Human-in-the-loop (HITL)
Definition
Human-in-the-loop means a human decides before an automated system executes a critical action - not after. For AI agents this concretely means defined tool calls are held until an authorized person approves or rejects them. The difference from mere logging: the human can intervene before anything happens.
Effective human-in-the-loop has three building blocks: rules that recognize critical actions (amounts, deletions, unusual hours), an approval channel that reaches decision-makers where they are (signed email links first, complemented by push, SMS, WhatsApp or Slack), and evidence that documents every decision permanently.
The EU AI Act turns the principle into an obligation for high-risk systems in Article 14: human oversight must be effective - able to intervene, not just watch.
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