[BUG] Model configuration not loading from CLAUDE.md - stuck on Haiku 4.5

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
Claude Code is not loading the model configuration specified in CLAUDE.md, remaining on Haiku 4.5 even after configuration updates
and restarts.

What Should Happen?

## Expected Behavior
Claude Code should load claude-sonnet-4-6 as specified in the CLAUDE.md configuration

## Actual Behavior

• Claude Code continues using Haiku 4.5
• The .claude.json configuration file exists but has no modelId field
• Attempts to manually edit .claude.json are overwritten by the system

## Environment

• OS: Windows 11 Enterprise 10.0.22631
• Current Model: claude-haiku-4-5
• Expected Model: claude-sonnet-4-6

Error Messages/Logs

Steps to Reproduce

## Steps to Reproduce

1. Update CLAUDE.md to specify: claude-sonnet-4-6 as Default Model
2. Restart Claude Code
3. Observe that the model is still Haiku 4.5

Claude Model

Other

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Haiku 4.5

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_