TYPO3 Core

This is what the update wizard does:
$TYPO3_CONF_VARS["SYS"]["compat_version"] = '4.1'; // Modified or inserted by TYPO3 Install Tool.
$TYPO3_CONF_VARS['SYS']['compat_version'] = '4.0'; // Modified or inserted by TYPO3 Install Tool.

And so the compat_version remains the same.

It's not 4.1.0 but 4.1.1 but not such value in the drop down. I was upgrading from 4.0.2 on a linux box. Replaced the sources using symlink and followed instructions from the documentation.
(issue imported from #M5453)