Would you please explain what you mean?

The Hague Convention Relative to the Opening of Hostilities, 1907, Article 1, says "The Contracting Powers recognize that hostilities between themselves must not commence without previous and explicit warning, in the form either of a reasoned declaration of war or of an ultimatum with conditional declaration of war." There is nothing about passports there.

A diplomat requesting his passport of a receiving nation was the breach of diplomatic relations, and was often done before a declaration of war. However, it need not be, in which case the receiving nation would restrict the diplomats until they could be exchanged and transferred. (E.g., it took several months to arrange that for German diplomats in the US in 1917 and Japanese diplomats in the US in 1941-2.) Diplomats could also request their passports without a subsequent war.

This note has some quotations pertinent to this, but does not answer all your (or my) questions.