The present disclosure, in some aspects, provides Co-stimulatory Conditional Bispecific Redirected Activation constructs, or "co-stim COBRA," that are administered in an active prodrug format. Upon exposure to tumor proteases, the constructs are cleaved and activated, such that they can bind both tumor target antigens (TTAs) as well and immune cells (e.g., one or more types of immune cells), thus recruiting immune cells to tumor, resulting in treatment.