Is warmup actually running?

GET /warmup/health

Whether Warmerly's warmup workers are alive. A plain authenticated caller gets the derived flag:

{ "ok": true, "healthy": true }

healthy is true when the freshest worker heartbeat is under 10 minutes old. It is a platform-level answer, not a statement about your mailboxes: healthy: true with nothing sending means the problem is your campaign or mailbox configuration, and GET /campaigns/{id}/readiness will say which. Staff callers additionally get lastTick per worker.

POST /warmup/run exists but is ops-only: it triggers a planner/dispatcher pass across every workspace on the platform, so it returns 404 for a customer key. Warmup runs continuously on its own; there is nothing to trigger.