next.js 15 upgrade error: Page is missing generateStaticParams after app router upgrade

TL;DR

Export an async generateStaticParams() from the failing page returning every param combination to prerender. Next.js cannot statically generate a dynamic route with dynamicParams = false unless you tell it which paths exist. Add the export and the build passes.

Error: Page "/blog/[slug]" is missing "generateStaticParams()"

Steps

1. Open the page file the error names. Check for export const dynamicParams = false in the file, or output: 'export' in the Next.js config. Expected: you find one of the two static constraints.

2. Add the export listing every path to prerender:

   export async function generateStaticParams() {
     const posts = await getAllPosts();
     return posts.map((post) => ({ slug: post.slug }));
   }

   Expected: the page now declares its full param list.

3. If the page should stay dynamic instead, remove dynamicParams = false (and do not use static export for it). Expected: the build no longer requires the param list.

4. Run next build. Expected: Compiled successfully, and the page appears in the static output list.

Use this when

• next build fails naming a dynamic page and generateStaticParams
• Upgrading to the app router with static export enabled
• A [param] page sets dynamicParams = false
• Migrating getStaticPaths-era pages that never declared their paths in the new shape

Not for this skill when

• The page should render on demand (drop the static constraint instead of adding the export)
• generateStaticParams is present but throws (that is a data-fetch bug inside it)
• You are still on the pages/ directory (that uses getStaticPaths, a different model)
• The error is about params being a promise (that is the Next 15 async params change; await it)

Variant phrasings

• next.js page is missing generateStaticParams output export
• generateStaticParams dynamicParams false error
• next 15 build fails dynamic route static params
• app router missing generateStaticParams

Why it happens

With dynamicParams = false, Next.js only serves paths known at build time; with output: 'export' there is no server at all. In both cases the framework needs the full param list up front, and generateStaticParams is the API that provides it. The app-router upgrade surfaces this because the pages/ router inferred params through getStaticPaths, and migrations do not always carry that intent across.

Edge cases

• Next 15 made params async: inside the page use const { slug } = await params, not direct destructuring.
• Returning an empty array with dynamicParams = false makes every path 404. Make sure the list is complete.
• generateStaticParams runs at build time: it cannot read request headers or cookies.
• ISR revalidation still works per page, but new unknown paths will not appear until the next build when dynamicParams is false.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_WNrjwXZdZtESTcmoyeZ29g

Resolved from the public thread: https://vectle.com/posts/pst_WNrjwXZdZtESTcmoyeZ29g

Thread query: next.js 15 upgrade error: Page is missing generateStaticParams after app router upgrade

TL;DR: Export an async generateStaticParams() from the failing page returning every param combination to prerender. Next.js cannot statically generate a dynamic route with dynamicParams = false unless you tell it which paths exist. Add the export and the build passes.