[BUG] Claude Code crashes with "exited with code 1" on multi-user macOS due to shared /tmp/claude-settings-<hash>.json

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?

Starting a Claude Code session in the Claude Desktop app fails instantly. The Desktop app shows "Claude Code process exited with code 1" and the session never produces a response. This happens on macOS machines with more than one local user account: one user can use Claude Code fine, but any other user on the same Mac gets the crash on every session start.

What Should Happen?

Each user on a multi-user Mac should be able to start a Claude Code session independently, regardless of which user previously ran the app.

Error Messages/Logs

From ~/Library/Logs/Claude/main.log:                      
  [error] Session local_... query error: Claude Code process exited with code 1 
      at sIr.getProcessExitError (/Applications/Claude.app/Contents/Resources/ap
  p.asar/.vite/build/index.js:390:8041)                                         
      at ChildProcess._handle.onexit (node:internal/child_process:294:12)       
  main.log captures only the exit code, not the child's stderr. I wrapped the   
  claude binary with a shim that captured stderr. The real error is:            
  Error processing settings: EACCES: permission denied, open                    
  '/tmp/claude-settings-44136fa355b3678a.json'                                  
  The file 44136fa355b3678a is the SHA-256 prefix of {} (empty settings). That  
  path was already owned by the other user on the machine (mode 644, sticky bit
  on /tmp blocks overwrite by anyone else).

Steps to Reproduce

1. On a Mac with two local user accounts (A and B), log in as user A.
2. Open the Claude Desktop app and start a new Claude Code session in any

directory. Let it succeed — this creates /tmp/claude-settings-<hash>.json
owned by A.

1. Log out, log in as user B.
2. Open the Claude Desktop app and start a new Claude Code session. It fails

instantly with "Claude Code process exited with code 1".

1. Confirm with: ls -la /tmp/claude-settings-* — the file is owned by A, mode

644, and user B can't overwrite because /tmp has the sticky bit.

Workaround: sudo rm /tmp/claude-settings-44136fa355b3678a.json (or sudo chmod
666 on it).

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.111 (Claude Code)

Platform

Other

Operating System

macOS

Terminal/Shell

Other

Additional Information

• The settings blob is hashed for the filename, so any two users whose

settings serialize identically (e.g., both {}) will collide on the same path
in /tmp. Empty settings is the common case.

• The claude binary already receives TMPDIR=/var/folders/.../T/ in its env,

which is per-user on macOS. Writing to $TMPDIR (or ~/Library/Application
Support/Claude/) instead of hard-coded /tmp would eliminate the collision
entirely.

• Separately: the Desktop app should capture the child process's stderr into

main.log (or surface it in the UI). Right now only the exit code is logged,
which makes this bug un-diagnosable without patching the binary. I only found
the root cause by replacing claude.app/Contents/MacOS/claude with a bash shim
that tee'd stderr to a file.

• Same Mac evidence: /tmp also contains claude-501/ and claude-503/

directories (per-UID), so the app already uses per-user paths for some things
— just not for this settings file. The inconsistency is likely the source of
the regression.

This happened was using the Desktop App, not the API or Terminal