[BUG] spawn ENAMETOOLONG on Claude Code (Desktop) - all models, Windows only, works fine on Mac

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 Claude Code chat (Desktop app, Code tab — new, existing, empty) throws "spawn ENAMETOOLONG" immediately on Windows. This is specifically the Code tab, not Cowork.

Happens with every model I've tried, not just one. I also tried changing the effort/thinking setting — no change, error persists.

This was working before on Windows and stopped without me changing anything.

Critically, I tested the exact same account on macOS and it works perfectly there. This rules out an account-level or backend-side issue — it is specific to the Windows implementation of the Code tab's process spawning.

What Should Happen?

Claude Code (Desktop, Code tab) should start a chat session normally, the same way it does on macOS with the same account.

Error Messages/Logs

spawn ENAMETOOLONG

Steps to Reproduce

1. Sign into Claude Desktop on Windows with my account
2. Open the Code tab (not Cowork)
3. Start any chat — new, existing, or empty, with any model
4. spawn ENAMETOOLONG is thrown immediately
5. Tried switching models — same error on all of them
6. Tried changing the effort/thinking level — no change

Cross-check:

1. Sign into the exact same account on macOS with Claude Desktop
2. Open the Code tab, start a chat
3. Works without any error

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

1.17377.1 (2b3ab4)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

Confirmed the same Anthropic account works correctly on macOS (Code tab, same day), which rules out an account/backend-side cause. This strongly suggests a Windows-specific bug in how the Code tab spawns its subprocess.

This is happening in the Code tab specifically, not Cowork — worth noting since related issues (#64551, #60669, #69658) report the same error in the Cowork tab. May be the same underlying subprocess-spawning bug affecting both tabs, or a separate but similar issue in Code.

Claude Desktop version: 1.17377.1 (2b3ab4)
Windows build: 11 25H2