[BUG] MCP Filesystem server crashes on connect since v1.3883.0 update (macOS, Cowork)

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?

The built-in MCP Filesystem server crashes within 1-2 seconds of starting after the April 21 update. The error banner "MCP Filesystem: Server disconnected" appears on every session and cannot be resolved.

What Should Happen?

Filesystem server connects and stays connected as it did prior to v1.3883.0.

Error Messages/Logs

Server started and connected successfully
Server transport closed unexpectedly, this is likely due to the process exiting early
Server disconnected.

Steps to Reproduce

1. Open Claude desktop app (Cowork mode) on macOS
2. Observe "MCP Filesystem: Server disconnected" error banner immediately on load
3. Check ~/Library/Logs/Claude/mcp-server-filesystem.log — server starts then exits within 1-2 seconds

No user action required — crash occurs automatically on every session start.

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Unknown — last confirmed working April 17, 2026 (prior to v1.3883.0)

Claude Code Version

Claude 1.3883.0 (93ff6c) 2026-04-21T17:24:01.000Z

Platform

Other

Operating System

macOS

Terminal/Shell

iTerm2

Additional Information

This is a Claude Desktop App (Cowork mode) bug, not a CLI issue.

Troubleshooting already attempted: cache cleared, app reinstalled, Full Disk Access granted in macOS Privacy & Security, all trusted folder paths verified to exist, trusted folders list cleared entirely. Error persists across all attempts.