uvx/npx based MCP Servers are not working on Windows: "Tools: (none)"

What version of Codex is running?

codex-cli 0.28.0

Which model were you using?

any

What platform is your computer?

Microsoft Windows NT 10.0.19045.0 x64

What steps can reproduce the bug?

I configured several MCP servers in config.toml which work flawlessly in claude-code but codex is not able to determine the MCP Tools.

[mcp_servers]

[mcp_servers.context7]
command = 'C:\Windows\System32\cmd.exe'
args = ["/c", "npx", "-y", "@upstash/context7-mcp", "--api-key", "<REMOVED>"]

[mcp_servers.dart]
command = 'C:\scoop\apps\current\bin\dart.exe'
args = ["mcp-server"]

[mcp_servers.gitmcp]
command = 'C:\Windows\System32\cmd.exe'
args = ["/c", "-y", "mcp-remote","https://gitmcp.io/docs"]

[mcp_servers.sequential_thinking]
command = 'C:\Windows\System32\cmd.exe'
args = ["/c", "npx", "-y", "@modelcontextprotocol/server-sequential-thinking"]

[mcp_servers.serena]
command = 'C:\scoop\shims\uvx.exe'
args = [ "--from",
            "git+https://github.com/oraios/serena",
            "serena-mcp-server",
            "--context",
            "ide-assistant",
            "--enable-web-dashboard",
            "false",
            "--enable-gui-log-window",
            "false"]

[mcp_servers.zen]
command = 'C:\scoop\shims\uvx.exe'
args = ["--from", "git+https://github.com/BeehiveInnovations/zen-mcp-server","zen-mcp-server"]

What is the expected behavior?

A list of all the registered MCP servers including the available tools.

What do you see instead?

All except the dart mcp show "Tools: (none)"

/mcp

�  MCP Tools

  • Server: context7
    • Command: C:\Windows\System32\cmd.exe /c npx -y @upstash/context7-mcp --api-key <REMOVED>
    • Tools: (none)

  • Server: dart
    • Command: C:\scoop\apps\dart\current\bin\dart.exe mcp-server
    • Tools: add_roots, analyze_files, connect_dart_tooling_daemon, create_project, dart_fix, dart_format, get_active_location, get_runtime_errors, get_selected_widget, get_widget_tree, hot_reload,
hover, pub, pub_dev_search, remove_roots, resolve_workspace_symbol, run_tests, set_widget_selection_mode, signature_help

  • Server: gitmcp
    • Command: C:\Windows\System32\cmd.exe /c -y mcp-remote https://gitmcp.io/docs
    • Tools: (none)

  • Server: serena
    • Command: C:\scoop\shims\uvx.exe --from git+https://github.com/oraios/serena serena-mcp-server --context ide-assistant --enable-web-dashboard false --enable-gui-log-window false
    • Tools: (none)

  • Server: sequential_thinking
    • Command: C:\Windows\System32\cmd.exe /c npx -y @modelcontextprotocol/server-sequential-thinking
    • Tools: (none)

  • Server: zen
    • Command: C:\scoop\shims\uvx.exe --from git+https://github.com/BeehiveInnovations/zen-mcp-server zen-mcp-server
    • Tools: (none)

Additional information