[BUG] "spawn ENAMETOOLONG" - Cowork completely broken on Windows (all projects) - UPDATE: SELF FIX - Details in reply

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?

Every Cowork project throws spawn ENAMETOOLONG immediately on Windows. No tasks execute. No files are read or written. This is affecting all my projects in coworkall of a sudden without warning from what I could see.

Environment
OS: Windows 11
Claude Desktop version: 1.18286.0 (259c3f)
Account type: Max
Workspace folders tested: Multiple projects, all fail identically

What Should Happen?

Cowork runs as normal, instead as soon as I ask it to do anything, even in a new sessions, it fails.

Error Messages/Logs

"Something went wrong
Try sending your message again. If it keeps happening, share feedback so we can investigate.

spawn ENAMETOOLONG
You can restart the conversation from an earlier message."

Steps to Reproduce

Open Claude Desktop on Windows 11
Navigate to Cowork
Open any existing project (or create a new one)
Attempt to run any task

Result: spawn ENAMETOOLONG error fires immediately. No work is performed.

Expected: Cowork connects to the workspace and executes the task normally.

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.167

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

This appears to be the same underlying bug reported in:

• #64551 — spawn ENAMETOOLONG on Cowork workspace connection (closed)
• #60669 — spawn ENAMETOOLONG, account-specific (closed)
• #72725 — spawn ENAMETOOLONG on Code tab, Windows only (closed as duplicate)

All related issues have been closed without a shipped fix. The root cause identified by other reporters is that the subprocess command constructed by Cowork exceeds Windows' ~8,191 character CreateProcess limit. The Windows long path registry setting (LongPathsEnabled) does not affect command-line length limits and it is not something I can fix on my end from what I can see.

This is a blocking issue that makes Cowork entirely unusable on Windows.

So, yes there are "duplicates" but they've been closed so I can't post and add to them. This is super debilitating.