mcpb

mcpb is a small macOS CLI for launching Chromium-based browsers in MCP-compatible mode.

It looks up browsers dynamically from /Applications and ~/Applications, restarts them when needed, launches them with a dedicated MCP profile, and prints ready-to-paste config snippets for Claude Desktop, Claude Code, and Codex.

Features

• Runtime browser discovery with no hardcoded list of installed apps
• Case-insensitive browser selection through mcpb open --<browser>
• Safe restart prompt when the browser is already running
• Dedicated user-data directory for MCP mode
• Ready-to-paste config snippets for common MCP clients

Requirements

• macOS
• A Chromium-based browser installed in /Applications or ~/Applications
• Rust 1.86+ to build from source

Install

Build and install from the repository:

cargo install --path .

If you prefer a local dev build without installing:

cargo run -- open --<your browser name>

Usage

Open a browser in MCP mode:

mcpb open --<your browser name>

Override the debug port:

mcpb open --<your browser name> --port 9333

When the browser is already running, mcpb asks for confirmation before restarting it:

Browser "<your browser name>" must be restarted for MCP mode. Close it now? [Y/n]

On success it prints:

• the local debug endpoint
• a Claude Desktop JSON snippet
• a claude mcp add-json command for Claude Code
• a config.toml block for Codex

Supported Matching

The browser flag is matched case-insensitively against:

• the .app bundle name
• CFBundleName
• CFBundleExecutable

Examples:

• mcpb open --brave
• mcpb open --BrAvE
• mcpb open --dia
• mcpb open --chrome

Development

Run the test suite:

cargo test

Format the code:

cargo fmt

Notes

• mcpb is intentionally macOS-only in its current version.
• It always uses a dedicated MCP browser profile instead of your default browser profile.
• Malformed .app bundles are skipped during discovery instead of breaking the command.