Windows Desktop: external MCP server is difficult to enable / possible regression from codex-cli 0.132.0

Summary

On Windows Codex Desktop, I am trying to use the official MathWorks MATLAB MCP server (matlab/matlab-mcp-server) from Codex. The MATLAB MCP server itself installs and responds to MCP JSON-RPC, but the current Codex Desktop / bundled CLI path does not make it straightforward to enable or surface the MCP server in the Desktop app. The user reports they cannot see it enabled in Settings, and we suspect this is a regression or behavior change compared with codex-cli 0.132.0.

Environment

• OS: Windows
• Codex Desktop package path observed: C:\Program Files\WindowsApps\OpenAI.Codex_26.616.6631.0_x64__2p2nqsd0c76g0\...
• Bundled CLI observed: codex-cli 0.142.0-alpha.6
• Older CLI installed separately for comparison: @openai/codex@0.132.0, reports codex-cli 0.132.0
• MATLAB: R2025b
• MATLAB MCP server: github.com/matlab/matlab-mcp-server v0.11.0

What worked

Downloaded and ran the official MATLAB MCP server binary:

C:\Users\Ruibo\.local\bin\matlab-mcp-server-windows-x64.exe --version

Output:

github.com/matlab/matlab-mcp-server v0.11.0

Manual MCP JSON-RPC handshake succeeded against the server and tools/list returned the expected tools:

• check_matlab_code
• detect_matlab_toolboxes
• evaluate_matlab_code
• run_matlab_file
• run_matlab_test_file

So the MATLAB MCP server binary itself appears valid.

What is confusing / failing

The Desktop app does not appear to show the MATLAB MCP server as enabled/available in Settings or in the active tool list. The active Desktop app still uses bundled codex-cli 0.142.0-alpha.6, while 0.132.0 was installed only as a separate project-local CLI. That separate install does not affect Desktop app MCP tool discovery.

There also appears to be a rough edge on Windows with non-ASCII paths: the MCP server log showed the --initial-working-folder path containing Chinese characters rendered as mojibake. Example project path contains 师姐的代码, but the log recorded it as garbled text. This may be separate from the Desktop MCP enablement issue, but it makes debugging harder.

Expected behavior

There should be a documented and reliable way in Codex Desktop on Windows to add/enable an external stdio MCP server such as:

[mcp_servers.matlab]
command = 'C:\Users\Ruibo\.local\bin\matlab-mcp-server-windows-x64.exe'
args = [
  '--matlab-root=C:\Program Files\MATLAB\R2025b',
  '--initial-working-folder=C:\Users\Ruibo\Documents\MATLAB',
  '--matlab-display-mode=nodesktop',
  '--matlab-session-mode=auto',
  '--disable-telemetry=true'
]
startup_timeout_sec = 300

After restart, the server should appear in the Desktop app's available MCP tools, or the UI/logs should show a clear configuration error.

Actual behavior

The MATLAB MCP server is not visible/usable from the Desktop app tools list/settings in this setup. Installing @openai/codex@0.132.0 separately works for terminal CLI versioning, but does not change Desktop app behavior.

Request

Could you clarify whether current Codex Desktop builds support external mcp_servers.* config on Windows in the same way the CLI does? If support regressed after 0.132.0, please consider restoring it or documenting the new configuration path. Better diagnostics for failed MCP server loading in Desktop Settings would also help.