Unclear It is not clear which command tool runs this check, the Bash tool or the PowerShell tool, or whether the check is always on.
What
Claude Code now refuses to run a command that contains either of two invisible characters:
- U+FEFF, the byte order mark, a hidden marker sometimes left at the start of text files
- U+180E, the Mongolian vowel separator
The command is not run. The message says which character was found and explains how to write it safely if it is really wanted. The suggested form, $([char]0xFEFF), is written for PowerShell, the Windows command shell.
Why
These characters cannot be seen on screen, so a command containing one can do something other than what it appears to do. A command like that now fails with a clear explanation instead of running.
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubt
It is not clear which command tool runs this check, the Bash tool or the PowerShell tool, or whether the check is always on.