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My notes on Anthropic's substantial essay about how they built their multi-agent research system, which has finally talked me around to taking multi-agent LLM prompt engineering seriously simonwillison.net/2025/Jun/14/...

simonwillison.netAnthropic: How we built our multi-agent research systemOK, I'm sold on multi-agent LLM systems now. I've been pretty skeptical of these until recently: why make your life more complicated by running multiple different prompts in parallel when …

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It's natural progression, teamwork with project management. I expect to soon see increasingly large AI organizations working like that. But I also expect that at some point there's reversal to consolidating work to increasingly powerful individual AIs.

I’m curious how you would implement this for a less open ended research agent. Do you still give the planning agent freedom to spin up dynamic sub agents at will or would you get better results from a fixed set of purpose built subagents which are task specific?

The skepticism was warranted: naive multi-agent means n times the cost with n times the failure modes. What changed is the orchestrator pattern — one strong model directing parallel narrow agents with bounded tools. Coordination beats consensus.