You'll notice
The general-purpose name sanitizer now avoids producing Windows-reserved names like CON or NUL
What
Claude Code's general-purpose function for cleaning up identifiers, such as those used for artifact or file names, now checks whether the cleaned-up result matches a name Windows reserves for devices (CON, PRN, AUX, NUL, COM1-COM9, LPT1-LPT9). If it does, an underscore is added to the front of the name.
Why
Windows treats these names specially and can fail to create a file or folder with one of them, so this prevents Claude Code from generating an identifier that would break on Windows.