Browser Use IAB backend fails on multi-user macOS when shared temp socket path is owned by another user

[AaronRayRay]

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

26.429.61741

What subscription do you have?

Pro 20x

What platform is your computer?

Darwin 25.4.0 arm64 arm

What issue are you seeing?

Browser Use in Codex Desktop fails to connect to the in-app browser backend on a shared macOS machine with multiple local user accounts.

Observed error:

Failed to connect to browser-use backend "iab". No Codex IAB backends were discovered.

Local diagnosis, with user names redacted:

• Browser Use appears to use /tmp/codex-browser-use on macOS.
• That directory was owned by a different macOS user than the active Codex session.
• It contained stale Browser Use socket files from the other user account.
• The active user account could not write to /tmp/codex-browser-use.
• lsof showed no active process listening on those socket files.
• Codex processes were running under more than one macOS user account.

So the failure appears to happen before any website or browser page is reached. Browser Use cannot discover or connect to a usable IAB backend for the active Codex user session.

What steps can reproduce the bug?

Uploaded thread: 019dfe88-7ded-7a60-bc50-9c88dec3cff7

What is the expected behavior?

Browser Use should connect to the in-app browser backend for the active Codex Desktop user session on a shared macOS machine, or provide a clear diagnostic if another local user's stale socket state is blocking it.

Additional information

I have redacted the local macOS usernames from this report. The uploaded thread attached to the issue contains the original Codex context and can be used for more detail if available to the Codex team.