“ The way Codebreaker worked was simple: Somebody would watch an in-game live feed and log the catcher’s signs into the spreadsheet, as well as the type of pitch that was actually thrown. With that information, Codebreaker determined how the signs corresponded with different pitches. Once decoded, that information would be communicated through intermediaries to a baserunner, who would relay them to the hitter.”

So it wouldn’t matter if they switched things up every inning, after just a few pitches in an inning the software had it figured out and then they were communicating it live time to the field.

Btw, BYU grad Mark Rober has a YouTube video on how software can do this, pretty interesting.

https://www.youtube.com/watch?v=PmlRbfSavbI