E2B Code Execution Agent

An advanced Mastra template that provides a coding agent capable of planning, writing, executing, and iterating on code in secure, isolated E2B sandboxes with comprehensive file management and development workflow capabilities.

Overview

This template demonstrates how to build an AI coding assistant that can work with real development environments. The agent can create sandboxes, manage files and directories, execute code in multiple languages, and monitor development workflows - all within secure, isolated E2B environments.

Features

  • Secure Code Execution: Run Python, JavaScript, and TypeScript code in isolated E2B sandboxes
  • Complete File Management: Create, read, write, delete files and directories with batch operations
  • Multi-Language Support: Execute code in Python, JavaScript, and TypeScript environments
  • Live Development Monitoring: Watch directory changes and monitor development workflows
  • Command Execution: Run shell commands, install packages, and manage dependencies
  • Memory System: Persistent conversation memory with semantic recall and working memory
  • Development Workflows: Professional development patterns with build automation

Prerequisites

  • Node.js 20 or higher
  • E2B API key (sign up at e2b.dev)
  • OpenAI API key

Setup

  1. Clone and install dependencies:

     1git clone https://github.com/mastra-ai/template-coding-agent.git
 2cd template-coding-agent
 3pnpm install

  2. Set up environment variables:

     1cp .env.example .env
 2# Edit .env and add your API keys
     1E2B_API_KEY="your-e2b-api-key-here"
 2OPENAI_API_KEY="your-openai-api-key-here"

  3. Start the development server:

    pnpm run dev

Architecture

Core Components

Coding Agent (src/mastra/agents/coding-agent.ts)

The main agent with comprehensive development capabilities:

  • Sandbox Management: Creates and manages isolated execution environments
  • Code Execution: Runs code with real-time output capture
  • File Operations: Complete CRUD operations for files and directories
  • Development Monitoring: Watches for changes and monitors workflows
  • Memory Integration: Maintains conversation context and project history

E2B Tools (src/mastra/tools/e2b.ts)

Complete toolkit for sandbox interaction:

Sandbox Management:

  • createSandbox - Initialize new isolated environments
  • Connection management with timeout handling

Code Execution:

  • runCode - Execute Python, JavaScript, TypeScript code
  • Real-time output capture and error handling
  • Environment variable and timeout configuration

File Operations:

  • writeFile - Create individual files
  • writeFiles - Batch create multiple files for project setup
  • readFile - Read file contents for analysis and validation
  • listFiles - Explore directory structures
  • deleteFile - Clean up files and directories
  • createDirectory - Set up project structures

File Information & Monitoring:

  • getFileInfo - Get detailed file metadata
  • checkFileExists - Validate file existence for conditional logic
  • getFileSize - Monitor file sizes and track changes
  • watchDirectory - Live monitoring of file system changes

Development Workflow:

  • runCommand - Execute shell commands, build scripts, package management

Memory System

The agent includes a configured memory system:

  • Thread Management: Automatic conversation title generation
  • Semantic Recall: Search through previous interactions
  • Working Memory: Maintains context across interactions
  • Vector Storage: Semantic search capabilities with LibSQLVector

Configuration

Environment Variables

 1E2B_API_KEY=your_e2b_api_key_here
 2OPENAI_API_KEY=your_openai_api_key_here

Customization

You can customize the agent behavior by modifying the instructions in src/mastra/agents/coding-agent.ts:

 1export const codingAgent = new Agent({
 2  name: 'Coding Agent',
 3  instructions: `
 4    // Customize agent instructions here
 5    // Focus on specific languages, frameworks, or development patterns
 6  `,
 7  model: openai('gpt-4.1'),
 8  // ... other configuration
 9});

Common Issues

"E2B_API_KEY is not set"

  • Make sure you've set the environment variable
  • Check that your API key is valid and has sufficient credits
  • Verify your E2B account is properly configured

"Sandbox creation failed"

  • Check your E2B API key and account status
  • Ensure you haven't exceeded sandbox limits
  • Verify network connectivity to E2B services

"Code execution timeout"

  • Increase timeout values for long-running operations
  • Break down complex operations into smaller steps
  • Monitor resource usage and optimize code

"File operation errors"

  • Validate file paths and permissions
  • Check sandbox file system limits
  • Ensure directories exist before file operations

"Agent stopping with tool-call reason"

  • Increase maxSteps in the agent configuration

Development

Project Structure

 1src/mastra/
 2      agents/
 3        coding-agent.ts              # Main coding agent with development capabilities
 4      tools/
 5        e2b.ts                      # Complete E2B sandbox interaction toolkit
 6      index.ts                        # Mastra configuration with storage and logging