Concept doc captures the design for coordinated API evolution in agent ecosystems: InterfaceChange entity, draft→published→resolved lifecycle, TPSC-derived dependency routing, inbox-based notifications, pre-change coordination via planned_for, and deliberate deferral of webhooks. CUST-WP-0033 workplan: 6 tasks (model, API, dispatch integration, MCP tools, dashboard, webhook EP). Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>