Hi, I gonna repeat my question here

I think I found a bug/unexpected behavior in core.async: https://gist.github.com/alexander-yakushev/a03b1b6dd14c531cb6d00bd75d8519a8

After a take, the first pending put into a fixed-buffer channel always succeeds, even if the buffer is full. In my case, it leads to the buffer growing infinitely.

I suppose, the offending code is here https://github.com/clojure/core.async/blob/master/src/main/clojure/clojure/core/async/impl/channels.clj#L179

what you are seeing is an artifact of how transducers that can produce more than one output (like cat) work with channels

they more or less ignore the limits

the transducer stuff which ignores fixed buffer size limits was added after the fact, so things that were valid like "if someone takes I can put" come out all weird