[BUG] Welcome banner shows wrong model name ("sonnet" instead of "opus") in exported conversation

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 welcome banner in an exported conversation displays sonnet · API Usage Billing even though the session was running on Opus 4.7 the entire time.

<img width="562" height="170" alt="Image" src="https://github.com/user-attachments/assets/dee4376b-e31f-496a-a64d-d0b47351ae93" />

What Should Happen?

The banner should show opus · API Usage Billing (matching the actual model used).

Error Messages/Logs

Steps to Reproduce

1. Start a Claude Code session on Opus (claude-opus-4-7)

<img width="850" height="167" alt="Image" src="https://github.com/user-attachments/assets/e97fdbbf-bec1-4b00-a098-8547ccb62920" />

1. Run /export to export the conversation
2. Open the exported .txt file
3. Check the welcome banner at the top

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.117

Platform

AWS Bedrock

Operating System

macOS

Terminal/Shell

Other

Additional Information

Asking the model "which model are you?" within the same session correctly returns Opus 4.7. The issue appears to be in the banner/export rendering, not the actual model selection... I hope at least.