[BUG] Cowork Save Skill fails with INVALID_PATH when Mac username contains a space

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?

App version: 1.5354.0 (9a9e3d)
OS: macOS
Bug: The Save Skill button in Cowork fails with the following error when the Mac username contains a space:

LocalFileAccessError: [INVALID_PATH] Failed to resolve path: /Users/davesfingerprint macbook/Library/Application Support/Claude/local-agent-mode-sessions/.../outputs/smart-sequence.skill

Cowork is constructing file paths internally that include the Mac username but is not escaping or quoting spaces, making the path unresolvable. This blocks the Save Skill flow entirely for any user whose Mac username contains a space.

Steps to reproduce:

1. Use Cowork on a Mac where the username contains a space
2. Generate a .skill file
3. Click Save Skill on the file card
4. Error appears immediately

What Should Happen?

Expected behavior: Skill saves successfully regardless of spaces in the username path.

Error Messages/Logs

LocalFileAccessError: [INVALID_PATH] Failed to resolve path: /Users/davesfingerprint macbook/Library/Application Support/Claude/local-agent-mode-sessions/.../outputs/smart-sequence.skill

Steps to Reproduce

1. Use Cowork on a Mac where the username contains a space
2. Generate a .skill file
3. Click Save Skill on the file card
4. Error appears immediately

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

1.5354.0 (9a9e3d)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_