vercel-labs · vercel-gh-bot-2 · Jul 21, 2026
diff --git a/test/production/app-dir/isr-index-cache-key/app/[slug]/page.tsx b/test/production/app-dir/isr-index-cache-key/app/[slug]/page.tsx
@@ -0,0 +1,7 @@
+import { notFound } from 'next/navigation'
+
+export const dynamicParams = true
+
+export default function SlugPage() {
+  notFound()
+}
diff --git a/test/production/app-dir/isr-index-cache-key/app/layout.tsx b/test/production/app-dir/isr-index-cache-key/app/layout.tsx
@@ -0,0 +1,8 @@
+import { ReactNode } from 'react'
+export default function Root({ children }: { children: ReactNode }) {
+  return (
+    <html>
+      <body>{children}</body>
+    </html>
+  )
+}
diff --git a/test/production/app-dir/isr-index-cache-key/app/page.tsx b/test/production/app-dir/isr-index-cache-key/app/page.tsx
@@ -0,0 +1,5 @@
+export const revalidate = 1
+
+export default function Page() {
+  return <p data-generation={Date.now()}>home</p>
+}
diff --git a/test/production/app-dir/isr-index-cache-key/isr-index-cache-key.test.ts b/test/production/app-dir/isr-index-cache-key/isr-index-cache-key.test.ts
@@ -0,0 +1,47 @@
+import { nextTestSetup } from 'e2e-utils'
+import { retry } from 'next-test-utils'
+
+describe('app dir ISR index cache key', () => {
+  const { next } = nextTestSetup({
+    files: __dirname,
+  })
+
+  function getGeneration(html: string) {
+    const match = html.match(/data-generation="(\d+)"/)
+    if (!match) throw new Error('Missing home generation')
+    return Number(match[1])
+  }
+
+  it('does not let a not-found /index request poison the home cache', async () => {
+    const initialHome = await next.fetch('/')
+    expect(initialHome.status).toBe(200)
+    const initialGeneration = getGeneration(await initialHome.text())
+
+    let currentGeneration = initialGeneration
+    await retry(async () => {
+      const home = await next.fetch('/')
+      expect(home.status).toBe(200)
+      currentGeneration = getGeneration(await home.text())
+      expect(currentGeneration).toBeGreaterThan(initialGeneration)
+    }, 5000)
+
+    await retry(
+      () => {
+        expect(Date.now()).toBeGreaterThanOrEqual(currentGeneration + 1000)
+      },
+      3000,
+      100
+    )
+
+    await (await next.fetch('/index')).text()
+    await retry(async () => {
+      const index = await next.fetch('/index')
+      expect(index.status).toBe(404)
+      await index.text()
+    }, 5000)
+
+    const finalHome = await next.fetch('/')
+    expect(finalHome.status).toBe(200)
+    expect(getGeneration(await finalHome.text())).toBeGreaterThan(0)
+  })
+})
diff --git a/test/production/app-dir/isr-index-cache-key/next.config.js b/test/production/app-dir/isr-index-cache-key/next.config.js
@@ -0,0 +1,6 @@
+/**
+ * @type {import('next').NextConfig}
+ */
+const nextConfig = {}
+
+module.exports = nextConfig