Sandbox gains a remotely switched write block for an unlistable .git/worktrees folder

What

The sandbox is the protective boundary that limits what Claude Code's commands can read and write on your computer. Its settings code now has a rule that blocks writes to a git worktrees folder (.git/worktrees, where git keeps track of extra working copies of a repository) when that folder cannot be listed.

• unlistableWorktreesDenyApplied is a new piece of state recording whether this block is in effect. It sits next to the existing state for paired write-deny rules.
• builtConfigUnlistableWorktreesDenied is where that state comes from. It is worked out each time a sandbox configuration is built.
• The state is restored when a configuration is installed and compared whenever settings change.
• A change to the matching GrowthBook setting now makes the sandbox reapply its rules. GrowthBook is a service that lets Anthropic turn features on or off remotely.

The block only covers a worktrees folder that cannot be listed. The release itself does not show whether the switch starts on or off. Nothing has been read about the related gate, tengu_quiet_medlar, so its state is unknown.

Why

In practice, the sandbox may now refuse writes inside .git/worktrees when that folder cannot be read. Because the switch is remote, this behaviour can change between sessions even if Claude Code is not updated. If writes to git worktrees are refused inside the sandbox, this rule is one place to look.