Stitch Fix uses a set of algorithms inspired by genetic modeling to generate design suggestions for new exclusive clothing items, combining attributes from best-selling products to produce new style combinations. Human designers review algorithmic suggestions and make final decisions before items are manufactured.

Stitch Fix calls this program 'Hybrid Designs.' Three algorithms work together: one identifies best-selling parent styles, a second suggests complementary attribute variations (e.g., different necklines or sleeves), and a third adds random variation. Together, the algorithms search through approximately 30 trillion potential attribute combinations to produce nine design suggestions. Human designers then evaluate cultural fit and fashion context before approving items for production. The program launched its first pieces in June 2016. As of 2025, Stitch Fix announced it is also integrating newer generative AI tools into private-brand design development.