ActPlane: Programmable OS-Level Policy Enforcement for Agent Harnesses

2026-06-23

AI Summary

This work addresses the semantic gap faced by current AI agents in enforcing natural language policies: the intended policy semantics are difficult to enforce precisely and interpretably at the system level. To bridge this gap, the authors propose a novel approach that integrates agent-side context with kernel-level enforcement mechanisms. For the first time, policy context is preserved on the agent side, while a domain-specific language (DSL) for information flow control (IFC), implemented via eBPF, enables comprehensive, action-level policy enforcement within the operating system kernel. This framework supports cross-event data-flow and ordering constraints, significantly improving policy compliance rates by covering indirect execution paths invisible to conventional tool-call interception. The system incurs only 1.9%–8.4% runtime overhead and provides semantically clear feedback instead of ambiguous errors.

Abstract

AI agents increasingly run in production through harnesses, the software around the LLM, including an engine that enforces safety and effectiveness policies, e.g., 'run tests before committing.' Enforcing these policies requires bridging a semantic gap: policy intent is expressed in underspecified natural language, while enforcement must act on concrete system actions, e.g., which test to run. Many policies also define event ordering or data flow actions. Yet existing approaches fall short. Tool-call guardrails miss system actions that bypass the tool layer, while OS sandboxes control resource access instead of actions, returning opaque errors that confuse the agent. Our key insight is that policy context lives within the agent closest to the task, while enforcement must happen at the OS to cover all execution paths. We introduce ActPlane, a policy engine that lets agents declare policies and enforces them in the OS kernel with semantic feedback and isolation. ActPlane uses a simple information-flow control (IFC) DSL to support cross-event policies. We implement ActPlane with eBPF and evaluate it on policies from the empirical study, coding-task benchmarks, and safety benchmarks. ActPlane improves policy compliance, including on indirect execution paths that tool-call interception cannot observe, with 1.9%-8.4% overhead. ActPlane is at https://github.com/eunomia-bpf/ActPlane

Problem

• policy enforcement
• AI agents
• semantic gap
• system actions
• information-flow control

Innovation

• policy enforcement
• eBPF
• information-flow control
• AI agent harness
• OS-level security