The behavior layer The MUSCLE system.
Reusable behavior templates that make a SKEL production move—without giving plugins direct access to mutate your story.
Reusable behavior with the safety rails left on.
A BONE connects a capability. A MUSCLE describes what should happen around it—check continuity, enforce a house style, route work, process a result, or stop a bad export—while Genlock keeps final control.
A MUSCLE (*.muscle.json) is a portable behavior manifest. It can subscribe to safe lifecycle moments—import, validation, prompt assembly, generation routing, render completion, and export—and declare how the host should invoke it through CLI, MCP, or API.
Power with boundaries
MUSCLEs return proposed patches instead of touching the production directly. Genlock checks every patch against capabilities you approved, refuses changes to locked content, applies the set atomically, and rolls back anything that would invalidate the document.