[app] Codex Security scan thread fails to start on macOS

What version of the Codex App are you using (From “About Codex” dialog)?

Codex Desktop 26.803.41515 (build 6321)

What subscription do you have?

ChatGPT account (the exact plan does not appear relevant to scan-thread startup)

What platform is your computer?

Darwin 25.4.0 arm64 arm

Codex Security plugin: 0.1.18

What issue are you seeing?

In the Codex Security flow, the scan setup can be opened, but the scan thread does not start normally after the setup is confirmed. No usable running scan thread or scan progress is produced, so the security scan cannot proceed beyond the launch handoff.

The failure occurs before repository analysis begins. The UI should not leave the user without a running scan or a clear recoverable error.

What steps can reproduce the bug?

1. Open a local Git repository in Codex Desktop on macOS.
2. Ask Codex Security to run a repository security scan.
3. Complete the scan setup and click Start scan.
4. Wait for Codex to create and start the scan thread.
5. Observe that no usable running scan thread starts and scan progress does not begin.
6. Retry or reopen the scan setup; the flow still does not recover reliably.

What is the expected behavior?

• Clicking Start scan should create a running scan thread and return a durable scan identifier.
• The scan should enter its first execution phase and show visible progress.
• If scan-thread creation fails, the app should show an explicit error and allow a clean retry.
• Retrying should clear stale startup state rather than leaving an orphaned waiter or permanently blocking future scans.

Additional information

#31954 reports a similar scan-start handoff failure on Windows, where the start request times out and leaves an orphaned waiter. This report covers macOS with newer Codex Desktop and Codex Security versions; it does not assume the same root cause.

No repository content, local path, thread ID, or account identifier is included.