Beta Command Line Tools offered as update—why?
Apple has also now fixed the same issue which occurred with macOS 10.14 Mojave offering CLTools for macOS 10.15 Catalina. For a short time, the 10.14 catalog included 10.15's tools, but this has since been removed from this catalog and only included in the beta catalog.


https://swscan.apple.com/content/catalogs/others/index-10.14-10.13-10.12-10.11-10.10-10.9-mountainlion-lion-snowleopard-leopard.merged-1.sucatalog.gz




A removal package has not been provided for removing the 10.15 tools specifically this year. You can try removing the tools using the removal package for 10.14 or removing them completely, then reinstall them:


http://swcdn.apple.com/content/downloads/11/13/041-71563/s1da971g95kch5ljsghwjufij12crr2o5b/CLTools_macOS_DevSDK_Remove_1014.pkg
How do I uninstall the command line tools for Xcode?




Apple fixed the issue for macOS 10.13 High Sierra. Refresh the updates with ⌘R and the update should disappear.

This was a bug on Apple's part. Apple has incorrectly released this update to everyone, not just those on a beta upgrade path.

If the update is still shown, you can hide it by right-clicking and choosing Hide Update.



If you've installed the update and realised your tools are broken, you can remove these tools using CLTools_macOS_SDK_Remove_1014.pkg from Apple:


http://swcdn.apple.com/content/downloads/01/53/091-65367/h0b7b20hoylsqj7pih1htv5b9oa9y4z4gq/CLTools_macOS_SDK_Remove_1014.pkg




The update was incorrectly provided in the default software update catalog on High Sierra: https://swscan.apple.com/content/catalogs/others/index-10.13-10.12-10.11-10.10-10.9-mountainlion-lion-snowleopard-leopard.merged-1.sucatalog.gz.

The update is provided for beta and developers in their associated catalogs:


https://swscan.apple.com/content/catalogs/others/index-10.13beta-10.13-10.12-10.11-10.10-10.9-mountainlion-lion-snowleopard-leopard.merged-1.sucatalog.gz
https://swscan.apple.com/content/catalogs/others/index-10.13seed-10.13-10.12-10.11-10.10-10.9-mountainlion-lion-snowleopard-leopard.merged-1.sucatalog.gz




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