Hi all, I’m looking for a way to initiate a call from the RTS into Haskell (base function) running and evaluating an IO function using the non-threaded RTS. For the threaded RTS I can use rts_evalIO with the RTS capability, but for the non-threaded I can’t find a way that doesn’t trigger the if (cap->in_haskell) { errorBelch("schedule: re-entered unsafely.\n" " Perhaps a 'foreign import unsafe' should be 'safe'?"); stg_exit(EXIT_FAILURE); } Clause in the scheduler. Taking a look at how the non-threaded I/O manager currently works on Windows, it seems that re-uses the TSO from the blocked thread doing the I/O call to give notifications back. This approach doesn’t work for me since the new I/O manager doesn’t block doing a foreign call boundary, instead It blocks in Haskell on an MVar, and I only want to wake up very specific threads. In short, does anyone know of a way to initialize an I/O operation from the non-threaded RTS? Thanks, Tamar