[BUG] Xcode 26.6 Plugin Defaults to Fable, even when not available

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?

I had been using the Claude Agent plugin in Xcode 26.3. After updating to 26.6, I had to re-install the plugin and re-authenticate. Initial use worked, but after 2-3 prompts, I got the following error: "API Error: Fable 5 requires usage credits. Update Claude Code to the latest version to learn more". In Xcode > Settings > Intelligence > Claude Agent the Model was set to Default, which it had always been. Much thrashing ensued, finally fixed by changing the Model to Sonnet and restarting Xcode. The issue then is that "Default" now apparently resolves to Fable, even for accounts (like mine) which do not have usage credits enabled, and are therefore unable to use Fable.

What Should Happen?

The Default setting should resolve to a model the user has access to, preferably the model they had been using before the Xcode update.

Error Messages/Logs

Steps to Reproduce

1. Run Xcode 26.3 with Claude Agent's Model set to Default.
2. Update to Xcode 26.6

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.216

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_