You should be able to come up with something. Fundamentally, the role of the executor is to be the bridge between sync and async code: it isn't async itself b

You should be able to come up with something. Fundamentally, the role of the executor is to be the bridge between sync and async code: it isn't async itself but is responsible for making all the async code move forward. No async code will do anything when the executor isn't active. The way I split up the game code, raw event handling and rendering was written as a standard, synchronous, game loop. The game logic update was written with async code, and once per frame, I call the executor which keeps control until none of the async tasks can make further progress. You can probably do something similar in your case: find somewhere in the existing program where it isn't disruptive to do arbitrary work, and have the executor do its work there.