Windows/WSL often throws EPERM when npm touches files locked by AV/IDEs or on restricted mounts. Release locks, fix ownership, shorten paths, and re-run npm with user-owned locations.
EPERM indicates the OS blocked the requested filesystem operation even before checking permissions. In npm this happens when Windows/WSL or security tools deny rename/unlink/mkdir on node_modules, or when the path lives on a restricted mount or long path. It is common on Windows with Defender/AV, long paths, or VS Code holding handles; on WSL2 working on /mnt/c (NTFS); and in Docker/CI when the workspace is owned by a different user. Unlike EACCES, EPERM often points to policy or a lock rather than simple UNIX mode bits.
Copy the path from the error. On Windows, use Resource Monitor or handle.exe <path> to see which process holds it.
Close VS Code/terminals watching the repo. Add Defender/AV exclusions for the project and npm cache. Retry from a fresh shell.
On WSL, clone to ~/projects (ext4) instead of /mnt/c. Shorten Windows paths to avoid MAX_PATH issues.
npm config set cache ~/.npm-cache
mkdir -p ~/.npm-global
npm config set prefix ~/.npm-global
export PATH="$HOME/.npm-global/bin:$PATH"
rm -rf node_modules package-lock.json
npm cache clean --forcenpm ciRun containers with matching UID/GID or chown the workspace volume before npm install so the OS does not reject operations.
EPERM on Windows often disappears when Developer Mode is enabled (symlink/rename policies are relaxed) and Defender exclusions are set. In CI, artifacts copied from root-owned build steps can cause EPERM in later non-root steps—clean and chown the workspace between steps. If a corporate policy forces read-only attributes, install dependencies in a per-user cache/prefix outside the locked directory.
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