[BUG] Cowork Windows: Non-ASCII (Japanese) Windows username causes path mojibake and ENOENT, preventing startup

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?

Cowork fails to start on Windows when the Windows username contains Japanese (multibyte) characters.

The app incorrectly decodes the username path — Japanese characters are interpreted as Shift_JIS instead of UTF-8, resulting in mojibake (garbled text). This causes ENOENT errors because the garbled path does not exist.

Note: The original username and mojibake output have been partially redacted for privacy.

• Expected path: C:\Users\今村\AppData\Roaming\Claude\...
• Actual path in log: C:\Users\莉頑搗\AppData\Roaming\Claude\...

Chat mode works normally. Only Cowork is affected.

What Should Happen?

Claude Desktop should correctly handle non-ASCII (CJK) Windows usernames without requiring users to change system locale settings. Cowork should start successfully regardless of whether the Windows username contains Japanese, Chinese, Korean, or other multibyte characters.

Error Messages/Logs

From %LOCALAPPDATA%\Packages\Claude_<package_id>\LocalCache\Roaming\Claude\logs\main.log:

2026-02-21 09:47:41 [info] Loaded 1 persisted sessions from C:\Users\莉頑搗\AppData\Roaming\Claude\local-agent-mode-sessions\...
2026-02-21 09:47:41 [error] Failed to read sessions directory: ENOENT: no such file or directory, scandir 'C:\Users\莉頑搗\AppData\Roaming\Claude\claude-code-sessions\...'
2026-02-21 09:47:41 [error] [LocalSessionManager] loadSessions failed during account transition, restoring previous sessions ENOENT: no such file or directory, scandir 'C:\Users\莉頑搗\AppData\Roaming\Claude\claude-code-sessions\...'

Note: Username in log paths has been redacted. The mojibake pattern (莉頑搗) is consistent with UTF-8 bytes being decoded as Shift_JIS.

Steps to Reproduce

1. Create a Windows user account with Japanese (or other CJK) characters in the username (e.g. 今村)
2. Install Claude Desktop v1.1.3830 on Windows 11
3. Launch Claude Desktop and switch to Cowork tab
4. Cowork fails to start — sessions directory cannot be found due to mojibake in the path

Workaround: Enable "Beta: Use Unicode UTF-8 for worldwide language support" in Windows Region settings (Settings → Time & Language → Language & Region → Administrative language settings → Change system locale), then restart Windows. After this change, Cowork starts successfully.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude Desktop v1.1.3830 (not Claude Code CLI)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

Environment Details

• OS: Windows 11 (Build 10.0.26200)
• CPU: Intel Core Ultra 7 155H
• RAM: 32GB
• This is Claude Desktop Cowork, not Claude Code CLI

Root Cause Analysis

The mojibake pattern (e.g. 今村 → 莉頑搗) is consistent with UTF-8 encoded bytes being incorrectly decoded as Shift_JIS. This is the same encoding issue reported in #24641 (macOS VM process name mojibake on Japanese locale), but on Windows it causes a functional failure (ENOENT) rather than just a cosmetic issue.

Workaround

Enabling Windows UTF-8 system locale resolves the issue, but this should not be required as it can affect other applications.

Impact

This likely affects all Windows users with CJK (Japanese, Chinese, Korean) characters in their Windows username — a very common configuration in East Asian countries.

Related Issues

• #24641 (VM process name mojibake on Japanese locale - macOS, same UTF-8 → Shift_JIS pattern)
• #15768 (Panic when processing Japanese text)
• #18285 (Korean folder name encoding issues in Cowork)