[BUG] Went from 0% to 100% U5 hour usage in 10 min on Opus 4.8

### Preflight Checklist

- [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) 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 updated to latest verison of claude and was at around 1% 5 day usage and after 10 minutes of using Opus 4.8, i was at 100%. I added $10 more in credits on my max plan and that lasted 2 minutes.

### What Should Happen?

not go to 100%

### Error Messages/Logs

```shell

```

### Steps to Reproduce

n/a

### Claude Model

None

### Is this a regression?

Yes, this worked in a previous version

### Last Working Version

_No response_

### Claude Code Version

Claude 1.46388.4 (50e62f) 2026-09-05T01:57:47.000Z

### Platform

Anthropic API

### Operating System

macOS

### Terminal/Shell

Terminal.app (macOS)

### Additional Information

_No response_

No repository file, test, log, or reproducible steps are provided. Start by reproducing the usage jump with Claude Code 1.46388.4 on macOS through the Anthropic API, then compare usage before and after the reported regression; done means identifying a reliable cause and verifying that a comparable session no longer exhausts the U5 allowance unexpectedly.

索引モデルが issue の本文から書いたものです。