additionalWritePaths in sandbox settings not honored

Summary

The sandbox.additionalWritePaths setting in both .claude/settings.local.json and ~/.claude/settings.json is not being applied to the sandbox filesystem allowlist.

Steps to reproduce

1. Add additionalWritePaths to .claude/settings.local.json:

``json
{
"sandbox": {
"enabled": true,
"additionalWritePaths": [
"/Users/me/.cache"
]
}
}
``

1. Restart Claude Code
2. Attempt to write to that path:

``
echo "test" > ~/.cache/test-file
``

Result: operation not permitted

The sandbox config printed at session start confirms the path is not in the filesystem write allowlist, despite being set in settings.

What I tried

• Setting in .claude/settings.local.json — not honored
• Setting in .claude/settings.json (project-level) — not honored
• Setting in ~/.claude/settings.json (global) — not honored
• Using ~/.cache (tilde) vs /Users/me/.cache (absolute) — neither works

Impact

This blocks tools that need to write to common cache/config directories from working inside the sandbox. Specific examples:

• GPG signing fails because gpg can't create lock files in ~/.gnupg
• prek (pre-commit hook runner) fails because it can't write logs to ~/.cache/prek/

Workarounds exist for some tools (e.g., setting PREK_HOME to $TMPDIR), but not all (GPG requires write access to its home directory for lock files).

Environment

• macOS (Darwin 25.4.0)
• Claude Code CLI