Moderator: igrr
Arduino upload to the ESP8266 overwrites the AT program. You can, of course, reinstall the AT binary.
If you need an interpreter to run code, try the ESP8266 BASIC.
Also, there are other good interpreters such as microPython, Forth, Javascript...
It is fairly easy to write your own "serial command" language in Arduino... assuming you do not get too complicated, the parser should be straightforward.
Ray