If you haven’t upgraded to 0.20.0 please read the upgrading guide. v0.21.0 of the runtime introduces some minor bug fixes/improvements, as well as adding compatibility for Next.js 15 and React 19.

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Breaking Changes

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Pages Router’s custom Document

If your site is using Pages router, the Makeswift custom Document export has been moved from @makeswift/runtime/next to @makeswift/runtime/next/document. To migrate, adjust the custom Document import in src/pages/_document.ts as follows: 
- export { Document as default } from '@makeswift/runtime/next'
+ export { Document as default } from '@makeswift/runtime/next/document'
Here is the link to the official release notes.