While we cannot automatically generate GIF from this asciicast (the process is very resource intensive), you can use asciicast2gif to do it yourself. Once you have it installed run the following command in your terminal:
asciicast2gif <%= @file_url %> demo.gif If you have Docker installed then just run this command:
docker run --rm -v $PWD:/data asciinema/asciicast2gif <%= @file_url %> demo.gif