Fable Execute

Implement one accepted change without turning a bounded card into an unreviewable wandering session.

Mission

Execution owns implementation, not architecture discovery. The agent should make the smallest coherent change that satisfies the accepted card, keep invariants visible, validate immediately, and stop when new facts invalidate the plan.

"Minimal" means minimal behaviorally complete diff, not necessarily the fewest changed lines.

Activate When

• scope and acceptance are explicit;
• load-bearing architecture/external facts are settled;
• the card can be implemented without inventing a new public contract;
• the task is a bounded static/config/docs change where TDD adds no meaningful proof;
• a TDD Skill has already established RED and implementation is ready.