Lattice MCP Server

Automates Lattice HR objectives (create, update, delete, list) via browser session replay. No API key required — authenticates through SSO and persists the session for headless Playwright reuse.

Prerequisites

• Python 3.10+
• Chrome/Chromium (for SSO login)
• A display environment (local machine or X-forwarded) for initial login

Installation

pip install lattice-mcp
playwright install chromium

Authentication

The server uses a saved Playwright browser session (~/.config/lattice/browser-state.json). You must log in once via SSO to create it.

Option A: Local machine with a display

lattice ui login [--hostname <your-company>.latticehq.com]

If --hostname is omitted, it falls back to the LATTICE_WEB_HOSTNAME environment variable (see Configuration).

A Chromium window opens — complete your SSO login. The window closes automatically once authenticated and the session is saved. The session is reusable until it expires on Lattice's side (typically days to weeks).

Option B: Headless server (attach to running Chrome)

# On a machine with a display, start Chrome with remote debugging:
google-chrome --remote-debugging-port=9223 --user-data-dir=/tmp/chrome-lattice --no-first-run &

# Complete SSO in that browser, then capture the session:
lattice ui login --cdp-url http://127.0.0.1:9223

Session expiry

If tools return "Session expired", re-run lattice ui login — or let the agent call the lattice_ui_login MCP tool, which opens the login window for you (you still complete the SSO yourself).

Configuration

All configuration is via environment variables — no code changes needed to point at your own Lattice tenant:

lattice ui login also accepts --hostname directly (takes precedence over the env var). The hostname is not saved with the session — the MCP server re-reads LATTICE_WEB_HOSTNAME on every call, so set it wherever the server is launched (see below).

To find your user entity ID: open any Lattice page filtered to your objectives and copy the UUID from the URL (ownerEntityIdsFilter=...), or inspect a GraphQL response in your browser's devtools.

MCP Server Setup (Claude Code)

Add to your project's .mcp.json:

{
  "mcpServers": {
    "lattice": {
      "command": "lattice-mcp",
      "env": {
        "LATTICE_WEB_HOSTNAME": "<your-company>.latticehq.com",
        "LATTICE_USER_ENTITY_ID": "<your-user-entity-uuid>"
      }
    }
  }
}

Restart Claude Code to load the server. The tools appear as lattice_* in your session.

Available Tools

Example usage (via Claude Code)

> list my lattice objectives
> create a lattice objective titled "Ship feature X"
> update objective <entityId> status green comment "Merged PR, deploying tomorrow"
> delete objective <entityId>

Multi-server workflow (with Jira MCP)

If you also have a Jira MCP server in your session, you can chain them:

> fetch PLAT-0000 and PLAT-0001 from jira, then create lattice objectives from their summaries

Claude calls the Jira server to get ticket details, then calls lattice_create_objective for each — no glue code needed.

How It Works

1. Tools launch headless Chromium with the saved session cookies
2. Navigate to the relevant Lattice page
3. Interact with the UI (fill forms, click buttons) via Playwright
4. GraphQL mutations fire as a side-effect of the UI interaction
5. Cloudflare passes because the session includes valid clearance cookies

There is no direct API access — Lattice does not issue API keys to non-admins. See DESIGN.md for the full decision log.

Troubleshooting