diff --git a/packages/next/src/server/lib/patch-fetch.ts b/packages/next/src/server/lib/patch-fetch.ts
index 0eeec7013e73..12f82741de7f 100644
--- a/packages/next/src/server/lib/patch-fetch.ts
+++ b/packages/next/src/server/lib/patch-fetch.ts
@@ -803,15 +803,27 @@ export function createPatchedFetcher(
if (isRequestInput) {
const reqInput: Request = input as any
- const reqOptions: RequestInit = {
- body: (reqInput as any)._ogBody || reqInput.body,
- }
+ const reqOptions: RequestInit = {}
for (const field of requestInputFields) {
// @ts-expect-error custom fields
reqOptions[field] = reqInput[field]
}
- input = new Request(reqInput.url, reqOptions)
+
+ const ogBody = (reqInput as any)._ogBody
+ if (ogBody !== undefined) {
+ reqOptions.body = ogBody
+ input = new Request(reqInput.url, reqOptions)
+ } else {
+ // When _ogBody is absent, the body stream hasn't been consumed.
+ // Pass the original Request object instead of reqInput.url to
+ // preserve the internal body source, which Node 24.14+ (undici)
+ // requires to be non-null for requests with a body.
+ if (isStale) {
+ reqOptions.signal = null
+ }
+ input = new Request(reqInput, reqOptions)
+ }
} else if (init) {
const { _ogBody, body, signal, ...otherInput } =
init as RequestInit & { _ogBody?: any }
diff --git a/test/e2e/app-dir/patch-fetch-request-body/app/api/test-post/route.ts b/test/e2e/app-dir/patch-fetch-request-body/app/api/test-post/route.ts
new file mode 100644
index 000000000000..c18a2b17fdbc
--- /dev/null
+++ b/test/e2e/app-dir/patch-fetch-request-body/app/api/test-post/route.ts
@@ -0,0 +1,16 @@
+import { NextResponse } from 'next/server'
+
+export async function POST() {
+ const req = new Request(
+ `http://localhost:${process.env.EXTERNAL_SERVER_PORT}/post`,
+ {
+ method: 'POST',
+ body: JSON.stringify({ key: 'value' }),
+ headers: { 'Content-Type': 'application/json' },
+ }
+ )
+
+ const res = await fetch(req)
+ const data = await res.json()
+ return NextResponse.json({ status: res.status, data })
+}
diff --git a/test/e2e/app-dir/patch-fetch-request-body/app/layout.tsx b/test/e2e/app-dir/patch-fetch-request-body/app/layout.tsx
new file mode 100644
index 000000000000..888614deda3b
--- /dev/null
+++ b/test/e2e/app-dir/patch-fetch-request-body/app/layout.tsx
@@ -0,0 +1,8 @@
+import { ReactNode } from 'react'
+export default function Root({ children }: { children: ReactNode }) {
+ return (
+
+ {children}
+
+ )
+}
diff --git a/test/e2e/app-dir/patch-fetch-request-body/app/page.tsx b/test/e2e/app-dir/patch-fetch-request-body/app/page.tsx
new file mode 100644
index 000000000000..ff7159d9149f
--- /dev/null
+++ b/test/e2e/app-dir/patch-fetch-request-body/app/page.tsx
@@ -0,0 +1,3 @@
+export default function Page() {
+ return hello world
+}
diff --git a/test/e2e/app-dir/patch-fetch-request-body/next.config.js b/test/e2e/app-dir/patch-fetch-request-body/next.config.js
new file mode 100644
index 000000000000..807126e4cf0b
--- /dev/null
+++ b/test/e2e/app-dir/patch-fetch-request-body/next.config.js
@@ -0,0 +1,6 @@
+/**
+ * @type {import('next').NextConfig}
+ */
+const nextConfig = {}
+
+module.exports = nextConfig
diff --git a/test/e2e/app-dir/patch-fetch-request-body/patch-fetch-request-body.test.ts b/test/e2e/app-dir/patch-fetch-request-body/patch-fetch-request-body.test.ts
new file mode 100644
index 000000000000..ec114f2c578d
--- /dev/null
+++ b/test/e2e/app-dir/patch-fetch-request-body/patch-fetch-request-body.test.ts
@@ -0,0 +1,53 @@
+import { nextTestSetup } from 'e2e-utils'
+import { findPort } from 'next-test-utils'
+import http from 'http'
+
+describe('patch-fetch-request-body', () => {
+ let externalServerPort: number
+ let externalServer: http.Server
+
+ const { next, skipped } = nextTestSetup({
+ files: __dirname,
+ skipStart: true,
+ skipDeployment: true,
+ })
+
+ if (skipped) {
+ return
+ }
+
+ beforeAll(async () => {
+ externalServerPort = await findPort()
+
+ externalServer = http.createServer((req, res) => {
+ req.resume()
+ req.on('end', () => {
+ res.writeHead(401, { 'Content-Type': 'application/json' })
+ res.end(JSON.stringify({ status: 401 }))
+ })
+ })
+
+ await new Promise((resolve, reject) => {
+ externalServer.listen(externalServerPort, () => resolve())
+ externalServer.once('error', reject)
+ })
+
+ next.env.EXTERNAL_SERVER_PORT = String(externalServerPort)
+ await next.start()
+ })
+
+ afterAll(() => {
+ externalServer?.close()
+ })
+
+ // On Node 24.14+, patch-fetch previously reconstructed the Request using
+ // reqInput.url which lost the internal body source. undici then threw
+ // "TypeError: expected non-null body source" when sending the request.
+ it('should preserve Request body source for uncached POST requests', async () => {
+ const res = await next.fetch('/api/test-post', { method: 'POST' })
+ expect(res.status).toBe(200)
+
+ const json = await res.json()
+ expect(json.status).toBe(401)
+ })
+})