@a13xu/lucid

MCP server for Claude Code — persistent memory, smart code indexing, and code quality validation. Works out of the box with zero configuration.

Token-efficient memory, code indexing, and validation for Claude Code agents — backed by SQLite + FTS5.

Stores a persistent knowledge graph (entities, relations, observations), indexes source files as compressed binary with change detection, retrieves minimal relevant context via TF-IDF or Qdrant, and validates code for LLM drift patterns. Supports TypeScript, JavaScript, Python, Vue, Nuxt.

Install

Requirements: Node.js 18+

# Option 1 — global install (recommended, faster startup)
npm install -g @a13xu/lucid
claude mcp add --transport stdio lucid -- lucid

# Option 2 — no install needed (uses npx on each start)
claude mcp add --transport stdio lucid -- npx -y @a13xu/lucid

Or add to .mcp.json in your project root:

{
  "mcpServers": {
    "lucid": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "@a13xu/lucid"],
      "env": {
        "MEMORY_DB_PATH": "/your/project/.claude/memory.db"
      }
    }
  }
}

Default DB path: ~/.claude/memory.db

Quick start

1. "Index this project" → init_project()        → scans CLAUDE.md, package.json, src/**
2. Write code          → sync_file(path)         → compressed + hashed + diff stored
3. "What's relevant?"  → get_context("auth flow") → TF-IDF ranked skeletons, ~500 tokens
4. "What changed?"     → get_recent(hours=2)      → line diffs of recent edits
5. "Where is X used?"  → grep_code("X")           → matching lines only, ~30 tokens
6. "What do we know?"  → recall("query")          → knowledge graph search

Tools (30)

Memory

Code indexing

Token optimization

Logic Guardian

Reward system

Code Quality Guard

Web Dev Skills

Token optimization in depth

How get_context works

query: "auth middleware"
         ↓
  1. TF-IDF score all indexed files against query
     (or Qdrant top-k if QDRANT_URL is set)
         ↓
  2. Boost recently-modified files (+0.3 score)
         ↓
  3. Apply whitelist dirs filter (if configured)
         ↓
  4. For each file within token budget:
       file < maxTokensPerFile  → return full source
       file > maxTokensPerFile  → return skeleton only
                                   (imports + signatures + TODOs)
                                   + relevant fragments around query terms
         ↓
  output: ~500–2000 tokens  vs  5000–20000 for reading full files

Skeleton pruning (AST-based)

Large files are replaced with their structural skeleton:

// src/middleware/auth.ts [skeleton]
// Validates JWT tokens and attaches user to request context

import { Request, Response, NextFunction } from "express"
import { verifyToken } from "../services/jwt.js"

// — exports —
export function authMiddleware(req: Request, res: Response, next: NextFunction): void { … }
export function requireRole(role: string): RequestHandler { … }
export type AuthenticatedRequest = Request & { user: User }

vs reading the full 200-line file.

Qdrant vector search (optional)

Set env vars to enable semantic search instead of TF-IDF:

QDRANT_URL=http://localhost:6333
QDRANT_API_KEY=your-key          # optional
OPENAI_API_KEY=sk-...            # for embeddings
EMBEDDING_MODEL=text-embedding-3-small  # optional

Or in .mcp.json:

{
  "mcpServers": {
    "lucid": {
      "command": "npx", "args": ["-y", "@a13xu/lucid"],
      "env": {
        "QDRANT_URL": "http://localhost:6333",
        "OPENAI_API_KEY": "sk-..."
      }
    }
  }
}

Falls back to TF-IDF automatically if Qdrant is unreachable.

Configuration (lucid.config.json)

Create in your project root to customize behavior:

{
  "whitelistDirs": ["src", "backend", "api"],
  "blacklistDirs": ["migrations", "fixtures"],
  "maxTokensPerFile": 400,
  "maxContextTokens": 6000,
  "recentWindowHours": 12
}

Why no vectors by default?

Code has explicit structure — no NLP needed for most queries:

TF-IDF is fast, deterministic, and requires zero external services. Qdrant is available when you need semantic similarity across large codebases.

Why SQLite + FTS5?

Entity types

person · project · decision · pattern · tool · config · bug · convention

Relation types

uses · depends_on · created_by · part_of · replaced_by · conflicts_with · tested_by

Debugging

echo '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"capabilities":{},"clientInfo":{"name":"test","version":"1.0"},"protocolVersion":"2024-11-05"}}' \
  | npx @a13xu/lucid

In Claude Code: run /mcp — you should see lucid with 20 tools.

Contributing

Bug reports and pull requests are welcome on GitHub.

1. Fork the repo
2. npm install → npm run build
3. Test locally: claude mcp add --transport stdio lucid-dev -- node /path/to/lucid/build/index.js
4. Open a PR

Tech stack

• Runtime: Node.js 18+, TypeScript, ES modules
• MCP SDK: @modelcontextprotocol/sdk
• Database: better-sqlite3 (synchronous, WAL mode)
• Compression: Node.js built-in zlib (deflate level 9)
• Hashing: SHA-256 via crypto (change detection)
• Ranking: TF-IDF (built-in) or Qdrant (optional, via REST)
• Validation: zod
• Transport: stdio