Overview
Sub-graphs, handoffs, and shared state.
Why it matters
Multi-agent topologies (router + workers, hierarchical, mesh) are the frontier of LangGraph — and where the GraphRAG retriever from Level 2 plugs in as a tool.
Where this sits in the stack
Multi-agent orchestration is one of the load-bearing decisions in a KG/RAG/agent system: choices made here propagate to retrieval quality, agent reliability, cost per query, and the on-call burden of whoever ships it. Teams that name this trade-off explicitly ship faster than teams that leave it implicit.