Install and set up
There are two ways to use Studio, and both read and write the same
.stuntdouble/ files in your project:
- From your coding agent. Install the plugin once, then set up each project. Your agent's session is the actor.
- In your browser. Run
npx stuntdouble studioin a project, on a model connection you set up.
Before you start
- Node 22.18 or later. Check with
node --version. - Google Chrome. Or Playwright's Chromium, if you'd rather not install
Chrome (
npx playwright install chromium). - A coding agent or a model key. Claude Code gets the full plugin: the
local server, the Studio commands
(
/stuntdouble:setup,/stuntdouble:runand the rest) and the cloud runs server. Studio in your browser needs an Anthropic API key or an OpenAI-compatible endpoint instead.
Install in Claude Code
Add the plugin
claude plugin marketplace add stunt-double/stuntdouble-mcp
claude plugin install stuntdouble@stuntdoublePlugins load when a session starts, so start a new Claude Code session after installing.
Set up your project
Open Claude Code in your project folder and run:
/stuntdouble:setupSetup runs doctor first and tells you how local runs are billed. It then asks for three things:
- the URL to test (localhost is fine),
- who the user is,
- what must be true when they're done.
From your answers it writes .stuntdouble/ with an actor, a checklist of 3 to
8 checks and a .gitignore. See files and commands
for what each file holds.
Run it
/stuntdouble:run <checklist>Replace <checklist> with the checklist's file name, without .json.
Run a checklist explains what happens next.
Other agents
Any MCP client can start the local server over stdio:
npx -y stuntdouble mcpAdd that command as a stdio server in your client's MCP settings. The
/stuntdouble: commands are Claude Code plugin commands, so in other clients
ask your agent to set up and run a checklist in plain words.
The package is stuntdouble on npm,
under the Apache-2.0 license.
Open Studio in your browser
In your project folder, run:
npx stuntdouble studioStudio opens on 127.0.0.1 and covers setup, actors and checklists, runs,
the live view and results. A project with no .stuntdouble/ yet asks for the
address to test and starts you with a first actor and checklist to edit.
Set the model in Settings: an Anthropic API key (or ANTHROPIC_API_KEY from
your environment), or an OpenAI-compatible endpoint such as OpenAI,
OpenRouter, or a local model in Ollama or LM Studio. The key stays in
~/.stuntdouble/credentials.json, readable by you only, and never goes into
the project. Studio never uses a Claude subscription.
A run your agent starts shows up in Studio, and the other way round. To run a checklist from the terminal on the same connection:
npx stuntdouble run <checklist>No account needed
Studio never asks you to sign in. You only need a Stunt Double account when you move a checklist to cloud runs.