It lasts at most one hour, and a capability tied to a work session stops working when that session ends.
Operations have names such as source.read, source.write, knowledge.write or db.read, and an agent receives only those that the role of the team member it works for already allows. Agent sessions never receive project administration, secrets management, deploy configuration, tagging or force-push, whatever the role. Every use is checked again: signature, expiry, revocation, that team member's membership and, for a session capability, whether the session is still active.
This is why revoking someone's access in Managers takes effect for their agents too: once the membership is gone, the capabilities their agents hold open nothing. A capability presented for a different project opens nothing either.