Vol. V · The Harness · V.3
Subagents
A subagent is a nested loop with a narrower prompt, a fresh or sliced context, and a written return value. It is the isolation primitive of modern harnesses.
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Doctrine
- Spawn a subagent to protect the parent's window, to parallelize, or to apply a different skill set — not for decoration.
- The return value is a document or a structured result, not a transcript.
- Depth cap. Breadth cap. Timeout. Subagents without budgets are process leaks.
Why isolation beats a bigger prompt
A researcher subagent that dumps 40 search results into the parent's window has failed. A researcher that writes notes.md and returns a 30-line brief has succeeded. Deep Agents and DeerFlow both treat the filesystem as the bus between parent and child.
Anti-patterns
- Subagents that inherit every secret and every tool of the parent.
- Waiting on a chain of nested subagents when a worker pool would do.