Identity Intersection Rule

How the identity intersection rule works

The identity intersection rule constrains an agent to the overlap between the human user’s permissions and the agent’s own baseline permissions. That keeps the agent from acting with broader authority than the user intended and makes authorization a runtime decision rather than a one-time login outcome.

Its core security value is that it preserves least privilege even when the agent has access to tools, APIs, or delegated automation paths. The rule is most useful when the agent can execute real actions, because the permission boundary must be checked at the moment of each action.

In practice, the rule helps separate what the user is allowed to do from what the agent is trusted to do by default. That distinction matters when workflows cross systems, because a single overbroad agent permission set can silently expand the blast radius of a user session.

Where the rule fits in agent authorization

The identity intersection rule is a runtime authorization pattern for agentic systems. It does not replace authentication or identity proofing; instead, it governs which action survives when user intent, user permissions, and agent baseline permissions do not fully align.

This makes it especially relevant in delegated workflows, where an agent may act on behalf of a user but should not inherit all of the user’s standing access. A good implementation treats each tool call, transaction, or privileged operation as a fresh authorization check, not a blanket approval from the start of the session.

That runtime model is what keeps an autonomous workflow bounded. Without it, the agent’s access model can drift into “whatever the platform can do,” which is exactly the kind of authority expansion this rule is meant to prevent.

Relationship to least privilege and delegated authority

The rule is best understood as an access control guardrail for delegated action. It blends the principle of least privilege with a practical constraint: an agent should only be able to do what both the user and the platform policy permit, not the maximum of either one alone.

That is why the rule is often paired with scoped tool permissions, per-action authorization, and explicit entitlement boundaries. In identity terms, it helps ensure that the user remains the source of intent while the agent remains a bounded executor.

For readers who want the broader identity context, NHIMG’s Ultimate Guide to NHIs explains the wider class of non-human identities this pattern often protects, while the Identity Security Programme Guide covers how organisations structure governance around those access decisions.

Why the runtime check matters

What makes this rule distinctive is timing. A login-time approval only establishes that an identity may enter a system; it does not guarantee that every later action is still appropriate. Runtime enforcement prevents permission creep from becoming invisible inside a long-lived agent session.

The practical consequence is that each action remains tied to current policy and current scope. That is especially important where agents can chain steps, because an earlier allowed action can otherwise become a stepping stone to a later, more sensitive one.

Runtime checks also create a cleaner audit story. When each action is evaluated against the intersection, reviewers can tell whether the agent was acting inside its delegated envelope or whether a workflow tried to push beyond it.

Risk and Threat Considerations

The main risk is authority amplification: if the intersection rule is weak, misapplied, or bypassed, an agent can execute actions beyond the user’s intended scope. That creates an immediate privilege and trust problem, especially in systems where one agent session can reach multiple tools or downstream services.

Failure mechanism: A permissive agent baseline, stale delegation, or missing per-action check allows the agent to inherit broader authority than the user actually authorized, turning a bounded task into overprivileged execution.

Impact: The result can be unauthorized changes, data exposure, lateral movement through connected systems, or abuse of privileged workflows that were never meant to be available to the original user request.

Practitioner Guidance

What to watch for: Pay close attention to any design that evaluates permission only once, at session start, or that treats the agent as a full surrogate for the user. Those models are usually too coarse for real delegated action and can hide privilege expansion until after damage is done.

Governance implication: Ownership should be explicit for both sides of the intersection, the user’s entitlements and the agent’s baseline authority. If either side is unclear, the resulting permission boundary will also be unclear, which is a policy problem as much as a technical one.

Practitioner takeaway: Treat every agent action as an authorization event, not a background consequence of being logged in.

Related resources from NHI Mgmt Group

• Why do rule-based fraud controls fail against modern identity abuse?
• Why does the Travel Rule matter for identity governance?
• What breaks when identity governance still relies on manual approvals and rule maintenance at scale?
• What happens when digital footprint analysis is used as the only decision rule for identity verification?