Is it permissible for the mother to be her son's agent in marriage and to marry him off?

It is not permissible to appoint a woman as an agent in the marriage contract, whether in offering or accepting, because she does not possess the right to contract her own marriage initially, so similarly, she does not possess it for others. However, if the mother's role is to search for and inquire about a suitable woman, and then another man whom you appoint as your agent contracts the marriage, there is no harm in that.