HOT: A concurrent automated theorem prover based on higher-order tableaux. HOT is an automated higher-order theorem prover based on ℋ𝒯ℰ an extensional higher-order tableaux calculus. The first part of this paper introduces an improved variant of the calculus which closely corresponds to the proof procedure implemented in HOT. The second part discusses HOT’s design that can be characterized as a concurrent blackboard architecture. We show the usefulness of the implementation by including benchmark results for over one hundred solved problems from logic and set theory.