Definition
Multiple specialized agents collaborating — typically a router/orchestrator that delegates to sub-agents.
In practice
Common pattern: a planner agent breaks down the task, sub-agents (researcher, writer, classifier) each handle a slice, an aggregator combines results. Useful for tasks that genuinely span domains. Risky for the same reason — every additional agent multiplies the failure surface. Don't reach for multi-agent until single-agent + tools has clearly failed.