Claude Browser

Multiple persistent browser tabs inside VS Code, drivable by Claude over MCP.

Open GitHub in one editor group and a Claude terminal in another. Stay signed in across restarts. Let Claude read and click the same page you are looking at, without leaving the editor.

What it does

• Many tabs, not one. Each browser tab is an editor tab, so it splits, drags between groups, and reopens where you left it.
• Sessions persist. Cookies and local storage survive a restart and are shared by every tab, so signing into Slack once is enough.
• Sites that refuse to be framed still work. GitHub, Slack and Google all send X-Frame-Options: DENY, which is why the built-in Simple Browser cannot show them.
• Claude drives it. The extension hosts an MCP endpoint with tools to list tabs, navigate, snapshot a page, click, type, and read the console.
• It is a real DOM. Not a video stream of a browser: input latency is native, text selection and the find widget work, and audio plays.

Getting started

yarn install
yarn build

Press <kbd>F5</kbd> to launch an Extension Development Host, then run Claude Browser: Open Browser Tab from the command palette.

To let Claude drive it, open a terminal in the same window and run claude. The extension writes its endpoint into the workspace .mcp.json, so the tools are there already. Run Claude Browser: Show MCP Endpoint if you would rather register it by hand.

Commands

Command	What it does
Claude Browser: Open Browser Tab	Opens a URL in a new tab.
Claude Browser: Open Browser Tab to the Side	Same, in the group beside the current one.
Claude Browser: Open Bookmarked Site	Picks from claudeBrowser.bookmarks.
Claude Browser: Reload Active Tab	Reloads the focused tab.
Claude Browser: Zoom In / Zoom Out / Reset Zoom	Scales the page only, not the editor. Remembered per site.
Claude Browser: Open Active Tab in System Browser	Hands the current URL to the OS.
Claude Browser: Sign Out of Everything	Clears stored cookies and mirrored storage.
Claude Browser: Show MCP Endpoint	Shows the endpoint URL and the claude mcp add command.
Claude Browser: Show Log	Opens the output channel.

Settings

Setting	Default	Purpose
claudeBrowser.homepage	https://github.com	Opened when no URL is given.
claudeBrowser.bookmarks	GitHub, Slack	Sites in the Bookmarks view.
claudeBrowser.proxyPort	41998	Loopback port for the proxy. Changing it resets page storage.
claudeBrowser.mcpPort	41999	Loopback port for the MCP endpoint.
claudeBrowser.writeWorkspaceMcpConfig	true	Write the endpoint into the workspace .mcp.json.
claudeBrowser.allowScriptEvaluation	true	Expose the evaluate_script tool.
claudeBrowser.mirrorLocalStorage	true	Copy each site's local storage into extension storage.

How it works, in one paragraph

A VS Code webview is a sandboxed iframe, and the sites worth keeping open refuse to be framed. So the extension runs a local rewriting proxy: each site is served from its own loopback origin such as github.com.s.localhost:41998, with the framing and transport headers rewritten on the way through. Cookies never reach the browser at all; the proxy holds them and re-attaches them upstream, which is the only way __Host- prefixed session cookies can survive being served from a different origin. A small shim is injected into every page to reroute its network calls, keep navigation on the proxy, and carry out commands from MCP tools.

The details, and the things this approach cannot do, are in docs/.

Documentation

• Architecture — the pieces and how they talk
• Proxy — origin mapping, header rewriting, the page shim
• Persistence — where sessions live and what survives what
• MCP — the tools and how to connect
• Security — the threat model and the request guard
• Limitations — what does not work, and why
• Development — building, testing, releasing