Subagent
A helper agent with its own clean context window.
A separate agent invocation that the main agent delegates to. The subagent works in its own context and returns only a distilled result, keeping the parent’s window clean.
Subagents are context management disguised as delegation. Searching forty files and reporting three findings costs one paragraph of the parent’s context instead of forty files’ worth.
The reason to delegate is context isolation, not parallelism, and the isolation is what you are buying. A subagent absorbs a noisy search — twenty files, four dead ends — and returns two paragraphs. The parent context stays small and the quality of its subsequent decisions stays high.
The search that should not pollute the parent
Finding which of two hundred files implement an interface.
Delegate it. The subagent reads widely in its own window and returns the three file paths and a one-line summary. The parent never sees the twenty dead ends, which is precisely why its next decision is better.
Delegation has a coordination cost
Splitting a task across five subagents writing to the same codebase.
They duplicate work, make conflicting edits, and the parent now has to reconcile them. Delegation pays when the subtasks are genuinely independent and the return value is small. Otherwise a single well-resourced context is cheaper.
- docsCreate custom subagents ↗
Specialist agents with their own context, tool restrictions and permission scoping — subagent delegation as a product feature.
- blogHow we built our multi-agent research system ↗
Production account of a lead-agent plus subagents architecture, including when delegation helps and what the coordination costs are.
- docsTools — Agents SDK ↗
The full tool taxonomy in one place: hosted tools, runtime tools, function tools, agents-as-tools, shell, computer use, and programmatic tool calling.
Agent
A model given tools, a goal and permission to keep going on its own.
Harness · Scaffold
Everything around the model that makes it an agent.
Handoff
Passing work to a fresh context, deliberately and with a written brief.
Context
Everything the model can currently see.
Progressive Disclosure
Reveal detail only when it becomes relevant.