The andon cord

On a Toyota line, a worker who sees a defect pulls a cord that signals a problem and, unresolved, halts production. The radical part was never the cord. It was that stopping the line was treated as correct behavior rather than as a cost, so problems surfaced immediately instead of traveling downstream inside finished work.

This is the direct ancestor of agent escalation design. The modern question is who pulls the cord when the process completes in eight seconds and nobody is watching, which is why the gate insists the trigger must fire by itself.