New setting blocks file writes outside the working directories

What

A new permissions setting, blockWritesOutsideWorkingDirectories (in full, permissions.blockWritesOutsideWorkingDirectories), stops Claude Code from writing files outside the working directories. The working directories are the folders the session has been given to work in. The setting mirrors the existing blockReadsOutsideWorkingDirectories, which does the same for reading.

• Refuses writes by the file tools Write, Edit and NotebookEdit outside the working directories, in every permission mode.
• Refuses writes to Claude Code's own settings files while it is on.
• Removes the EnterWorktree and ExitWorktree tools from the tools Claude is offered.
• Does not limit shell commands, MCP tools (tools supplied by outside servers) or hooks (your own scripts that Claude Code runs at set moments).
• When a write is refused, the message tells you to add the folder with /add-dir or remove the setting.
• The description of blockReadsOutsideWorkingDirectories now says that no allow rule lifts it.
• For remote execution, the sandbox settings now drop blockWritesOutsideWorkingDirectories as well as blockReadsOutsideWorkingDirectories before the settings are forwarded. Before, only the read setting was dropped.

Why

This gives a firm limit on where Claude's file tools can write. Two things to watch: shell commands, MCP tools and hooks can still write elsewhere, and the setting is not passed on to remote runs, so a remote session will not enforce it.