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

[Anupheaus]

Preflight Checklist

• I have searched existing issues and this hasn't been reported yet
• This is a single bug report (please file separate reports for different bugs)
• 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

[github-actions]

Found 3 possible duplicate issues:

1. [BUG] BUG] Cowork still fails on macOS with "Sandbox dependencies not available" — bubblewrap check not fixed (re: #19996) #25939
2. [BUG] Cowork crashes on M4 Mac - seccomp killed error #19047
3. [BUG] Cowork fails on macOS - checks for bubblewrap (Linux-only) instead of using Seatbelt #19996

This issue will be automatically closed as a duplicate in 3 days.

• If your issue is a duplicate, please close it and 👍 the existing issue instead
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🤖 Generated with Claude Code

[dannon]

Different root cause (maybe) but same error message — I had "Sandbox failed to initialize" across the board (every bash command, including trivial ones). Asking Claude to surface the actual error details helped diagnose it. In my case the error referenced a specific binary path (~/.local/share/claude/versions/2.1.56) that no longer existed — I'd had a Claude Code session open in tmux for several days and CC had auto-updated in the meantime, so the old version's binary was gone and the sandbox couldn't launch it.

Closing that stale session and resuming it (or starting fresh) picked up the current binary and everything worked immediately.

May or may not be the same thing here, but worth asking Claude for the full error rather than just "Sandbox failed to initialize" — there's usually more detail available that points to the actual cause.

[github-actions]

Closing for now — inactive for too long. Please open a new issue if this is still relevant.

[github-actions]

This issue has been automatically locked since it was closed and has not had any activity for 7 days. If you're experiencing a similar issue, please file a new issue and reference this one if it's relevant.