Quick answer
Make the configured allowed directory and requested path use the same uppercase drive letter, for example C: instead of c:. Restart the MCP client. This only partially worked in the source report, so do not widen access to the whole drive.
The exact error
Access denied - path outside allowed directories: c:\... not in C:\...Do not use this guide for a merely similar message. The workaround is scoped to this signature and the environments below.
Match your environment
- Windows
- MCP Filesystem server via NPX
- Claude Desktop, Windsurf, or another MCP client
What to do
- 01
Compare the two paths
If one side starts with c: and the allowed root starts with C:, you have the reported signature.
- 02
Normalize the configured root
Edit the MCP server arguments so the allowed directory uses an uppercase drive letter and fully resolved path.
C:\Users\you\Documents - 03
Normalize the requested path
Open the project and invoke the tool from a path that uses the same drive-letter casing. Restart the client so the server receives the updated root.
- 04
Keep the boundary narrow
Do not solve a comparison bug by granting C:\ or your entire profile. If casing does not help, update the server and report exact versions.
What likely happened
The reports show Windows-equivalent paths compared with different drive-letter casing. The server treated the textual mismatch as outside the allowlist even though Windows treats them as the same drive.
First-hand sources
Source links support the environment and workaround claims above. An issue being closed does not by itself mean a fix shipped.