[BUG] Opus usage charged when using Haiku model

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?

I've noticed an issue with usage billing where Opus model usage is being charged even though I'm exclusively using the Haiku model. This billing discrepancy has caused unexpected quota exhaustion for a model I haven't been using.
While using --model haiku in headless mode, Opus usage is being charged instead. This has resulted in:

• Significant consumption of my weekly general limit
• Depletion of Opus quota despite never selecting or using the Opus model

What Should Happen?

• When using Haiku model, only Haiku usage should be counted
• Opus usage counter should remain unchanged when Haiku is selected

Error Messages/Logs

Steps to Reproduce

1. Run Claude Code in headless mode with Haiku model:

claude -p 'example prompt' --model haiku

1. Execute multiple prompts using the --model haiku flag
2. Check usage statistics

Claude Model

Other

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.0.31

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Other

Additional Information

• I have not manually selected Opus model at any point
• All my recent work has been done with --model haiku or --model sonnet flag in headless mode
• Despite this, Opus usage metrics show consumption