Move MCP authorization to per-request context so a gateway can enforce on every call

Agentic AI Foundation·medium signal

The maturing MCP spec is pushing requests to carry their own authorization context instead of relying on a trusted long-lived session, which lets a gateway inspect and enforce policy on every single call rather than once at connect time. For anyone self-hosting MCP servers, this collapses a whole class of session-hijack and confused-deputy risks. Architect new servers around stateless per-request checks now rather than session trust.