line-desktop-mcp

Unofficial community project. Not affiliated with, endorsed by, or supported by LINE Corporation or LY Corporation. It reads your own logged-in account through the LINE Chrome Extension. Read tools are side-effect free; clear_session is the only destructive tool and needs explicit confirmation.

An MCP server that lets an AI client read your LINE chats. It wraps line-ext-msg>=2.0,<3, drives a dedicated headless Chrome over CDP, and exposes LINE as MCP tools.

Requirements

• Windows (Chrome discovery and process control use Windows paths and PowerShell)
• Google Chrome installed
• A LINE account you can log into with a QR scan
• uv installed, which provides uvx

You do not install the LINE Chrome Extension yourself. The first run opens the Web Store page and waits while you install it.

Quick start

1. Add the server to your MCP client

Claude Desktop:

{
  "mcpServers": {
    "line-desktop": {
      "command": "uvx",
      "args": ["line-desktop-mcp@latest"]
    }
  }
}

opencode:

{
  "mcp": {
    "line-desktop-mcp": {
      "type": "local",
      "command": ["uvx", "line-desktop-mcp@latest"]
    }
  }
}

@latest asks uvx for the newest published version and refreshes its cache on every launch, so you keep getting updates without editing the config. If you prefer a fixed version for reproducibility, use line-desktop-mcp@2.0.0 instead.

2. First run

Ask your client to call line_status with its defaults. That one call runs the whole setup:

1. starts a dedicated headless Chrome profile,
2. installs the LINE extension if it is missing (it opens the Web Store and keeps polling until the install finishes),
3. waits for the app to render,
4. shows the QR in a small Line Desktop MCP dialog.

Scan the QR with your phone and enter the PIN if LINE asks for it. When you are already logged in, step 4 is skipped and the call returns at once.

Chrome is left running on purpose. The LINE session lives in that Chrome process, not on disk, so closing Chrome or rebooting means scanning again. Only clear_session logs out on purpose.

3. Everyday use

Once setup is done, just ask your AI client. Things that work well:

• "Which LINE chats have unread messages?"
• "Read the last messages in the family chat."
• "Search the Work room for 'invoice' since 2026-09-01."
• "Show me the image someone posted yesterday" (ask for include_media=true).

Tools

Read tools never write files and never download media. Every result uses an ok / data / error envelope, and a failure carries a next field that tells the AI what to ask you to do.

Tool	What it does
line_status	Checks the five readiness steps. With wait_for_login=true (the default) it also installs the extension if missing and waits for the QR login, all in one continuous call. Pass wait_for_login=false for a quick check that fails fast.
list_rooms	Lists chat rooms with unread counts and a preview. Optional unread_only and query filters.
get_messages	Reads the latest messages, optionally opening a room first. Filters by date, range, sender, or keyword. include_media=true embeds image bubbles as data URIs for the AI to see.
unread_digest	Unread rooms with the latest preview. Cheapest way to answer "what is unread".
unread_full	Unread rooms with their message bodies, one room at a time, with per-room progress.
search_messages	Searches a keyword inside the rooms you pass. The scope is required on purpose: scanning every room costs seconds per room.
probe_session	Reports login state plus a redacted storage probe. Safe to call any time, no side effects.
clear_session	Wipes the LINE login only, keeping the extension. Destructive, needs confirm=true, and the next call needs a new QR scan.

How it works

• Room references. A room can be named by index, data-mid, or a substring of its name. Prefer data-mid or the name: index values shift when rooms reorder.
• Dates. Use YYYY-MM-DD. get_messages takes a single date or a date_from / date_to range.
• Scroll. Reads backfill by scrolling up to limit, bounded to about 8 seconds. Pass scroll=false to read only what is on screen, which is fast.
• Media. Image bubbles are text only by default. include_media=true adds a data URI in memory, and nothing is written to disk.
• Search scope. search_messages only scans the rooms you pass, and a bad reference becomes a RoomNotFound entry instead of failing the whole call.
• Rendered rows only. LINE uses a virtualized list, so a deep history still returns only what the DOM holds, even for a wide date range.
• Sessions. The session belongs to the running Chrome process. Keep Chrome open to avoid scanning again.

Configuration

All settings are environment variables. The MCP sets the first three defaults before the library loads, and setdefault means your own values win.

Variable	Default	Purpose
LINE_EXT_MSG_PROFILE	%LOCALAPPDATA%\line-desktop-mcp	Chrome profile used by the server
LINE_EXT_MSG_PORT	9223	CDP debug port. A separate port keeps the MCP off the line-ext-msg CLI, which uses 9222. The library reuses whatever Chrome answers a debug port, regardless of profile, so the port is what actually isolates the two.
LINE_EXT_MSG_DIALOG_TITLE	Line Desktop MCP	Title of the QR login dialog and its header
LINE_DESKTOP_MCP_LOG	unset	Set to INFO or DEBUG to mirror library progress on stderr

The library writes a few runtime files under session/ in the server working directory: qr.png and qr_status.json during login, chrome.pid for the debug Chrome, and a redacted probe before clear_session. The folder is git-ignored.

Privacy and safety

• The server reads your own account. It does not use any LINE API and does not send your data anywhere except back to your MCP client.
• probe_session returns key names with type and length only, never secret values.
• clear_session is the only destructive tool. Without confirm=true it refuses safely and changes nothing.
• Nothing is saved unless you ask for it through your client; read tools leave no files behind.

Troubleshooting

• Login looks flaky. Call probe_session first to check logged_in without changing anything.
• The extension is missing. The first call opens the Web Store page and keeps polling until the install finishes, then continues on its own.
• Rooms cannot be read after a LINE update. The selectors live in line-ext-msg. Dump the DOM and send it upstream to tune them.
• The first call fails with a client-side timeout. A cold Chrome start can take longer than your MCP client's default request timeout. Retry once Chrome is warm, or raise the server timeout in your client config.

For developers

uv sync
uv run line-desktop-mcp --help
uv run line-desktop-mcp

Run with HTTP transport for remote access:

uv run line-desktop-mcp --transport http --port 8000

Run via the FastMCP CLI:

uv run fastmcp run src/line_desktop_mcp/server.py:mcp

Test a local wheel before release:

uv build
uvx --from ./dist/line_desktop_mcp-2.0.0-py3-none-any.whl line-desktop-mcp --help

Tests

uv run python -m unittest discover -s tests -v

Browser-free unit tests only (room resolving, envelopes, login status, session gate, env defaults, CLI defaults). No Chrome needed.

Lint and type check:

uv run ruff check .
uv run ruff format --check .
uv run mypy

CI runs all three plus the tests on Python 3.10 to 3.14.

Structure

src/line_desktop_mcp/
  server.py         # FastMCP wiring, instructions, and env defaults
  cli.py            # argparse + mcp.run(), installed as `line-desktop-mcp`
  __main__.py       # `python -m line_desktop_mcp`
  tools/line_msg.py # LINE tools (status, rooms, messages, search)
  tools/session.py  # Session tools (probe_session read-only, clear_session destructive)

Add a new tool domain by creating tools/<domain>.py with a register_<domain>_tools(mcp) function, then calling it from server.py.

Publish

uv build
uv publish

Requires requires-python = ">=3.10" and the line-desktop-mcp console script defined in pyproject.toml.