The agent kill switch: build it before you need it
Runaways compound at machine speed — the kill switch has to be faster than the agent. What it is, how it works, and why ceilings mean you rarely need it.
The kill switch is the control you hope never to use — which is exactly why you build it first. A runaway doesn't wait for a committee.
Speed is the requirement
Agents spend at machine speed; a retry loop can bill thousands in minutes. The kill switch must disable spending instantly — one action, affecting the agent, the fleet, or the merchant, enforced on the next transaction.
Why ceilings mean you rarely need it
The kill switch is the emergency brake; velocity limits and spend caps are the cruise control. A governed agent hits its cap and stops on its own — the switch stays in the glovebox. That's the design: stop the bleeding, contain, understand, prevent →