Because they only see a slice of the agent’s behaviour. If an agent can perform local file actions, shell commands or stdio-based tool calls, network-only policy will miss part of the decision surface. Effective governance needs enforcement at the runtime boundary where the agent actually acts.
What a runtime policy gateway can and cannot see
A runtime policy gateway is useful, but it is rarely the whole enforcement plane. It usually sees the traffic or tool calls that pass through it, not every local action an agent can take once it is executing. If the agent can read files, write files, launch shell commands, or call stdio-connected tools, those actions can happen outside a network-only policy decision point.
That gap matters because agent behaviour is not limited to one interface. An agent may make a policy-compliant API call and still take a risky local action in the same task. A gateway that watches only outbound requests can approve the visible step while missing the hidden step that changes state, moves data, or expands access.
Runtime enforcement therefore has to match the agent’s actual execution surface, not just the network path. For AI agents that means policy should be applied where the action is executed, and the control should cover the local operating environment as well as remote services.
Where the blind spots come from in practice
Blind spots usually appear when teams treat the gateway as a universal control instead of one boundary in a larger system. The agent may have a local workspace, inherited process permissions, mounted credentials, cached tokens, or a tool runner that can reach files and commands without going back through the same policy layer.
That is why protocol-level governance alone can fail against tool misuse. The policy layer may be excellent at inspecting requests, but it cannot fully judge the safety of a shell command, a filesystem write, or a local helper process if those actions are executed below its visibility line.
A useful way to think about this is to separate intent from execution. The policy gateway may validate the intended call, while the runtime boundary must constrain what the agent can actually do with the permissions and tools already present in the environment.
How to close the gap without overtrusting the gateway
Effective control is layered. A gateway can remain valuable for request filtering, policy decisioning, and telemetry, but it should be paired with local enforcement that limits file access, command execution, tool scope, and credential reach. In other words, the runtime boundary has to be enforced at the point of action, not only at the point of network mediation.
That is the same logic behind least privilege for agents: give the smallest practical tool set, scope access to the task, and require stronger approval when an action can create durable change. NHIMG’s AI Agent Authorisation Guide is useful here because it treats per-action authorisation and just-in-time access as the core control pattern, not an optional enhancement.
It also helps to distinguish policy from observability. The gateway can log what it saw, but the local runtime should also emit evidence of file operations, process launches, tool invocations, and any access to sensitive material. Without both layers, teams tend to discover only the network-visible half of an incident.
Risk and Threat Considerations
Runtime policy gateways create a false sense of completeness when they protect only the visible request path. The residual risk is that an agent can still modify local state, invoke hidden tooling, or use inherited permissions to cause impact that the gateway never inspects.
Failure mechanism: The enforcement point sits too far from the action surface, so non-network operations bypass the policy decision and can still change files, execute commands, or use local trust relationships.
Impact: Attackers or misconfigured agents can exfiltrate data, stage persistence, alter code or configuration, and amplify a small prompt or tool abuse into broader compromise.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Agentic AI Top 10 addresses the attack and risk surface, while NIST SP 800-53 Rev 5 and NIST Zero Trust (SP 800-207) set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Agentic AI Top 10 | ASI02 — Tool Misuse | Runtime gateways miss local tool use and command execution. |
| ASI03 — Identity & Privilege Abuse | Agents can bypass network policy through inherited local privileges. | |
| Recommendation — Constrain agent tools to the smallest task-scoped set and enforce per-action approval for risky operations. Bind each agent action to least-privilege authority and revoke standing access that exceeds task need. | ||
| NIST SP 800-53 Rev 5 | AC-6 — Least Privilege | The core issue is excess execution capability outside the gateway. |
| IA-5 — Authenticator Management | Local and delegated credentials can be exposed if runtime actions are unconstrained. | |
| Recommendation — Limit agent and helper-process permissions to the minimum required for each task. Rotate and tightly control any credentials the agent or its tools can reach. | ||
| NIST Zero Trust (SP 800-207) | PL-8 — Network and System Communications Protection | Policy must extend beyond network inspection to the runtime boundary. |
| Recommendation — Place enforcement as close as possible to the protected resource and not only at the network edge. | ||
Practitioner Guidance
What to prioritise: Start by mapping every place the agent can act, then verify which of those actions are actually covered by policy, logging, and approval. If the answer depends on “the gateway will catch it,” treat that as a design gap until proven otherwise.
What to verify: Check whether local file access, shell execution, stdio tools, and credential-bearing processes are constrained separately from network calls. The control is only credible when the runtime boundary is enforced where the state change happens.
Practitioner takeaway: A gateway is a useful checkpoint, but it is not a complete safety model unless the agent cannot do meaningful work outside its view.