Repository navigation
useObservable: add getServerSnapshot to useSyncExternalStore for SSR #748
Description
`useObservable` calls `useSyncExternalStore(subscribe, getSnapshot)` with only two arguments. React 18 requires a third `getServerSnapshot` for server rendering. Without it, React throws during SSR and Next.js App Router falls back to client rendering for any subtree using a reactfire hook.
The fix is to pass a `getServerSnapshot` that returns the same seeded `immutableStatus` the client snapshot returns. The server snapshot must be stable across server/client to avoid hydration mismatches, so `initialData` seeding is the natural tie-in.
Flagged in the arch review as a V5 "just do it" item: not a spike, not blocked on any API decision.
Activity
tyler-reitz commentedon Jul 21, 2026
Surfaced during sandbox validation of #739. From the PR comment:
Fix: pass
getServerSnapshotreturning the same seededimmutableStatusthe client snapshot returns. Must be stable across server/client to avoid hydration mismatches —initialDataseeding is the natural tie-in.fix(ssr): add getServerSnapshot to useObservable's useSyncExternalStore
fix(ssr): add getServerSnapshot to useObservable's useSyncExternalSto…