It appears that the total buffer size wants to be <viewport rows> + <scrollback>, however when I hook it up in vscode to be 10, I notice that the amount of scrollback provided is not 10 and seems to alternate between 2 values.

Running ll to get a chunk of output, I get 6 lines of scrollback the first time, 8 the second time, 5 the third, 7 the fourth, etc. It should be exactly 10 every time.