Lesson 8 / 25

Why Use Subagents

Keep the main context clean by sending noisy research or search work to a separate agent.

Context isolation

Searching a large codebase fills the context with file contents you only needed once. A subagent does that exploring in its own context window and reports back a short answer. The main conversation stays small, focused and cheaper.

Delegate, isolate, summarise

A subagent works in its own context and returns only a short result to the main agent.

Three steps: delegate, work in isolation, return a summary.
Figure 3.1 — Delegate, isolate and summarise.

Sending an intern to the library

Instead of reading ten books yourself, you send an intern who returns with a one-page summary. You keep your desk clear for the real decision.

Do not delegate everything

Each subagent starts with no memory of the conversation, so it needs a self-contained brief. For small tasks the overhead of writing that brief is larger than doing the work directly.

Quick check: What is the main benefit of a subagent?

  • It keeps noisy work out of the main context
  • It removes the need for tools
  • It makes the model smarter
  • It guarantees correct answers
Answer

It keeps noisy work out of the main context — Isolation protects the main context from large intermediate output.