[BUG] Claude Code stuck in 1M context mode after model switch, blocking Pro user

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?

Hi Anthropic Support,

I'm a Pro plan user and encountered a bug in Claude Code (VS Code extension) that forced me to clear my entire conversation, resulting in lost context and wasted usage.

What happened:

• I started a session using Opus with high effort mode
• I switched to Sonnet mid-session
• After switching, Claude Code appeared to inherit a 1M context window, which Pro users should not have access to
• I received the error: "API Error: Extra usage is required for 1M context"
• The compact option was also not showing, leaving me with no way to manage context
• The only fix was to clear the entire conversation, losing all context and wasting significant usage to get back to the same point

This appears related to GitHub issues #42616, #45390, and #45847.

I'd also appreciate a review of whether my usage was fairly consumed given the bug forced me to restart.

Thank you

What Should Happen?

Expected behavior:

• Switching models mid-session should not cause the session to inherit a 1M context window on a Pro plan
• The compact option should remain available as a fallback
• Users should not be forced to clear their conversation to recover from this state

Error Messages/Logs

Steps to Reproduce

Environment:

• Plan: Pro
• Interface: Claude Code (VS Code extension)
• Trigger: Switching from Opus (high effort) to Sonnet mid-session

Claude Model

Not sure / Multiple models

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

don't know

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_