sandbox-npm-install

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

1. Copies package.json, package-lock.json, and .npmrc (if present) to a local ext4 directory
2. Runs npm ci (or npm install if no lockfile) on the local filesystem
3. Symlinks node_modules back into the workspace
4. Verifies known native binaries (esbuild, rollup, lightningcss, vite) if present
5. 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             # Run project tests
npm run build        # Build the project
npm run dev          # Start dev server

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.