Boundary Discipline

Keep ownership and state boundaries visible in the implementation rather than repairing them after the work is mixed together.

Activation gate

Apply this principle only when evidence in the current task identifies both:

1. a declared boundary, such as an approved path, repository owner, package responsibility, trust boundary, or location for runtime/private state; and
2. a proposed or necessary change that would cross, duplicate, or blur that boundary.

The boundary must come from the approved task, repository guidance, an existing ownership contract, or observed repository structure. Do not infer a boundary from directory names alone, load this principle for every multi-file change, or use it to expand the task.

Decision rule

Keep each concern with its declared owner; when an outcome spans owners, use an explicit interface or split and hand off the work instead of copying, relocating, or silently sharing ownership.

Apply the rule before editing: