Multi-agent systems split a task across specialists. They're often worse than a single well-designed agent — but when they win, they win big.
The four canonical patterns
Supervisor
- One router agent that doesn't do work, only delegates.
- Worker agents specialized (researcher, coder, summarizer).
- Supervisor decides which worker handles each step.
- LangGraph supervisor template models this directly.
Hierarchical (manager → team)
- Multi-level supervisors. A "team-of-teams" structure.
- Used when subtasks are themselves complex multi-agent problems.
- Real-world: customer support (intent router → topic specialist → reply drafter).
Collaborative (peer)
- Multiple agents working in parallel on the same problem.
- Aggregator combines outputs.
- Pattern: parallel research → synthesizer.
- Useful when diversity of approach matters (like an ensemble).
Debate
- Two+ agents argue opposing positions.
- Aggregator (often a third "judge" agent) decides.
- Used to surface edge cases, improve factuality, reduce single-model bias.
- Du et al. 2023 ("Improving Factuality and Reasoning in Language Models through Multiagent Debate").
When multi-agent beats single agent
- Specialization yields quality — coder model + reviewer model > generalist.
- Tool space is too large for one agent's prompt — split by domain.
- Diversity of approach helps — debate, ensemble.
When multi-agent loses
- Coordination overhead dominates the win — agents talking to agents accumulates errors.
- Cost — each agent burns tokens; total > monolithic.
- Latency — sequential agents linearize; parallel needs careful aggregation.
- Eval is harder — you now have N agents to evaluate.
The most common bad pattern
A "council" of generic agents (CEO agent, CTO agent, designer agent) that talk in circles. This is theater, not engineering. Real multi-agent systems use specialists with distinct tools and distinct prompts, not personality role-play.
Production rule
Start single-agent. Add agents only when the eval shows specialization or diversity is the bottleneck. Otherwise you're paying coordination cost for no quality gain.