OAuth Token Exchange (RFC 8693)
An OAuth 2.0 extension that lets a party trade one token for another — used in agent identity to implement Delegated Authority (On-Behalf-Of) and just-in-time privilege narrowing. Two capabilities matter for agents. First, delegation: the exchanged token can carry the user as `sub` and the agent as a nested `act` (actor) claim, so downstream services see both identities instead of the agent impersonating the user. Second, scope reduction: an agent holding a broad base token can exchange it, immediately before a sensitive call, for a narrowly-scoped, audience-restricted, short-lived token — so a compromised agent can only replay tokens for the exact resource it was mid-task on, not its entire accumulated access. RFC 8693 is a stable standard; the OpenID Foundation and the March 2026 IETF agent-auth draft both build their delegation model on it.
Written by Max Zeshut
Founder at Agentmelt · Last updated Sep 9, 2026
Example
A data agent holds a base token scoped to 'analytics.read'. Before exporting one report it exchanges that token for an ephemeral token bound to `audience=warehouse.reports`, scoped to a single dataset, expiring in 5 minutes. If the agent is hijacked 20 minutes later, that token is already dead and can't be replayed against any other warehouse resource.
Frequently asked questions
- How does token exchange reduce blast radius?
- By replacing one long-lived broad token with many short-lived narrow ones minted per action. The agent never holds a token more powerful than the current step needs, and each token is bound to a specific audience so it can't be replayed elsewhere. Combined with Delegated Authority (On-Behalf-Of), the result is that a compromised agent's reachable scope collapses to whatever it happened to be doing at the moment of compromise.