Microsoft (Oct 19, 2026) announced Guardian Agents that "watch and moderate every action of every agent, before it happens, 24/7" — but published no implementation. Watchdog is the drill kit: a FastAPI guardian that scores every agent action and routes it to ALLOW, STEP-UP, HOLD-FOR-HUMAN, or HALT-AND-ISOLATE. Policy template, runbook, identity registry, risk rubric, containment playbook included. 17 tests passing. Not cost routing, not an audit — runtime supervision by safety.