[BUG] Background tasks run by Claude Code causes rapid usage over hours, despite idle compute

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?

While running background tasks (training a model) in VS Code, I was charged for usage as the tasks ran simply by keeping VS Code open. It used up my entire Max subscription, then continued to charge for extra usage until I noticed and intervened. The usage was massive, $60-70 in extra usage after consuming my entire remaining Max subscription. I would have to conclude it does this for any task running in background, while computing anything specific as the task ran.

<img width="1235" height="434" alt="Image" src="https://github.com/user-attachments/assets/7a0cb7f3-f475-4d8f-bd39-891d27f71fab" />

What Should Happen?

A background task should be able to run if started by Claude Code, and it's execution shouldn't consume an enormous amount of usage.

Error Messages/Logs

Steps to Reproduce

1.) Create a script that will run over many hours, such as fine tuning an LLM.
2.) Have Claude Code run this in VS Code
3.) Have a Max subscription with extra usage enabled, and auto renew extra usage.
4.) Be close to end of Max subscription (I had 8% left).

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.79 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

Please adjust usage/billing, I didn't think anyone would realize a Max subscription is being used so rapidly by Claude running background task