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Variance Authority

Open-source tools for developers and coding agents: source intelligence, live test inspection, test selection and reduction, UI analysis, and change verification.

For agents: Open-source tools for developers and coding agents covering test selection, live test inspection, UI analysis and change verification, with docs and agent skill

test inspectiontest selectioncoding agentschange verificationopen source

Their llms.txt

The beginning of the file, from our validated copy saved 2026-10-23T12:03:01.544Z. Cached copy · Source on variance-authority.dev

# Variance Authority

> Open-source tools for developers and coding agents: source intelligence, live test inspection, test selection and reduction, UI analysis, and change verification.

Every documented page serves the Markdown it is built from beside it:
append `/index.md` to the page's path. Links within that Markdown point at
the Markdown of the page they name.

## Start here

- Install the CLI: `npm install --save-dev @variance-authority/cli`. It installs the `variance` command and ships the agent skills under `node_modules/@variance-authority/cli/skills/`.
- [Link the agent skills](https://variance-authority.dev/agents/cli/index.md#point-an-agent-at-it) into your agent's own skills directory.
- [Choose an agent workflow](https://variance-authority.dev/agents/index.md): Three questions with three different owners: a hung test, a screenshot that changed, and a symbol you cannot name. Only the last can be answered without a run behind it. Each is matched below to the reading it needs and the guide that sets that reading up.
- [Visual review integrations](https://variance-authority.dev/start/index.md): One question picks your guide: which harness already puts the app in the UI state you want to review — a Playwright spec, a built Storybook, a served route, a jsdom unit test, Vitest browser mode, an Rstest suite, or a mount nobody else owns. Whichever row of the table below you land on ends the same way: that state gets a baseline image you approved, and a later run that moves pixels reports the component that drew them and the file:line it was written at.
- [Source](https://github.com/Variance-Authority/variance-authority): every package's README, beside the code it documents.

## Examples

Repositories to clone and run, each installing the published packages.

- [example-playwright](https://github.com/Variance-Authority/example-playwright): visual review from inside a Playwright test
- [example-storybook](https://github.com/Variance-Authority/example-storybook): visual review of every story in a Storybook
- [example-vitest](https://github.com/Variance-Authority/example-vitest): visual review from a unit test
- [example-running-app](https://github.com/Variance-Authority/example-running-app): visual review against an application that is already running
- [example-static-site](https://github.com/Variance-Authority/example-static-site): visual review of a built static site
- [example-divergence](https://github.com/Variance-Authority/example-divergence): one input rendered two ways, and where the renderings part
- [example-history](https://github.com/Variance-Authority/example-history): what a design token has drifted to across many approved reviews
- [example-tribunal](https://github.com/Variance-Authority/example-tribunal): a storefront read twice and reviewed once in the review console
- [example-workers](https://github.com/Variance-Authority/example-workers): test selection across Cloudflare Workers, joined by a Sentry trace
- [example-tester-
…

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