I need a onCommit functionality for stm. I know there is the stm-io-hooks [1] package. But it seems so big for such a small thing and then I have to translate everything to their monad. lift lift lift ... So I thought of a little hack to solve the issue and I'm wondering if this is safe to use. My understanding of stm internals is very limited. It's basically just a TChan with IO actions in it and there is another thread waiting to execute anything inserted into it. import Control.Concurrent.STM.TChan onCommitChan :: TChan (IO ()) {-# NOINLINE onCommit #-} onCommitChan = unsafePerformIO $ do chan <- newTChanIO forkIO $ forever $ atomically $ readTChan chan return chan onCommit :: IO () -> STM () onCommit = writeTChan onCommitChan It would be cool if an onCommit hook could be directly added to the stm package. Silvio [1] https://hackage.haskell.org/package/stm-io-hooks-1.0.1