Let coding agents use your browser (MCP)

Flecha has a built-in Model Context Protocol server. Turn it on and coding agents such as Claude Code, Cursor and Windsurf can work in the browser you already use, with your real tabs, sign-ins and dev servers. Ask “why does checkout redirect twice?” and the agent can open the page, read the console, take a screenshot and try a fix.

Turn it on

1. Set up the helper. The MCP server runs inside it.

2. Open Settings (⌘,) › Developer › Coding Agents and turn on Let coding agents use Flecha.

3. Copy the setup for your agent:

   • Claude Code › Copy Command. See Claude Code.
   • Other MCP clients › Copy Config, a JSON block for Cursor, Windsurf and others. See Cursor.

Caution

An agent with the token has full access to your regular tabs: it can read any page you’re signed in to and act on it. Only connect agents you trust, and remember that pages can contain text written to mislead an agent.

How it connects

• Transport: MCP over Streamable HTTP, at http://127.0.0.1:7390/mcp. If port 7390 is busy, Flecha uses the next free one up to 7399. Settings shows the address it’s using.
• Local only: the server listens on 127.0.0.1 and refuses requests for any other host name.
• Token: every request needs Authorization: Bearer <token>. Flecha creates a random token the first time you turn the bridge on. It is only shown inside the copied command or config.
• New Token in the same pane replaces it, which disconnects every agent using the old one at once.
• Turning the toggle off stops the server.

What agents can see

• Your tabs in every Space, plus favorites and pinned tabs that aren’t loaded.
• Not incognito windows, and not pages in a Flechinha window.

While an agent works, the sidebar shows Agent connected, then what it’s doing (“Agent is reading the page”, “Agent is clicking …”), and highlights the tab it’s driving.

Tools

Every tool that takes tabId uses the active tab when you leave it out. Tab ids come from list_tabs.

Tool	Inputs	What it does
list_tabs	none	Lists tabs with id, title, url, space, zone (favorites, pinned or today) and active.
open_tab	url, background?	Opens a URL, or search text, in a new tab and waits for it to load. Returns the new tabId.
activate_tab	tabId	Brings a tab on screen.
close_tab	tabId	Closes a tab. Pinned tabs and favorites are unloaded instead.
navigate	tabId?, url?, action?	Loads a URL, or goes back, forward or reload, and waits for the page to settle.
read_page	tabId?, format?, maxChars?	Returns the page as text (the default), html or links, up to 40,000 characters unless you set maxChars.
screenshot	tabId?	A PNG of the tab, at most 1280 px wide. Brings the tab on screen first.
console_logs	tabId?, level?, limit?	The latest console messages (error, warning, info or debug), 50 by default. Flecha keeps the last 500 per tab, including messages from before the agent connected.
click	tabId?, selector	Scrolls to the element matching a CSS selector and clicks its centre with a real mouse event.
type	tabId?, selector?, text, clear?, submit?	Types into the element, or the focused one. clear empties it first; submit presses Enter.
press_key	tabId?, key	Presses Enter, Tab, Escape, Backspace, Delete, an arrow key, Home, End, PageUp, PageDown, space or a single character.
evaluate	tabId?, expression	Runs JavaScript in the page and returns the result as JSON. Promises are awaited.
wait_for	tabId?, selector?, timeoutMs?	Waits for an element to appear, or for loading to finish when there’s no selector. Times out after 10 seconds by default.

Troubleshooting

Settings says “Starting…” and never shows an address. The helper isn’t registered. Run the helper setup, then turn the toggle off and on.

The agent gets 401 “Missing or wrong token”. The token changed. Copy the command or config again and update your agent.

“No free port for the agent bridge”. Ports 7390 to 7399 are all in use. Free one and turn the toggle off and on.

A tool says “Flecha didn’t answer … within N s”. The page didn’t respond, for example because it’s stuck in a long script. Reload the tab and try again.