⚠ MCP client for `r-studio` failed to start: MCP startup failed: Permission denied (os error 13)

What version of Codex CLI is running?

codex-cli 0.114.0

What subscription do you have?

Pro

Which model were you using?

Any

What platform is your computer?

Linux 6.17.0-19-generic x86_64 x86_64

What terminal emulator and version are you using (if applicable)?

_No response_

What issue are you seeing?

Trying to link codex via a mcp bridge (from Rstudo claudeR: https://github.com/imnmv/clauder) leads to message:

⚠ MCP client for r-studio failed to start: MCP startup failed: Permission denied (os error 13) ⚠ MCP startup incomplete (failed: r-studio)

In my case, the underlying problem was not the MCP handshake itself. The configured launcher command could not be executed by the environment:

1. First configuration used Snap uvx:

• command: /snap/bin/uvx
• args: clauder-mcp

1. That failed because /snap/bin/uvx was not executable in this context and returned Permission denied.
2. I had to install clauder-mcp myself using python venv:

```
python3 -m venv ~/venv-clauder-mcp
~/venv-clauder-mcp/bin/pip install clauder-mcp
codex mcp remove r-studio
codex mcp add r-studio ~/venv-clauder-mcp/bin/clauder-mcp

### What steps can reproduce the bug?



  1. Configure an MCP server with a nonexistent binary path.
  2. Start a fresh Codex session.
  3. Observe that the failure is still reported only as MCP startup failure, without enough context to quickly identify the bad executable path.


### What is the expected behavior?

Expected behavior: seamless integration of codex to mcp on Ubuntu (as is the case for Claude).

Also, documentation for codex mcp is really minimal, compare to claude code mcp which is much more exhaustive (https://code.claude.com/docs/en/mcp) no wonder why mcp worked seamlessly for Claude but not for Codex. 



### Additional information

_No response_