Running "ykchalresp -N ..." with a yubikey that requires key press will cause all other invocations of ykchalresp to return the same error "Yubikey core error: operation would block" until the button is actually pressed.
Maybe ykchalresp could need a -p/--ping option too, as there are several programs (like yubikey-luks) that tests for the presence of the yubikey by sending a request to it... thus you either need a keypress on the key to make that test succeed (without -N), or cause the key to be unusable for unlocking (when using -N).
Running "ykchalresp -N ..." with a yubikey that requires key press will cause all other invocations of ykchalresp to return the same error "Yubikey core error: operation would block" until the button is actually pressed.
Maybe ykchalresp could need a -p/--ping option too, as there are several programs (like yubikey-luks) that tests for the presence of the yubikey by sending a request to it... thus you either need a keypress on the key to make that test succeed (without -N), or cause the key to be unusable for unlocking (when using -N).