[BUG] Sandbox sets TMPDIR=/tmp/claude but directory doesn't exist and /tmp is read-only

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?

The sandbox (bubblewrap) sets TMPDIR=/tmp/claude as an environment variable, but:

1. /tmp/claude directory does not exist on disk
2. /tmp is mounted read-only inside the sandbox, so the directory **cannot be

created**

1. The actual writable path is /tmp/claude-<UID>/ (e.g., /tmp/claude-1001/)
2. settings.json env.TMPDIR is overridden by the sandbox's forced TMPDIR

This causes any tool that writes to $TMPDIR (e.g., Vite/Wrangler via npm run) to fail with ENOENT.

What Should Happen?

One of:

• Sandbox should set TMPDIR to the actually existing and writable path

(/tmp/claude-<UID>/)

• Sandbox should create /tmp/claude before mounting /tmp as read-only
• settings.json env.TMPDIR should not be overridden by the sandbox

Error Messages/Logs

ENOENT: no such file or directory, mkdir '/tmp/claude'

Steps to Reproduce

1. Enable sandbox in settings.json: "sandbox": { "enabled": true }
2. Run any npm dev server that uses TMPDIR (e.g., Vite or Wrangler project): npm run dev
3. Observe: ENOENT: no such file or directory, mkdir '/tmp/claude'
4. Verify mismatch inside sandbox:

• echo $TMPDIR → /tmp/claude (forced by sandbox)
• mkdir -p /tmp/claude → Read-only file system
• ls /tmp/claude-1001/ → exists and writable

1. Workaround confirms the cause: TMPDIR=/tmp/claude-1001 npm run dev → works

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.63 (Claude Code)

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

• Environment: WSL2 (Ubuntu) on Windows, WezTerm terminal
• UID: 1001 (non-root user)
• The write.allowOnly list includes both /tmp/claude and /tmp/claude-1001/, but only

/tmp/claude-1001/ actually exists on disk

• settings.json env.TMPDIR=/tmp/claude-1001 is set but overridden by the sandbox
• This affects any tool spawned inside the sandbox that respects TMPDIR (Node.js, Python, Wrangler, Vite, etc.)