au courant

Question

Is "au courant" invariable, or does it agree with the gender and number of the person?

Maarten Kamp · Accepted Answer

Courant is a masculine noun here, no agreement, the ’adjectival locution’ is invariable. Short expression effectively  ‘(à le) courant’, with the obligatory contraction to ‘au courant’. 
https://dictionnaire.lerobert.com/definition/courant
https://www.dictionnaire-academie.fr/article/DNP0625