Vercel build fails with 403 from Notion loadPageChunk endpoint

Description

My Vercel deployment started failing while fetching a public Notion page.

The build request to the following endpoint returns 403 Forbidden:

https://www.notion.so/api/v3/loadPageChunk

This causes the Next.js build to fail while collecting page data.

Error

page load error {
  pageId: '1d2fe6fa-8992-80b0-87ff-f187979d7b89',
  spaceId: undefined
}

403 [POST] "https://www.notion.so/api/v3/loadPageChunk": 403 Forbidden

Error: Error loading page "1d2fe6fa-8992-80b0-87ff-f187979d7b89"

Build error occurred
Error: Failed to collect page data for /[pageId]

ELIFECYCLE Command failed with exit code 1.
Error: Command "pnpm run build" exited with 1

The Notion page is public and can be opened without signing in, so this does not appear to be a page permission or page ID issue.

Workaround

Setting the following Vercel environment variable fixes the build:

NOTION_API_BASE_URL=https://app.notion.com/api/v3

After redeploying, the site builds and loads successfully.

Related upstream issue

This appears to be related to:

• https://github.com/NotionX/react-notion-x/issues/710
• https://github.com/NotionX/react-notion-x/pull/711

Suggested improvement

Would it make sense to temporarily document this environment-variable workaround in the README, or update the dependency once the upstream fix is released?

Thank you!