The present disclosure methods for identifying binding partners using cell surface display libraries, where the cells of the library display engineered peptides on their cell surfaces for identification of peptides that bind to targets of interest. The engineered peptides are preferably expressed in the cells under conditions that provide both secretion and display of the engineered peptides on the cell surfaces, thus providing access of the engineered peptides to identify potential binding pairs. The cell libraries cab be engineered using an automated editing system that provides for one or more targeted edits per cell.