Multi-Agent vs Single-Agent Architecture in 2026: When the Crew Beats the Soloist

The pitch for multi-agent systems is intoxicating. You take a complex task, decompose it into specialized roles, hand each role to its own agent, and coordinate them through a planner. The planner delegates. The workers execute. The critic reviews. The orchestrator stitches it together. It looks like a software team, except the team is a swarm of LLMs and they never go to lunch. I bought this pitch in 2024 and built three different multi-agent systems before I admitted that two of them would have been better as a single agent with good tools. The third one genuinely needed multiple agents.