The Error
Cannot write file: path is outside the workspace root
The Fix
# Check your current workspace root
pwd
# Ensure the target path is under this directory
# BAD: /tmp/output.json
# BAD: ../other-project/file.ts
# GOOD: /Users/you/project/output/result.json
# If you need the file elsewhere, write it inside the workspace first
# then move it manually after Claude finishes
Why This Works
Claude Code restricts file writes to the workspace root directory (the directory where the session was started) as a security boundary. This prevents accidental or malicious writes to system directories, other projects, or sensitive locations. All file operations must target paths that resolve to somewhere inside the workspace tree.
If That Doesn’t Work
# Create a symlink inside your workspace pointing to the target location
ln -s /path/to/external/dir ./external-link
# Or start Claude Code from a parent directory that encompasses both locations
cd /Users/you/projects && claude
# Or use Bash tool to write outside workspace (if permissions allow)
echo "content" > /path/to/external/file.txt
The Bash tool has broader filesystem access than the Write tool, though sandbox mode may still restrict it.
Prevention
Add to your CLAUDE.md:
All generated files must be written inside the project workspace. For outputs needed in external locations, write to a local output/ directory and include a post-processing step to copy them to their final destination.