[BUG] VS Codium extension ignores model configuration and defaults to Opus 4.1

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?

The VS Code/VSCodium extension's model selector dropdown shows Opus 4.1 as the only Opus option, while the CLI has access to the latest Opus 4.6 (released February 5, 2026). Current behavior:
Extension UI displays:
✓ Default (recommended): Sonnet 4.5
Opus 4.1 (outdated)
CLI claude --model claude-opus-4-6 works correctly
This suggests the extension's model list is hardcoded or read from a static manifest that doesn't sync with the API's available models. Screenshot attached: [Your screenshot showing Opus 4.1 in dropdown]

What Should Happen?

The extension's model selector should display all currently available models via the API, including:
Sonnet 4.5 ✓ (currently works)
Opus 4.6 (missing - shows 4.1 instead)
Any future model releases without requiring extension updates
Ideally, the model list should be fetched dynamically from the API instead of being bundled statically in the extension package.

Error Messages/Logs

No error messages - the extension simply doesn't offer the latest model in the UI dropdown. However, forcing the model via CLI works:
claude --model claude-opus-4-6
# Successfully connects with Opus 4.6

Steps to Reproduce

Open VS Code/VSCodium with Claude Code extension installed
Click on the model selector (top-right or command palette)
Observe the "Opus" option shows version 4.1
Compare with CLI: run claude --model claude-opus-4-6 in terminal
CLI successfully uses Opus 4.6, while extension UI doesn't offer it
Expected: Extension shows Opus 4.6 as selectable option
Actual: Extension only shows Opus 4.1 (outdated by 2 releases)

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.0.13

Claude Code Version

2.1.37

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

Workaround
Users can bypass the extension UI by launching from the terminal:
cd "path/to/workspace"
claude --model claude-opus-4-6
This works perfectly and uses the latest model, confirming the issue is in the extension's UI layer, not the underlying CLI.
Root Cause Analysis
The extension likely:
Bundles a static models.json or similar file
Only updates this file when a new extension version is published
Doesn't query the API for available models dynamically
Suggested Fix
Implement dynamic model fetching:
On extension load, query Anthropic API for available models
Cache the list with TTL (e.g., 24h) to avoid excessive API calls
Fall back to hardcoded list only if API query fails
Related Issues
Similar to #14919 (if it exists - check before submitting)
Timeline Context
Opus 4.6: Released February 5, 2026 ✅ Available in CLI
Opus 4.5: Released November 2025 (not shown in UI either)
Opus 4.1: Released August 2025 ⚠️ Only version shown in extension
This means the extension is 6 months behind on Opus releases.