ESA is a layer atop CLIM functionality to provide an Emacs-Style Application framework. Currently, it provides support for a top-level application loop, commands including numeric arguments, nested command tables (for key sequences), keyboard macros, buffer management, filesystem interaction, and support for self-documenting applications. It was developed initially for Climacs, a Common Lisp Emacs, but other McCLIM applications such as Gsharp and a CLIM file manager also use portions of its functionality.

ESA is bundled with McCLIM, it is no longer a standalone system.