Apparently: https://fr.m.wikipedia.org/wiki/Rétention_de_sûreté_en_France

In French criminal law, “rétention de sûreté” is a procedure for placing prisoners who have served their sentence, but who present a very high risk of reoffending because they generally suffer from a serious personality disorder, in a socio-medico-judicial security center. This measure is limited to convictions for the most serious crimes, in particular sex crimes, and must be expressly provided for in the sentencing decision

Translated with DeepL

I couldn’t find an English source, even the English wiki article on preventive detention doesn’t list France.