The ANSI support doesn't work properly with edlin, the issue can be noticed when you try to use the history of the shell and the prompt prefix has ANSI (https://github.com/elixir-lang/elixir/issues/6448). The problem is that when a `\e` character appears, it handles it like a new line, dropping the buffer before it. The solution is to always add the `\e` to the buffer like a regular character and handle it when writing the buffer instead.