[BUG] Sandbox failed to initialize on macOS 26 Tahoe (Darwin 25.2.0, arm64)

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?

Enabling sandbox in settings causes all Bash tool calls to fail with Sandbox failed to initialize. — no additional error details provided.

The macOS Seatbelt framework itself works fine (sandbox-exec -n no-network echo "test" succeeds), so the issue appears to be in Claude Code's sandbox initialization logic, not in the OS-level sandbox.

What Should Happen?

Bash commands should execute within the macOS Seatbelt sandbox, with autoAllowBashIfSandboxed: true auto-approving commands that stay within sandbox boundaries. This would allow read-only and safe operations to run without individual permission prompts.

Error Messages/Logs

Sandbox failed to initialize.

Steps to Reproduce

1. Add the sandbox config above to ~/.claude/settings.json
2. Open Claude Code (CLI or VSCode extension)
3. Run any Bash command (even echo "test")

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.41

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

• sandbox-exec works natively on this system — the Seatbelt framework is functional
• The error occurs for all commands, including trivial ones like echo
• No symlinks involved — tested from a direct (non-symlinked) project directory
• Removing the sandbox config from settings restores normal behavior

Environment

| Aspect | Details |
|---|---|
| OS | macOS 26.2 Tahoe (BuildVersion 25C56) |
| Kernel | Darwin 25.2.0 (xnu-12377.61.12~1/RELEASE_ARM64_T6041) |
| Architecture | arm64 (Apple Silicon) |
| Claude Code | 2.1.41 |
| Node.js | v20.19.4 (via nvm) |
| Context | VSCode extension |
| sandbox-exec | /usr/bin/sandbox-exec — functional |