Devcontainer Setup Guide

Run Claude Code with --dangerously-skip-permissions safely using Anthropic's official devcontainer approach.

Overview

The devcontainer feature creates an isolated Docker environment where Claude can operate with full autonomy while protecting your host system. This implements Anthropic's official devcontainer approach.

Why Use a Devcontainer?

Without Devcontainer	With Devcontainer
Claude asks permission for every file operation	Claude operates autonomously
Manual approval interrupts workflow	Uninterrupted AI development
Direct access to host filesystem	Isolated environment
Full network access	Allowlisted domains only

Quick Start

# 1. Set your API key
export ANTHROPIC_API_KEY="sk-ant-..."

# 2. Run the setup script
./setup-devcontainer.sh

# 3. Start the container (VS Code)
# Cmd/Ctrl+Shift+P → "Dev Containers: Reopen in Container"

# 4. Run Claude with full autonomy (inside container)
claude --dangerously-skip-permissions

Installation Options

Option 1: Setup Script (Recommended)

# Download and run (if not in the repo)
curl -sL https://raw.githubusercontent.com/PaulDuvall/claude-code/main/setup-devcontainer.sh | bash

# Or if you have the repo cloned
./setup-devcontainer.sh

Option 2: Slash Command

If you have Claude Code Custom Commands installed:

claude
/xdevcontainer

Option 3: Manual Setup

Create .devcontainer/devcontainer.json and .devcontainer/Dockerfile manually following the examples in the xdevcontainer.md command documentation.

Setup Script Options

Basic Usage

# Full setup with all security features (recommended)
./setup-devcontainer.sh

# Preview what would be created without writing files
./setup-devcontainer.sh --dry-run

Configuration Flags

Flag	Description
`--help`, `-h`	Show help message
`--dry-run`	Preview files without creating them
`--force`	Overwrite existing configuration
`--minimal`	Minimal tooling (Node.js, Git only)
`--no-network-firewall`	Disable network restrictions
`--strict`	Fail if prerequisites missing (for CI)
`--allow-domain DOMAIN`	Add custom domain to allowlist

Tooling Options

Full Tooling (Default):

Node.js
Python with boto3, requests
Git
GitHub CLI
AWS CLI
Docker-in-Docker

Minimal Tooling (--minimal):

Node.js
Git
GitHub CLI

Examples

# Minimal setup without network restrictions
./setup-devcontainer.sh --minimal --no-network-firewall

# Add custom domains for enterprise registries
./setup-devcontainer.sh --allow-domain internal.registry.com --allow-domain npm.mycompany.com

# CI/CD usage with strict validation
./setup-devcontainer.sh --strict

# Using environment variable for extra domains
DEVCONTAINER_EXTRA_DOMAINS="internal.registry.com,npm.mycompany.com" ./setup-devcontainer.sh

Security Features

Network Firewall

By default, the container only allows outbound connections to:

Domain	Purpose
`api.anthropic.com`	Claude API
`github.com`	Git operations
`registry.npmjs.org`	NPM packages
`pypi.org`	Python packages
`files.pythonhosted.org`	Python package files

All other HTTPS (443) and HTTP (80) traffic is blocked.

Container Isolation

--cap-drop=ALL: Drops all Linux capabilities
--security-opt=no-new-privileges: Prevents privilege escalation
Non-root user: Runs as vscode user
No host mounts: Isolated from host filesystem by default

Adding Custom Domains

For enterprise environments with private registries:

# Via command line flag (can be used multiple times)
./setup-devcontainer.sh --allow-domain internal.registry.com

# Via environment variable (space or comma separated)
export DEVCONTAINER_EXTRA_DOMAINS="registry1.company.com,registry2.company.com"
./setup-devcontainer.sh

Using the Devcontainer

With VS Code

Install the Dev Containers extension
Open your project folder
Press Cmd/Ctrl+Shift+P and select "Dev Containers: Reopen in Container"
Wait for the container to build and start
Open terminal and run: claude --dangerously-skip-permissions

