Tab Hammer MCP Server

Tab Hammer

Tab Hammer is a Chrome extension that shows every open Chrome window, tab group, and tab as a live outline, in its own window or docked in Chrome's side panel. You can rename, rearrange, hibernate, and restore windows and tabs from the outline, see a screenshot preview of any tab before switching to it, carry your outline across computers through your own Google Drive, and let an AI agent like Claude Code organize your tabs through its MCP server.

Tab Hammer and Tabs Outliner

Tab Hammer is a spiritual successor to Tabs Outliner, the long-running extension that shows your tabs as an outline in its own window. If you've used Tabs Outliner, the core ideas will feel familiar: a dedicated outline window, closing a window without losing it, and bringing it back later.

Tab Hammer takes the same idea and builds on modern Chrome:

• Built for Manifest V3 and Chrome's native tab groups, which show up in the outline as groups.
• Hibernate and a Recently closed trash — hibernate a window or tab to close it in Chrome but keep it in the outline, dimmed, until you click it back open. Deleted rows go to a Recently closed section you can restore from for seven days.
• Previews — a screenshot of each tab, shown in a panel under the outline as you hover or move through it.
• Sync across computers through a hidden app-data folder in your own Google Drive, with daily checkpoints you can restore from. There's no Tab Hammer server.
• Your other Chrome Sync devices, phones included, in the same view.
• AI agent control through an MCP server, so an agent can list and rearrange tabs for you.

Features

• Float or dock — use the outline as its own floating window, or dock it in Chrome's side panel, where it opens in every window and marks the one it sits in. One button in the header switches between the two.
• A live outline of every window, tab group, and tab, kept in sync as you browse, with Tab Hammer's own IDs so a window keeps its name and place across a browser restart.
• Search tabs by title or URL.
• Shortcut — Alt+Shift+H (Option+Shift+H on a Mac) opens Tab Hammer or brings it to the front, like its toolbar button; change it at chrome://extensions/shortcuts.
• Keyboard and mouse — the search box works like a command palette: type anywhere to search, ↑/↓ to move the highlight (Shift to extend the selection), Cmd/Ctrl-↓ to open a tab or expand a window or group, Cmd/Ctrl-↑ to collapse or go up a level, Option/Alt-↑/↓ to move a window, Enter or double-click to switch to a tab (or reopen a hibernated one), Cmd/Ctrl-Backspace to move the selection to the trash, and Esc to clear the search, then the selection. Click, Cmd/Ctrl-click, and Shift-click select too.
• Drag and drop to move tabs, groups, and whole windows.
• Rename windows, and give each computer a name for your other computers to see.
• Hibernate a window or tab, and Move to trash, with a Recently closed section to restore from for seven days.
• Previews — a panel under the outline shows a screenshot of the tab you hover or move to. Previews are taken as you browse; Capture missing screenshots every tab without one and Refresh all re-captures every tab, one at a time in the background, with progress and a Stop button. Clear previews wipes them all.
• Close duplicates — close tabs whose page is already open in another tab.
• Copy all URLs — right-click a window to copy its tabs' URLs, one per line.
• Other devices — view another computer's outline, a checkpoint, or a Chrome Sync device read-only, then Open here (a copy) or Restore all (missing windows come back hibernated).
• AI agent control — see Connect an AI agent (MCP).

Install

Chrome Web Store: coming soon. Homepage: https://boltcreative.com/tab-hammer.

From source:

npm install
npm run build

Then in Chrome: chrome://extensions → enable Developer mode → Load unpacked → select the packages/extension/dist/ folder. Click the toolbar icon to open Tab Hammer.

Connect an AI agent (MCP)

Tab Hammer includes an MCP server, so an AI agent (Claude Code, Claude Desktop, Codex, Cursor, VS Code, Windsurf, or any other MCP client) can see every open window, group, and tab and rearrange them: "group my research tabs", "close the duplicates", "move everything about the trip into its own window". With the extension installed, set it up with one command (Node 20 or newer):

npx tab-hammer-mcp install

It registers Tab Hammer's native host with every Chromium browser it finds (Chrome, Chrome Beta/Dev/Canary, Chromium, Brave, Edge, Arc) and the MCP server with every agent it finds, on macOS, Linux, and Windows. Then reload Tab Hammer (or click its toolbar icon) so it connects, and restart your agent. Agents get these tools: list_tabs, focus_tab, open_tabs, move_tabs, group_tabs, ungroup_tabs, update_group, and close_tabs; most agents ask before running each one unless you allow it.

For an agent it doesn't know, install prints the config to paste (a node command and the server's path). npx tab-hammer-mcp with no command runs the MCP server itself over stdio, which is how MCP registries launch it.

