Claude Desktop Filesystem extension ships outdated dist with root path normalization bug

[PeopleGradial]

Bug

The Filesystem MCP server extension bundled with Claude Desktop (macOS) ships a compiled dist/path-utils.js that contains a bug already fixed in the source.

The bug

normalizePath("/") returns "" (empty string), causing the server to crash on startup with:

Error accessing directory : Error: ENOENT: no such file or directory, stat ''

Root cause

The installed extension (version 2025.8.21) has the old regex in dist/path-utils.js:

return p.replace(/\/+/g, '/').replace(/\/+$/, '');

This strips the trailing slash from /, producing an empty string.

Already fixed in source

The current TypeScript source (src/filesystem/path-utils.ts) uses a negative lookbehind that correctly preserves /:

return p.replace(/\/+/g, '/').replace(/(?<!^)\/$/, '');

There are even existing tests for this case:

expect(normalizePath('/')).toBe('/');
expect(normalizePath('///')).toBe('/');

Steps to reproduce

1. Install the Filesystem MCP server extension in Claude Desktop (macOS)
2. Add / as an allowed directory
3. Restart Claude Desktop
4. Server crashes immediately — visible in ~/Library/Logs/Claude/mcp-server-Filesystem.log

Expected

The extension should ship a build that includes the root path fix from the source.

Environment

• Claude Desktop on macOS (Darwin 25.3.0, Apple Silicon)
• Extension: ant.dir.ant.anthropic.filesystem
• Installed @modelcontextprotocol/server-filesystem version: 2025.8.21
• Upstream source version: 0.6.3

[xXMrNidaXx]

This is a build/release pipeline issue — the extension bundle shipped to Claude Desktop users doesn't match the source.

Immediate workaround for affected users:

1. Find the installed extension:

   ~/Library/Application\ Support/Claude/claude_desktop_config.json
   

   Check mcpServers.filesystem.command for the path to the installed package.

2. Patch the regex directly in dist/path-utils.js:

   // Change this:
   return p.replace(/\/+/g, '/').replace(/\/+$/, '');
   
   // To this:
   return p.replace(/\/+/g, '/').replace(/(?<!^)\/$/, '');

3. Or, install the upstream version directly instead of using the bundled extension:

   npm install -g @modelcontextprotocol/server-filesystem@latest

   Then update claude_desktop_config.json to point to the global install.

Root cause speculation:

The extension version 2025.8.21 suggests a snapshot from August 2025. If the fix landed after that snapshot was taken, it wouldn't be in the bundled build. The versioning gap (2025.8.21 vs upstream 0.6.3) makes it hard to track which commits are included.

Suggestion for maintainers:

Consider adding a CI check that verifies the dist/ output is deterministic and matches a clean rebuild from src/. This would catch cases where dist/ gets out of sync with src/ before a release.