[BUG] Claude Code for VS Code: cannot choose Sonnet 4.6

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 use Claude Code in Antigravity (VS Code fork)
Plan: Pro
Issue: Model picker has no plain "Sonnet 4.6" option. "Default" label says Sonnet 4.6 but resolves to claude-opus-4-6. The only Sonnet option is "Sonnet (1M context)" which uses extra usage instead of subscription usage.

<img width="679" height="374" alt="Image" src="https://github.com/user-attachments/assets/51f59f79-5444-4b0e-a1f7-46bee2ceca0e" />

Choosing any other model seems to work:

<img width="1076" height="226" alt="Image" src="https://github.com/user-attachments/assets/eb29664f-3bb9-4168-8f89-bdcfd0889419" />

But, when I choose "Default (Recommended)", which is supposed to be Sonnet 4.6:

<img width="1077" height="70" alt="Image" src="https://github.com/user-attachments/assets/54f9f0d4-d21c-4379-8f5b-324ae6c91da6" />

What Should Happen?

Claude Code should display "Switched to claude-sonnet-4-6" and switch to sonnet 4.6
There should be a non-1M "Sonnet 4.6" option in the dropdown

Error Messages/Logs

Steps to Reproduce

1. Open Claude Code for VS Code (non-terminal option)
2. Use /model and choose Default or Sonnet 4.6

Claude Model

Not sure / Multiple models

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.85 (Claude Code)

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_