State Machine

Model behavior as a finite state machine to eliminate impossible states and make every transition explicit.

Agent contract

This skill is for state-machine design, not tool installation. Model first; choose tools later only when the model needs them.

Before changing code, produce or hold in working context:

1. Finite states with one-line meaning.
2. Events that can occur.
3. Transition table: current state, event, optional guard, actions, next state.
4. Impossible states the model prevents.
5. Smallest implementation shape that preserves the model.