MCP Session Bridge

A free MCP (Model Context Protocol) server that exposes authenticated browser-session automation: session_* tools that run in the user's own Chrome profile and real logged-in session, which cloud browser APIs cannot do. A free standalone mode is also available; it launches a dedicated automation browser so the same session_* tools work without the extension or a license.

What it does

• Serves MCP over stdio (newline-delimited JSON-RPC) to any client that speaks the Model Context Protocol. The setup guide covers the common ones.

• Uses a dual-transport design:

  • Extension mode (free; Pro tools gated by the extension) — forwards calls over a local, owner-only relay socket to a native messaging host that Chrome spawns, and from there to the T3rnel Browser extension, which executes them against the live authenticated tabs.

  • Standalone mode (free) — launches its own headful or headless CDP browser on a persistent profile and drives it directly. No license, no extension, and no access to the user's everyday browser.

• Returns structured page context, form values, snapshots, and screenshots without shipping session cookies to a remote browser.

Related MCP server: Chromeflow

Price

The bridge itself is free, and this package enforces no licence of its own.

Extension mode reaches the buyer's real authenticated session through the T3rnel Browser extension, and the Pro tools it exposes are gated by that extension's own Pro tier — $29.99 once, three devices. Standalone mode is free and needs neither the extension nor a licence. There is no separate subscription for this package, and nothing here checks for one; earlier drafts of this file advertised $9/mo and $39/mo tiers that were never implemented, never enforced and never purchasable.

Project layout

• src/server.js — MCP stdio server: tool surface, schema validation, dual-transport routing, relay client with reconnect and timeouts, and standalone CDP launcher.

• src/cdp.js — standalone CDP browser management and WebSocket client.

• src/native-host.js — native messaging host spawned by Chrome; owns the relay socket and multiplexes concurrent MCP servers.

• src/framing.js — the 4-byte length-prefixed JSON framing shared by native messaging and the relay socket.

• src/tools.js — the session_* tool definitions, validation, and mapping to the extension's browser_* tools.

• src/license.js — offline Ed25519 license verification helpers used by the extension and tests.

• src/install.js — --install / --uninstall native host registration for Chrome, Chromium, Brave and Edge.

• docs/setup-guide.md — installing on the common MCP clients, plus verification and troubleshooting.

• docs/chrome-validation-checklist.md — end-to-end validation steps for Chrome with the T3rnel Browser extension.

• ads/ — ad-copy.md, the shared headline and description copy used when submitting to MCPize, Smithery, mcp.so and PulseMCP.

• tests/ — node --test suite, including end-to-end tests through a real relay socket and native-messaging framing, plus standalone-mode coverage.

Browser support

Extension mode needs the T3rnel Browser extension, which installs on Chrome, Brave, Edge and Chromium from one package. Opera implements no side-panel API and Firefox no debugger API, so both are partly supported; the extension's manifest generator states which capabilities are absent on each. Standalone mode has no browser requirement at all — it launches its own CDP browser.

The extension exposes 99 browser tools, all of which are reachable over this bridge subject to the extension's own Pro gating and its approval gate.

Supported clients

• Claude Code / Claude Cowork

• Cursor

• VS Code

• Windsurf / Devin Desktop

• Google Antigravity

• IntelliJ

• Codex

• Grok Build

• Kimi Code / Kimi Desktop

• JCode

• Cline

• OpenCode

• Continue.dev

• KiloCode

• Roo Code

• Aider

• OpenClaw

• Hermes

• OpenFang

• Any client that speaks MCP stdio

Install the T3rnel Browser extension

The bridge works best with the T3rnel Browser extension, which lets your AI drive the browser you are already signed into:

https://t3ratech.github.io/t3rnel-browser-plugin/

Licence

Source-available, not open source. See LICENSE for the terms.

In short: the published npm package is free to use for any purpose, commercial or otherwise; you may read and locally modify this source; you may not redistribute it or publish a derivative without written permission.

Directory listings that expect an SPDX identifier will report "no licence" for this repository. That is expected — GitHub detects the file and classifies it as other / NOASSERTION, because the terms are bespoke rather than one of the recognised open-source licences. The licence exists; it simply is not an OSI one.