Session Updates in Subdomain Environments Are Not Reflected Automatically Across Domains

[geunheejung]

Environment

• "next": "14.1.1"
• "next-auth": "^5.0.0-beta.25"
• Page Routes

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Issue Description

Our service operates under two subdomains: uk.domain.city and kr.domain.city.
We have configured cookies to be shared across subdomains.

However, when a user logs in or logs out on the uk subdomain, the session update is not automatically reflected on the kr subdomain unless the page is manually refreshed.

From my understanding, <SessionProvider/> is responsible for keeping session data in sync across different parts of the application.
Looking into the internal implementation, it seems that the Broadcast Channel API is used to synchronize session changes across different tabs.

Since subdomains have different origins, could this be the reason why the session update is not reflected across them?

If so, what would be the best approach to ensure session updates are automatically synchronized across subdomains?
Any guidance would be greatly appreciated.

Thank you!