# MCP Multi-Language Sandbox
[](https://www.typescriptlang.org/)
[](https://modelcontextprotocol.io/)
[](https://opensource.org/licenses/MIT)
[]()
> Execute code securely in 6 programming languages with Docker isolation, designed for [Claude Code](https://claude.com/claude-code) via [Model Context Protocol (MCP)](https://modelcontextprotocol.io/).
## What is this?
A local MCP server that lets Claude execute code in isolated Docker containers. Think of it as your own private code sandbox - **100% free**, **100% local**, no cloud dependencies.
**Why use this instead of cloud sandboxes?**
- **Free**: No per-execution costs (vs ~$0.10/run on cloud services)
- **Fast**: 0ms container acquisition with pooling (vs 2-5s cold starts)
- **Private**: Code never leaves your machine
- **Customizable**: Add your own languages, packages, security rules
## Features
- **6 Languages**: Python, TypeScript, JavaScript, Go, Rust, Bash
- **Container Pooling**: Pre-warmed containers for instant execution
- **Package Caching**: Install once, reuse forever (SHA256-based)
- **ML Runtime**: numpy, pandas, sklearn, torch, mlx pre-installed
- **Security**: Seccomp profiles, capability dropping, audit logging
- **Sessions**: Persistent state with TTL and auto-cleanup
## Quick Start
### Prerequisites
- [Node.js](https://nodejs.org/) >= 18.0.0
- [Docker Desktop](https://www.docker.com/products/docker-desktop/)
- [Claude Code CLI](https://claude.com/claude-code) (optional, for MCP integration)
### Installation
```bash
# Clone the repository
git clone https://github.com/Pit-CL/mcp-multilang-sandbox.git
cd mcp-multilang-sandbox
# Install dependencies
npm install
# Build
npm run build
# Run tests (optional)
npm run test:mcp
```
### Add to Claude Code
```bash
# Add as MCP server
claude mcp add multilang-sandbox node /path/to/mcp-multilang-sandbox/dist/mcp/server.js
# Verify it's connected
claude mcp list
# Should show: multilang-sandbox ✓ Connected
```
### Manual Configuration
Add to your Claude settings (`~/.claude.json` or VS Code settings):
```json
{
"mcpServers": {
"multilang-sandbox": {
"command": "node",
"args": ["/path/to/mcp-multilang-sandbox/dist/mcp/server.js"],
"env": {
"LOG_LEVEL": "info"
}
}
}
}
```
## Usage
Once configured, Claude can use these tools:
### Execute Code
```typescript
// Python
sandbox_execute({ language: 'python', code: 'print("Hello!")' })
// TypeScript
sandbox_execute({ language: 'typescript', code: 'console.log("Hello!")' })
// With ML libraries (numpy, pandas, sklearn, torch)
sandbox_execute({
language: 'python',
code: 'import numpy as np; print(np.array([1,2,3]))',
ml: true
})
```
### Persistent Sessions
```typescript
// Create a session
sandbox_session({ action: 'create', name: 'my-project', language: 'python' })
// Execute in session (state persists)
sandbox_execute({ language: 'python', code: 'x = 42', session: 'my-project' })
sandbox_execute({ language: 'python', code: 'print(x)', session: 'my-project' }) // prints 42
// Install packages
sandbox_install({ session: 'my-project', packages: ['pandas', 'requests'] })
// Cleanup
sandbox_session({ action: 'destroy', name: 'my-project' })
```
### File Operations
```typescript
// Write a file
sandbox_file_ops({ session: 'my-project', operation: 'write', path: 'data.csv', content: 'a,b\n1,2' })
// Read it back
sandbox_file_ops({ session: 'my-project', operation: 'read', path: 'data.csv' })
```
### System Stats
```typescript
// View pool, cache, and session stats
sandbox_inspect({ target: 'all' })
// Security audit
