Why does Codex fail to detect build_macos

[BarnoTD]

I added XCodeBuild Config to OpenAI Codex (macOS client, not CLI). this is my config:

Then I prompted codex to run a build for an Xcode project app on macOS and to stop if it failed. This is Codex's response:

You do have it available in this Codex session. I’m not installing or discovering it from your repo; it’s exposed to me as a built-in tool namespace:

mcp__xcodebuildmcp__

That means the app/session has an XcodeBuild MCP server configured already, with callable tools like:

session_show_defaults
session_set_defaults
list_schemes
build_sim
build_run_sim
test_sim
clean

But in this configured version, the actual build tools are iOS Simulator-focused. That’s why I could set macOS defaults through the MCP, but could not run a macOS build through it. For macOS builds, I still need plain xcodebuild from the terminal unless your MCP server adds a macOS build tool.

This issue is not available on iOS builds though.