Tandem Browser

A programmable workspace where human intent and AI capability meet — on the web that already exists.

Tandem is a local-first Electron browser that shifts the AI from a sidebar next to your browser into the browser itself. Same tabs, same cookies, same logged-in sessions, same page you are looking at right now. The agent reads the accessibility tree, watches the live network, can rewrite the UI of the site you are on, and hands back to you when something needs a human. You are both in one runtime.

That shift matters because it is what makes a bunch of things actually possible for the first time:

• Automate real SaaS without an API — Gmail, Coolblue, Funda, your bank's portal, your internal admin tool. If you can use it in a browser, your agent can use it in Tandem, in your real logged-in session.
• Rewrite live UI on any site — “add a price-per-square-meter column to this listing view” becomes a userscript the agent injects into the real page while you keep scrolling.
• See beyond pixels — accessibility tree + DOM + live network log + DevTools. The agent can answer “what API did this page just hit and what came back?” without anything leaving your machine.
• Real co-browsing — you and one or more agents in the same browser at the same time, across tabs and workspaces, with tab locks and explicit handoffs.
• Cold-start usable — point a capable model (Claude, Cursor, a local Ollama model) at a fresh Tandem install and a normal web task works on day one. No per-site recipes to author, no retrain-per-flow phase.
• Bring any AI — Tandem is model-agnostic. Any agent that speaks MCP or HTTP works — Claude, GPT, Gemini, local Ollama, LM Studio, custom scripts. Swap models when a cheaper or faster one ships. Run two at once. Go fully offline with a local model. The browser doesn't care which brain you plug in.

It works on the web that already exists — no site has to opt in, no new protocol has to land. Agents connect on the same machine or remotely over Tailscale, and multiple agents can share one browser without stepping on each other. An 8-layer security perimeter sits between web content and the agent layer, because when an AI has access to a real browser, a hidden instruction in a page is remote code execution without an exploit.

Connect via MCP (Claude Code, Claude Desktop, Cursor, Windsurf, Ollama, any MCP client) or a 300+ endpoint HTTP API. The everyday version of the pitch: it feels like going on the internet with a brilliant teammate — not like using a chatbot parked next to a browser.

What Tandem is not

• Not an AI sidebar. A chat panel next to a browser still leaves the AI outside the page.
• Not RPA or pixel automation. No brittle coordinates, no record-and-replay macros. The agent works with structure.
• Not screenshot-driven automation. Screenshot loops are slow, fragile, and expensive. Tandem gives the agent the page as semantic structure first.
• Not just another Chromium wrapper. This is a daily-driver browser with a serious security perimeter around a first-class agent layer.
• Not “chat with this webpage.” The agent opens tabs, fills forms, logs in, hands back for a CAPTCHA, injects a userscript, and comes back to finish — as one continuous piece of work.
• Not a cloud service. Your browser, your machine, your sessions, your data. There is no Tandem backend.

What's new now

Tandem Browser now supports:

• local MCP and local HTTP access
• remote MCP over Tailscale
• remote HTTP over Tailscale
• multiple agents connected to the same browser at once
• in-product pairing and onboarding through Settings -> Connected Agents

Want the fastest path in?

• Try Tandem locally -> Quick Start
• Read the docs and API surfaces -> docs/ and docs/INDEX.md
• Ask questions or share workflows -> GitHub Discussions
• Support development -> GitHub Sponsors

What Can An Agent Do?

257 tools total — full parity with the HTTP API.

Why Not Just Use Playwright?

Playwright gives you a headless browser that you control. Tandem Browser gives you the user's real browser — their tabs, their sessions, their cookies, their extensions. The agent doesn't start from scratch; it joins what's already there.

Plus:

• Security model: 8 layers between web content and the agent, including prompt injection defense. Playwright has none.
• Shared context: the agent sees what the human is doing and vice versa
• Stealth: websites see a normal Chrome browser, not an automation tool
• Background tabs: operate on any tab without stealing focus
• Human-in-the-loop: captchas, risky actions, and ambiguous cases go back to the human

Tandem Browser vs WebMCP

WebMCP is an important new idea, but it solves a different layer of the stack.

WebMCP helps websites become more agent-readable. Tandem Browser helps humans and agents work together in the real browser, across the web.

These ideas can coexist. Tandem Browser is not anti-WebMCP. If more sites expose cleaner agent surfaces, great. But Tandem Browser's job is broader: shared human-AI browser work, local-first control, and governance around what the agent is doing.

For the longer version, see docs/tandem-browser-vs-webmcp.md.

Quick Start

macOS Apple Silicon (M1+) — download the signed and notarized binary:

Download Tandem Browser v1.0.0 →

1. Open the .dmg, drag Tandem Browser to Applications, launch it
2. Open Settings → Connected Agents and scroll to Connect your AI to Tandem
3. Choose On this machine or On another machine
4. Click Generate connection instructions
5. Click Copy instructions and paste into your AI agent

That's it. Tandem publishes its own bootstrap surface — the agent reads /agent and connects automatically.

Windows 11 x64 — download the installer or portable build:

Download Tandem Browser v1.11.0 →

Windows builds are official Tandem Browser downloads, but they are currently unsigned. Windows may show an unknown publisher or SmartScreen warning during install. Code signing is planned, but Windows is supported now.

Building from source

For Linux, Windows, macOS, or if you want to hack on Tandem itself:

git clone https://github.com/hydro13/tandem-browser.git
cd tandem-browser
npm install
npm start

macOS and Windows are supported platforms. Linux is best-effort.

Start Here

Depending on what you want t