Your Session, My Policy: An MCP Gateway Authorization Bypass in Agentgateway, and the Move to Stateless MCP

Enterprise MCP gateways centralize authentication, routing, and tool authorization. Agentgateway versions before v1.4.0 let a session from one route reuse a sensitive backend under another route's permissive policy. Agentgateway v1.4.0 fixes the issue. MCP 2026-07-28 removes protocol sessions from the core.