Lain MCP server

LAIN-mcp

Structural Code Intelligence & Multi-Agent Coordination for AI Assistants.

Give your coding agents an in-memory graph brain instead of making them guess from flat text.

What is LAIN?

LAIN is a persistent, high-performance code intelligence and coordination engine built specifically for AI coding agents (Claude Code, Cursor, Copilot, Codex, Agy, Cline, Windsurf, etc.) over the Model Context Protocol (MCP).

Instead of treating code as unstructured flat text or relying on fuzzy keyword searches, LAIN indexes your codebase into an in-memory, typed structural property graph (using Tree-sitter, language servers, and Git commit history). It then exposes a rich suite of deterministic MCP tools that allow AI agents to navigate, reason about, and modify complex codebases without hallucinations, blind edits, or context-window waste.

See it run

• Instant Answers: Federation overview, repo health, and call graphs answered in milliseconds.
• Hot Reload: Edit repos.yaml or workspaces.yaml; the server updates live without dropping a single active MCP session.
• Interactive Tool Console: Exercise any MCP tool directly from the web browser; Copy as cURL gives agents and operators instant reproducibility.

[!NOTE]

The demo is kept as a single GIF so it plays inline without storing duplicate video encodings in the repository.

How it fits together

flowchart TB
    subgraph Clients["AI Agents & Developers"]
        A["AI Coding Agent<br/>(Claude Code / Cursor / Agy / Codex)"]
        B["Developer / Operator<br/>(Browser Command Center)"]
    end

    subgraph Transports["MCP & Web Transports"]
        S["stdio (single-repo)"]
        H["HTTP :9999 (JSON-RPC & SSE)"]
    end

    subgraph Core["LAIN Core Engine"]
        EX["Unified MCP Tool Dispatcher"]
        G["In-Memory Graph Engine<br/>(Petgraph · UUID v5)"]
        PRES["Presence & Claim Registry<br/>(Advisory Leases & Locks)"]
        FED["Federation Engine<br/>(N Repositories)"]
    end

    subgraph Sources["Code Analysis & Storage"]
        TS["Tree-sitter AST Parser"]
        LSP["Language Servers (rust-analyzer, pylsp...)"]
        GIT["Git Commit History (Co-change radar)"]
        BIN[".lain/graph.bin (Persistent Cache)"]
    end

    A -->|MCP JSON-RPC| S
    A -->|MCP HTTP| H
    B -->|GET /| H
    S --> EX
    H --> EX
    EX --> G
    EX --> PRES
    EX --> FED
    G <--> BIN
    G --> TS
    G --> LSP
    G --> GIT

Shortened. The full README is on GitHub.