Agent-Warden: eBPF-Based Kernel-Native Process-File Provenance Tracking for LLM Agents
LLM agents execute dynamically generated process and file operations that are often invisible to application-layer tracing. We present Agent-Warden, an extended Berkeley Packet Filter (eBPF)-based provenance monitor for tracking task and regular-file states across process creation, file access, and process termination. Agent-Warden provides two interchangeable state backends: a PID-keyed hash-map backend for compatible kernels lacking BPF local-storage support and a task/inode-local-storage backend that couples state reclamation to kernel-object lifetimes. The system emits incremental causal edges to user space for asynchronous graph reconstruction and applies conservative exit-triggered causal aggregation to preserve causal context for short-lived proxy tasks. In a controlled file-mediated propagation scenario, Agent-Warden reconstructed a cross-process causal chain that was absent from the application-layer trace. On x86-64 and ARM64 bare-metal hosts, the evaluated workloads showed 0.2-3.5% end-to-end overhead and 0.6-3.7% additional system CPU time. These results indicate that the prototype provides kernel-level visibility with the measured overheads in the evaluated settings.