Full concurrent sync mode with external data sources for Jotai (v4?)

[lqhuang]

Hi community,

Last year I proposed and improved the main interface for jotai-ai

• feat: a new API design to allow customizations jotaijs/jotai-ai#15
  • test: Add companion ui tests for useChat from upstream jotaijs/jotai-ai#16
• feature: Refactor jotai-ai to fit new architecture since AI SDK v5 jotaijs/jotai-ai#20
  • the main context we'd like to discuss, long texts
  • Would you mind taking a quick look when you have a moment
  • Or I also wrote a blog post with a linear timeline about it

However, the latest one (jotaijs/jotai-ai#20) has stalled and hasn't seen much progress.

Asides from Alex's interests shifting, I believe another important reason is that Jotai itself currently lacks a built-in mechanism to sync external data source or store efficiently. This often results in one more redundant re-renders.

This basically what useSyncExternalStore solves. But we know that Jotai doesn't use useSyncExternalStore internally, since it doesn't support time slicing. So, solving re-render issue within my PR felt out of scope.

I originally considered seeking help with upstream or submitting a temporary workaround inspired atomWithObserver and recoil's syncEffect, but I couldn't find the time to finalize it. Despite that, I've been still closely following the news and progress of Jotai. Like recently, Naman created a PoC project gh:nmn/react-concurrent-jotai to explore Jotai style atoms in React 19.

In #3351, Dashi introduced a new API called useAtomSyncVal which leverages useSyncExternalStore internally. This is sufficient to address the tearing and redundant re-rendering issues. However, as a tradeoff, it cannot take full advantage of concurrent rendering features, which are one of Jotai's most brilliant core principles.

As Dashi has clarified new features and breaking changes are not the scope of Jotai v3.0. So I'd love to discuss the possibility of addressing these sync problems in Jotai v3.x or v4. And I'm interested if the new features introduced in React 19 will help to resolve the time slicing issue when syncing with external sources.

Other related discussions

• gh:pmndrs/jotai/discussions/1487 - Synchronizing atoms with external sources
• gh:pmndrs/jotai/discussions/3170 - RFC: Migrate to useSyncExternalStore for Concurrent Rendering Safety

Love to hear your voices!

Regards,
Lanqing

[dai-shi]

Thanks for opening up a new discussion.

It feels to me like there are two aspects:

• concurrent safe atom: for v4+ if react supports use(store) or something.
• atom synced with external data source: third-party library like jotai-redux.