You might need to provide some additional information about your setup (org-version, etc.). This works for me in org 9.1.9.

John

-----------------------------------
Professor John Kitchin 
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803


On Mon, Apr 1, 2019 at 1:07 PM Joao Cortes <joaooneillcortes@outlook.pt> wrote:
Consider the following python source block,

#+begin_src python :results output : session :dir ./run
        import os;
        cwd = os.getcwd()
        print(cwd)
#+end_src

The dir header arg should change the directory used to run the session,
in this case to the directory "../base/run", where "base" is the parent
directory the file visited by the current buffer. Instead, I get
"../base". Is this a bug?

Thank you
Joao Cortes