Max Nikulin <manikulin@gmail.com> writes:

>> Do you have any ideas how to work around the deliberately constructed
>> header argument values like in your example?
>
> Perhaps `gensym' may be used to create a symbol that can not appear in a 
> document. I am unsure if the following `pcase' variant may be improved
> ...
> ;; or ob-shell-argument-literal-symbol
> (defconst ob-literal-symbol (gensym "literal"))

Good idea.
I am attaching tentative fix that uses the proposed approach.
Not yet merging - need to go through other babel backends and make them
use the new API.