The Vendor Dependency Ledger: Why Upstream Outages Are Now an Agency Margin Problem

Agencies no longer sell only their own work; they sell the uptime of a stack they do not control, and every unmonitored third-party dependency converts someone else's incident into your client-facing failure. The economics flip once you treat vendor health as a billable managed layer: detection time becomes a retention asset, and alert hygiene becomes the cost control that keeps that layer profitable.