x-nextjs-postponed response header is set unexpectedly

[pieh]

https://github.com/vercel/next.js/blob/1b5f518a6fbb6f6481f3bfcd31c13d4be072202a/test/e2e/app-dir/segment-cache/prefetch-runtime/prefetch-runtime.test.ts#L1114-L1120

We fail on this step as we do initiate request and not reusing previously fetched prefetch data. I track it down as far as the fact that we do set x-nextjs-postponed: 1 response header on the response which lead to treating response as partial ( https://github.com/vercel/next.js/blob/1b5f518a6fbb6f6481f3bfcd31c13d4be072202a/packages/next/src/client/components/segment-cache-impl/cache.ts#L1752-L1758 ) and therefore forcing another request to be made and not reusing prefetched one.

Data

The following is parsed automatically by the Next.js repo e2e test report generator.

test: runtime prefetching errors should trigger error boundaries for errors that occurred in runtime-prefetched content
reason: x-nextjs-postponed response header is set unexpectedly