Basically an implementation like the following leaks space:

source :: Monad m => [Int] -> ConduitT i Int m ()
source s = case s of
  [] -> pure ()
  n : ns -> yield n *> source ns

Switching to >> avoids the problem. That makes me believe that the implementation of *>could/should be optimized.

To be honest I don't fully understand what causes the different behavior (my assumption is that the applicative implementation isn't aware of the container and so the monad implementation takes shortcuts).

A (maybe dirty) hack to solve this problem is to just implement *> with >> by adding

    (*>) = (>>)
    {-# INLINE (*>) #-}

to

(See https://stackoverflow.com/questions/73460640/haskell-based-file-streaming-causes-memory-leak for the original problem)

Please let me know if I was unclear or if I could provide further information. Also I'm willing to provide a PR (but need some guidance if a more sophisticated solution is required).