Identity Context Required for Runtime AI Policy Enforcement in the Execution Path

Identity as a decision input, not an access management topic

Access management answers whether a principal may reach a system. Runtime policy enforcement asks a narrower and more frequent question: should this specific interaction or tool call proceed, and in what form? The answer can be to allow it, redact part of it, block it, rate limit it, or escalate it for human approval. Each of those outcomes depends on knowing who or what is acting at that moment.

This guide treats the enforcement point as a consumer of identity. Identity providers, workload identity infrastructure, and token issuers remain the source of truth. The enforcement point does not create identities. It receives them, evaluates them against policy before the action executes, and keeps a record of what it saw. NIST guidance on agentic infrastructure supports this placement: policy enforcement should sit around the agent and between the agent and the systems, data, credentials, and environments it uses, so that separation of policy from reasoning is enforced by architecture rather than by the model's behavior.

The practical consequence is that an enforcement layer is only as precise as the identity context it receives. If the context is missing or collapsed, policy defaults to over-broad rules or blanket blocks, and neither produces defensible evidence.

Four identities that need to stay distinct

Enterprise architectures usually carry several identities in a single request. Treating them as one is the most common source of inconsistent policy outcomes. NIST describes agent identity as cryptographically verifiable, distinguishable from human users and service accounts, and ideally tied to a specific workload, environment, and approved configuration.

• User identity: The human who initiated or authorized the request. Supplies role, group, and the entitlements that bound what the agent may do for that person. Typically arrives as token claims from the identity provider.
• Agent identity: A logical agent has one persistent identity, with its credentials and deployment-specific identities verifiably linked to it. The enforcement record should resolve a runtime instance or credential back to that persistent identity, and it should have an owner.
• Service or application identity: The workload or application through which the request passes. Zero trust models for cloud-native applications base authorization on application and service identities in addition to network parameters and user identities.
• Tool or MCP server identity: The target of the call. Verifying a remote server (for example by certificate pinning or cryptographic verification) is a separate control from identifying the caller, and both are inputs to the decision.

Mapping attributes to enforcement actions

The sources support a working set of attributes: agent identity and ownership, user identity, entitlements or role, application or service identity, tool or server identity, and token scope and lifetime. Session context is also commonly useful, though the guidance on it is less detailed. What matters is that each attribute is tied to a decision it makes possible.

Allow and block decisions depend on the combination of agent identity, user entitlements, and target. An agent may be permitted to call a tool for one user and not for another, so agent identity alone is not enough. Redact decisions depend on the entitlements of the person on whose behalf the agent acts. The same response may be returned in full to one user and masked for another.

Rate limiting needs a stable agent identity. When several agents share a credential, limits apply to the credential and one noisy agent consumes the budget of the others. This is one reason NCCoE material favors unique agent identity and eliminating shared identity or credentials across agents and services.

Escalation needs ownership. NIST states that organization-defined risk thresholds should trigger human review through components that reach the correct authority. Without a recorded agent owner and the requesting user, the approval request has nowhere accurate to go. Where approvals are used, they should be bound to the specific action and arguments so an approval cannot be reused for a different call.

Authorization inputs can be evaluated locally from token claims, such as JWT claims, or externally at a policy decision point. Both patterns are valid. The requirement is that the claims or attributes present at decision time are the ones recorded.

Where identity context breaks down

Identity usually degrades at hop boundaries. A user authenticates to an application. The application calls an agent, the agent calls a tool, and the tool calls a backend. At each step the credential in use can change, and the upstream identity can be dropped.

The first failure is shared or service-level credentials. If an agent reaches a tool through a generic service account, the tool and the enforcement point see the service account, not the agent or the user. Policy can then only be written for the account, which tends to be over-broad.

The second is lost delegation. When an agent acts on behalf of a user, policy needs both identities and the limits of the delegated authority. How to handle delegation of authority in on-behalf-of scenarios is posed as an open question in NCCoE material on agent identity and authorization, so architects should not assume that a standard mechanism carries this context end to end. Where it is not carried, the enforcement point should be able to receive it from the calling application and treat its absence as a policy input, for example by restricting or escalating the action.

The third is identity drift. A redeployed agent produces a new runtime instance and new credentials. The identity model should distinguish changes that preserve the agent's identity from changes that create a new agent, otherwise audit history fragments.

The fourth is unverified targets and exposed secrets. Trusting a tool response from an unverified remote server undermines the decision. Credentials placed in prompts, code, or configuration, or left unredacted in outputs and logs, defeat least-privilege design. Credentials should be accessible only through enforced policy controls.

Identity as part of the evidence record

A decision that cannot be reconstructed is hard to defend. NCCoE material calls for linking specific agent actions to an identity so that actions, data generated, and outcomes are visible. For an auditor, that translates into a record per decision that states who or what acted, on whose behalf, with which entitlements, through which application, against which tool or data, what policy applied, and what the outcome was.

Regulatory text is generally less specific than architects would like. The EU AI Act, in recital 71, states that comprehensible information on how high-risk AI systems are developed and perform throughout their lifetime is essential for traceability, compliance verification, and monitoring. As of November 2026, that language supports retaining decision-level records but does not itself prescribe identity fields. Organizations should define the fields from their own policy and the frameworks they are assessed against.

Records should capture the attributes as evaluated, not as later looked up. Group membership, token scope, and agent ownership change over time, and a record that references current state cannot show what was true when the decision was made. Credentials and secrets should be redacted from the record itself.

Trussed enforces policy in the execution path across models, agents, tools, and MCP servers, at the level of individual interactions and tool calls. Enforcement generates audit-ready evidence that is mapped to HIPAA, NAIC, NYDFS, the EU AI Act, and NIST. The scope is the interaction and the tool call, not business transaction identity or workflow-level tracing.