[BUG] Claude Code became very hungry

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 went on a 3-wk vacations. When I got back Sonnet 5 was there waiting, alongside v2.1.2xx Claude Code update. I worked a lot with Opus 5 before, as I needed 1M context for refactoring of legacy system; after I got back I needed to continue and what I noticed – after upgrading Claude Code – that it eats probably twice as much tokens as it used to. This behavior is supported by much longer time needed to response.

I'm pretty sure it's not model change, but some v2.1.1xx -> v2.1.2xx updates to system prompts or how tools are being used.

What Should Happen?

The prompt and tooling was close-to-perfection at v2.1.1xx. I'm not sure how can we check what's changed, but the change was in wrong direction. Or right direction if the business decision was to burn more tokens. $$$

Error Messages/Logs

Steps to Reproduce

Can't really tell the steps, because they're based on your source code.

I'm just wondering if anyone else noticed this behavior?

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

v2.1.1xx

Claude Code Version

v2.1.220

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Up #72486 #77673 #74803