The Sacramento Three & Up Challenge is the current testing ground for Missing Middles. Entries are evaluated for financial feasibility, constructability, and policy translation, not just design quality, and the challenge is structured to produce outputs that outlast the competition itself. These include the Missing Middles Feasibility Engine, prototype drawings, pro forma templates, permitting pathway documentation, pattern book entries, and publicly accessible findings from the challenge process.

The Feasibility Engine is the centerpiece of that toolkit and is currently in proof-of-concept development. It helps test design concepts against basic underwriting assumptions, including unit count, construction cost, rents or sales values, soft costs, financing, and return thresholds.