
     req: BaseNextRequest | IncomingMessage,
     parsedUrl: UrlWithParsedQuery
   ) {
-    const rewriteParams = {}
+    const rewriteParams: Record<string, string> = {}
     let fsPathname = parsedUrl.pathname
 
     const matchesPage = () => {
@@ -250,6 +254,28 @@ export function getServerUtils({
       }
 
       if (params) {
+        try {
+          // An interception rewrite might reference a dynamic param for a route the user
+          // is currently on, which wouldn't be extractable from the matched route params.
+          // This attempts to extract the dynamic params from the provided router state.
+          if (isInterceptionRouteRewrite(rewrite as Rewrite)) {
+            const stateHeader =
+              req.headers[NEXT_ROUTER_STATE_TREE_HEADER.toLowerCase()]
+
+            if (stateHeader) {
+              params = {
+                ...getSelectedParams(
+                  parseAndValidateFlightRouterState(stateHeader)
+                ),
+                ...params,
+              }
+            }
+          }
+        } catch (err) {
+          // this is a no-op -- we couldn't extract dynamic params from the provided router state,
+          // so we'll just use the params from the route matcher
+        }
+
         const { parsedDestination, destQuery } = prepareDestination({
           appendParamsToQuery: true,
           destination: rewrite.destination,
@@ -266,6 +292,20 @@ export function getServerUtils({
         Object.assign(parsedUrl.query, parsedDestination.query)
         delete (parsedDestination as any).query
 
+        // for each property in parsedUrl.query, if the value is parametrized (eg :foo), look up the value
+        // in rewriteParams and replace the parametrized value with the actual value
+        // this is used when the rewrite destination does not contain the original source param
+        // and so the value is still parametrized and needs to be replaced with the actual rewrite param
+        Object.entries(parsedUrl.query).forEach(([key, value]) => {
+          if (value && typeof value === 'string' && value.startsWith(':')) {
+            const paramName = value.slice(1)
+            const actualValue = rewriteParams[paramName]
+            if (actualValue) {
+              parsedUrl.query[key] = actualValue
+            }
+          }
+        })
+
         Object.assign(parsedUrl, parsedDestination)
 
         fsPathname = parsedUrl.pathname

test/e2e/app-dir/parallel-routes-and-interception-nested-dynamic-routes/app/[foo_id]/[bar_id]/@modal/(...)baz_id/[baz_id]/page.tsx

@@ -0,0 +1,3 @@
+export default function Home() {
+  return <p>intercepted!</p>
+}

test/e2e/app-dir/parallel-routes-and-interception-nested-dynamic-routes/app/[foo_id]/[bar_id]/@modal/default.tsx

@@ -0,0 +1,3 @@
+export default function Default() {
+  return null
+}

test/e2e/app-dir/parallel-routes-and-interception-nested-dynamic-routes/app/[foo_id]/[bar_id]/layout.tsx

@@ -0,0 +1,11 @@
+export default function Layout(props: {
+  children: React.ReactNode
+  modal: React.ReactNode
+}) {
+  return (
+    <>
+      {props.children}
+      {props.modal}
+    </>
+  )
+}

test/e2e/app-dir/parallel-routes-and-interception-nested-dynamic-routes/app/[foo_id]/[bar_id]/page.tsx

@@ -0,0 +1,15 @@
+import Link from 'next/link'
+
+export default async function Page(props: {
+  params: Promise<{ foo_id: string; bar_id: string }>
+}) {
+  const params = await props.params
+  return (
+    <>
+      <h1>
+        foo id {params.foo_id}, bar id {params.bar_id}
+      </h1>
+      <Link href="/baz_id/1">Link to bug report 1</Link>
+    </>
+  )
+}

test/e2e/app-dir/parallel-routes-and-interception-nested-dynamic-routes/app/baz_id/[baz_id]/page.tsx

@@ -0,0 +1,8 @@
+export default async function Home({
+  params,
+}: {
+  params: Promise<{ baz_id: string }>
+}) {
+  const { baz_id } = await params
+  return <p>baz_id/{baz_id}</p>
+}

test/e2e/app-dir/parallel-routes-and-interception-nested-dynamic-routes/app/layout.tsx

@@ -0,0 +1,11 @@
+export default function RootLayout({
+  children,
+}: {
+  children: React.ReactNode
+}) {
+  return (
+    <html lang="en">
+      <body>{children}</body>
+    </html>
+  )
+}

test/e2e/app-dir/parallel-routes-and-interception-nested-dynamic-routes/app/page.tsx

@@ -0,0 +1,5 @@
+import Link from 'next/link'
+
+export default function Home() {
+  return <Link href="/1/1">Start from /1/1</Link>
+}

test/e2e/app-dir/parallel-routes-and-interception-nested-dynamic-routes/next.config.js

@@ -0,0 +1,6 @@
+/**
+ * @type {import('next').NextConfig}
+ */
+const nextConfig = {}
+
+module.exports = nextConfig