How it fits together: the agent starts the MCP server; the browser starts a small native messaging host for Tab Hammer; the two meet on a local socket (~/.tab-hammer/bridge.sock, readable only by you; a per-user named pipe on Windows). Nothing runs unless the browser and the agent are. The installer copies the host and server to ~/.tab-hammer/mcp (%LOCALAPPDATA%\TabHammer\mcp on Windows), because macOS won't let a browser run programs from inside ~/Documents without a permission prompt and npx clears its cache; both run with the node you installed with, so re-run install if you move or remove that Node. Because it's a copy, updates arrive only when you re-run npx tab-hammer-mcp@latest install; doctor tells you when a newer version is out.

From a checkout, npm run install-mcp builds the package and runs the same installer. After that, npm run dev keeps the installed host and server up to date with the checkout's source (it never installs on its own).

Permissions

Tab Hammer asks for these when you install it:

• Read and change your tabs (tabs, tabGroups, webNavigation): to show every window, group, and tab in the outline, move and close them for you, and match the windows Chrome restores after a restart back to their rows.
• Access to all sites (<all_urls>): to screenshot the page a window is showing for its tab preview. You can withhold it; Tab Hammer then shows a banner offering to grant it, and works without previews until you do.
• Debugger (debugger): to screenshot background tabs. It's attached only while you run Capture missing or Refresh all, one tab at a time, so Chrome shows its "started debugging this browser" banner only during those runs (see below to hide it). Chrome doesn't allow this permission to be optional.
• Communicate with cooperating native applications (nativeMessaging): the bridge to an AI agent such as Claude Code. It does nothing unless you've installed the MCP server.
• storage, favicon, system.display, alarms, identity, sidePanel, and contextMenus, which add no install warning: settings, tab icons from Chrome's cache, keeping the window on a connected screen, checking for your other computers' outlines every 5 minutes, signing in to your own Google Drive for sync, the docked side-panel mode, and the toolbar icon's right-click menu.

Asked for only when you use the feature:

• Your other devices' tabs (sessions): the devices panel asks when you click Show your phones and other Chrome Sync devices.

Previews are stored only on your computer, and each is kept as long as a window in your outline (open, hibernated, or recently closed) still has a tab at that address.

Privacy

Tab Hammer has no server and collects nothing. Your outline and previews stay in your browser; if you turn on sync, your outline is stored in a hidden app-data folder in your own Google Drive that only Tab Hammer can read. Incognito windows and tabs are never captured. See the privacy policy for the details.

Hiding Chrome's debugging banner

Capture missing and Refresh all screenshot background tabs by briefly attaching Chrome's debugger, so Chrome shows a "started debugging this browser" banner while they run. Hover and everyday previews never attach it.

You can hide the banner by launching Chrome with the --silent-debugger-extension-api flag. The trade-off: it hides the banner for every extension that uses the debugger, not just Tab Hammer. On macOS, npm run make:chrome-launcher builds a small Google Chrome silent debugger.app in ~/Applications (pass another folder as an argument) that launches your normal Chrome, same profile, with that flag. Quit Chrome completely (⌘Q) and launch it from that app; to undo, launch Chrome normally.

Developing

npm install
npm run dev

The dev server writes the extension to ~/.tab-hammer/dist (set TAB_HAMMER_DEV_DIR to use another folder). Load that folder unpacked in chrome://extensions once; after that, most changes to the view or the service worker reload the running extension automatically.

The manifest has a fixed public key, so the extension gets the same ID wherever it's built: storage, previews, and permission grants carry over between builds, checkouts, and worktrees. To try a different checkout, stop npm run dev and start it in the other one; the running extension reloads onto the new build.

Before opening a pull request, run the completion gate:

npm run gate

It runs the typechecker, linter, formatter check, unit tests, and the end-to-end Playwright suite against a headless Chromium with its own throwaway profile. The gate builds into packages/extension/dist-e2e/, so it never touches the ~/.tab-hammer/dist build your Chrome is using.

See CONTRIBUTING.md for setup details and AGENTS.md for the architecture.

Repository layout

npm workspaces, one package per process:

• packages/extension — the Chrome extension (service worker, outline view, tests).
• packages/mcp — the tab-hammer-mcp npm package: the MCP server agents start, the native host the browser starts, and the installer.
• packages/protocol — the message types both sides compile against.
• docs/superpowers — design specs and implementation plans written while building Tab Hammer (historical records, not necessarily current).

Contributing

Contributions are welcome. See CONTRIBUTING.md.

License

MIT