Lien

/ljɛ̃/ — French for "link"

A code-intelligence layer for AI agents: structural analysis + fast lexical search. 100% local, 100% private.

Lien connects AI coding assistants like Cursor and Claude Code to your codebase through the Model Context Protocol (MCP). Its core value is structural: reverse dependencies and blast radius, complexity hotspots, and test associations — the questions an agent needs answered before it edits your code. Alongside that, it offers fast lexical code search (FTS5/BM25 over code, docstrings, and identifier-split symbol names). Everything runs locally, with no embedding model to download — installs in seconds and indexes offline.

📚 Full Documentation | 🚀 Getting Started | 🔍 How It Works

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Features

• 🔍 Impact Analysis - Find all dependents and blast radius before refactoring, with risk assessment
• 📊 Complexity Analysis - Human-friendly metrics: test paths, mental load, time to understand
• 🧪 Test Associations - Know which tests cover a file before you touch it
• 🚀 Lexical Search - Fast full-text (FTS5/BM25) keyword search over code, docstrings, and identifier-split symbol names
• 🔒 100% Local & Private - All analysis happens on your machine
• 📦 No Model Download - No embeddings, no ~100MB model — tiny install, instant offline indexing
• 🎯 MCP Integration - Works seamlessly with Cursor, Claude Code, and other MCP-compatible tools
• ⚡ Fast - Sub-millisecond file context; minutes to index large codebases
• 🆓 Free Forever - No API costs, no subscriptions, no usage limits (applies to the local MCP/search tooling — Lien Review's agent pass uses your own LLM key and has its own token cost)
• 🏗️ Framework-Aware & Monorepo - Auto-detects 12+ ecosystems; supports 15+ languages

Quick Start

Claude Code (recommended) — one-time plugin install

/plugin marketplace add getlien/lien
/plugin install lien

That's it. Lien's MCP tools and hooks are now available in every Claude Code session, in every repo — including a hook that enhances Claude Code's built-in Explore agent with Lien-tool guidance. First use in a new git repo triggers a one-time index automatically — no lien init per project.

Other editors (Cursor, Windsurf, OpenCode, Kilo Code, Antigravity)

# 1. Install
npm install -g @liendev/lien

# 2. Wire it up for your editor
lien init

# 3. Restart your editor and start asking questions

lien init writes the right MCP config for your editor and (for Claude Code's legacy per-project flow, via lien init --legacy) copies an Explore agent into .claude/agents/. Lien auto-detects your project and indexes on first use.

👉 Full installation guide

MCP Tools

Lien exposes 6 powerful tools via Model Context Protocol:

Tool	Description
search_code	Full-text (BM25) keyword code search
find_similar	Find similar code patterns
get_files_context	Get file context with test associations
list_functions	List symbols by pattern
get_dependents	Impact analysis (what depends on this?)
get_complexity	Tech debt analysis with human-friendly metrics

Complexity Metrics

Lien tracks code complexity with intuitive outputs:

• 🔀 Test paths - Cyclomatic complexity as "needs ~X tests for full coverage"
• 🧠 Mental load - Cognitive complexity with nesting penalty
• ⏱️ Time to understand - Halstead effort as readable duration (~2h 30m)
• 🐛 Estimated bugs - Halstead prediction (Volume / 3000)

Lien Review

Lien Review is a self-hostable GitHub Action that reviews pull requests: complexity analysis, agent-driven bug review, and a PR summary — posted back as inline comments and workflow annotations. No server, no database, no recurring bill.

# .github/workflows/lien-review.yml
name: Lien Review

on:
  pull_request:

permissions:
  contents: read
  pull-requests: write

jobs:
  review:
    runs-on: ubuntu-latest
    steps:
      - uses: getlien/lien-review@v1
        with:
          openrouter-api-key: ${{ secrets.OPENROUTER_API_KEY }}

That single uses: line is the whole integration — Lien self-clones the PR by SHA using the workflow's own token, so no actions/checkout step is needed.

Feature	Description
Complexity analysis	Flags new/worsened cyclomatic, cognitive, and Halstead complexity violations
Agent bug review	LLM-driven review for correctness bugs (OpenRouter or Anthropic)
PR summary	A concise summary of the change, posted as a step summary
Advisory by default	fail-on: never — the check never blocks a PR unless you opt in

👉 Lien Review guide · Action reference

Git Worktrees

A linked git worktree (git worktree add) automatically shares the main checkout's index instead of building a full independent copy — a read-only base plus a small per-worktree overlay for whatever's actually changed. No setup required; set LIEN_WORKTREE_STANDALONE=1 to opt out and get a fully independent index for that worktree.

👉 How it works

Documentation

• Installation - npm, npx, or local setup
• Getting Started - Step-by-step configuration for Cursor or Claude Code
• Configuration - Customize indexing, thresholds, performance
• CLI Commands - Full command reference
• MCP Tools - Complete API reference for all 6 tools
• Lien Review - GitHub Action PR review setup
• How It Works - Architecture overview

Supported Languages

TypeScript • JavaScript • Vue • Python • PHP • Liquid • Go • Rust • Java • C/C++ • Ruby • Swift • Kotlin • C# • Scala • Markdown

Ecosystem Presets: 12 ecosystem presets including Node.js, Python, PHP, Laravel, Ruby, Rails, Rust, JVM, Swift, .NET, Django, and Astro (auto-detected)

Contributing

Contributions welcome! See CONTRIBUTING.md for guidelines.

Support

• 🐛 Issues - Report bugs or request features
• 💬 Discussions - Ask questions and share ideas

License

AGPL-3.0 © Alf Henderson

Lien is free forever for local use. The AGPL license ensures that:

• ✅ You can use Lien locally without restrictions
• ✅ You can modify and distribute Lien freely
• ✅ Improvements get contributed back to the community
• ✅ We can sustain long-term development

For questions about licensing, contact us at [email protected]

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Made with ❤️ for developers who value privacy and local-first tools.