Full‑Stack Coding Agent Starter Kit

An AI-powered coding assistant that writes, executes, and previews code in isolated E2B sandboxes. Built with Cedar-OS for chat UI, Mastra for agent orchestration, and E2B for secure, ephemeral execution.

What's inside the kit

This production-ready starter kit includes everything you need to build an AI coding agent that can generate complete applications with natural language. You'll get:

• Cedar-OS chat interface - Beautiful, production-ready chat UI with real-time streaming support
• Mastra agent orchestration - Powerful agent framework with tools, planning, and state management
• E2B sandbox execution - Secure, isolated environments for running code with multiple pre-configured templates
• Multi-language support - Generate and execute Python, JavaScript, TypeScript, React, Next.js, Vue, Streamlit, and Gradio apps
• Complete file management - Full CRUD operations on files and directories within sandboxes
• Live code execution - Run code with real-time output streaming and error handling
• Code preview - Syntax-highlighted code viewer with file tree navigation
• Live web preview - See your web applications running in real-time with iframe preview
• Thread-scoped sandboxes - Each conversation has its own isolated development environment
• State persistence - File trees, code, and sandbox info persist across page refreshes

Prerequisites

• Node.js 18+ (20+ recommended)
• OpenAI API key - For the AI model
• E2B API key - For secure sandbox execution
• Familiarity with TypeScript, Node, and React
• Basic terminal skills
• Understanding of async/await patterns

What you'll build

An AI coding agent that can:

• Generate complete applications from natural language descriptions
• Choose the right environment - Automatically selects from multiple E2B templates (Python, Next.js, Streamlit, Gradio, Vue)
• Manage project files - Create, read, update, and delete files and directories
• Execute code safely - Run code in isolated sandboxes with automatic timeout management
• Preview live applications - Display running web apps with real-time updates
• Stream responses - Real-time token streaming with server-sent events (SSE)
• Persist across sessions - Maintain sandbox state and file trees between conversations
• Handle errors gracefully - Production-ready error boundaries and retry logic

Key Features

🎯 AI-Powered Code Generation

• Natural language to code across multiple languages and frameworks
• Smart template selection based on project requirements
• Complete project setup with dependencies and build tools

🔐 Secure E2B Sandboxes

• code-interpreter-v1 - Python data analysis and notebook-style execution
• nextjs-developer - Next.js apps with TypeScript and Tailwind
• streamlit-developer - Python UI apps with live reload
• gradio-developer - Python demo applications
• vue-developer - Vue/Nuxt applications
• Automatic resource cleanup and timeout management

💻 Complete Development Workflow

• File operations (create, read, edit, delete files and directories)
• Command execution (npm/pip install, build commands, dev servers)
• Real-time code execution with output streaming
• Build automation and package management

🎨 Modern UI & Preview

• Code preview with syntax highlighting and file tree
• Live web preview for running applications
• Dual view modes (Code/Web) with seamless switching
• Sandbox status tracking with expiration timers

Safety & Production-Ready

This starter kit includes enterprise-grade safety features:

• Execution timeouts - Automatic sandbox cleanup after inactivity
• Resource isolation - Each conversation runs in its own E2B sandbox
• Error boundaries - Production-ready error handling throughout the app
• Secure API key management - Environment variables and best practices
• Rate limiting ready - Built-in patterns for managing API costs
• Auth integration - Optional Auth0 for AI Agents support

Get Started

Clone the repository and follow the Quick Start guide to launch your AI coding agent in minutes. The kit includes:

• Complete monorepo setup with Next.js frontend and Mastra backend
• Development environment configuration
• API key setup instructions
• Example prompts to test the agent
• Deployment guide for production