[BUG] Claude Desktop falls back to Safari for SSO login when default browser is Arc

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 logging in to the Claude desktop app, the SSO login popup (workos.com) opens
in Safari instead of my default browser, Arc.

My macOS default browser is set to Arc (System Settings → Desktop & Dock → Default
web browser → Arc), and it is correctly registered as the https handler. Despite
this, the app bypasses Arc and falls back to Safari for the login window.

This looks like the same fallback behavior reported in #37036 (which was closed as
not planned). In that report the default browser was Finicky; here it's Arc, a
standard, widely used browser — so the fallback shouldn't be happening.

What Should Happen?

The login popup should open in the system default browser (Arc), the same as it
does for recognized browsers like Chrome and Safari.

Error Messages/Logs

Steps to Reproduce

1. Set Arc as the default web browser in macOS.
2. Log out of the Claude desktop app completely.
3. Log back in via SSO.
4. Observe the login popup opens in Safari, not Arc.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude 1.15200.0

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

Reproducible every login. Changing/re-registering the default browser and rebuilding
LaunchServices does not affect it, which indicates the browser choice is made inside
the app rather than via the OS default-browser setting.