system
A chat on subreddit /r/me_irl
human
Individual letters and numbers are easy enough via morse code so saying Ba2 for bishop to a2 is an easy message, they then just get a computer to decide the best possible moves and wirelessly vibrate the code to the player

In theory
gpt
Actually makes sense

Although i think if he used all this effort to learn how to play chess instead of cheating, it would have been way more effective