With CLI

# Start the container
devcontainer up --workspace-folder .

# Execute commands inside
devcontainer exec --workspace-folder . claude --dangerously-skip-permissions

# Or get a shell
devcontainer exec --workspace-folder . bash

Installing devcontainer CLI

npm install -g @devcontainers/cli

CI/CD Integration

GitHub Actions Example

name: Claude Code in Devcontainer

on: [push]

jobs:
  claude-review:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Setup devcontainer
        run: ./setup-devcontainer.sh --strict
        env:
          ANTHROPIC_API_KEY: ${{ secrets.ANTHROPIC_API_KEY }}

      - name: Build container
        run: devcontainer up --workspace-folder .

      - name: Run Claude
        run: |
          devcontainer exec --workspace-folder . \
            claude --dangerously-skip-permissions \
            "Review this codebase and suggest improvements"

Using `--strict` Mode

The --strict flag is designed for CI environments:

Fails immediately if Docker is not installed
Fails if Docker daemon is not running
Fails if ANTHROPIC_API_KEY is not set
Provides clear error messages for debugging

# Will exit with error code if prerequisites missing
./setup-devcontainer.sh --strict

Troubleshooting

Docker Not Found

ERROR: Docker not found. Install Docker to use devcontainers.

Solution: Install Docker Desktop or Docker Engine.

Docker Daemon Not Running

WARNING: Docker daemon is not running.

Solution: Start Docker Desktop or run sudo systemctl start docker.

API Key Not Set

WARNING: ANTHROPIC_API_KEY not set.

Solution: Set the environment variable before running the container:

export ANTHROPIC_API_KEY="sk-ant-..."

Container Build Fails

If the container fails to build:

Check Docker has enough disk space

Try rebuilding without cache:

devcontainer up --workspace-folder . --remove-existing-container

Check for network issues downloading base images

Network Firewall Blocking Required Service

If you need to access a domain that's blocked:

# Add the domain to the allowlist
./setup-devcontainer.sh --force --allow-domain your-service.com

# Rebuild the container
devcontainer up --workspace-folder . --remove-existing-container

Verifying Firewall Rules

Inside the container, check iptables rules:

# View current rules
sudo iptables -L OUTPUT -n -v

# Test connectivity (should work)
curl -I https://api.anthropic.com

# Test blocked domain (should fail)
curl -I https://example.com

Security Considerations

Safe For

Your own trusted projects
Development and testing workflows
CI/CD automation with Claude
Learning and experimentation

Avoid For

Untrusted repositories: Prompt injection risk from malicious code
Projects with unreviewed credentials: Claude can access anything in the container
Production systems: Use proper security controls for production

Credential Handling

Important: Any credentials passed to the container are accessible to Claude.

Best practices:

Use minimal credentials with limited scope
Rotate credentials regularly
Use temporary/session credentials when possible
Review what credentials you're passing via remoteEnv

File Reference

Generated Files

The setup script creates:

.devcontainer/
├── devcontainer.json    # Container configuration
└── Dockerfile           # Container image definition

devcontainer.json Structure

{
  "name": "Claude Code Sandbox",
  "build": { "dockerfile": "Dockerfile" },
  "features": { /* Development tools */ },
  "postCreateCommand": "npm install -g @anthropic-ai/claude-code",
  "remoteEnv": { /* Environment variables from host */ },
  "runArgs": ["--cap-drop=ALL", "--security-opt=no-new-privileges"],
  "mounts": [],
  "customizations": { "vscode": { /* VS Code settings */ } }
}

Environment Variables Passed

Variable	Purpose
`ANTHROPIC_API_KEY`	Claude API authentication
`GITHUB_TOKEN`	GitHub operations
`AWS_ACCESS_KEY_ID`	AWS access
`AWS_SECRET_ACCESS_KEY`	AWS secret
`AWS_DEFAULT_REGION`	AWS region

FilesExpand file tree

devcontainer-guide.md

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