[BUG] [Cowork] macOS Seatbelt blocks write to /sessions/.../tmp — Bash completely broken

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?

Environment:

• Product: Claude desktop app, Cowork mode
• Hardware: Mac Mini, macOS
• Session path: /sessions/gallant-hopeful-davinci/

Error (on every Bash operation):
EACCES: permission denied, mkdir '/sessions/gallant-hopeful-davinci/tmp'

Root cause (per Anthropic support clarification):
Cowork's macOS Seatbelt profile does not grant write access to the
/sessions/gallant-hopeful-davinci/tmp directory. This is separate from
the settings.json permission system — it is an OS-level sandbox restriction
that needs to be fixed in Cowork's Seatbelt profile.

Impact:
All Bash, Write, and Edit tool operations are completely blocked.
Skills requiring subprocess execution (docx, pptx, xlsx) are unusable.

What was tried (all had no effect):

• allowWrite: ["/sessions", "/sessions/", "/tmp", "/tmp/"] in settings.json
• sandbox.excludedCommands: ["bash ", "sh "]
• sandbox.enabled: false
• Multiple full Mac Mini restarts

None of these work because settings.json controls Claude Code's internal
approval system, NOT macOS Seatbelt. The fix must be in Cowork's
Seatbelt profile to allow writes to the session tmp directory.

What Should Happen?

Root cause (per Anthropic support clarification):
Cowork's macOS Seatbelt profile does not grant write access to the
/sessions/gallant-hopeful-davinci/tmp directory. This is separate from
the settings.json permission system — it is an OS-level sandbox restriction
that needs to be fixed in Cowork's Seatbelt profile.

Impact:
All Bash, Write, and Edit tool operations are completely blocked.
Skills requiring subprocess execution (docx, pptx, xlsx) are unusable.

Error Messages/Logs

**Error (on every Bash operation):**
EACCES: permission denied, mkdir '/sessions/gallant-hopeful-davinci/tmp'

Steps to Reproduce

What was tried (all had no effect):

• allowWrite: ["/sessions", "/sessions/", "/tmp", "/tmp/"] in settings.json
• sandbox.excludedCommands: ["bash ", "sh "]
• sandbox.enabled: false
• Multiple full Mac Mini restarts

None of these work because settings.json controls Claude Code's internal
approval system, NOT macOS Seatbelt. The fix must be in Cowork's
Seatbelt profile to allow writes to the session tmp directory.

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

The one previous to this one Claude 1.3883.0 (93ff6c) 2026-04-21T17:24:01.000Z

Claude Code Version

Claude 1.3883.0 (93ff6c) 2026-04-21T17:24:01.000Z

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_