Early in the chain
Ordering is the whole design. Evaluated after routing or accounting, revocation would still deny the call but only after work had been done on behalf of an identity that should have had none.
A gateway capability that lets an organisation immediately cut off a compromised or disallowed user or agent from downstream AI resources.
Access granted through many applications and credentials has to be revocable from one place. When an agent misbehaves or a credential is compromised, the response cannot be a coordinated change across every calling system.
Revocation needs to take effect immediately and centrally, deny before any downstream model call is made, and behave correctly for streaming requests that may already be in flight, all while adding as little as possible to the requests it does let through.
Shared ownership stated as such. Nothing here claims sole authorship of a platform.
Place the check early in the chain, ahead of resolution and routing, so a denied identity never reaches a provider and never incurs cost.
Keep the policy narrow: identify, compare, deny. A revocation mechanism is only trustworthy if its behaviour is obvious, and breadth here would buy nothing.
Return an explicit authorisation error instead of a generic failure, so the outcome is unambiguous to the caller and to whoever is reading the logs later.
The ones with a real cost on the other side.
Ordering is the whole design. Evaluated after routing or accounting, revocation would still deny the call but only after work had been done on behalf of an identity that should have had none.
The temptation is to generalise this into a policy engine. A control meant to be reached for in an incident should be simple enough to reason about under pressure.
An immediate governance mechanism preventing selected identities from invoking protected AI resources, applied centrally instead of application by application.