I had this text conversation:
The response (the white bubble on the bottom left) consists of two ways of pronouncing the affirmative answer word 'yes': 'yes' and 'yeah'. We all use both of these, and I would have said pretty interchangeably, but here it does look like there's some functional difference between them.
It appears that 'yeah' has been used to agree with a statement and 'yes' to answer a question. This isn't a rule, by any means: you can certainly answer a question with 'yeah' or agree to a statement with 'yes'. But it's interesting that the distinction was made here.