CLAIM-2026-08-27-05

In the Enterprise-Managed Authorization flow, the MCP client obtains an Identity Assertion JWT Authorization Grant from the enterprise IdP and exchanges it for an access token; the specification directs authorization servers to map IdP claims to permissions, to use the subject claim "as the primary stable identifier for the user", and to determine "who the employee is and what the employee can access".

Why it matters

The authority carried on the wire is the employee's, delegated. A directory entry for the agent and a user-subject token are different things, and only the second is what the resource server enforces on.

Sources

• modelcontex2026enterpris