Hey @maymine, we recently updated flyctl to behave more like the standard OpenSSH client. Since you’re specifying an explicit command (with -C) and trying to run an interactive console, I think you will need to use the --pty option now: fly ssh console --pty -C "rails/bin/rails console". This tells the SSH server to run the program in a virtual terminal, which (like the standard ssh command) won’t be done by default when you provide an explicit command.
If this is the problem, then I’m so sorry that you got caught by this change!—it’s just that many other people expected it to work like OpenSSH and ran into problems when it didn’t.
(It looks like there are some docs that are out of date, so I’m going to go update those now.)