What unit should be passed between the construction unit and the contracting unit and the contact activities related to the construction project contract

According to Article 1.0.5 of the National Standard GB/T 50319-2013 Specification for Supervision of Construction Works of the People's Republic of China, "Within the scope of supervision of construction works, the contact activities between the construction unit and the construction unit relating to the construction contract shall be carried out through the engineering supervision unit". Therefore, the answer to this question is "engineering supervision unit".