Initial thoughts about TanStack AI, and its positioning vs Vercel's AI SDK:
Framing
I like that they are pushing 'no vendor lock-in' in their blog post (that's how all AI libs should be).
But I think they're subtly benefiting from the impression that all Vercel libraries (i.e. the AI SDK) MUST be trying to lock you in somehow.
The AI SDK is vendor-agnostic, with a great DX whether you use Vercel's built-in gateway or the model providers. IMO, the type safety and isomorphic features are more interesting.
Devtools (TanStack wins)
TanStack AI immediately ships with dev tools. Hell yes, why the AI SDK haven't done this already boggles the mind.
Per-model Type Safety (Inconclusive)
One weakness of the AI SDK is that the options you pass to the provider are not strongly typed. You can attempt to use structured outputs on a model that doesn't support them, and it won't warn you at compile time. TanStack AI _will_ give you these warnings.
This is a nice-to-have in my book, I usually know the capabilities of the models I'm using before I go to code.
One other common complaint is that once you're _in_ the AI SDK ecosystem, it's pretty hard to do advanced provider-specific shenanigans. No idea if this will be easier in TanStack AI - my bet is it's probably a wash.
Features (AI SDK)
I really like that TanStack AI ships with tool approvals built in. The isomorphic tool definitions are a nice upgrade on the AI SDK's - you can still have isomorphic tool schemas in the AI SDK, but not the entire tool. I imagine that TanStack's isomorphic API will be really nice to use, just like query/router etc.
From what I'm reading in the docs, the AI SDK gives you a ton more control over the stream (with custom data parts) than TanStack AI does. TanStack AI's docs are more skewed towards agents than workflows.
However, I'm intrigued to see how this develops - if anyone can create a beautiful type-safe API for streaming custom data over the wire, it's the TanStack query team.
Finally, the pure number of providers from the AI SDK is way beyond what TanStack can offer right now.
Conclusion
Don't adopt just yet. It's got a long way to go to catch up to the AI SDK's feature set. Duh, it's an alpha.
But it's an impressive launch. If they can nail the type safe streaming DX better than the AI SDK (I do think there's headroom here) it'll be hard to top.