Is it permissible for the woman's guardian (walī) to be the agent and one of the two witnesses in the marriage contract (ʿaqd al-nikāḥ)?

If the question is about the woman’s guardian acting as an agent for the husband, then according to the majority of jurists, it is permissible for one person to undertake both sides of the contract in marriage. However, it is not permissible for the guardian or his agent to be one of the two witnesses in the marriage. So he cannot be a witness, even if he delegates, because the agent is his representative. And the testimony of the guardian to the contract of his ward is not permissible because he is suspected of concealing her. Nor is the testimony of the one who undertakes the contract valid.