Best Claude Code Subagents in 2026 (and How to Build Your Own)

The best Claude Code subagents are focused roles you delegate to: a planner, a code reviewer, a tester, a debugger, and a researcher. Each runs in its own context with its own tools, does one job well, and returns a clean result without flooding your main session. You define them as Markdown files in your .claude/agents/ folder, and you can write your own in a few minutes.

This guide ranks the roles worth setting up first, then shows you exactly how to build a custom one.

What a subagent actually is

A subagent is a specialized agent the main Claude Code session can hand a task to. It has its own instructions, its own allowed tools, and its own fresh context window. When the main agent delegates, the subagent works, returns a final message, and its intermediate tool output stays out of your main conversation.

That last part is the real win. A long search or a noisy test run can eat your main context. A subagent absorbs that noise and hands back only the conclusion. For the deeper design rationale, see sub-agent design and sub-agent best practices.

The 5 subagents worth setting up first

1. The planner

A planner takes a feature request and returns an ordered, step-by-step build plan: what to change, in what order, and what depends on what. You run it before any code is written. It keeps the main agent from charging into a large task without a map. Pair it with spec-driven development for the strongest results.

2. The code reviewer

A reviewer reads the diff with one job: find bugs, security gaps, and sloppy patterns. The trick is that it reviews with fresh eyes and a skeptical prompt, so it is not biased by the reasoning that produced the code. Give it read-only tools and a prompt that tells it to default to flagging anything uncertain.

3. The tester

A tester writes tests for new code and runs them, then reports pass or fail. Delegating this keeps the verify step honest: the agent that wrote the feature is not the one grading it. Test runs are also noisy, which is exactly the kind of output a subagent should absorb.

4. The debugger

When something breaks, a debugger subagent reproduces the failure, narrows it down, and reports the root cause. Debugging burns a lot of tool calls and dead ends, so isolating it in a subagent protects your main session from the clutter while still solving the problem.

5. The explorer

An explorer searches your codebase (or the web) to answer a question and returns a short summary instead of dumping every file it read. When answering means sweeping many files, this is the subagent that keeps the conclusion and throws away the noise. See task distribution for how to fan several of these out at once.

How to build your own subagent

A subagent is just a Markdown file in .claude/agents/. Here is a complete, working code reviewer you can drop in.

---
name: code-reviewer
description: Reviews the current diff for bugs, security issues, and risky patterns. Use after writing or editing code, before committing.
tools: Read, Grep, Glob, Bash
---

You are a skeptical senior code reviewer. Review only the current diff.

Focus, in order:
1. Correctness bugs that would break at runtime.
2. Security issues: missing auth checks, unsafe input handling, leaked secrets, missing row-level security.
3. Risky patterns: duplicated logic, swallowed errors, untested edge cases.

Rules:
- Default to flagging anything you are unsure about.
- Quote the file and line for every finding.
- Do not rewrite the code. Report findings only.

Your final message is the review. Return a short list of findings, each with file, line, severity, and a one-line fix. If the diff is clean, say so plainly.

The frontmatter does three things. name is the agent's id. description tells the main session when to delegate to it, so write it as a trigger ("use after writing code"). tools limits what it can touch; a reviewer only needs to read and search, so it gets no write access.

The body is the system prompt. Keep the role narrow, list the rules, and end by telling the agent that its final message is the return value, so it returns a clean result instead of a chatty summary. For more on this, see custom agents.

Three rules for good subagents

1. One job each. A subagent that does two things does both worse. Split it.
2. Least tools. Give it only the tools the job needs. A reviewer that cannot write code cannot accidentally change it.
3. Clean returns. Write the prompt so the final message is exactly the data the main session wants, not a paragraph about what it did.

Get those right and your main session stays clear while focused subagents do the heavy, noisy work. For coordinating several at once, read agent teams best practices. For the difference between a subagent and a forked session, see Claude Code fork and subagent.

Starting from a pre-built set

If you would rather not write every subagent from scratch, community collections like VoltAgent's awesome-claude-code-subagents bundle dozens of role definitions you can install and adapt. And if your goal is to ship a product, Build This Now is a $29 one-time Claude Code kit that ships specialist agents and a production stack together, so the planning, building, and testing roles are already wired around auth, payments, and a secure database.

FAQ

What is a Claude Code subagent? A subagent is a specialized agent with its own instructions, tools, and context window that the main session delegates a task to. It does its job, returns a result, and keeps its noisy tool output out of the main conversation. Subagents are defined as Markdown files in your .claude/agents/ folder.

How do I create a custom subagent in Claude Code? Create a Markdown file in .claude/agents/ with frontmatter for name, description, and allowed tools, followed by a system prompt describing its role and rules. Keep it narrow, give it only the tools it needs, and write the prompt so its final message returns exactly the result you want.

What are the most useful Claude Code subagents to set up? A planner, a code reviewer, a tester, a debugger, and a researcher or explorer. These cover the parts of building where a fresh, focused context beats one overloaded session.

How many subagents should I run? Set up the five core roles first, then add more only when a real, repeated task justifies it. Each subagent should have one clear job; a pile of overlapping agents is harder to manage than a few sharp ones.