When two people say the same thing at the same time what do people say in France? In English it’s “Jinx!”
My kids and their friends say:
then, if that was simultaneous again:
Double chips !
Triple chips !
and so on until one wins.
When more than two people say the same thing at the same time, one might also say:
Chips personnel !
to win the "contest".
The loser has to stay mute until his/her first name is pronounced by anyone.
Here is a reference: https://warriors-en-savates.skyrock.com/1309936278-La-Loi-du-Chips.html
A "micro-poll" shows that this expression is known by young people between 11 and 20 years old in both Paris area and Brittany but mostly unknown by older people.
In my extended family, we say
Les grands esprits se rencontrent
(I've never heard of "chips" in the other responses.)
I don't know if there is an "official" word for this situation.
But, your question reminds me, when i was a child, we used to say "Chips" simultaneously.
So, if our "Chips" was originally a distortion of your "Jinx"... This is very funny.