[BUG] Claude Code UI shows "Opus 4.7" but actual model is "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?

Description

The Claude Code UI displays "Opus 4.7 · 보통" in the model selector,
but the system prompt explicitly identifies the model as Sonnet 4.6.
This is a critical billing/transparency issue — users selecting Opus 4.7
may be charged Opus rates while receiving Sonnet 4.6 responses.

What Should Happen?

• UI model selection matches the actual backend model used
• OR clear documentation of fallback/routing behavior

Error Messages/Logs

**System prompt excerpt (auto-injected by Claude Code):**
> "You are powered by the model named Sonnet 4.6.
>  The exact model ID is claude-sonnet-4-6."

Steps to Reproduce

1. Open Claude Code
2. Select model "Opus 4.7" in the model picker
3. Start a new conversation
4. Ask the model: "What model are you? Check the system prompt for your model ID."
5. Model responds: claude-sonnet-4-6 (Sonnet 4.6)
6. UI still shows "Opus 4.7"

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

not sure

Claude Code Version

most updated version

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

The discrepancy was discovered when the model itself flagged the mismatch
in a working session. Consistent across multiple conversations.