[BUG] Model selection per-session not persisting — switching models in one window overrides all other windows

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 two Claude Code windows on the same machine, switching the model in one window (e.g. to Sonnet) overwrites the global model setting, causing the other window (which had Opus selected) to silently switch to Sonnet on next open.

What Should Happen?

Each window should remember its own model selection, or at minimum warn that changing the model will affect other sessions.

Error Messages/Logs

Steps to Reproduce

Steps to reproduce:

1. Open Claude Code window/session A, set model to Opus
2. Open Claude Code window/session B, set model to Sonnet
3. Close window A and reopen it
4. Window A now shows Sonnet instead of Opus

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude Code version: 2.1.128 (VS Code extension)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_