[BUG] Model setting in settings.json ignored on new session startup

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?

New sessions ignore the model setting in global settings.json and default to Sonnet 4.5 instead of the configured model.

What Should Happen?

New sessions should use the model specified in ~/.claude/settings.json

Error Messages/Logs

Steps to Reproduce

1. Set "model": "us.anthropic.claude-sonnet-4-6" in ~/.claude/settings.json
2. Wait at least a week to ensure setting persists
3. Start a completely new session
4. Check the model ID in the system environment description at session start
5. Observe it shows Sonnet 4.5 instead of the configured 4.6

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.165

Platform

AWS Bedrock

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

Environment

• OS: Windows 11 Home 10.0.26200
• Shell: bash
• Platform: win32
• Current model shown: us.anthropic.claude-sonnet-4-5-20250929-v1:0
• Configured model: us.anthropic.claude-sonnet-4-6

## Configuration Files
Global settings.json content:
```json
{
"model": "us.anthropic.claude-sonnet-4-6",
"enabledPlugins": {
"atlassian@claude-plugins-official": true,
"slack@claude-plugins-official": true
},
"alwaysThinkingEnabled": true,
"effortLevel": "xhigh"
}

No project-level settings.json exists that would override this.