Every Twill task runs inside an isolated cloud sandbox based on Ubuntu 22.04. The sandbox comes pre-loaded with common languages, tools, and services so your agent can build, test, and verify changes without extra setup.
Languages and Runtimes
Your agent has immediate access to:
- Node.js (LTS) with npm, managed via nvm
- Python 3 with pip
- Bash
Need a different language version? The Dev Environment Agent installs additional runtimes as part of your project’s entrypoint script.
Package Managers
| Manager | Use case |
|---|
| pnpm | Fast, disk-efficient Node.js package manager |
| npm | Bundled with Node.js |
| uv | Fast Python package manager |
| pip | Standard Python packages |
Docker Support
Sandboxes include a full Docker engine. Your agent can build images, run containers, and use Docker Compose to spin up databases, caches, and other services your project depends on.
# The agent can run your project's Docker Compose stack
docker compose up -d
Docker Compose is available as a plugin (docker compose), not as a
standalone binary.
| Tool | Purpose |
|---|
| git | Version control |
| gh | GitHub CLI for PRs, issues, and actions |
| jq | JSON processing |
| make | Build automation |
| curl, wget | HTTP requests |
| openssl | TLS and crypto utilities |
Cloud CLIs
Agents can interact with cloud services when you provide credentials through environment variables:
- AWS CLI v2
- Google Cloud CLI
Add your cloud credentials as environment secrets in your repository settings.
The agent uses them to run deploys, access cloud databases, or pull assets
during builds.
Browser Automation
Sandboxes include a headless Chromium browser. The agent uses it to:
- Verify UI changes by navigating your running app
- Take screenshots of before/after states
- Test form submissions, navigation flows, and interactive elements
- Record browser sessions for review
Tools like Puppeteer and Playwright automatically detect the pre-installed browser with no additional download or configuration needed.
Virtual Display
A virtual display (Xvfb) is available for testing desktop applications or tools that require a screen. This powers Twill’s computer-use capabilities, including screenshot capture and mouse/keyboard automation.
SSH and Web Terminal
Each sandbox exposes:
- SSH for direct terminal access
- Web terminal for browser-based access to the sandbox shell
These are used by Twill’s live preview feature.
What About Missing Dependencies?
You don’t need to worry about gaps in the sandbox. When your project needs something that isn’t pre-installed, the Dev Environment Agent handles it automatically:
- Detects your project’s requirements from lockfiles, configs, and CI workflows
- Generates an entrypoint script that installs missing dependencies
- Persists the configuration so future tasks start faster
If a dependency issue comes up mid-task, the agent self-heals by diagnosing the problem and updating the environment. 
