--settings writes cache to shared /tmp/, causing EACCES when two macOS user accounts share a Mac

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?

When the bundled Claude Code CLI is invoked with --settings <json>, it writes a cache file to
/tmp/claude-settings-<sha256-prefix-of-json>.json with mode 0644. Because /tmp is shared across all macOS user
accounts on the same machine — and because identical --settings values hash to the same path — the second user to
launch Claude.app on a shared Mac gets EACCES and the CLI exits with code 1 in under a second.

Environment

• macOS (any recent version — /tmp shared, $TMPDIR per-user)
• Claude.app desktop 1.7196.0
• Bundled Claude Code CLI 2.1.138
• Two macOS user accounts on the same Mac, both using Claude.app

Repro

1. macOS Mac with two user accounts, e.g. userA and userB
2. userA logs in, launches Claude.app, sends a message → works. The desktop app spawns the bundled CLI with --settings

'{}' (among other args), and the CLI creates /tmp/claude-settings-44136fa355b3678a.json (mode 0644, owner userA)

1. userB logs in (or switches to their account), launches Claude.app, sends a message
2. Desktop app spawns the same bundled CLI with the same --settings '{}'. The CLI tries to open the existing

/tmp/claude-settings-44136fa355b3678a.json for write, gets EACCES, and exits 1

Expected

The CLI should write its per-invocation settings cache to a path that doesn't collide across user accounts (or should
fall back gracefully on EACCES).

Actual

stderr:

Error processing settings: EACCES: permission denied, open '/tmp/claude-settings-44136fa355b3678a.json'

Process exits with code 1, before producing any stream-json output. The desktop app surfaces this as the generic
banner:

▎ Claude Code crashed
▎ Try sending your message again. If it keeps happening, share feedback so we can investigate.
▎ Claude Code process exited with code 1

The user has no in-app indication of the actual cause — every new session, every retry, every reinstall fails
identically.

Suggested fix

Use $TMPDIR (which is per-user on macOS, e.g. /var/folders/<hash>/.../T/) instead of /tmp. Node's os.tmpdir() already
returns the right per-user path on macOS. Something like:

path.join(os.tmpdir(), claude-settings-${hash}.json)

If /tmp is intentional for cross-process sharing within one user, consider including the UID in the filename (e.g.
claude-settings-${uid}-${hash}.json) or scoping under /tmp/claude-${uid}/.

Workaround

Until fixed, the affected user has to delete the offending file each time the other user has launched the app more
recently:

sudo rm /tmp/claude-settings-<hash>.json

sudo chmod 666 on the file works as a longer-term workaround if the CLI does in-place rewrites rather than
unlink-and-recreate.

Impact

Affects any shared-Mac setup with multiple macOS user accounts (work + personal on the same machine, family computers,
lab machines, etc.).

What Should Happen?

claude code in app should be working

Error Messages/Logs

Claude Code crashed
Try sending your message again. If it keeps happening, share feedback so we can investigate.

Claude Code process exited with code 1

Steps to Reproduce

just use claude code from the mac's app

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.141 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_