It doesn’t need to look ahead, all of the words are already in the prompt behind the current position, so it just needs to use the existing context to infer the next word

Also on my second try, I gave it a slightly invalid sentence. The prompt was..

    Unscramble the following: waffles eat with like cheese you.

It responded with:

    You like to eat waffles with cheese.

But notice that the prompt doesn’t have the word “to” anywhere in it. But it was the most likely word that was supposed to go there.