Worktrees are refused when git could write outside the repository through a link

A worktree is a separate working folder of a git repository. Claude Code now checks the repository's git folder before making one. If git could write outside the repository through any of these, Claude Code refuses to create the worktree:

• a link to somewhere else
• a symbolic ref, which is a git pointer to another name
• a hard-linked entry, a file shared with another location

When resuming a worktree in that state, Claude Code keeps the old base instead of updating it. The error message tells you to use a plain clone. The check sits behind a server-side switch that is on unless it is switched off remotely.