Terminal emulators (xterm, iterm2 etc) are emulating something like a VT220 which were called "glass terminals" to differentiate them from earlier terminals whi

Terminal emulators (xterm, iterm2 etc) are emulating something like a VT220 which were called "glass terminals" to differentiate them from earlier terminals which were keyboards attached to printers. So there's still this underlying concept of an endless spool of paper, and that's what you see when you scroll back. A scroll is literally a long piece of paper. Anyway that means if you cat some long file and then hit control-c, whatever was output before you aborted still has to be sent to your terminal emulator so it can write it to this paper (save it to the scrollback buffer). This sucks on a slow connection. mosh is running the emulator on the remote side of the connection and the client that you're interacting with locally just syncs periodically to whatever is currently being shown on the screen. So it doesn't have to send all of the output, which as you've seen, does break local scrollback. But it's a great solution for the problem it was designed to solve which is making terminals work over slow and/or unreliable network connections. If you pair it with gnu screen or tmux, then they become the terminal emulator and maintain the scrollback buffer, so you can still scroll back and see all of the paper. You just can't do it with the slider on your local window because your local emulator doesn't have access to the full contents of the buffer. I turn off scrollbars in rxvt and just rely on screen to maintain the buffer and use command keys to go back when I need to.