The red* family of proof assistants

The core RedPRL Development Team (Carlo Angiuli, Evan Cavallo, Kuen-Bang Hou (Favonia), and Jon Sterling) has developed several experimental proof assistants for Cartesian cubical type theory under the supervision of Robert Harper.

The cooltt proof assistant

We are currently developing cooltt, a prototype proof assistant for Cartesian cubical type theory, building on our previous work on the redtt proof assistant. cooltt supports systems for eliminating disjunctions of cofibrations, implementing the full definitional η-law.

We welcome new contributors!

Screenshot of cooltt.

The redtt proof assistant

A proof assistant for Cartesian cubical type theory. Notable features include extension types, user-defined (parametric) higher inductive types, and rudimentary higher-order unification; redtt pioneered the boundary-sensitive treatment of holes that now appears in Cubical Agda and cooltt.

Publications and talks

Screenshot of redtt.

The RedPRL proof assistant

A tactic-based proof assistant for computational Cartesian cubical type theory inspired by Nuprl. RedPRL implements a two-level cubical type theory which includes univalent universes, some higher inductive types, and strict equality types with equality reflection.

Publications and talks

Screenshot of RedPRL.


This research was sponsored by the Air Force Office of Scientific Research under grant number FA9550-15-1-0053 and the National Science Foundation under grant number DMS-1638352. We thank the Logic and Semantics Group at Aarhus University for their hospitality in during the summer of 2018, during which part of this work was undertaken. We also thank the Isaac Newton Institute for Mathematical Sciences for its support and hospitality during the program "Big Proof" when part of this work was undertaken; the program was supported by the Engineering and Physical Sciences Research Council under grant number EP/K032208/1. The views and conclusions contained here are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of any sponsoring institution, government or any other entity.