MCP Setup (Claude Code)¶

Lattice exposes an MCP server so Claude Code can read and write your memory atoms during any conversation.

What this gives you¶

Claude Code remembers decisions, preferences, and facts across sessions
You can ask Claude "what did I decide about X?" and get a grounded answer
Captures made during a coding session are persisted to Lattice automatically

Prerequisites¶

Lattice daemon running (uv run lattice-daemon)
Claude Code installed

Configure the MCP server¶

Add Lattice to your Claude Code MCP config. Claude Code reads from ~/.claude/mcp_servers.json (global) or .mcp.json in the project directory (project-local).

Option A: Project-local (recommended for this repo)¶

Create .mcp.json in your project root:

{
  "mcpServers": {
    "lattice": {
      "command": "uv",
      "args": ["run", "lattice"],
      "cwd": "/path/to/your/lattice-repo",
      "env": {
        "LLM_PROVIDER": "ollama",
        "LLM_MODEL": "gemma4",
        "LATTICE_DIR": "/Users/yourname/.lattice"
      }
    }
  }
}

Option B: Global (available in all projects)¶

claude mcp add lattice -- uv run --directory /path/to/lattice-repo lattice

Then set env vars in your shell profile so uv run lattice picks them up.

Verify¶

In Claude Code, run:

/mcp

You should see lattice listed as a connected server with tools: lattice_ingest, lattice_capture, lattice_select, lattice_answer, lattice_status.

Available MCP tools¶

Tool	What it does
`lattice_ingest`	Save a fact or chunk of conversation to memory
`lattice_capture`	Save a session summary (use at end of conversation)
`lattice_select`	Find relevant atoms for a query (no synthesis)
`lattice_answer`	Find atoms + synthesize a prose answer
`lattice_status`	Atom count, streak, today's activity

Usage in conversation¶

Claude Code will call these tools automatically based on your instructions. You can also invoke them explicitly:

What did I decide about the database schema?

Claude Code will call lattice_answer with your question and return a cited answer from your atoms.

Save this decision: we're using PostgreSQL with UUID primary keys

Claude Code will call lattice_ingest with the fact.

Wrap up

At end-of-session, Claude Code will call lattice_capture with a summary of decisions made.

How the MCP server connects to the daemon¶

server.py is the MCP stdio entrypoint. It holds one shared LatticeDB instance. Write operations (ingest, capture) are delegated over the Unix socket to the daemon — the daemon is the sole writer. Read operations (select, answer) run directly against the local DB cache.

This means:

The MCP server does not need to be restarted when the daemon restarts
Writes from Claude Code and writes from the web UI land in the same atom store
The daemon must be running for writes to succeed; reads work even if the daemon is down

Troubleshooting¶

"Connection refused" on ingest

The daemon is not running. Start it with uv run lattice-daemon.

Tools visible but lattice_answer returns empty results

No atoms in the store yet. Capture a few facts first, then ask.

MCP server not appearing in /mcp

Check that cwd and LATTICE_DIR in .mcp.json point to the correct paths. Use absolute paths.