How do I audit which agent acted under my identity across a delegation chain?

When an orchestrating AI agent delegates a subtask to a sub-agent, which then calls a third-party API under the original user's OAuth token, the identity chain spans multiple providers and authentication methods with no single audit trail capturing the complete path. MCP added OAuth 2.1 support but the specification has no mechanism for chaining delegated authority across hops or for revoking a mid-chain agent's permission without revoking the entire session. A2A provides agent discovery and request signing but explicitly defers all authorization decisions to other protocols that do not exist yet. Research published in April 2026 identifies recursive delegation accountability as one of five unresolved critical gaps in current agent identity standards. A user who authorizes one agent today has no practical way to inspect, limit, or revoke what downstream agents did on their behalf.