# GhostLink
**A security-hardened MCP server that gives AI coding agents safe, deterministic access to local repositories.**
[](https://github.com/bgorzelic/ghostlink/actions/workflows/ci-typescript.yml)
[](https://www.npmjs.com/package/@bgorzelic/ghostlink)
[](tsconfig.json)
[](.nvmrc)
[](tests/)
[](LICENSE)
Add it to any MCP client that supports STDIO. For Claude Code, create `.mcp.json` in the target repo root:
```json
{
"mcpServers": {
"ghostlink": {
"command": "npx",
"args": ["-y", "@bgorzelic/ghostlink"],
"env": {
"GHOSTLINK_REPO_ROOT": "/path/to/target/repo"
}
}
}
}
```
Then run `claude` in that directory — six repo tools appear, all confined to `GHOSTLINK_REPO_ROOT`. Every tool call returns the same deterministic `ToolEnvelope`:
```json
{
"ok": true,
"data": { ... },
"provenance": { "tool": "repo.search", "timestamp": "2026-02-24T...", "duration_ms": 42 }
}
```
On error, `"error": { "code": "...", "message": "..." }` replaces `"data"`. Full tool schemas: [docs/TOOLS.md](docs/TOOLS.md).
## Tools
| Tool | Description |
|---|---|
| `repo.search` | Ripgrep-powered regex search with glob filtering, deterministic ordering, and output caps (max 200 results) |
| `repo.read_file` | File read with size caps (max 10MB), binary detection, and truncation flags |
| `repo.apply_patch` | Unified diff patching with dry-run mode, full sandbox validation, and atomic rollback on failure |
| `repo.run` | Curated command execution (test, lint, typecheck, build, smoke) -- no arbitrary shell, allowlisted args only |
| `git.status` | Normalized git status with branch info, ahead/behind tracking, and sorted file entries |
| `git.diff` | Staged or unstaged diff with path filtering, sandbox validation, and output caps (max 2MB) |
## What is GhostLink?
GhostLink is a local-first [Model Context Protocol](https://modelcontextprotocol.io) server that exposes your codebase to AI coding agents through a small set of policy-gated tools. It solves a specific problem: AI agents need to search, read, patch, and verify code, but giving them raw shell access is a liability. GhostLink provides a sandboxed capability plane where every tool call is confined to a single repository root, every output follows a deterministic JSON shape, and every invocation is audit-logged.
## Why GhostLink?
| Capability | What it means |
|---|---|
| Secure local dev plane | Repo-root sandbox, no shell execution, JSONL audit trail on every tool call |
| Deterministic output | Same input produces the same JSON envelope shape -- enables golden tests and predictable agent consumption |
| Policy enforcement | Command allowlists, output caps, truncation flags, timeout enforcement -- the AI cannot do unbounded damage |
| Agent loop foundation | Built for the search, read, patch, verify cycle that autonomous coding agents run in a loop |
| Multi-server composition | One GhostLink instance per repo, composable with other MCP servers in the same client session |
| Production-ready Phase 2 base | Transport abstraction, schema versioning, and auth hook seams are preserved in the architecture today |
## Architecture
GhostLink is a three-layer stack designed for extensibility without core changes:
```mermaid
flowchart TD
T["Transport -- src/index.ts
STDIO now, HTTP/SSE in Phase 2"]
S["Server factory -- src/server.ts
Transport-agnostic tool registration via MCP SDK + Zod schemas"]
TL["Tools -- src/core/tools/*
Six tools, each returning ToolEnvelope<T>"]
P["Policy -- src/core/policy/*
Sandbox enforcement, audit logging, output caps"]
T --> S --> TL --> P
```
The `createServer()` factory knows nothing about transport. Adding HTTP/SSE in Phase 2 means writing a new transport binding and auth middleware -- the server factory and all tool implementations remain unchanged. Phase 3 (agent runtime) adds memory resources and orchestration as consumers of GhostLink, not modifications to it.
## Quick Start
### Prerequisites
- Node.js 18+
- ripgrep (`brew install ripgrep`)
- A git repository to expose
### Install
From npm:
```bash
npm install @bgorzelic/ghostlink
```
Or from source:
```bash
git clone https://github.com/bgorzelic/ghostlink.git
cd ghostlink
npm install
npm run build
```
### Smoke Test (Raw STDIO)
GhostLink speaks JSON-RPC 2.0 over STDIO. Test it directly:
```bash
echo '{"jsonrpc":"2.0","id":1,"method":"tools/list"}' | \
GHOSTLINK_REPO_ROOT=/path/to/target/repo node dist/index.js
```
This returns all 6 tools and their schemas.
