[BUG] Opus 4.5 showing in Claude Code CLI, but not showing in Claude Code VSCode extension

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 am on Windows 11 ARM, Max 20x plan, CLI works with Opus 4.5, extension doesn't no matter how I reset and reinstall the extension with cache removed.
Extension version : anthropic.claude-code@2.0.46
Claude Code version: 2.0.69

I also tried to force it in the configuration of the vscode json file by changing the default model name. It fall back to Sonnet 4.5.

<img width="479" height="139" alt="Image" src="https://github.com/user-attachments/assets/09447d1f-1185-4482-88b3-671c41e134e2" />

What Should Happen?

Claude Code extension interface shall allow selection of Opus 4.5 instead of Opus 4.1.

Error Messages/Logs

Steps to Reproduce

Steps to Reproduce:

1. Install Claude Code VS Code extension from marketplace
2. Authenticate with Max plan account
3. Open a project folder in VS Code
4. Click the Spark icon to open Claude Code panel
5. Start a new conversation (Ctrl+N)
6. Open model picker via /model command or UI dropdown
7. Observe available models - Opus 4.5 is not listed (only shows Opus 4.1)
8. Alternatively, set "claudeCode.selectedModel": "claude-opus-4-5-20251101" in VS Code settings.json
9. Reload VS Code
10. Start new conversation and send any message
11. Receive error:

Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.37.content.0.type: Expected `thinking` or `redacted_thinking`, but found `tool_use`. When `thinking` is enabled, a final `assistant` message must start with a thinking block..."}}

Expected Behavior:
Opus 4.5 should appear in the model picker and work correctly, matching the CLI behavior.

Actual Behavior:

• Opus 4.5 not shown in model picker
• Manually setting the model string causes API errors related to extended thinking

Workaround:
Using CLI directly (claude --model claude-opus-4-5-20251101) works correctly.

Additional Context:

• Disabling extended thinking does not resolve the issue
• Clean reinstall of extension and clearing ~/.claude folder does not resolve
• CLI on same machine with same account works perfectly with Opus 4.5

Claude Model

Opus

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.0.69

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_