Quick start

The harness ships as a Claude Code plugin. Install it once per product repo, at project scope, and commit the settings file. Everyone who opens that repo in Claude Code and trusts the folder then gets the same skills, the same design reviewer, and the same catalogue.

Before you start

You need Claude Code installed and signed in. Open a session at the root of your product repo, not a subdirectory — skills read the repo they run in, and a session opened deeper may not trigger them.

Add the harness

These are the steps for Claude Code in the terminal or a code editor. On the desktop app, follow the desktop steps instead.

Run two commands in your Claude Code session, one at a time — send the first and wait for it to finish before you send the second. Pasted together they read as a single command and the install never runs.

First, register the harness repository as a plugin marketplace:

/plugin marketplace add transformteamsg/dx-harness

Then install the dx-harness plugin from it:

/plugin install dx-harness@dx-harness

The command opens the plugin's details and asks you to choose a scope. Select Install for all collaborators on this repository (project scope). Claude Code records the plugin in .claude/settings.json.

That gives you the skills, the design reviewer agent, and the catalogue. The catalogue ships inside the plugin, so your repo never carries its own copy of the standard.

Verify the installation

Type /dx-harness:dx-design. It asks what you want and routes you to the right skill; if it responds, the install worked.

If nothing happens:

• Confirm dx-harness appears and is enabled — run /plugin in the terminal, or in the desktop app select + next to the prompt box, then Plugins.
• Confirm your session is open at the repo root, not a subdirectory.
• Restart Claude Code and try again.

Share it with your team

The install turns the plugin on in .claude/settings.json. Add the harness marketplace to the same file, so it holds both entries:

{
  "extraKnownMarketplaces": {
    "dx-harness": {
      "source": { "source": "github", "repo": "transformteamsg/dx-harness" }
    }
  },
  "enabledPlugins": {
    "dx-harness@dx-harness": true
  }
}

Commit the file. When a teammate opens the repo in Claude Code and accepts the workspace trust dialog, Claude Code registers the marketplace and loads the plugin from it. They don't run an install command.

If the plugin doesn't load for a teammate, they can install it once, in a terminal:

claude plugin marketplace add transformteamsg/dx-harness

claude plugin install dx-harness@dx-harness --scope project

Teammates on the desktop app follow the desktop steps instead.

Install on the Claude Code desktop app

In the desktop app, plugins live in the Code tab's local sessions, under the + button next to the prompt box. A local session also has an integrated terminal, which opens in your session's folder. Open it from the Views menu.

A cloud session, including Claude Code in the browser at claude.ai/code, has no plugin browser. It doesn't load the plugins you install on your machine or the ones your repo's .claude/settings.json turns on.

1. In the Code tab, start a local session and pick your product repo's root folder.

2. Register the harness marketplace. Open the integrated terminal and run:

   claude plugin marketplace add transformteamsg/dx-harness

   This needs the claude command. If the terminal can't find it, install Claude Code for the terminal with its setup guide. The app's local sessions read the same settings files as the terminal.

3. Select + next to the prompt box, then Plugins, then Add plugin. The plugin browser lists plugins from the marketplaces you've added. Select dx-harness and choose this project as the scope.

4. Type / in a chat to choose a skill, or send /dx-harness:dx-design.

+ → Plugins also lists your installed plugins, and Manage plugins enables, disables, or uninstalls one. To update, run the Stay current terminal commands in the integrated terminal. Where this page says restart Claude Code, quit and reopen the app.

Then continue with the one-time machine setup below.

Set up your machine, once

You don't have to do this before you start. The plugin is turned on per repo, but a few tools are per machine. When you ask /dx-harness:dx-design to shape something, it checks two things first: that the agent-browser command is available, and that your repo has a DESIGN.md. If the command is missing, it sends you to setup. If DESIGN.md is missing, it offers to define your design language.

It doesn't check the rest of your machine. Run /dx-harness:dx-design-setup to verify the complete checklist. It runs each check and asks before it installs anything. The checklist includes:

• agent-browser — captures the screenshots the verify phase grades.
• gh, authenticated — lets /dx-harness:dx-design-feedback file an issue the moment the harness confuses you.
• Python with PyYAML — runs the deterministic check scripts.
• Commit signing — set up once per machine.
• The design-ticket tracker — wired to your repo.

Stay current

Plugin updates are manual: auto-update is off by default for a third-party marketplace like this one. When the catalogue or the skills change, update in two steps. On the desktop app, run the terminal commands in the integrated terminal.

First, refresh the marketplace's listing. This updates the list of plugins, not the plugin you installed. Run this in a Claude Code session:

/plugin marketplace update dx-harness

Or run this in a terminal:

claude plugin marketplace update dx-harness

Then update the plugin itself. Open it on the Installed tab in /plugin and select Update now, or run this in a terminal:

claude plugin update dx-harness@dx-harness

On Claude Code versions before 2.1.281, add --scope project to that command. The new version loads in your next session, or after you run /reload-plugins.

The skills and the catalogue are versioned together, so one update moves both.

Adopt the harness for a whole product repo

Installing gives you the tools. Making a repo harness-ready is six more items: declared product context, a component manifest, skills verified, deterministic checks, record locations, and a named waiver approver. Work through them once per repo.

If you work on the harness itself, open Claude Code in the harness repo and skip all of this — its skills load automatically from the repo.