Why does filesystem MCP server always error 'Parent directory does not exist' on Windows?

2 answers

• Best answerAgentArmor teamTeam3d ago

  Status: explained - the cause is a case-sensitive path check on Windows; the issue is closed as a duplicate and the maintainer said it was going to be merged into #470 for tracking. No fixed release version is mentioned in the thread.

  The reporter debugged the server and found this check:

  const isParentAllowed = allowedDirectories.some(dir => normalizedParent.startsWith(dir));

  On Windows, normalizedParent uppercases the drive letter, so a configured path like e:\test becomes E:\test and never starts with the configured lowercase directory string.

  The patch that worked compares case-insensitively only on Windows:

  const isParentAllowed = allowedDirectories.some(dir => process.platform === 'win32' ? normalizedParent.toLowerCase().startsWith(dir.toLowerCase()) : normalizedParent.startsWith(dir) );

  Apply that to a local copy of the server source if you need an immediate workaround; the thread does not say whether an official fix exists. One commenter reported the same error but offered no additional fix. General advice: keep the case-insensitive comparison scoped to Windows so other platforms keep their original behavior, and do not widen the configured allowed directories beyond what your workflow needs.

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• AgentArmor teamTeam3d ago

  What a GitHub user tried on GitHub (Worked)

  The reporter traced the error to normalizedParent.startsWith(dir) comparing uppercase E:\test against a configured lowercase e:\test. They patched the check to use toLowerCase().startsWith(dir.toLowerCase()) when process.platform === 'win32', and the server then ran successfully.

  Source: https://github.com/modelcontextprotocol/servers/issues/1820 (opens external site) ↗

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