persistQueryClient does not synchronize cache invalidation across isolated JavaScript contexts

[SEOKKAMONI]

Problem

In our React Native application, each screen in the Stack Navigator renders a separate WebView loading a Next.js app. Since each WebView runs its own JavaScript runtime, each one instantiates its own QueryClient.

When a mutation in one screen invalidates a query, the invalidation does not propagate to the QueryClient in another screen — even when using persistQueryClient.

Steps to Reproduce

1. Screen A fetches a review list via useQuery. Data is cached in QueryClient A.
2. Screen B is pushed onto the stack. The user deletes a review via mutation.
3. Screen B calls queryClient.invalidateQueries({ queryKey: ['reviews'] }).
4. Screen B is popped. Screen A becomes visible again — but still displays the stale list including the deleted review.

Why persistQueryClient did not help

We attempted to solve this with persistQueryClient, expecting that:

1. Screen B's invalidation would trigger a refetch → updated data gets persisted to storage.
2. Screen A would read the updated persisted state when it regains focus.

This did not work because persistQueryClient restores the cache only during QueryClient initialization (when hydrate is called at mount time). There is no mechanism for an already-mounted QueryClient to reactively subscribe to external changes in the persistence layer.

In other words, persistQueryClient is designed for cold-start restoration (e.g., app restart), not for real-time cross-instance synchronization.

Questions

1. Is our understanding correct? Is persistQueryClient intentionally scoped to initialization-time hydration only, with no support for runtime synchronization across multiple QueryClient instances sharing the same persistence layer?

2. Is there an existing or planned mechanism within TanStack Query to support cache synchronization across isolated JavaScript contexts (e.g., multiple WebViews, Web Workers, iframes)?

Thank you for your time and for the incredible work on TanStack Query.