[BUG] Windows: MCP filesystem broken in v1.1.2512 - regression from v1.1.2321 (Feb 10, 2026)

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?

MCP filesystem server connects successfully and shows as "running" in Claude Desktop, but Claude cannot access or use the registered tools in conversations.

Critical Timeline:

• Feb 6-8, 2026: Version 1.1.2321 - MCP worked perfectly ✅
• Feb 10, 2026 11:44 AM: Auto-updated to 1.1.2512 - MCP broke ❌

This is a version regression confirmed by main.log analysis.

What Should Happen?

When the MCP filesystem server shows "running" status and logs confirm successful tool registration, Claude should:

1. Recognize the available MCP tools
2. Be able to use filesystem tools (read_file, write_file, list_directory, etc.)
3. Access configured directories as it did in version 1.1.2321

• ✅ Server shows "running" badge in Settings → Developer
• ✅ Logs show successful initialization and handshake
• ✅ Server loads all tools (confirmed in logs)
• ❌ Claude in conversations reports: "I don't have access to any MCP servers"
• ❌ Tools are not available to Claude despite server being healthy

Error Messages/Logs

- **Product:** Claude Desktop (Windows)
- **OS:** Windows 11 with WSL
- **Node.js:** v22.21.0
- **Version when working:** 1.1.2321 (Feb 6-8, 2026)
- **Version when broken:** 1.1.2512 (Feb 10, 2026)
- **Date of regression:** February 10, 2026 at 11:44 AM

### Update Timeline (from main.log):

Working version:

2026-02-08 19:10:22 [info] Starting app { appVersion: '1.1.2321' ... }


Update occurred:

2026-02-10 11:43:49 [info] Found an update, downloading
2026-02-10 11:44:15 [info] Update downloaded and ready to install { releaseName: '1.1.2512' }


Broken version started:

2026-02-10 11:44:13 [info] Starting app { appVersion: '1.1.2512' ... }


### Server Status (successful connection):

2026-02-10T16:51:19.431Z [filesystem] [info] Message from server: 
{"jsonrpc":"2.0","id":1,"result":{"tools":[...]}}


Server successfully loads tools including:
- read_file
- write_file
- list_directory
- list_allowed_directories
- create_directory
- move_file
- search_files
- get_file_info
- etc.

Steps to Reproduce

1. Configure MCP filesystem in %APPDATA%\Claude\claude_desktop_config.json:

{
  "mcpServers": {
    "filesystem": {
      "command": "npx",
      "args": [
        "-y",
        "@modelcontextprotocol/server-filesystem",
        "C:\\Users\\mail\\Documents\\Claude",
        "C:\\Users\\mail\\AIWorkspace_junction_symbolic_link"
      ]
    }
  }
}

1. Restart Claude Desktop completely
2. Verify in Settings → Developer → Local MCP servers shows "running"
3. Check logs to confirm server connected successfully
4. Start a new conversation
5. Ask Claude: "What folders do you have access to?"
6. Observe: Claude reports no access to MCP servers

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

1.1.2321

Claude Code Version

1.1.2512

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

Issue occurs on Claude Desktop. Bug report written by Claude.