Kitsune

Bring your coding agent into Firefox—and keep working alongside it.

Kitsune lets AI agents like Claude Code, Codex, Pi, and OpenCode use the Firefox, Zen, or LibreWolf browser you already have open. Your sessions, cookies, and extensions stay in place. No Playwright, Chromium, or WebDriver required.

Research in background tabs, prepare form drafts, and continue browser tasks with an agent you already use—not a separate browser or built-in AI assistant.

Two principles guide every trade-off: the user's browser belongs to the user, and fewer, sharper tools. See Philosophy.

Why Kitsune?

• Work alongside your agent. Agent-created tabs open in the background. Writes to a tab you are actively using are held, and closing your own tabs requires a separate confirmation step. These protections reduce interference; OS-level clicks and site-opened popups still have focus and input limitations.
• Choose how much to delegate. Configure KITSUNE_MODE=read, draft, or act to limit the available tools and bridge requests. Draft mode allows supported field input without click or submit tools; sites may still autosave edits. The default is act, not a restricted mode. See Task modes.
• Keep the tool list small. Start with Playwright MCP's 25 core tools. Kitsune's other tools stay off until you allow them, and the agent can find and call the ones you allow without restarting its session. See Choosing tools.
• Recover without blindly repeating work. With the optional automation capability, interrupted batch, parallel, and workflow calls can be resumed without resending successful writes. Uncertain writes require an observation before retrying. Checkpoints are temporary and do not survive a bridge restart.

What can it do?

• Research the web. Search, read pages, and summarize findings with links.
• Interact with websites. Click, type, select options, and fill forms—even on sites you're already signed into.
• Capture and extract. Take screenshots or turn page content into text and Markdown.
• Work across tabs. Keep research and tasks in separate tabs without replacing the page you're using.

_{A real browser session, captured with Kitsune and sped up.}

How do I use it?

1. Connect once. Install uv, then follow the MCP setup for your agent below. Install the browser extension in Firefox, Zen, or LibreWolf: the signed build installs once, while the developer build (needed for browser_evaluate) is a temporary add-on.

2. Keep your browser open. Kitsune starts its shared bridge automatically. Ask your agent to check the connection before your first task.

3. Ask in plain language. For example:

   Research these three products in new background tabs and compare them with source links. Leave my current tab alone.

   Inspect this page's form and fill a draft. Don't submit it yet.

   Open Hacker News in a background tab and summarize the top three stories with links.

   For an enforced draft-only tool surface, configure KITSUNE_MODE=draft before starting the MCP client; asking in plain language does not change the mode.

Use a dedicated browser profile and only give access to accounts the agent needs. Ask for confirmation before sending, purchasing, or deleting anything. The opt-in ask-before-act policy makes the bridge hold submits, payment pages, JavaScript, and cookie access until the agent repeats the call with a confirmation token. That second step is not proof of human approval, and these controls do not prevent prompt injection. Read the security guidance before using sensitive accounts.

MCP setup

All clients launch the same local stdio server: uvx --from kitsune-browser-mcp kitsune. Choose one setup method for each client you use. Several clients can share the same bridge; keep their Kitsune versions and install sources consistent.

CLI registration: Claude Code, Codex, and Pi

Claude Code — available in every project with --scope user:

claude mcp add --scope user kitsune -- uvx --from kitsune-browser-mcp kitsune

Codex CLI — registers the server in ~/.codex/config.toml:

codex mcp add kitsune -- uvx --from kitsune-browser-mcp kitsune

Pi — uses built-in MCP support with user-level configuration by default:

pi mcp add kitsune -- uvx --from kitsune-browser-mcp kitsune
pi mcp list

Add --local before kitsune to register Pi's server only for the current project. In an already running Pi session, run /reload, then /mcp to inspect the connection. If an MCP adapter extension overrides Pi's built-in support, follow that extension's configuration instructions instead.

OpenCode

Merge this into ~/.config/opencode/opencode.json (global) or opencode.json in your project root. OpenCode uses an mcp object and a command array, not mcpServers:

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "kitsune": {
      "type": "local",
      "command": ["uvx", "--from", "kitsune-browser-mcp", "kitsune"],
      "enabled": true
    }
  }
}

JSON configuration: Pi, Claude Desktop, and Cursor

These clients share the same mcpServers format. As an alternative to CLI registration where available, merge the following entry into your client's config; keep any existing servers:

{
  "mcpServers": {
    "kitsune": {
      "command": "uvx",
      "args": ["--from", "kitsune-browser-mcp", "kitsune"]
    }
  }
}

Restart or reconnect your client after configuring it, then ask it to list your tabs (browser_tabs with action: "list"); an error's hint says what to fix. GUI apps may need the full path returned by which uvx instead of uvx if they do not inherit your shell's PATH.

Choosing tools

By default Kitsune publishes exactly Playwright MCP's 25 core tools (same names, descriptions and schemas), driving your own browser, so prompts and clients written for Playwright MCP work unchanged (Core tools). Kitsune's own tools come in capability groups that you enable with KITSUNE_CAPS in the MCP server's environment:

To keep the agent's tool list small, allow more than you publish. With KITSUNE_CAPS=all and KITSUNE_PUBLISH=core, the agent starts with the core tools and finds and calls the others in the same session (Finding tools without a restart). For example, with Claude Code:

claude mcp add --scope user kitsune -e KITSUNE_CAPS=all -e KITSUNE_PUBLISH=core -- uvx --from kitsune-browser-mcp kitsune

In the JSON configurations above, add "env": {"KITSUNE_CAPS": "all", "KITSUNE_PUBLISH": "core"} next to "args". The bridge checks the groups on every request, batch steps included, and tools you call without a tab act on the agent's current tab, not the one you are looking at.

Upgrading from 0.3? The devtools, parallel, windows and session groups were replaced by the groups above, and all no longer includes storage. A configuration that names a removed group fails at startup; see Tools for where each tool went.

For Codex's TOML alternative, environment variables, version pinning, and upgrades, see Installation.

For the details: Tools · Configuration · Troubleshooting · Updating · API reference · Development

For architecture, product trade-offs, and the wider browser MCP landscape, see Positioning.

MIT · Based on ZenLink and ZenLink-MCP by Jay-Quan. Credits · License