Contextual Agent Authorization Mesh (CAAM)

This document specifies the Contextual Agent Authorization Mesh (CAAM), an authorization profile composable with the Agent Registration and Discovery Protocol (ARDP) I-D.pioli-agent-discovery and other discovery mechanisms. CAAM defines the Post-Discovery Authorization Handshake: the runtime authorization layer that governs agent behavior after an agent has been discovered through ARDP but before it is permitted to execute tool calls or delegate authority. CAAM provides a sidecar-based authorization mediator for enforcing Relationship-Based Access Control (ReBAC), purpose-bound delegation, and cryptographically verifiable intent propagation in Human-to-Agent (H2A) and Agent-to-Agent (A2A) flows. It bridges identity provenance frameworks -- the Interoperability Profiling for Secure Identity in the Enterprise (IPSIE) IPSIE and the Secure Production Identity Framework for Everyone (SPIFFE) SPIFFE -- with the ARDP control plane, leveraging OpenID XAA for coarse-grained delegation, a Knowledge Graph for real-time relationship inference, and the Remote ATtestation procedureS (RATS) architecture RFC9334 for cryptographically verifiable attestation of agent execution environments. The Session Context Object (SCO) defined herein is encoded as a JSON Web Token (JWT) RFC7519 or a CBOR Web Token (CWT) RFC8392, and carries a new "ctx" (Contextual Assertion) claim that binds the agent's delegated authority to a specific purpose, session, and trust chain.