A ruler can neutralize a planned coup by striking first with a counter-coup.

Evidence

The Parisian Leaguers did not expect to seize power without a fight, and had anticipated that the King might have to be prodded into some rash act of violence which would incite a popular uprising. But the massed column of Swiss swinging down the Rue Saint-Honoré while evidently promising violence scarcely suggested rashness. It looked as though the King, with unexpected courage and decision, intended to forestall by a coup d’état, the coup d’état planned against him. — Garrett Mattingly, The Defeat of the Spanish Armada, 496

Categorization

• XREF: This preemption dynamic echoes later warning in the book about Spanish invasion timing, and parallels general coup/counter-coup logic in other histories.
• corroborated: 2 independent passages support this claim — Garrett Mattingly, The Defeat of the Spanish Armada, 496