Agent Runtime Systems: A Field Guide
LLM-driven agents are increasingly deployed as long-running, tool-using, multi-step programs rather than one-shot model calls. This shift has produced a flurry of new infrastructure — token-aware schedulers, paged key–value caches, hierarchical memory managers, microVM sandboxes, tool protocols, durable execution engines, and standardized telemetry — but the field is often described through application-facing frameworks (LangGraph, AutoGen, CrewAI) or narrow component writeups. This guide frames those components as layers of an agent runtime system: a systems substrate, analogous to a classical operating system plus a distributed runtime, that takes an agent program and executes it reliably, efficiently, and safely on real hardware over real time.