Run Your AI Coding Agent in Containers - Complete Beginner's Guide

Key Takeaways

• Dev containers bundle your entire development environment (libraries, SDKs, runtimes) into a secure, self-contained container
• The same configuration works locally via Docker Desktop and in the cloud via GitHub Codespaces
• AI coding agents execute commands inside the container, creating a safe sandbox for experimentation
• VS Code maintains your personal settings and extensions while connecting to different containerized environments

Dev Container Workflow

flowchart LR
    Config[devcontainer.json] --> Local{Run Where?}
    Local -->|Local| Docker[Docker Desktop]
    Local -->|Cloud| Codespaces[GitHub Codespaces]
    Docker --> VSCode[VS Code Connected]
    Codespaces --> Browser[VS Code in Browser]
    VSCode --> Agent[AI Agent Executes
in Container]
    Browser --> Agent

Getting Started

1. Install prerequisites: Dev Containers extension + Docker Desktop
2. Try a sample: Remote Explorer → Try a Dev Container Sample
3. Add to existing project: Command palette → "Add Dev Container Configuration Files"
4. Let Copilot configure it: Ask the agent to customize based on your project's dependencies

Configuration Structure

.devcontainer/
└── devcontainer.json    # Image, extensions, ports, post-create commands

Key configuration options:

• image or dockerfile: Base container environment
• customizations.vscode.extensions: Extensions installed in container
• forwardPorts: Ports exposed to local machine
• postCreateCommand: Setup scripts to run after container creation

Code Snippets

Basic devcontainer.json

{
  "name": "Node.js",
  "image": "mcr.microsoft.com/devcontainers/javascript-node:22",
  "forwardPorts": [3000, 9000],
  "postCreateCommand": "npm install",
  "customizations": {
    "vscode": {
      "extensions": ["dbaeumer.vscode-eslint"]
    }
  }
}

Why This Matters for AI Agents

When AI agents execute commands (builds, tests, file operations), everything happens inside the container. This provides:

• Safety: Agent can't accidentally modify your host system
• Reproducibility: Same environment across machines and team members
• Isolation: Multiple projects with conflicting dependencies don't interfere

Notable Quotes

"Wouldn't it be awesome if either when I'm coding or an agent is executing commands that everything is happening completely separated off from my machine, creating a safe environment for any type of work or experimentation?"

"Dev containers create that private secure development environment and all the dependencies that I want for complete customization."

Connections

• introducing-agent-skills-in-vs-code - Same author exploring another VS Code AI capability: portable instruction folders that transform agents into domain-specific experts