Claude sessions could not work inside the user's own profile: the desktop
app's browser lost synthetic pastes and typing in Medium's editor, and a
browser-wide --remote-debugging-port would hand every session to any local
process. The connector is a built-in extension, off until turned on in
Settings > Extensions, that serves MCP on 127.0.0.1 behind a per-install
token and drives one tab at a time through that tab's webContents.debugger.
- Host: a "tab-control" capability (built-in add-ons only) for listing,
opening, navigating, closing and focusing tabs, handing out web tabs'
webContents (never Settings, extension or home tabs), and a toolbar chip
plus tab outline while a client is connected; the chip's X stops it.
Built-in add-ons can ship "defaultEnabled": false.
- Tools: list_tabs, open_tab, navigate, activate_tab, close_tab, screenshot,
read_page_text, snapshot (accessibility tree with refs), click, type
(insertText + real Enter), press_key, paste_html / paste_text (system
clipboard + webContents.paste, clipboard restored), upload_file
(DOM.setFileInputFiles), wait_for, and evaluate behind its own switch.
- Safety: first use of each site asks the user; password and one-time-code
fields are refused; uploads only from folders the user added; requests
from web pages or foreign Host headers are refused; every action is
logged with a timestamp in the panel and actions.log.
- Claude Desktop runs stdio-shim.cjs through the Theseus executable in Node
mode.
- Tests: unit (protocol, auth, policy, shim) and an end-to-end run on a
throwaway profile that types, pastes HTML with a heading and a link, and
uploads a PNG on a local page.
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