Newton Browser Host

Local MCP host for the Newton Browser extension.

Run

newton-browser

The host listens on 127.0.0.1:17321, exposes an MCP server over stdio, and relays commands to the loaded unpacked Newton Browser extension over localhost WebSocket. It has no database and no platform dependency.

Extension Pairing

1. Build the extension runtime:

   pnpm extension:build

2. Load unpacked from:

   apps/extension

3. Start this host process. The extension discovers the localhost host in the background; the popup only shows connected/disconnected status.

MCP Tools

The stdio server exposes the browser.* tools documented in the canonical skill.

MCP Client Config

Use the host as a stdio MCP server. Keep normal network access disabled for the calling agent when you want local-only operation; the extension and host only need localhost.

{
  "mcpServers": {
    "newton-browser": {
      "command": "npx",
      "args": ["-y", "newton-browser"]
    }
  }
}

Install the extension first, then use this npx configuration in Codex, Claude Code, Claude Desktop, or any compatible stdio client. Development can run the compiled apps/mcp-server/dist/index.js after pnpm build.

Privacy Boundary

The host and extension run on the user's machine. Browser control traffic stays on localhost. Page observations and screenshots only leave the machine if the calling agent sends them to its model provider.

Safety

The host runs the Newton Browser safety floor before relaying mutating actions. Blocked actions return a blocked result. Commit-like actions are relayed without a human approval prompt; Newton Browser is a local hands-and-eyes tool for the worker, not a moderation layer.