Hello Chuck, On Monday, 27 Sep 2021 at 18:28, Berry, Charles wrote: > > It looks like you have `(setq ess-eval-visibly t)' here. I think that is a default setting. Thanks again for your suggestion. The following patch to be applied on top of the previous one, solves the issue. #+begin_src R :session *R* :results output :async yes Sys.sleep(5) 1:5 #+end_src #+RESULTS: : [1] 1 2 3 4 5 The function (ess-eval-buffer), when the parameter VIS is nil, misled me in the sense that it inverses the value of ess-eval-visibly. Note as well that all the tests in test-ob-R.el passed including the tests for async evaluation from [1] ob-session-async. [1]: https://github.com/jackkamm/ob-session-async/.