Opus requests return 500 Internal Server Error in VS Code extension; Sonnet works fine on same session

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 using Claude Opus in the Claude Code VS Code extension, requests fail with a 500 Internal Server Error. Switching the model to Sonnet in the same session/authentication works without any issue. I also confirmed Opus is responding normally on claude.ai during the same time window, so this appears isolated to the VS Code extension's handling of Opus specifically.

What Should Happen?

Opus should respond normally in the VS Code extension, the same as Sonnet does and the same as Opus does on claude.ai.

Error Messages/Logs

API Error: 500 Internal server error. This is a server-side issue, usually temporary — try again in a moment. If it persists, check https://status.claude.com.

Steps to Reproduce

Open Claude Code extension in VS Code (Windows, PowerShell)
Select Claude Opus as the model
Send any prompt
Observe: request fails with "API Error: 500 Internal server error"
Switch model to Sonnet — same prompt succeeds normally
Confirmed Opus works fine on claude.ai during the same window, using a Claude subscription (Pro/Max/Team) login, not an API key

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Worked almost 30 minutes ago

Claude Code Version

2.1.154

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Authenticated via Claude subscription (Pro/Max/Team) login, not an API key. Issue has persisted for over an hour. Possibly related to #78114 ("opus models 4.6+ not available in vs c...") — please check for overlap before treating as separate.