flagging that from what I can tell from the React sdk code path the tracking callback for experiment assignment is called during render rather than as a side effect (useFeature doesn't have a

useEffect

anywhere)

Yes, tracking is done synchronously.

feels pretty clearly a side effect which shouldn't happen during render?

Yeah, that's a good point. The React SDK is just a thin wrapper around the JavaScript SDK and it's not easy with the current structure to put the tracking callback inside a useEffect hook. I'll think about this a bit.