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MCPX_STDIO_SPAWN_EACCES

Severity: error Domain: STDIO

What happened​

The configured command exists on PATH, but the OS refused to execute it (EACCES). The subprocess never started.

Common causes​

  • The file is missing the executable bit (chmod +x).
  • The file is on a noexec-mounted volume (e.g. some /tmp or NFS mounts).
  • macOS Gatekeeper / quarantine flagged a downloaded binary.
  • AppArmor / SELinux denied the exec syscall.

How to fix​

Restore the executable bit​

ls -l "$(which <command>)"        # check current mode
chmod +x "$(which <command>)"     # add execute permission

macOS quarantine​

If the binary was downloaded outside the App Store / Homebrew, macOS may have quarantined it:

xattr -d com.apple.quarantine "$(which <command>)"

For pre-built tray bundles, prefer the signed/notarised DMG — see Installation.

Move off a noexec volume​

mount | grep noexec
# Reinstall the tool to ~/.local/bin or /usr/local/bin instead of /tmp

AppArmor / SELinux​

Check the audit log for DENIED exec:

sudo dmesg | grep -i denied
sudo journalctl -t audit | grep DENIED

Adjust the policy or run the upstream server in Docker isolation to sidestep host policy.