[BUG] --settings <json> writes to shared /tmp/claude-settings-<hash>.json, blocks all but first macOS user account

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?

The bundled CLI's --settings <json> flag hashes the input JSON and writes it to a deterministic path: /tmp/claude-settings-<hash>.json.

Because /tmp/ is shared across all macOS user accounts on the machine, and the hash does not include getuid() (or username), identical --settings arguments produce
identical paths across users. Whichever user spawns the CLI first creates the file with default mode 0644 (owner-write only). Every other macOS user account on the same
Mac then gets EACCES on every spawn and exits 1 before producing any output.

When this CLI is invoked by Claude Desktop, Desktop spawns it through Claude.app/Contents/Helpers/disclaimer, which appears to swallow the child's stderr — so the
underlying EACCES never reaches ~/Library/Logs/Claude/main.log. The only desktop-side signal is Claude Code process exited with code 1, hadFirstResponse=false. Manually
reproducing the spawn from the affected account is required to surface the actual error.

TMPDIR env var is not honored — setting TMPDIR=$HOME/Library/Caches/... does not redirect the file; the CLI still writes to /tmp/. So a per-user TMPDIR is not
an available workaround.

What Should Happen?

Two macOS user accounts on the same Mac should each be able to use Claude Desktop / the bundled CLI concurrently, without interfering.

Any of the following would fix this:

• Include getuid() (or os.userInfo().username) in the hash so per-user paths don't collide.
• Write to os.tmpdir() / $TMPDIR / $XDG_CACHE_HOME (each macOS user already has a private $TMPDIR under /var/folders/.../T/) instead of hardcoded /tmp/.
• Create the file with mode 0666. The cache is content-addressed (same input → same hash → same bytes), so concurrent writes from different users produce identical

content and sharing is data-safe.

Error Messages/Logs

# Reproduced manually under the affected account:
  $ echo '' | "$HOME/Applications/Claude.app/Contents/Helpers/disclaimer" \
     "$HOME/Library/Application Support/Claude/claude-code/2.1.128/claude.app/Contents/MacOS/claude" \
     --output-format stream-json --verbose --input-format stream-json \
     --setting-sources=user,project,local --settings '{}'
  Error processing settings: EACCES: permission denied, open '/tmp/claude-settings-44136fa355b3678a.json'

  # What Claude Desktop logs (with no child stderr):
  [info] Using Claude Code binary at: /Users/<user>/Library/Application Support/Claude/claude-code/2.1.128/claude.app/Contents/MacOS/claude
  [error] Session ... query error: Claude Code process exited with code 1
  [CCD CycleHealth] unhealthy cycle for ... (0s, hadFirstResponse=false, reason=no_response)

  # File state on disk:
  $ ls -la /tmp/claude-settings-*
  -rw-r--r--@ 1 <userA>  wheel  2 /tmp/claude-settings-44136fa355b3678a.json

  $ cat /tmp/claude-settings-44136fa355b3678a.json
  {}

Steps to Reproduce

1. On a Mac with two user accounts (A and B), install Claude Desktop in each user's ~/Applications/.
2. User A logs in and opens Claude Desktop. The desktop CCD spawns the bundled CLI with --settings '{}'. Session works. /tmp/claude-settings-44136fa355b3678a.json is

now owned by A, mode 0644.

1. User B fast-user-switches in and opens Claude Desktop. Every session fails with exit 1 and hadFirstResponse=false. UI never renders a response.
2. Manually reproduce B's spawn from a Terminal in B's account:

echo '' | "$HOME/Applications/Claude.app/Contents/Helpers/disclaimer" \
"$HOME/Library/Application Support/Claude/claude-code/2.1.128/claude.app/Contents/MacOS/claude" \
--output-format stream-json --verbose --input-format stream-json \
--setting-sources=user,project,local --settings '{}'

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

1. Confirm TMPDIR is not honored:

mkdir -p "$HOME/Library/Caches/claude-tmp-test"
TMPDIR="$HOME/Library/Caches/claude-tmp-test" echo '' | \
"$HOME/Applications/Claude.app/Contents/Helpers/disclaimer" \
"$HOME/Library/Application Support/Claude/claude-code/2.1.128/claude.app/Contents/MacOS/claude" \
--output-format stream-json --verbose --input-format stream-json \
--setting-sources=user,project,local --settings '{}'

→ Still EACCES on /tmp/claude-settings-*.json. $TMPDIR is empty.

Claude Model

Not sure / Multiple models

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.128 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

• macOS 26.4.1 (arm64), build 25E253
• Claude Desktop 1.6259.1
• Bundled CLI path: ~/Library/Application Support/Claude/claude-code/2.1.128/claude.app/Contents/MacOS/claude
• Desktop spawns the CLI via Contents/Helpers/disclaimer, which appears to suppress the child's stderr — that's why the EACCES never surfaces in main.log and the only

desktop-side signal is the generic "process exited with code 1".