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io.github.sushruth/zen-devtools-mcp

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Attach firefox-devtools-mcp to your running Zen or Firefox, auto-restarting with Marionette.

Source code Documentation

Install

The installation steps are in the documentation below. Documentation

Documentation

From the project's README on GitHub, refreshed weekly. Links open on GitHub.

Contents
  1. zen-devtools-mcp
  2. Install / run
  3. Options
  4. MCP client config
  5. Notes

zen-devtools-mcp

Wraps @mozilla/firefox-devtools-mcp so it attaches to your already-running Firefox-based browser — Zen Browser, Firefox, or any fork — instead of launching a throwaway instance.

The upstream --connectExisting mode requires the browser to have been launched with Marionette enabled. Plain relaunches (clicking the dock icon, open -a Zen) don't set that, so attaching fails. This wrapper fixes that: if Marionette isn't up, it gracefully quits the browser (session restore keeps your tabs), relaunches it with --marionette, waits for the port, then starts the MCP.

Install / run

No install needed — run it straight from GitHub:

npx github:sushruth/zen-devtools-mcp
bunx github:sushruth/zen-devtools-mcp

Options

FlagDefaultWhat it controls
--appZenmacOS app name for open -a / quit
--processzenprocess name for pgrep -x
--port2828Marionette port to probe and listen on

Examples:

# Firefox instead of Zen
npx github:sushruth/zen-devtools-mcp --app Firefox --process firefox

# Zen with a custom Marionette port
npx github:sushruth/zen-devtools-mcp --port 2829

MCP client config

OpenCode example:

"zen-devtools": {
  "type": "local",
  "command": ["npx", "-y", "github:sushruth/zen-devtools-mcp"],
  "enabled": true
},
"firefox-devtools": {
  "type": "local",
  "command": ["npx", "-y", "github:sushruth/zen-devtools-mcp",
              "--app", "Firefox", "--process", "firefox", "--port", "2829"],
  "enabled": true
}

Claude Code (claude mcp add-json zen-devtools '<json>' or .mcp.json):

"zen-devtools": {
  "command": "npx",
  "args": ["-y", "github:sushruth/zen-devtools-mcp"]
}

Notes

  • Session restore preserves tabs across wrapper-triggered restarts.
  • Marionette can't be enabled on a live browser process — a restart is unavoidable the first time.
  • macOS-only (open, osascript, pgrep).
  • Passes --connectExisting --enableScript to the underlying MCP; it inherits stdio from its parent.

Frequently asked questions

What is io.github.sushruth/zen-devtools-mcp?

Attach firefox-devtools-mcp to your running Zen or Firefox, auto-restarting with Marionette.

How do I install io.github.sushruth/zen-devtools-mcp?

Follow the installation steps in its documentation, shown on this page and in its repository.

Is io.github.sushruth/zen-devtools-mcp open source?

Yes. Its code is on GitHub under the MIT license.

Who maintains io.github.sushruth/zen-devtools-mcp?

It is published by sushruth. AI.tn lists it but does not maintain or endorse it.

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