Visible cmd.exe windows spawn during npm update checks — disruptive on multi-session setups

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Description:

Environment

• OS: Windows 11 Pro 10.0.26200
• Claude Code version: 2.1.80
• Shell: Windows Terminal + cmd.exe / bash (Git for Windows)
• Node.js: via C:\Program Files\nodejs\

Bug Description

On Windows, Claude Code periodically spawns visible black cmd.exe popup windows to
perform npm update checks. These windows flash briefly and close, but are visually
disruptive — especially when running multiple Claude Code sessions simultaneously (e.g.
a multi-tab ACP harness setup), where the frequency multiplies linearly with the
number of sessions.

Commands observed spawning visible windows (via Sysinternals Process Monitor):
cmd.exe /q /d /s /c "npm ^"view^" ^"@anthropic-ai/claude-code@latest^" ^"version^""
cmd.exe /c CALL "C:\Program Files\nodejs\node.exe" "C:\Program
Files\nodejs\node_modules\..."
cmd.exe /c "ver"
cmd.exe /d /s /c "where.exe bash"
cmd.exe /d /s /c "echo $PATH"

Impact

• With 1 session: intermittent flashes every few minutes
• With 4 sessions: near-constant flashing, visually indistinguishable from

malware/runaway process behavior

• During investigation, these popups were initially mistaken for a security incident,

requiring ~2 hours of process tracing with Sysinternals Process Monitor to identify the
root cause

What Should Happen?

Expected Behavior
All background operations (update checks, environment detection) should use WindowStyle
Hidden or equivalent (CREATE_NO_WINDOW flag) on Windows so no visible cmd.exe window
appears.

Workaround

None currently available. --no-update-check flag does not exist.

Suggested Fix

When spawning child processes on Windows for background operations, use:

• Node.js: { windowsHide: true } in child_process.spawn() / exec() options
• This is a single-flag fix that would eliminate all visible popups

Error Messages/Logs

2 cmd shell windows pop open every 2min then close.  Have done extensive troubleshooting and root cause identified above.

Steps to Reproduce

Not sure

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

na

Claude Code Version

Claude Code version: 2.1.80

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_