AAIF migration guide for MCP 2026-07-28 release candidate. Frames prior stateful stdio-oriented design as bottleneck for load-balanced/Kubernetes/multi-region deployments. Comparison table: session model → self-contained requests; sticky sessions → round-robin; Tasks/MCP Apps as official extensions; OAuth 2.1 + OIDC hardening plus Enterprise-Managed Authorization (EMA) extension; Roots/Sampling/Logging/DCR/HTTP+SSE proposed for deprecation with earliest removal July 28, 2027. Explicit-handle pattern for application state. Migration checklists for server and client maintainers. Note: post authored against RC; readers should verify against final July 28 ship.