spawn undefined\System32\WindowsPowerShell" error during Sanity login

This is a Windows-specific environment variable issue where the Sanity CLI can't find PowerShell because the SystemRoot environment variable is undefined or missing. The error spawn undefined\System32\WindowsPowerShell\v1.0\powershell ENOENT shows that it's trying to construct the path to PowerShell but getting "undefined" instead of C:\Windows.

Here are the solutions to fix this:

Solution 1: Set the SystemRoot environment variable

The SystemRoot environment variable is missing or not accessible. You need to set it:

1. Open Command Prompt as Administrator
2. Run: setx SystemRoot C:\Windows /M
3. Close and reopen your terminal
4. Try npm create sanity@latest again

Solution 2: Use the login URL manually

If the above doesn't work, you can manually authenticate:

1. Run npm create sanity@latest again
2. When it fails, copy the login URL from the error message (the https://api.sanity.io/v1/auth/login/google?... part)
3. Manually paste it into your browser
4. Complete the authentication there
5. The CLI should detect the successful login

Solution 3: Try a different terminal

Sometimes this is terminal-specific. Try using:

• Windows Command Prompt (cmd.exe) instead of PowerShell
• Git Bash if you have it installed
• WSL (Windows Subsystem for Linux) - as mentioned in this Sanity answer, this has been reported to work when Windows terminals fail

Solution 4: Update Node.js

You're running Node.js v18.12.1. Try updating to a more recent Node.js version (Node 20+ is now recommended for Sanity Studio v4). Sometimes environment variable handling is improved in newer Node versions.

Solution 5: Check environment variables manually

Verify your environment variables are intact:

1. Open System Properties → Advanced → Environment Variables
2. Check that SystemRoot exists in System variables and is set to C:\Windows
3. If it's missing, add it manually through the GUI

The root cause is that the Sanity CLI uses the open package to launch your browser for authentication, which on Windows tries to use PowerShell, but it can't construct the correct path without the SystemRoot variable. Solution 1 is usually the quickest fix!