Thanks for looking at this, Federico!

Your patch looks good to me, just one comment below:

> --- a/lisp/eshell/em-dirs.el
> +++ b/lisp/eshell/em-dirs.el
> @@ -191,6 +191,9 @@ eshell-dirs-initialize
>  		        (unless (ring-empty-p eshell-last-dir-ring)
>  			  (expand-file-name
>  			   (ring-ref eshell-last-dir-ring 0))))
> +            t)
> +           ("INSIDE_EMACS" ,(lambda (_indices)
> +                              (format "%s,eshell" emacs-version))
>              t))))

Why did you unquote the lambda here?

-- 
Pierre Neidhardt
https://ambrevar.xyz/