Anthropic guide favors a single main agent loop over subagent sprawl
Anthropic published an 18-minute guide recommending a default design of one model, one context window and one open-ended tool loop. It advises putting domain procedures in skills and hard limits or lookups in tools, while retaining subagents when context degradation, disposable-context parallelism or excessive tools and conflicting instructions are measured problems. The guide also cites one customer whose single loop ran roughly twice as fast as its multi-agent harness and says several deployments saw better quality, lower cost and lower latency.
Anthropic’s guide gives agent builders concrete criteria for deciding when to simplify their architecture, although the deployment comparisons are vendor-reported and the Reddit discussion adds no independently verified results.
Anthropic published an 18-minute guide on Oct 22 called "When to fold subagents into your main agent loop." It is aimed at enterprise agent builders, but the lessons apply to anyone who set up a pile of subagents in Claude Code.
Main points:
- Default to one model, one context window, one open-ended tool loop. Put domain procedures into skills and hard limits and lookups into tools. Let the model write and revise its own plan. - Keep subagents only when you measure degradation from context bloat, need parallel work with disposable context, or the agent struggles with too many tools or conflicting instructions. - One customer's single loop ran roughly 2x faster than its multi-agent harness. Several deployments saw better quality, lower cost and lower latency. - Tool choice tends to degrade past 30-50 tool definitions in the system prompt. Group tools by user intent and use tool search with deferred loading. - Anthropic cut Claude Code's own system prompt for newer models by over 80%. - Start with evals before you refactor. 10 golden examples are enough to begin. Run each task more than once, because one regression only showed in one of two runs. - Failure modes they list for big orgs: lost context between agents, subagent sprawl, the "Frankenprompt" where every team adds rules, overly local evals, latency. - New /claude-api skills for the migration: build-eval, prompt-audit, hillclimb, cost-optimize, plus /skill-creator and /skill-doctor. There is a kit on GitHub (anthropics/single-agent-loop-kit).
I had about six subagents at one point and ended up using two. This article matches what I saw: most of them were just skills with a separate context window.
Where do subagents still earn their place for you, and how many do you actually use day to day?
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