# Chunk by CircleCI

> Chunk is CircleCI's inner-loop platform: it validates AI-generated code before it reaches CI. Chunk sidecars sync your local working tree to a clean Linux microVM on CircleCI and run your tests there, so a coding agent gets deterministic pass/fail feedback while it works, not after a full pipeline run.
>
> Chunk works with Claude Code, Cursor, or any AI coding agent, and is driven by the Chunk CLI and a set of agent skills. Agents setting Chunk up for a user should start with **Get Started**, then load the skills in **Agent Skills**.

## Get Started

- [Install and configure the Chunk CLI](https://circleci.com/docs/guides/toolkit/install-and-configure-the-chunk-cli/index.md): Install with `brew install CircleCI-Public/circleci/chunk`, initialize a project with `chunk init`, and authenticate with `chunk auth set circleci`.
- [How to use the Chunk CLI](https://circleci.com/docs/guides/toolkit/how-to-use-chunk-cli/index.md): Commands for initializing projects, managing sidecars, running validations, generating review prompts, and installing agent skills.
- [Chunk CLI on GitHub](https://github.com/CircleCI-Public/chunk-cli): Source, releases, and issue tracker for the CLI.

## Agent Skills

- [Chunk plugin](https://github.com/CircleCI-Public/skills/tree/main/plugins/chunk): The `chunk` plugin in the CircleCI Skills repository. Installs in Claude Code, Codex, or any agent that reads SKILL.md.
- [chunk-sidecar-setup](https://github.com/CircleCI-Public/skills/blob/main/plugins/chunk/skills/chunk-sidecar-setup/SKILL.md): First-time onboarding: authentication, org ID, sidecar creation, dependency installation, and snapshot creation.
- [chunk-sidecar](https://github.com/CircleCI-Public/skills/blob/main/plugins/chunk/skills/chunk-sidecar/SKILL.md): The validation dev loop: sync edits to a sidecar and run tests there. Also covers snapshots, custom sidecar images, and scaffolding `.circleci/test-suites.yml` for Smarter Testing.
- [chunk-review](https://github.com/CircleCI-Public/skills/blob/main/plugins/chunk/skills/chunk-review/SKILL.md): Reviews a local diff or GitHub PR against the team's review standards in `.chunk/context/review-prompt.md`.
- [chunk-testing-gaps](https://github.com/CircleCI-Public/skills/blob/main/plugins/chunk/skills/chunk-testing-gaps/SKILL.md): Mutation testing that runs mutants on parallel sidecars to find code paths your tests don't cover.
- [chunk](https://github.com/CircleCI-Public/skills/blob/main/plugins/chunk/skills/chunk/SKILL.md): General Chunk CLI reference for setup, authentication, validation, and skill installation.

## Learn More

- [Chunk by CircleCI](https://chunk.ai/): Product page with the three-step quickstart and use cases.
- [Introducing Chunk sidecars](https://circleci.com/blog/chunk-sidecars/): Why inner-loop validation matters for agent-written code and how sidecars work.
- [Chunk sidecar and microbuilds now available on every CircleCI plan](https://circleci.com/changelog/chunk-sidecar-and-microbuilds-now-in-preview-for-performance-and-scale-plans/): Availability announcement.
- [Chunk demo video](https://www.youtube.com/watch?v=aYcyUc3SJcs): Walkthrough of sidecars in an agent session.
- [CircleCI](https://circleci.com/llms.txt): Index for the CircleCI CI/CD platform that Chunk runs on.