Claude Code Subagents — Delegate Work, Keep Context

Every Claude Code session has a single context window. The longer you work, the more it fills with search results, file contents, and exploration noise. Subagents fix this.

A subagent runs in its own context window. It does the work, returns a summary, and the exploration stays out of your main conversation. Think of it as handing a task to a colleague who reports back with the answer, not the journey.

Claude Code ships with three built-in subagents:

- Explore — runs on Haiku (fast, cheap), read-only. Use it for file discovery and codebase search without polluting your main context.

- Plan — read-only research agent that gathers context before presenting a plan. Activates automatically in plan mode.

- General-purpose — full tool access, inherits your model. For complex multi-step tasks that need both reading and writing.

You can also define custom subagents. They're markdown files with YAML frontmatter — same format as skills. Drop one in ~/.claude/agents/ and it's available in every project.

What makes custom subagents powerful:

1. You control which tools they can access (read-only reviewer, write-capable fixer, etc.)

2. You can route them to cheaper models — Haiku for exploration, Sonnet for analysis

3. Each gets a focused system prompt so it stays on task

4. They can't spawn other subagents, which prevents infinite nesting

The mental model: delegate when the side work would flood your context with stuff you won't reference again. Research, verification, batch processing, code review — all good candidates. Keep implementation and decision-making in your main session.

One detail worth knowing: subagents work within a single session. If you need multiple agents running in parallel and communicating with each other, that's agent teams — a different pattern entirely.

Full docs: https://code.claude.com/docs/en/sub-agents

I wrote a deeper walkthrough on skills and agent architecture here: https://kjetilfuras.com/claude-code-agent-skills/

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