## Client Configuration
GhostLink works with any MCP client that supports STDIO transport. The `npx` snippet at the top of this page works everywhere; a source checkout uses `node` with the built entry point instead:
```json
{
"ghostlink": {
"command": "node",
"args": ["/absolute/path/to/ghostlink/dist/index.js"],
"env": {
"GHOSTLINK_REPO_ROOT": "/path/to/target/repo"
}
}
}
```
| Client | Where the config goes |
|---|---|
| Claude Code | `.mcp.json` in the target repo root (`mcpServers` key), then run `claude` there |
| Claude Desktop | `~/Library/Application Support/Claude/claude_desktop_config.json` (`mcpServers` key), then restart |
| Cursor, Windsurf, Cline, others | Your client's MCP server configuration -- consult its documentation for the file location |
The transport is always STDIO. Ready-to-use `.mcp.json` and CLAUDE.md templates for target projects live in [templates/](templates/).
## Security Model
GhostLink enforces defense-in-depth at every layer:
- **Repo-root sandbox** -- All file operations confined to `GHOSTLINK_REPO_ROOT`. Path traversal, symlink escape, null bytes, and absolute paths outside the root are all rejected before any filesystem access.
- **No shell execution** -- `repo.run` uses `spawn` with `shell: false`. Commands are limited to a fixed allowlist (test, lint, typecheck, build, smoke) with per-command argument allowlists. Environment is stripped to six safe variables.
- **Output caps** -- Every tool that returns bulk data enforces hard maximums (200 search results, 10MB file reads, 200KB stdout/stderr, 2MB diffs). Truncation is flagged, never silent.
- **Atomic patch rollback** -- `repo.apply_patch` validates all paths and computes all patches before writing anything. If any write fails, completed writes are rolled back to their original state.
- **Timeout enforcement** -- `repo.run` kills processes at configurable timeouts (default 120s, hard cap 300s) with SIGTERM then SIGKILL.
Full threat model and mitigations: [docs/SECURITY.md](docs/SECURITY.md).
## Audit Logging
Every tool call produces a JSONL audit entry: `{ts, tool, ok, duration_ms, error_code?, repo_root}`.
| `GHOSTLINK_LOG` | Behavior |
|---|---|
| `stdout` (default) | JSONL audit lines written to stderr |
| `file` | JSONL written to `logs/ghostlink.jsonl` (auto-rotates at 10MB) |
| `off` | No logging |
Set via environment variable:
```bash
GHOSTLINK_LOG=file GHOSTLINK_REPO_ROOT=/path/to/repo node dist/index.js
```
## Prompt Templates
[docs/PROMPTS.md](docs/PROMPTS.md) contains ready-to-use prompts for high-autonomy agent operation, including orchestrator prompts, sub-agent role definitions (Protocol Engineer, Toolsmith, Security Reviewer, Test Engineer, Docs Engineer), and multi-instance coordination patterns.
## Development
```bash
npm install # Install dependencies
npm test # Run test suite (108 tests via Vitest)
npm run lint # ESLint
npm run typecheck # TypeScript strict mode check
npm run build # Compile to dist/
npm run dev # Dev mode with auto-reload (tsx watch)
```
Full verification after edits:
```bash
npm test && npm run lint && npm run typecheck && npm run build
```
## Documentation
| Document | Description |
|---|---|
| [docs/TOOLS.md](docs/TOOLS.md) | Canonical tool schemas (versioned public API) |
| [docs/SECURITY.md](docs/SECURITY.md) | Threat model and mitigations |
| [docs/QUICKSTART.md](docs/QUICKSTART.md) | Setup, smoke tests, and client configuration walkthrough |
| [docs/INSPECTOR.md](docs/INSPECTOR.md) | MCP Inspector manual testing guide |
| [docs/PROMPTS.md](docs/PROMPTS.md) | Agent prompts for orchestration and sub-agent roles |
| [docs/ROADMAP_DETAILED.md](docs/ROADMAP_DETAILED.md) | Full product roadmap with Phase 2 and Phase 3 deliverables |
| [docs/WHY_GHOSTLINK.md](docs/WHY_GHOSTLINK.md) | Strategic value proposition and architecture rationale |
| [docs/ENGINEERING_REPORT_v0.1.0.md](docs/ENGINEERING_REPORT_v0.1.0.md) | v0.1.0 ship report with milestone history and decision log |
| [templates/](templates/) | Ready-to-use CLAUDE.md and .mcp.json templates for target projects |
## Roadmap
### Phase 1 -- Local STDIO [Shipped, v0.1.0]
Deterministic tool surface, repo-root sandbox, curated command execution, 108 tests, JSONL audit logging, npm package published.
### Phase 2 -- Remote Transport [Planned]
HTTP/SSE transport, OAuth 2.1 authentication, multi-user tenant separation, per-tenant rate limiting, schema versioning, structured audit logging with correlation IDs.
### Phase 3 -- Agent Runtime [Future]
Persistent memory resources exposed via MCP, optional policy-gated memory write tools, orchestration layer (external to GhostLink), evaluation loops, sub-agent coordination framework.
## License
ISC