In a hyper-formalistic holding in Mostafavi Law Group, APC v. Larry Rabineau, APC (D2d4 Mar. 3, 2021) No. B302344 (published), a judgment entered on an agreement under Code of Civil Procedure section 998 was vacated because the defendant's 998 offer did not include a signature line for the plaintiff to sign, even though the plaintiff signed it anyway. In a case of first impression, the Second District affirmed, holding a judgment may not be entered on a section 998 agreement in which the offer does not provide an acceptance provision.
I find this a very bizarre case. I would not be surprised if other District Courts of Appeal declined to follow it.