Async creates race conditions and even if you show me a proof that says there will never be a deadlock or other unexpected behavior I generally will believe that either there is an error in your proof or the actual executing code is different from the algorithm you've proved correct in some significant way.
Doing previews in a non-blocking way sounds really cool though, I'm not ragging on the concept, just saying I am mistrustful of async.
This is Rust, which is a language that doesn't have data races (though other kinds of races are certainly possible).
For an application like yazi async is likely a much more pleasurable experience to write code in than trying to manage threads and cancellations by hand.
Doing previews in a non-blocking way sounds really cool though, I'm not ragging on the concept, just saying I am mistrustful of async.