When to Use Multi-Agent Systems (And When Not To)

Multi-agent systems are having a moment. Every conference talk shows a diagram with six agents pointing at each other. Every framework ships with coordination primitives. The implicit message is that more agents equals more power. It does not. More agents equals more complexity, more failure modes, and more coordination overhead. The teams that build successful multi-agent systems are the ones who resisted adding agents until they had a specific, concrete reason to do so. This post covers the legitimate reasons to go multi-agent, three patterns that actually work in production, the pitfalls that catch most teams the first time, and a decision rule you can apply to your own use case. The Four Legitimate Reasons There are exactly four reasons to use multiple agents. If none of these apply, you do not need the complexity. Context window limits. Even with 1M-token context windows on Claude Opus 4.6, complex long-running tasks hit limits. A coding agent reasoning about a 500-file codebase w