[BUG] Sandbox Config tab filesystem restrictions dropping leading slash on WSL2

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

My ~/.claude/settings.json file in WSL2 includes the following:

    "permissions": {
    "deny": [
      "Read(/mnt/c/**)",
      "Write(/mnt/c/**)",
      "Edit(/mnt/c/**)",
      "Read(~/**)",
      "Write(~/**)",
      "Edit(~/**)",
      "Read(/home/username/**)",
      "Write(/home/username/**)",
      "Edit(/home/username/**)",
    ],
  "sandbox": {
    "enabled": true,
    "allowUnsandboxedCommands": false,
    "filesystem": {
      "denyRead": ["~/"],
      "denyEdit": ["~/"],
      "denyWrite": ["~/"],
    }
  }

When I use the /sandbox command in Claude Code the Config tab shows the read denies for /mnt/c are inside my ~/.claude directory as shown below:

  Filesystem Read Restrictions:
  Denied: /home/username/.claude/mnt/c, ~, /home/username/.claude/home/username,

  Filesystem Write Restrictions:
  Allowed: /dev/stdout, /dev/stderr, /dev/null, /dev/tty, /dev/dtracehelper, /dev/autofs_nowait, /tmp/claude,
  /private/tmp/claude, /home/username/.npm/_logs, /home/username/.claude/debug, ., /tmp/claude-1000/,
  /git-repos/ctmbatch, /git-repos/opsutils
  Denied within allowed: /home/username/.claude/settings.json, /etc/claude-code/managed-settings.json,
  /etc/claude-code/managed-settings.d, /mnt/c/Program Files/ClaudeCode/managed-settings.json, /mnt/c/Program
  Files/ClaudeCode/managed-settings.d, /home/username/.claude/mnt/c, ~,
  /home/username/.claude/home/username

I do not have an mnt/c sub-directory in ~/.claude and when I asked Claude Code about why that is happening it told me that the sandboxing on WSL2 must be dropping the leading slash and that I should raise a bug here.

What Should Happen?

Output on the /sandbox Config tab should use absolute paths:

  Filesystem Write Restrictions:
  Allowed: /dev/stdout, /dev/stderr, /dev/null, /dev/tty, /dev/dtracehelper, /dev/autofs_nowait, /tmp/claude,
  /private/tmp/claude, /home/username/.npm/_logs, /home/username/.claude/debug, ., /tmp/claude-1000/

  Denied within allowed: /home/username/.claude/settings.json, /etc/claude-code/managed-settings.json,
  /etc/claude-code/managed-settings.d, /mnt/c/Program Files/ClaudeCode/managed-settings.json, /mnt/c/Program
  Files/ClaudeCode/managed-settings.d, /mnt/c, ~, /home/username

Error Messages/Logs

Steps to Reproduce

1. Launch claude
2. /sandbox
3. Go to Config tab

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.136

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Windows Terminal

Additional Information

_No response_