ABCI stands for “Application Blockchain Interface”. ABCI is the interface between CometBFT (a state-machine replication engine) and your application (the actual state machine). It consists of a set of methods, each with a corresponding Request and Responsemessage type. To perform state-machine replication, CometBFT calls the ABCI methods on the ABCI application by sending the Request* messages and receiving the Response* messages in return.

All ABCI messages and methods are defined in protocol buffers. This allows CometBFT to run with applications written in many programming languages.

This specification is split as follows:

Decorative Orb