Transitions can also be guarded. This allows you to add a condition that needs to pass, in order for the transition to successfully fire. Guards are basically functions that should return a boolean. They have access to the interal context of the machine. When the guard evaluates as true, the transition is allowed.
const config = {
init: 'start',
states: {
start: {
CHANGE: {
target: 'end',
guard: (s: MachineState<{ ... }>) => s.context?.allowed,
},
},
end: {},
},
};