A self-modifying Common Lisp harness

Fri Aug 28, 2026 · 118 words

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cl-sm-harness is a self-improving agent harness for Claude Code, written in Common Lisp. It runs agent sessions through a browser UI or headlessly, with a tool catalog that includes reload_harness. That tool lets an agent read the Lisp source that is serving its session, edit it, and hot-reload the change into the live SBCL process. The harness and its UI are both modifiable from inside the running system. In a fork, the harness lives in harness/ beside the app/ directory it is helping build. Both are ordinary tracked parts of one repository, so harness changes and app changes land together as normal commits. The repository includes the Common Lisp SDK, session runtime, browser UI, tests, and Docker tooling.