@aman-c FusionAuth is completely running outside of Next.js. So it all depends on what you are using to make the call to FusionAuth.
My suggestion would be to implement a version of our React SDK
https://fusionauth.io/docs/sdks/react-sdk
Then anything clientside that needs details you can use the built in hooks, anything serverside you can use the cookie that sits at app.at or for identity app.idt.
If you have been using our quickstart you are most likely using next-auth which could be causing issues with the implementation. We have had a lot of internal discussion about removing this methodology moving forward to simplify our Next.js suggested implementation.
You can find out more about our cookies that are set in our Hosted Backend details.
https://fusionauth.io/docs/apis/hosted-backend