sandbox_security({ action: 'stats' })
```
## MCP Tools Reference
| Tool | Description |
|------|-------------|
| `sandbox_execute` | Execute code in any supported language |
| `sandbox_session` | Create/list/pause/resume/destroy sessions |
| `sandbox_install` | Install packages with caching |
| `sandbox_file_ops` | Read/write/list/delete files in sessions |
| `sandbox_inspect` | View system stats (pool, cache, sessions) |
| `sandbox_security` | View audit logs and security events |
## Architecture
```
┌─────────────────────────────────────────────────────────┐
│ Claude / MCP Client │
└───────────────────────────┬─────────────────────────────┘
│ JSON-RPC (stdio)
┌───────────────────────────▼─────────────────────────────┐
│ MCP Sandbox Server │
│ ┌────────────────────────────────────────────────────┐ │
│ │ Tools: execute | session | install | file_ops │ │
│ │ inspect | security │ │
│ ├────────────────────────────────────────────────────┤ │
│ │ Core: ContainerPool | PackageCache | Sessions │ │
│ ├────────────────────────────────────────────────────┤ │
│ │ Security: Seccomp | Capabilities | AuditLogger │ │
│ ├────────────────────────────────────────────────────┤ │
│ │ Runtimes: Python | TS | JS | Go | Rust | Bash │ │
│ └────────────────────────────────────────────────────┘ │
└───────────────────────────┬─────────────────────────────┘
│ Dockerode
┌───────────────────────────▼─────────────────────────────┐
│ Docker Engine │
│ [Container Pool] [Active Sessions] [Image Cache] │
└─────────────────────────────────────────────────────────┘
```
## Security
### 6 Layers of Protection
1. **Code Validation** - Pattern blocklist (os, subprocess, eval, exec)
2. **Seccomp Profiles** - Syscall filtering per language
3. **Capability Dropping** - CAP_DROP ALL
4. **Network Isolation** - NetworkMode: none
5. **Resource Limits** - Memory, CPU, PIDs, ulimits
6. **Audit Logging** - All operations tracked
### Blocked Syscalls
`ptrace`, `mount`, `umount`, `kexec_load`, `init_module`, `delete_module`, `reboot`, `bpf`, `userfaultfd`, and [more](src/security/seccomp.ts)
## Performance
| Metric | Value |
|--------|-------|
| Pool hit (warm) | **0ms** |
| Pool miss (cold) | ~80-100ms |
| Session create | ~85ms |
| Package cache hit | <1ms |
| Python execution | ~60ms |
| Bash execution | ~35ms |
## Development
```bash
# Watch mode (auto-rebuild)
npm run dev
# Type checking
npm run typecheck
# Run tests
npm run test:all # All tests
npm run test:mcp # MCP tools (19 tests)
npm run test:runtimes # Language runtimes
# Clean build
npm run clean && npm run build
```
## Project Structure
```
src/
├── mcp/server.ts # MCP server & tool handlers
├── core/
│ ├── ContainerPool.ts # Pre-warmed container pooling
│ ├── PackageCache.ts # SHA256-based package caching
│ └── SessionManager.ts # Persistent sessions with TTL
├── security/
│ ├── seccomp.ts # Syscall filtering profiles
│ └── AuditLogger.ts # Operation audit logging
├── runtimes/
│ ├── PythonRuntime.ts # + PythonMLRuntime for ML
│ ├── TypeScriptRuntime.ts
│ ├── JavaScriptRuntime.ts
│ ├── GoRuntime.ts
│ ├── RustRuntime.ts
│ └── BashRuntime.ts
└── docker/
├── DockerClient.ts # Dockerode wrapper
└── Container.ts # Container abstraction
```
## Contributing
Issues and PRs welcome! This started as a personal project to replace cloud sandboxes with something local and free.
## License
MIT
## Credits
Built with [@modelcontextprotocol/sdk](https://github.com/modelcontextprotocol/sdk), [Dockerode](https://github.com/apocas/dockerode), and [Zod](https://github.com/colinhacks/zod).
