There seems to be no love lost between Elon Musk and Sam Altman. The former allies turned rivals have played out their differences in the public, indicating the depth of their rift. The most recent case involves a tweet from the Open AI boss and the SpaceX chief executive’s response.

Elon Musk mocked rival Sam Altman after the OpenAI boss congratulated Donald Trump’s new “White House A.I. and Crypto Czar” David Sacks. The appointment of Elon Musk’s friend and fellow tech titan is the latest illustration of the Tesla founder’s influence in the president-elect’s new administration.