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Claude Code Atlas · free subagent library

Download a specialist. Run it for free.

Choose a focused helper for research, review, testing, debugging, or documentation. Download the complete file, place it in your project, and ask Claude Code to use it.

Browse free subagents Build my own
The short version

One bounded job. Its own context. A concise result returned.

No account, payment, repository upload, or ceremonial comment beneath a video required.

  • Preserve context

    Keep noisy exploration out of the main conversation.

  • Limit capability

    Give a specialist only the tools needed for its job.

  • Specify the return

    Define what evidence and conclusion must come back.

Three steps. No platform to join.

Download. Place. Ask.

The files are plain Markdown. You keep them, inspect them, edit them, and remove them whenever you like.

  1. 01

    Download the agent

    Choose one of the ready-made specialists below and download its complete .md file.

  2. 02

    Put it in your project

    Place the file inside .claude/agents/. Create the folders if they do not already exist.

  3. 03

    Ask Claude to use it

    For example: “Use the code-reviewer subagent to review the changes I just made.”

Review an agent’s instructions and permissions before you run it. Free does not mean infallible.

Ready-made and free to keep

Eight useful specialists. None with a blank cheque.

Each agent starts with the smallest practical permission set. Download it as supplied, or open it in the builder and change the brief before you install it.

  1. 01

    Read-only researcher

    Investigates a codebase and returns evidence without changing files.

    Use when
    You need file discovery, dependency tracing, or an answer supported by repository evidence.
    Do not use when
    The answer is already in the main conversation or the task requires implementation.
  2. 02

    Code reviewer

    Reviews a completed change for correctness, risk, and maintainability.

    Use when
    A meaningful change is ready for an independent read-only review.
    Do not use when
    You still need the same worker to implement the change it is reviewing.
  3. 03

    Bug investigator

    Traces a reproducible failure and proposes the most likely cause.

    Use when
    You have observed behaviour, expected behaviour, reproduction steps, or logs.
    Do not use when
    The problem statement is still too vague to identify a testable failure.
  4. 04

    Test planner

    Finds risk boundaries and proposes tests before implementation begins.

    Use when
    You want acceptance criteria and meaningful coverage before code is changed.
    Do not use when
    The task is a trivial, already-covered mechanical edit.
  5. 05

    Security checker

    Reviews a bounded surface for trust, secrets, permissions, and abuse paths.

    Use when
    A change touches authentication, input handling, data access, secrets, or external tools.
    Do not use when
    You need a formal penetration test or compliance certification.
  6. 06

    Documentation verifier

    Checks a product claim against current first-party documentation.

    Use when
    Commands, APIs, product behaviour, or version-specific claims may have changed.
    Do not use when
    The question can be answered solely from stable repository code.
  7. 07

    Accessibility reviewer

    Reviews interface code and rendered behaviour against practical accessibility checks.

    Use when
    A UI feature is ready for keyboard, semantics, contrast, and responsive review.
    Do not use when
    No interface or rendered behaviour is available to inspect.
  8. 08

    Performance auditor

    Finds measurable loading, rendering, and bundle bottlenecks.

    Use when
    A page or workflow has a defined performance concern and can be measured.
    Do not use when
    There is no baseline, route, or workload against which to compare.

Subagent Lab

Decide. Build. Check.

Use only the part you need. Everything runs in this browser; Sirrius Atlas does not receive your configuration.

Mark every statement that is true

Use the right context boundary

Not everything called an agent is the same thing.

Choose based on how long the work runs, whether it must report into the current conversation, and whether workers need to coordinate with each other.

  • Subagent

    Best use

    One focused side task inside the current session

    What comes back

    A result to the parent conversation

  • Forked skill

    Best use

    A reusable procedure that should run in isolated context

    What comes back

    The skill’s result to the invoking flow

  • Background agent

    Best use

    A separate, longer-running session

    What comes back

    A session you monitor or attach to

  • Agent team

    Best use

    Several sessions that communicate and coordinate

    What comes back

    Coordinated work across teammates

Product facts are based on current official Claude Code documentation. Version-specific fields should still be checked against your installed release.Read the official subagent documentation ↗

Subagents · questions answered

Before you install a specialist.

The context boundary, file location, permission model, and privacy details worth understanding before you copy a definition.

01Are the downloadable subagents really free?

Yes. The ready-made subagent files are free to download, inspect, edit, and use. No account or email address is required. You still need access to Claude Code, whose own plan or usage charges are separate from Sirrius Atlas.

02What is a Claude Code subagent?

A subagent is a specialized AI assistant that handles a focused task in its own context window and returns a result to the parent conversation. A custom subagent can have its own instructions, tool access, model, permissions, skills, memory, and execution settings.

03When should I use a subagent?

Use a subagent when a bounded side task would fill the main conversation with file reads, search results, logs, or other working context that will not be needed later. Keep small, tightly connected work in the main conversation.

04Does the Subagent Lab access my repository?

No. The generator and checker run entirely in your browser. Sirrius Atlas does not receive your configuration, access your repository, execute the definition, or connect to Claude Code.

05Where do custom subagent files go?

Project-specific subagents go in .claude/agents/ and can be committed with the repository. Personal subagents available across projects go in ~/.claude/agents/ on your machine.

06How do I run a downloaded subagent?

Place its Markdown file in your project’s .claude/agents/ folder, start Claude Code in that project, and ask Claude to use the named subagent for a bounded task. For example: “Use the code-reviewer subagent to review the changes I just made.”

07What is the safest tool configuration?

Start with the smallest allowlist that can complete the task. A research or review agent commonly needs Read, Grep, and Glob, and sometimes Bash. Add Edit, Write, skills, web access, or MCP servers only when the delegated job requires them.

08Is a subagent the same as an agent team?

No. A subagent handles a focused task within a session and reports a result to the parent. Agent teams are multiple sessions that can communicate and coordinate. Background agents and forked skills create different context and lifecycle boundaries again.

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