| name | sandbox-npm-install |
| description | Install npm packages in a Docker sandbox environment. Use this skill whenever you need to install, reinstall, or update node_modules inside a container where the workspace is mounted via virtiofs. Native binaries (esbuild, lightningcss, rollup) crash on virtiofs, so packages must be installed on the local ext4 filesystem and symlinked back. |
Sandbox npm Install
When to Use This Skill
Use this skill whenever:
- You need to install npm packages for the first time in a new sandbox session
package.json or package-lock.json has changed and you need to reinstall- You encounter native binary crashes with errors like
SIGILL, SIGSEGV, mmap, or unaligned sysNoHugePageOS
- The
node_modules directory is missing or corrupted
Prerequisites
- A Docker sandbox environment with a virtiofs-mounted workspace
- Node.js and npm available in the container
- A
package.json file in the target workspace
Background
Docker sandbox workspaces are typically mounted via virtiofs (file sync between the host and Linux VM). Native Go and Rust binaries (esbuild, lightningcss, rollup, etc.) crash with mmap alignment failures when executed from virtiofs on aarch64. The fix is to install on the container's local ext4 filesystem and symlink back into the workspace.
Step-by-Step Installation
Run the bundled install script from the workspace root:
bash scripts/install.sh
Common Options
| Option | Description |
|---|
--workspace <path> | Path to directory containing package.json (auto-detected if omitted) |
--playwright | Also install Playwright Chromium browser for E2E testing |
What the Script Does
- Copies
package.json, package-lock.json, and .npmrc (if present) to a local ext4 directory
- Runs
npm ci (or npm install if no lockfile) on the local filesystem
- Symlinks
node_modules back into the workspace
- Verifies known native binaries (esbuild, rollup, lightningcss, vite) if present
- Optionally installs Playwright browsers and system dependencies (uses
sudo when available)
If verification fails, run the script again — crashes can be intermittent during initial setup.
Post-Install Verification
After the script completes, verify your toolchain works. For example:
npm test
npm run build
npm run dev
Important Notes
- The local install directory (e.g.,
/home/agent/project-deps) is container-local and is NOT synced back to the host
- The
node_modules symlink appears as a broken link on the host — this is harmless since node_modules is typically gitignored
- Running
npm ci or npm install on the host naturally replaces the symlink with a real directory
- After any
package.json or package-lock.json change, re-run the install script
- Do NOT run
npm ci or npm install directly in the mounted workspace — native binaries will crash
Troubleshooting
| Problem | Solution |
|---|
SIGILL or SIGSEGV when running dev server | Re-run the install script; ensure you're not running npm install directly in the workspace |
node_modules not found after install | Check that the symlink exists: ls -la node_modules |
| Permission errors during install | Ensure the local deps directory is writable by the current user |
| Verification fails intermittently | Run the script again — native binary crashes can be non-deterministic on first load |
Vite Compatibility
If your project uses Vite, you may need to allow the symlinked path in server.fs.allow. Add the symlink target's parent directory (e.g., /home/agent/project-deps/) to your Vite config so that Vite can serve files through the symlink.
