  Contract-based design is a method to facilitate modular system design. While
there has been substantial progress on the theory of contracts, there has been
less progress on scalable algorithms for the algebraic operations in this
theory. In this paper, we present: 1) principles to implement a contract-based
design tool at scale and 2) Pacti, a tool that can efficiently compute these
operations. We then illustrate the use of Pacti in a variety of case studies.
